Bio 1 Exam 2

Front 1

All living things are made up of four classes of large biological molecules and they are...

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1. Carbohydrate

2. Lipid

3. Proteins

4. Nucleic Acid

Front 2

Macromolecules

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are large and complex molecules (can only be carbohydrates, proteins and nucleic acid)

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Polymer

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a long molecule consisting of many similar or identical building blocks linked by covalent bonds

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monomers

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the building blocks that create polymers

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enzymes

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specialized macromolecules that speed up chemical reactions (make and break down polymers)

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dehydration reaction

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a covalent bond in which they loose a water molecule, these are found in monomer connections

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Hydrolysis

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to break a dehydration reaction by adding a water molecule (to break up monomers)

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Carbohydrates

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are sugars and polymers of sugars

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monosaccharides

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simple sugars normally have molecular formulas that are a multiple of the unit CH2O (1:2:1)

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Carbohydrates are composed of..

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polysaccharides, polymers composed of many sugar building blocks

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disaccharides

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double sugars, consisting on two monosaccharides joined by a glycosidic linkage, (a covalent bond formed between two monosaccharides by a dehydration reaction.)

Front 12

The most common monosaccharide is..

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glucose (C6H12C6)

Front 13

What is the difference between an aldose or ketose sugar?

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the location of the carbonyl group. aldose has the carbonyl group at the end of the carbon skeleton (diagonal) where in a ketose sugar it is located within the carbon skeleton. (sideways)

Front 14

polysaccharides

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are marcromolecules, polymers with a few hundred to a few thousand monosaccharides joined by glycosidic linkages

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both plants and animals store sugars for later use in the form of...

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storage polysassharides

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plants store..

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starch a polymer of glucose monomers, as granules within the cellular structures known as plastids, which include chloroplasts.

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humans store..

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Glycogen, a polymer of glucose, this is stored mainly in the liver and muscle cells

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cellulose

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a major component of plant cell walls, is a polysaccharide, most abundant organic compound on Earth,polymer of glucose

Front 19

what is the difference between starch and cellulose in their glucose polymer make up?

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they have a slightly different ring structures for glucose. Glucose alpha (starch) the hydroxyl group attached to the 1 carbon is positioned below the plane of the ring where as in glucose beta the hydroxyl group is located above the plane of the ring

Front 20

what shape is cellulose?

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straight

Front 21

what shape is starch?

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largely helical

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chitin

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the carbohydrate (polysaccharide) to build their exoskeleton, made with beta glucose and has a nitrogen containing appendage

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why are lipids hydrophobic?

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it is because of their mostly hydrocarbon structure

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important type of lipids are

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1.fats

2.phospholipids

3. steroids

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Fats structure

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although fats are not polymers, they are large molecules assembled from smaller molecules by dehydration reactions

Front 26

the 2 smaller molecules composing fats are..

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glycerol and fatty acids

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glycerol..

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is an alcohol, each of its 3 carbons bares and hydroxyl group

Front 28

fatty acids..

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is composed of a long carbon skeleton, usually 16-18 carbons in length, the carbon at the end of the chain is a part of the carboxyl group, the functional group that gives these molecules the name fatty acids. The rest of the skeleton consists of hydrocarbon

Front 29

Saturated fatty acids

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have the maximum number of hydrogen atoms as possible and no double bonds "saturated with hydrogen" (solid at room temperature)

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unsaturated fatty acids

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one or more double bond "cis double bonds, which cause a kink in the hydrocarbon chain" (liquid at room temperature)

Front 31

triacylgcerol

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3 fatty acid molecules are each joined to a glycerol by an ester linkage, a bond between a hydroxyl group and a carboxyl group

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phospolipid

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2 fatty acids and a phosphate group are attached to a glycerol

The two fatty acid tails are hydrophobic, but thephosphate group and its attachments form ahydrophilic head

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when phospolipids are added to water they..

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self-assemble into double-layered structurescalled bilayers, they do this to create the cell membrane

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steroids

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are lipids characterized by a carbonskeleton consisting of four fused rings

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cholestrol

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a type of steroid, is a component inanimal cell membranes and a precursor fromwhich other steroids are synthesized

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proteins account for more than..

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50% of the drymass of most cells

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Enzymatic proteins

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Function: Selective acceleration ofchemical reactionsExample: Digestive enzymes catalyze thehydrolysis of bonds in food molecules.

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Defensive proteins

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Function: Protection against diseaseExample: Antibodies inactivate and helpdestroy viruses and bacteria.

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Storage proteins

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Function: Storage of amino acidsExamples: Casein, the protein of milk, is themajor source of amino acids for babymammals. Plants have storage proteins intheir seeds. Ovalbumin is the protein of eggwhite, used as an amino acid source for thedeveloping embryo

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Transport proteins

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Function: Transport of substancesExamples: Hemoglobin, the iron-containingprotein of vertebrate blood, transportsoxygen from the lungs to other parts of thebody. Other proteins transport moleculesacross membranes, as shown here.

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Hormonal proteins

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Function: Coordination of an organism’sactivitiesExample: Insulin, a hormone secreted by thepancreas, causes other tissues to take upglucose, thus regulating blood sugar,concentration.

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Receptor Proteins

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Function: Response of cell to chemicalstimuliExample: Receptors built into themembrane of a nerve cell detectsignaling molecules released by othernerve cells.

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Contractile and motor proteins

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Function: MovementExamples: Motor proteins are responsiblefor the undulations of cilia and flagella.Actin and myosin proteins are responsiblefor the contraction of muscles.Contractile and motor proteins

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structural proteins

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Function: SupportExamples: Keratin is the protein of hair,horns, feathers, and other skinappendages. Insects and spiders use silkfibers to make their cocoons and webs,respectively. Collagen and elastin proteinsprovide a fibrous framework in animalconnective tissues

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proteins are all constructed of the same set of..

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20 amino acids

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Polypeptides

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are unbranched polymers builtfrom these amino acids

Each polypeptide has a unique linear sequence ofamino acids, with a carboxyl end (C-terminus) andan amino end (N-terminus)

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protein

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is a biologically functional moleculethat consists of one or more polypeptides

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Amino Acids

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Amino acids are organicmolecules with amino andcarboxyl groupsAmino acids differ in theirproperties due to differingside chains, called R groups

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peptide bonds

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Amino acids are linked by covalent bonds

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the primary structure of a protein

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The primary structure of a protein is its uniquesequence of amino acids

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the secondary structure of a protein

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Secondary structure, found in most proteins,consists of coils and folds in the polypeptide chain (hydrogen bonds)

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Tertiary structure of a protein

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Tertiary structure is determined by interactionsamong various side chains (R groups)

the overall shape of apolypeptide, results from interactions betweenR groups, rather than interactions betweenbackbone constituents

These interactions include hydrogen bonds,ionic bonds, hydrophobic interactions, andvan der Waals interactions

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quaternary structure of a protein

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Quaternary structure results when a proteinconsists of multiple polypeptide chains

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what determines how a protein works?

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the structure, and the structure is determined by the sequence of amino acids

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Disulfide bridges

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strong covalent bonds that help reinforce the proteins structure

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A slight change in primary structure can affect aproteins structure and ability to function an example of this is..

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Sickle-cell disease, an inherited blood disorder,results from a single amino acid substitution inthe protein hemoglobin

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This loss of a proteins native structure iscalled

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denaturation

examples: salt concentration, pH, temp,environmental conditions, ect

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Chaperonins

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are protein molecules that assistthe proper folding of other proteins

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The amino acid sequence of a polypeptide isprogrammed by a unit of inheritance calleda

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gene

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Genes consist of

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DNA, a nucleic acid made of monomers called nucleotides

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There are two types of nucleic acids

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Deoxyribonucleic acid (DNA)

Ribonucleic acid (RNA)

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gene expression is the process in which

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DNA directs synthesis of messenger RNA (mRNA)and, through mRNA, controls protein synthesis

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Nucleic acids are polymers called

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polynucleotides

Each polynucleotide is made of monomers callednucleotides

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nucleotide

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Each nucleotide consists of a nitrogenous base, apentose sugar, and one or more phosphate groups

The portion of a nucleotide without the phosphategroup is called a nucleoside

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nitrogenous base + sugar=?

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nucleoside

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There are two families of nitrogenous bases..

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Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring

Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring

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In DNA, the sugar is

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deoxyribose

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in RNA, the sugaris

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ribose

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DNA molecules have

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two polynucleotidesspiraling around an imaginary axis, forming adouble helix

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The backbones run in opposite 5 → 3directions from each other, an arrangementreferred to as

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antiparallel

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complementary base pairing is when..

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Only certain bases in DNA pair up and formhydrogen bonds: adenine (A) always withthymine (T), and guanine (G) always withcytosine (C)

This feature of DNA structure makes it possibleto generate two identical copies of each DNAmolecule in a cell preparing to divide

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In RNA, thymine is replaced by

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uracil (U) so A and U pair

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While DNA always exists as a double helix,RNA molecules are

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more variable in form (single stranded)

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What are the four macromolecules?

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Nucleic acids, carbohydrates, protein and lipids

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For each of the above list the polymer and monomer they are madefrom.

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Polynucleotide -> nucleotides, polysaccharides -> simple sugars, polypeptide -> amino acids, none

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What reaction builds macromolecules?

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Dehydration synthesis

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What reaction breaks down macromolecules?

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Hydrolysis

Front 78

What is the basic formula for a carbohydrate?

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(CH2O)n

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What is the main component of the cellular membrane?

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Phospholipid bilayer

Front 80

How many amino acids are there?

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20

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What is the secondary structure of a protein?

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α-helix and β-pleated sheet

Front 82

What is a nucleotide build from?

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(deoxy)Ribose sugar, phosphate and nitrogenous base

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Why do we have DNA?

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Protein synthesis

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All organisms are made of

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cells

Front 85

In a light microscope (LM),

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visible light is passed through a specimen and then through glass lenses

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Scanning electron microscopes (SEMs)

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focus a beam of electrons onto the surface of a specimen, providing images that look 3-D

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Transmission electron microscopes (TEMs)

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focus a beam of electrons through a specimen

used mainly to study the internal structure of cells

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Basic features of all cells

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Plasma membrane

Semifluid substance called cytosol Chromosomes (carry genes)

Ribosomes (make proteins)

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Prokaryotic cells are characterized by having

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Cytoplasm bound by the plasma membrane

No nucleus

DNA in an unbound region called the nucleoid

No membrane-bound organelles

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Eukaryotic cells are characterized by having

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DNA in a nucleus that is bounded by a membranous nuclear envelope

Membrane-bound organelles

Cytoplasm in the region between the plasma membrane and nucleus

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The nucleus

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contains most of the cell’s genes and is usually the most conspicuous organelle

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The nuclear envelope

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encloses the nucleus, separating it from the cytoplasm

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The nuclear membrane

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is a double membrane; each membrane consists of a lipid bilayer

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The DNA and proteins of chromosomes are together called

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chromatin

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Chromatin condenses to form

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discrete chromosomes as acell prepares to divide

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Each chromosome is composed of

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a single DNA molecule associated with proteins

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The nucleolus is

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located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis

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Ribosomes

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are complexes made of ribosomal RNA and protein

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Ribosomes carry out protein synthesis in twolocations

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In the cytosol (free ribosomes)

On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

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The endomembrane system consists of

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Nuclear envelope

Endoplasmic reticulum

Golgi apparatus

Lysosomes

Vacuoles

Plasma membrane

These components are either continuous orconnected via transfer by vesicles

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The endoplasmic reticulum (ER)

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accounts for more than half of the total membrane in many eukaryotic cells

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The ER membrane is continuous with

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the nuclear envelope

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There are two distinct regions of ER

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Smooth ER, which lacks ribosomes

Rough ER, whose surface is studded with ribosomes

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The smooth ER

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Synthesizes lipids

Metabolizes carbohydrates

Detoxifies drugs and poisons

Stores calcium ions

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The rough ER

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Has bound ribosomes, which secrete glycoproteins(proteins covalently bonded to carbohydrates)

Distributes transport vesicles, secretory proteinssurrounded by membranes

Is a membrane factory for the cell

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The Golgi apparatus consists of

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flattened membranous sacs called cisternae

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Functions of the Golgi apparatus

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Modifies products of the ER

Manufactures certain macromolecules

Sorts and packages materials into transport vesicles

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A lysosome is

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-a membranous sac that digest macromolecules -Lysosomal enzymes work best in the acidicenvironment

-Hydrolytic enzymes and lysosomal membranesare made by rough ER and then transferred tothe Golgi apparatus for further processing

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Some types of cell can engulf another cell by __________; this forms a food vacuole

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phagocytosis

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Lysosomes also use enzymes to recycle thecell’s own organelles and macromolecules,a process called.....

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autophagy

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A lysosome fuses with the food vacuole and

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digests the molecules

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Vacuoles are..

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large vesicles derived from the ER and Golgi apparatus

Vacuoles perform a variety of functions in different kinds of cells

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Food vacuoles are formed by

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phagocytosis

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Contractile vacuoles

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found in many freshwater protists, pump excess water out of cells

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Central vacuoles

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found in many mature plant cells, hold organic compounds and water

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Mitochondria

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are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP

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Chloroplasts

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found in plants and algae, are the sites of photosynthesis

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Peroxisomes

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are oxidative organelles

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Mitochondria and chloroplasts have similaritieswith bacteria...

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Enveloped by a double membrane

Contain free ribosomes and circular DNA molecules

Grow and reproduce somewhat independently in cells

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These similarities between mitochondria and chloroplasts led to the

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endosymbiont theory

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Mitochondria are in nearly all eukaryotic cellsThey have a smooth outer membrane and an innermembrane folded into _______

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cristae

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The inner membrane creates two compartments

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intermembrane space and mitochondrial matrix

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Some metabolic steps of cellular respiration are catalyzedin ______________

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the mitochondrial matrix

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Cristae present a large surface area

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for enzymes that synthesize ATP

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Chloroplasts contain the green pigment

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chlorophyll, as well as enzymes

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Chloroplast structure includes

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Thylakoids, membranous sacs, stacked to form a granum

Stroma, the internal fluid

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The chloroplast is one of a group of plant organelles, called

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plastids

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Peroxisomes are

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specialized metabolic compartments bounded by a single membrane

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Peroxisomes produce

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hydrogen peroxide and convert it to water

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Peroxisomes perform

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reactions with many different functions

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How peroxisomes are related to other organelles is

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still unknown

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The cytoskeleton is

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a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles

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the cytoskeleton is composed of three types of molecular structures

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Microtubules

Microfilaments

Intermediate filaments

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the cytoskeleton interacts with

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motor proteins to produce motility

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The cytoskeleton helps to

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support the cell and maintain its shape

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In animal cells, microtubules grow out from a ___________ near the nucleus

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centrosome

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In animal cells, the centrosome has a pair of ___________, each with nine triplets ofmicrotubules arranged in a ring

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centrioles

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Microtubules control the beating of _______and _______, microtubule-containing extensions thatproject from some cells

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flagella and cilia

Front 139

Cilia and flagella differ in their

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beating patterns

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Cilia and flagella share a common structure

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A core of microtubules sheathed by the plasma membrane

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A __________ that anchors the cilium or flagellum

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basal body

Front 142

A motor protein called _______, which drives the bendingmovements of a cilium or flagellum

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dynein

Front 143

Microfilaments are

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solid rods about 7 nm in diameter, built as a twisted double chain of actin subunits

Front 144

The structural role of microfilaments is

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to bear tension, resisting pulling forces within the cell

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They form a 3-D network called the ______ just inside theplasma membrane to help support the cell’s shape

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cortex

Front 146

Intermediate filaments

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range in diameter from 8–12 nanometers, larger than microfilaments but smaller than microtubules

They support cell shape and fix organellesin place (more permanent)

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The _________ is an extracellular structure thatdistinguishes plant cells from animal cells

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cell wall

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The cell wall

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protects the plant cell, maintains its shape, and prevents excessive uptake of water

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Plant cell walls are made of

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cellulose fibers embedded in other polysaccharides and protein

Front 150

Plant cell walls may have multiple layers

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Primary cell wall: Relatively thin and flexible Middle lamella: Thin layer between primary walls of adjacent cells

Secondary cell wall (in some cells): Added between the plasma membrane and the primary cell wall

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Plasmodesmata are

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channels between adjacent plant cells

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Animal cells lack cell walls but are covered by anelaborate______________

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extracellular matrix (ECM)

Front 153

The ECM is made up of

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glycoproteins such as collagen, proteoglycans, and fibronectin

Front 154

ECM proteins bind to receptor proteins in theplasma membrane called

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integrins

Front 155

Three types of cell junctions are common inepithelial tissues

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At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

Desmosomes (anchoring junctions) fasten cells together into strong sheets

Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells

Front 156

What are the two main cell types?

Back 156

Prokaryotic and Eukaryotic

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What are the basic features of a cell?

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Plasma membrane, Ribosomes, DNA and Cytosol

Front 158

What is stored in the nucleus?

Back 158

DNA

Front 159

What makes up the endomembrane system?

Back 159

Nuclear envelope, ER, Golgi, Lysosomes, Vacoules, Plasma membrane

Front 160

What are the two types of ER?

Back 160

Rough and Smooth

Front 161

What features does a plant cell have that an animal cell does not?

Back 161

Cell wall, Central vacuole, and chloroplasts

Front 162

What is the function of the Golgi?

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Packaging and shipping

Front 163

What is the cytoskeleton composed of?

Back 163

Microtubules, Intermediate filaments, and Microfilaments

Front 164

What theory proposes a bacterial origin of some organelles?

Back 164

Endosymbiont

Front 165

How do cells communicate and/or link to each other?

Back 165

Plants = Plasmodesmata, Animals = Gap and tight junctions and desmosomes

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Back 166

Front 167

Back 167

diagram slide

Front 168

The plasma membrane is

Back 168

the boundary that separates the living cell from its surroundings

Front 169

The plasma membrane exhibits ___________, allowing some substances to crossit more easily than others

Back 169

selective permeability

Front 170

________are the mostabundant lipid in the plasmamembrane

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Phospholipids

Front 171

Phospholipids are

Back 171

amphipathic molecules, containing hydrophobic and hydrophilic regions

Front 172

A phospholipid bilayer can existas a stable boundary betweentwo

Back 172

aqueous compartments

Front 173

The _______ model states that a membraneis a fluid structure with a “mosaic” of variousproteins embedded in it

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fluid mosaic

Proteins are not randomly distributed in themembrane

Front 174

As temperatures cool, membranes switch from afluid state to a

Back 174

solid state

The temperature at which a membrane solidifiesdepends on the types of lipids

Front 175

Membranes rich in _________ acids are morefluid than those rich in__________acids

Back 175

unsaturated fatty, saturated fatty

Front 176

Membranes must be fluid to work properly; theyare usually about as fluid as

Back 176

salad oil

Front 177

The steroid cholesterol has different effects onmembrane fluidity at different temperatures

Back 177

At warm temperatures (such as 37°C),cholesterol restrains movement ofphospholipids

At cool temperatures, it maintains fluidity bypreventing tight packing

Front 178

Peripheral proteins are

Back 178

bound to the surface of the membrane

Front 179

Integral proteins

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penetrate the hydrophobic core

The hydrophobic regions of an integral proteinconsist of one or more stretches of nonpolaramino acids, often coiled into alpha helices

Front 180

Six major functions of membrane proteins

Back 180

Transport

Enzymatic activity

Signal transduction

Cell-cell recognition

Intercellular joining

Attachment to the cytoskeleton and extracellular matrix (ECM)

Front 181

Cells recognize each other by binding tomolecules, often containing

Back 181

carbohydrates

Front 182

Membrane carbohydrates may be covalentlybonded to lipids

Back 182

(forming glycolipids) or more commonly to proteins (forming glycoproteins)

so these help in cell to cell recognition

Front 183

Transport proteins

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allow passage of hydrophilic substances across the membrane

Front 184

Some transport proteins, called ___________, have a hydrophilic channel that certainmolecules or ions can use as a tunnel

Back 184

channel proteins

Front 185

Channel proteins called _______ facilitate thepassage of water

Back 185

aquaporins

Front 186

Diffusion is

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the tendency for molecules to spread out evenly into the available space

Front 187

At dynamic equilibrium,

Back 187

as many molecules cross the membrane in one direction as in the other

Front 188

Osmosis is

Back 188

the diffusion of water across a selectively permeable membrane

Water diffuses across a membrane from theregion of lower solute concentration to theregion of higher solute concentration until thesolute concentration is equal on both sides

Front 189

Tonicity is

Back 189

the ability of a surrounding solution to cause a cell to gain or lose water

Front 190

Isotonic solution:

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Solute concentration is the same as that inside the cell; no net change

Front 191

Hypertonic solution:

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Solute concentration is greater than that inside the cell; cell loses water

Front 192

Hypotonic solution:

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Solute concentration is less than that inside the cell; cell gains water

Front 193

Back 193

diagram

Front 194

Osmoregulation

Back 194

the control of solute concentrations and water balance, is a necessary adaptation

Front 195

cell walls help maintain

Back 195

water balance

Front 196

A plant cell in a hypotonic solution swells until the wall opposes uptake; the cell is now _______(firm)

Back 196

turgid

Front 197

If a plant cell and its surroundings are isotonic,there is no net movement of water into the cell;the cell becomes ______ (limp)

Back 197

flaccid

Front 198

In ___________, transport proteins speedthe passive movement of molecules across theplasma membrane

Back 198

facilitated diffusion

Front 199

Transport proteins include

Back 199

channel proteins and carrier proteins

Front 200

Ion channels facilitate the diffusion of ionsSome ion channels, called ________, open or closein response to a stimulus

Back 200

gated channels

Front 201

Active transport

Back 201

moves substances against their concentration gradients , this needs energy in the form of ATP

Active transport is performed by specificproteins embedded in the membranes

Front 202

Membrane potential is

Back 202

the voltage difference across a membrane

Voltage is created by differences in thedistribution of positive and negative ions acrossa membrane

Front 203

Two combined forces, collectively called theelectrochemical gradient, drive the diffusion ofions across a membrane

Back 203

A chemical force (the ion’s concentration gradient)

An electrical force (the effect of the membrane potential on the ion’s movement)

Front 204

Cotransport occurs when

Back 204

active transport of a solute indirectly drives transport of other substances

Front 205

Large molecules, such as______________ cross the membrane in bulk via vesiclesBulk transport requires energy

Back 205

polysaccharides and proteins

Front 206

In exocytosis

Back 206

transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell

Front 207

In endocytosis

Back 207

the cell takes in macromolecules by forming vesicles from the plasma membrane

Front 208

There are three types of endocytosis

Back 208

Phagocytosis (“cellular eating”)

Pinocytosis (“cellular drinking”)

Receptor-mediated endocytosis

Front 209

In phagocytosis

Back 209

a cell engulfs a particle in a vacuole then fuses with a lysosome

Front 210

In pinocytosis

Back 210

molecules dissolved in droplets are taken up when extracellular fluid is “gulped” into tiny vesicles

Front 211

In receptor-mediated endocytosis

Back 211

binding of ligands to receptors triggers vesicle formation

Front 212

A ligand

Back 212

is any molecule that binds specifically to a receptor site of another molecule

Front 213

What is selective permeability?

Back 213

Ability to allow certain molecules across the membrane more easily

Front 214

What is amphipathic?

Back 214

Both hydrophilic and hydrophobic

Front 215

What is a peripheral protein?

Back 215

Sits on the surface

Front 216

Why are glycoproteins important?

Back 216

Cell recognition

Front 217

What type of molecule passes the membrane easiest?

Back 217

Small, nonpolar molecules

Front 218

What are aquaporins?

Back 218

Allow water to cross the membrane

Front 219

What is diffusion?

Back 219

Substance moving down its concentration gradient

Front 220

What is osmosis?

Back 220

Diffusion of water across a selectively permeable membrane

Front 221

What will happen to a cell placed in a hypertonic solution?

Back 221

Shrivel (lose water)

Front 222

What is endocytosis?

Back 222

Bringing particles into the cell

Front 223

The cell extracts energy stored in

Back 223

sugars and other fuels and applies energy to perform work

Front 224

Some organisms even convert energy to light, asin

Back 224

bioluminescence

Front 225

Metabolism is

Back 225

the totality of an organism’s chemical reactions

Front 226

A metabolic pathway

Back 226

begins with a specific molecule and ends with a product

Front 227

Catabolic pathways

Back 227

release energy by breaking down complex molecules into simpler compounds

Front 228

Anabolic pathways

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consume energy to build complex molecules from simpler ones

Front 229

Bioenergetics is the study of how

Back 229

energy flows through living organisms

Front 230

Energy is

Back 230

the capacity to cause change

Front 231

Kinetic energy is

Back 231

energy associated with motion

Front 232

Heat (thermal energy) is

Back 232

kinetic energy associated with random movement of atoms or molecules

Front 233

Potential energy is

Back 233

energy that matter possesses because of its location or structure

Front 234

Chemical energy is

Back 234

potential energy available for release in a chemical reaction

Front 235

Thermodynamics is the study

Back 235

of energy transformations

Front 236

An isolated system

Back 236

is unable to exchange energy or matter with its surroundings

Front 237

In an open system

Back 237

energy and matter can be transferred between the system and its surroundings, organisms are open systems

Front 238

According to the first law of thermodynamics, the energy of theuniverse is constant

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Energy can be transferred and transformed, but it cannot be created or destroyed

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According to the second law of thermodynamics

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Every energy transfer or transformation increases the entropy (disorder) of the universe

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Cells create ___________ from less orderedmaterials

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ordered structures

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Organisms also replace __________ of matter andenergy with less orderedforms

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ordered forms

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Energy flows into anecosystem in the form of _____ and exits in the form of _____

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light, heat

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A living system’s __________ is energy that can dowork when temperature and pressure are uniform,as in a living cell

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free energy

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The change in free energy (∆G) during a process isrelated to the change in enthalpy, or change in totalenergy (∆H), change in entropy (∆S), andtemperature in Kelvin units

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(T) ∆G = ∆H - T∆S

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Only processes with a negative ∆G are

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spontaneous

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An exergonic reaction

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proceeds with a net release of free energy and is spontaneous

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An endergonic reaction

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absorbs free energy from its surroundings and is nonspontaneous

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Reactions in a closed system eventually reach _________ and then do no work

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equilibrium

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Cells are not in equilibrium; they are

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open systems experiencing a constant flow of materials

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A defining feature of life is that metabolism isnever at

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equilibrium

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A cell does three main kinds of work

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Chemical

Transport

Mechanical

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To do work, cells manage energy resources by ___________, the use of an exergonic process to drive anendergonic one

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energy coupling

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Most energy coupling in cells is mediated by

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ATP

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ATP (adenosinetriphosphate) is the cell’s

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energy shuttle

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ATP is composed of

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ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups

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The bonds between the phosphate groups of ATP’s tail can bebroken by

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hydrolysis

Energy is released from ATP when the terminal phosphate bondis broken

This release of energy comes from the chemical change to astate of lower free energy, not from the phosphate bondsthemselves

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ATP drives endergonic reactions by phosphorylation, transferringa phosphate group to some other molecule, such as a reactant

The recipient molecule is now called a

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phosphorylated intermediate

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A catalyst is a

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chemical agent that speeds up a reaction without being consumed by the reaction

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An enzyme is a

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catalytic protein

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The initial energy needed to start a chemicalreaction is called the

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free energy of activation, or activation energy (EA )

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Activation energy is often supplied in the formof _________ that the reactant moleculesabsorb from their surroundings

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thermal energy

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enzymes just speed up the chemical reaction time with the same amount of product

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The reactant that an enzyme acts on is calledthe enzyme’s

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substrate

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The enzyme binds to its substrate, forming an

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enzyme-substrate complex

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The _________ is the region on the enzymewhere the substrate binds

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active site

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Induced fit of a substrate brings

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chemical groups of the active site into positions

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diagram

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The active site can lower an EA barrier by

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Orienting substrates correctly

Straining substrate bonds

Providing a favorable microenvironment Covalently bonding to the substrate

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Cofactors are

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nonprotein enzyme helpers

Cofactors may be inorganic (such as a metal inionic form) or organic

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An organic cofactor is called a

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coenzyme

example: vitamins

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Competitive inhibitors

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bind to the active site of an enzyme, competing with the substrate

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Noncompetitive inhibitors

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bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

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Examples of inhibitors include

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toxins, poisons, pesticides, and antibiotics

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diagram

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Changes (mutations) in genes lead to changesin amino acid composition of an enzyme

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Altered amino acids in enzymes may result in novel enzyme activity or altered substrate specificity

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Most allosterically regulated enzymes are madefrom

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polypeptide subunits

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Each enzyme has _____ and _______ forms

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active and inactive

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The binding of an ______ stabilizes the active formof the enzyme

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activator

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The binding of an ________ stabilizes the inactiveform of the enzyme

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inhibitor

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In feedback inhibition

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the end product of a metabolic pathway shuts down the pathway Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed

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What is a catabolic pathway?

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Releases energy, breaks complex molecules into simpler ones

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What is the first law of thermodynamics?

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Energy can change form, but cannot be created or destroyed

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What is free energy?

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Ability to do work when temperature and pressure are uniform

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What is an endergonic reaction?

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Absorbs free energy and it not spontaneous

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What is energy coupling?

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Using an exergonic process to drive an endergonic one

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What is activation energy?

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Initial energy to start a reaction

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What is an enzyme?

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Catalytic protein

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What is a cofactor?

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Nonprotein, enzyme helper, may be inorganic or organic

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What is allosteric regulation?

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Either inhibiting or promoting an enzymes activity