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250 Cards in this Set

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  • Back
What is the hierarchical organization in biology?
molecule, cell, tissues, organ, organ system, organism, species, population, community, ecosystem
What is the difference between a holism approach and a reductionism approach?
Holism is based on the principle that a higher level of order cannot be meaningfully explained by examining component parts in isolation

Reductionism refers to the principle that a complex system can be understood by studying its component parts
What is the difference between inductive and deductive reasoning?
Inductive reasoning is done through the examination of many specific cases' hypotheses, general principles are constructed.

Deductive reasoning is making an inference from general premises to specific consequences, which logically follow if the premises are true.
What is the difference between homologous structures and analogous structures?
Name an example for each.
Homologous structures are similar structures that have the same evolutionary origin.
Like the leg of a cat and a human arm.

Analogous structures are structures whose form is determined by their function, not by a similar evolutionary origin.
Like a bat wing and a butterfly wing.
Who was Thomas Malthus?
He proposed the idea that nature puts limits on the geometric growth of populations due to the arithmetic growth of resources such as food.
What are isomers?
What is the difference between a steroisomer and a structural isomer?
Name an example for each.
Isomers are molecules with the same chemical formula but with a different form.

If there are differences in the actual structure of their carbon skeleton, we call them structural isomers.
Example: Fructose and Glucose

Stereoisomers have the same carbon skeleton but differ in how the groups attached to this skeleton are arranged in space.
Example: Glucose and Galactose
Major classes of macromolecules (polymers)
Proteins (polypeptides), nucleic acids, polysaccharides, lipids
Each polymer's monomer and the bonds associated with them
Proteins: amino acids; peptide bonds

Nucleic acids: nucleotides; phosphodiester bonds

Polysaccharides: monosaccharides (simple sugars); glycosidic bonds

Lipids: glycerol & fatty acids; ester bonds
What is condensation or the dehydration synthesis reaction?

What is the opposite?
The process in which two monomers or a monomer and a polymer are linked together by removing water when forming the covalent bond between them.

The opposite is hydrolysis.
What are proteins made of?
Proteins are made up of a chain of amino acids linked together through covalent peptide bonds.
What do proteins do?
Proteins function in metabolism, transport, cell recognition, and structure
What is an amino acid?
Amino acids are the monomer for proteins.

They consist of a central carbon bonded to carboxyl group, amino group, hydrogen, and a R-group.
What is the R-group in an amino acid?
Differences in R-groups distinguish property differences in amino acids.
What is a peptide bond?
It is the covalent bond attaching carbon (carboxyl end) of one amino acid to the nitrogen (amino end) of another amino acid leading to the formation of a protein.
What is the primary structure of protein?
Linear sequence of amino acids. It is the order.

It is ultimately is responsible for final functional shape of protein.
What is the secondary structure of protein?
Local structure of alpha helix or beta pleated sheets.

Stabilized by peptide-linkage hydrogen bonds

(no R-group interactions at this level)
What is the tertiary structure of protein?
Global structure of 3 dimensional folding

Result of amino acid side chain and R-group interactions
What is the quaternary structure of protein?
Protein with more than one linear sequence of amino acids

(more than one subunit)
What is denaturation?
Change in tertiary, sometimes secondary, protein form as a result of environmental changes in pH, or temperature impacting hydrogen bonds and/or R-group interactions.

Loss of form causes loss of function
Is denaturation always irreversible?
No, because of the primary structure keeping the order. The primary structure doesn't always change during denaturation and has the code still to reverse the process.
What are chaperone proteins?
They help in folding of proteins (primarily those with quaternary level of structure).
What is a motif?
What is another name for a motif?
Favored arrangements of multiple secondary structure elements that recur again and again in proteins.

Also known as supersecondary structures.
What is the difference between a motif and a domain?
The main difference is a domain can remain stable independently without the rest of the protein but motif can't be.

There can be an obvious difference in polypeptide chain size between a motif and a domain, but, more importantly, a motif is believed not to be able to fold to a stable structure, whereas a domain should.
What is a domain?
Smaller independent units of tertiary structure in a protein.

They are the the fundamental units of structure classification.
What is a lipid?
Nonpolar hydrophobic organic molecule that is insoluble in water.
What is a phospholipid?
Amphipathic lipid found in bilayers of biological membranes.

It has a hydrophilic head attached to (2) hydrophobic fatty acid tails (these are neutral);
What is the difference between saturated and unsaturated fatty acid tails?
What are they like at room temperature?
Where can you find each fat?
Saturated fatty acid tails are found in fat and have no double bonds.
They are solid at room temperature and are produced by animals.

Unsaturated fatty acid tails are found in oils and have a double bond because Hydrogen is missing.
They are liquid at room temperature. Plants make unsaturated fats.
What is a carbohydrate?
Water soluble organic compound consisting a chain or ring of carbon atoms to which hydrogen and oxygen atoms are attached.
What is the generalized empirical formula for carbohydrates?
What is an aldose?
Name an example
An aldose is a monosaccharide that contains only one aldehyde (-CH=O) group per molecule.

Glucose is an example of an aldose.
Fructose is a ___ with a ___.
Ketoses with a keto group.
What is a monosaccharide?
It is a carbohydrate monomer.
How do monosaccharides form and use what bonds?
They attach together through condensation/dehydration syntheses to form glycosidic bonds
What are the four polysaccharides?
Starch, glycogen, chitin, and cellulose.
What is the difference between starch and glycogen?
Starch is the energy storage in plants and glycogen is the energy storage in animals.
What is starch made up of?
Made up of amylose and amylopectin.
What is the difference between amylose and amylopectin?
They are both glycogen monomers but amylose is a very simple structure compared to amylopectin.

Also, amylopectin is insoluble.
What is glycogen made from?
Glucose monomers
What is the difference between cellulose and chitin?
They are both structural polysaccharides.

Cellulose is found in plants only while chitin is used by insects and other arthropods in exoskeletal structure.
What are nucleic acids?
Main two types?
Polymers made up of nucleotides.

Main types: DNA and RNA
What is the difference between DNA and RNA?
DNA: double stranded helix; deoxyribose sugar; thymine as one of the nitrogenous bases

RNA: single stranded; ribose sugar; uracil as one of the nitrogenous bases.
What is a nucleotide?
Repeating subunits found in nucleic acids.

Consists of three components: a pentose, a phosphate, and an organic nitrogenous base.
What are the differences between the nucleotides in RNA and DNA?
Pentose (5-carbon sugar)
In RNA, the pentose is ribose.
In DNA, the pentose is deoxyribose.

Pyrimidines (small, single ring molecules):
In RNA, there is (U) Uracil
In DNA, there is (T) Thymine
Both include (C) Cytosine

Purines (large double-ring molecules):
Both RNA and DNA have (A) Adenine and (G) Guanine.
What complements this sequence in DNA and RNA:
What is ATP?
Nucleotide consisting of Adenine, ribose sugar, and three phosphate groups.

Cells use ATP as energy like money for transactions.
Macromolecules are assembled in what kind of reactions?
Dehydration synthesis.
What reaction disassembles macromolecules?
What is the role of enzymes in dehydration synthesis and hydrolysis?
The process of positioning and stressing, termed catalysis, is important as it helps makes the reacting substances hold close together and ensures that the correct chemical bonds are stressed and broken.

This process is carried out within cells by enzymes.
What is the monomer for carbohydrates?
Monosaccharides, which are simple sugars and can contain as few as three carbon atoms.

The most important of the six-carbon monosaccharides for energy storage is glucose.
What is the monomer for lipids?
Fatty acids which are long-chain hydrocarbons with a carboxylic acid at one end.
What are the polymers for lipids?
Triglycerides which consist of three fatty acids.
What are the monomers for proteins?
Amino acids, which contain an amino group, and an acidic carboxyl group.
What are the monomers for nucelic acids?
Nucleotides, which consists of a pentose (5-carbon sugar), a phosphate, and a nitrogenous base.
The shape of a protein determines its ____.
What sort of bonding is responsible for secondary level of structure?
Hydrogen bonding
What determines tertiary level of structure?
The tertiary structure is stabilized by a number of forces including:

Hydrogen bonds between R groups of different amino acids, electrostatic attraction between R groups with opposite charge, hydrophobic exclusion of non polar R groups, and covalent bonds in the form of disulfides.

The stability of a protein, once it has folded into its tertiary shape, is strongly influenced by how well its interior fits together, i.e. the van der Waals forces.
What determines quaternary level of structure?
Consists of more than one practically identical sub-unit, not joined by strong bonds like the other levels.
Denaturation primarily effects what level of structure?
Quaternary structure
What environmental conditions can cause denaturation?
When the pH, temperature, or ionic concentration of the surrounding solution changes.
What are the pyrimidines?
Thymine, cytosine, uracil
What are the purines?
Adenine and Guanine
What is a micelle?
In water, the nonpolar tails of nearby lipid molecules aggregate away from the water, formind spherical micelles, or droplets, with the tails facing inward.
How do phospholipids form the cell's bilayer?
Phospholipids can arrange themselves into two layers; in both structures, the hydrophilic heads extend outward and the hydrophobic tails inward, creating a phospholipid bilayer.
Carbon can form what kind of bonds? What is the maximum of covalent bonds?
Carbon can form single, double, and triple bonds. Maximum of 4 covalent bonds.
What is a functional group?
Chemical groups that tend to act as units during chemical reactions and confer specific chemical properties on the molecules, or portions of the molecules, to which they are attached.
What is the polymerization in condensation synthesis reactions?
(noting the resulting bonds and if there is an output of energy)
Amino acid + amino acid = protein + H2O
(H from one amino acid and OH from second amino acid, removal creates peptide bond).
How could the occurrence of a single amino acid mutation affect the levels of protein structure?
"A single amino acid can drastically alter the structure."
(pg. 52)
What is the unifying characteristic of lipids?
They are insoluble to water.
What are the 3 parts of cell theory?
1. All organisms are composed of cells.
2. Cells are the smallest living things.
3. Cells arise only from pre-existing cells.
Who was Robert Hooke?
First to discover cells in 1665
What does a cytoplasm include?
Includes organelles, particles, and cytosol (gelatinous medium).
These diverse and many structures in an organelle allow separation in both ___ and ___ within the activities of the cell.
function and time
What does the plasma membrane do?
The plasma membrane is a phospholipid bilayer with proteins embedded in it.

It encloses a cell and separates its contents from its surroundings. It also functions in cell recognition, selective transportation in and out of cell, as receptors, in cell-to-cell adhesion, and in cell signaling
What limits cell size?
Surface area does not increase at the same rate as cell volume.
What is the basic difference between a prokaryote and a eukaryote cell?
Both prokaryote and eukaryote have genetic material but a eukaryote's is in a nucleus; prokaryotes have a cell wall just as plants do.
Describe a prokaryote.
Genetic information in DNA in single circular form
no membrane bound organelles
has cell capsule, cell wall and plasma membrane
has ribosomes
Eukaryotes can be categorized by their ____

Overall gross metabolic processes.

Autotrophs and Heterotrophs.
Where is ribosomal RNA produced?
Produced in nucleolus portion of nucleus
(ribosomal proteins produced and imported from cytoplasm)
What do nuclear pores do?
These protein structures regulate molecular traffic in and out of nucleus.

They allow proteins, carbohydrates, signal molecules and lipids to move in and RNA and ribosomes to move out of the nucleus.
What is the difference between rough ER and smooth ER?
Rough ER have ribosomes and is important in transporting substances into and out of the nucleus. It also serves as a storage area.

Smooth ER has no ribosomes attached to surface. It is also a storage area, but mainly for proteins.
What are ribosomes?
They are composed of RNA and proteins and make proteins for cell maintenance and growth.

If on the ER, it sysnthesizes proteins that are exported out of the cell.

If in the cytoplasm, it synthesizes proteins inside the cell.
What is the Golgi apparatus?
It looks like flattened sacs on top of each other.

It sorts, processes, packages, and delivers proteins and lipids throughout the cell.
What are lysosomes?
Lysosomes are membrane enclosed vessicles that form in the Golgi apparatus.

They contain enzymes that help the cell digest and destroy large molecules. They help white blood cells destroy foreign substances.

They recycle older or damaged organelles.
What are the two types of prokaryotes?
Archaea and bacteria
What is the mitochondria referred to and why?
Referred to as the "powerhouse" because it generates ATP
Rough ER has what on its surface?
Since the liver has a major role in detoxification, you would expect to find a large amount of what organelle?
Smooth ER because they are involved in carbohydrate synthesis, lipid metabolism, detoxification, and calcium storage in muscles.
What are ribosomes?
2 subunits (large and small) that consist of ribosomal RNA and proteins which are produced in nucleolus in eukaryotic cells.
What is the difference between bound and free ribosomes?
Bound ribosomes synthesize proteins that function outside of the cell.

Free ribosomes produce proteins directly into the cytoplasm; these proteins will end up in the nucleus, chloroplasts, mitochondria, or peroxisomes.
What is a signal sequence?
Directions for protein destination (key to targeting specific proteins to specific sites within cell)
What is the Golgi apparatus referred to as? Why?
The Golgi apparatus is referred to as the "post office" of cell.

Proteins shipped from ER via vesicles arrive at cis face; receptors in Golgi recognize modifications done in ER...sorts molecules, packages them, and moves them out of trans face to final destinations via vesicles.
What is the importance of sugar chains added to proteins and lipids in ER?
They are part of the targeting/address labels for protein destination.

These sugar chains can also act as a recognition/identity component of the protein once it reaches its destination.
Who makes lysosomes?
The Golgi apparatus
What do lysosomes do?
Participates in phagocytosis, recycling organic material, and apoptosis.
What is apoptosis?
Programmed cell death.
What is the difference between a primary lysosome and a secondary lysosome?
Primary lysosomes are bound by lipid membrane and remain inactive until pH drops to enzyme activation level.

Primary lysosomes become secondary lysosomes after fusing with a phagosome (vesicle containing food or other material).

It becomes active by using ATP and pumping hydrogen ions into itself, the internal environment of the lysosome becomes acidic with now activated hydrolytic enzymes ready to digest introduced material.
What do active lysosomes do?
The lysosome that is active and has enzymes will digest a variety of all organic molecules. It helps to keep a buildup of any specific organic substance in control.
What is a peroxisome?
A vessicle that helps contain and rid body of toxic substances by making them into helpful things like water and oxygen.
What is endosymbiosis theory?
Proposal that eukaryotic organelles evolved through a symbiotic relationship where one cell engulfed a second cell and a symbiotic relationship developed.
What is cellular respiration and where does it occur?
It is the utilization of energy in the chemical bonds of "food" to produce ATP

It occurs in cytoplasm and mitochondria
What is the cytoskeleton made up of?
Microfilaments (assembled from actin) and microtubules (assembled from tubulin)
What is the difference between flagellum and cilia?
Cilia move materials across the ciliated cell surface and flagellum move the actual cell.
What does the cytoskeleton do?
The cytoskeleton provides cell shape, scaffolding for enzymes in certain areas of the cell, helps to organize cellular activity and movement of substances within the cell.
Describe the plasma membrane.
It is a phospholipid bilayer with embedded proteins.
What does the plasma membrane do?
It regulates what passes into and out of the cell, cell-to cell recognition, connection and adhesion, cell communication
Describe the nucleus.
It is a structure that contains chromosomes and is surrounded by a double membrane.
What does the nucleus do?
It gives instructions for protein synthesis and cell reproduction, contains genetic information.
Describe chromosomes.
They are long threads of DNA that dorm a complex with protein.
What do chromosomes do?
They contain hereditary information used to direct synthesis of proteins.
Describe the nucleolus.
It is the site of genes for rRNA synthesis.
What does the nucleolus do?
It synthesizes rRNA and assembles ribosomes.
Describe ribosomes.
They are small complex assemblies of protein and RNA, often bound to ER.
What do ribosomes do?
They are sites of protein synthesis.
Describe the ER.
It is a network of internal membranes.
What does the ER do?
It makes intracellular compartments which forms transport vesicles, participates in lipid synthesis and synthesis of membrane or secreted proteins.
Describe the Golgi apparatus.
Stacks of flattened vesicles.
What does the Golgi apparatus do?
It packages proteins for export from the cell, forms secretory vesicles.
Describe lysosomes.
Vesicles derived from Golgi apparatus that contain hydrolytic digestive enzymes.
What do lysosomes do?
Digest worn-out organelles and cell debris, digest material taken up by endocytosis.
Describe microbodies.
Vesicles that are fomed from incorporation of lipids and proteins and that contain oxidative and other enzymes.
What do microbodies do?
Isolate particular chemical activities from rest of cell.
Describe mitochondria.
Bacteria-like elements with double membrane.
What does the mitochondria do?
"Power plants" of the cell, sites of oxidative metabolism.
Describe chloroplasts.
Bacteria-like elements with double membrane surrounding a third, thylakoid membrane containing chlorophyll.
What do chloroplasts do?
Sites of photosynthesis.
Describe the cytoskeleton.
Network of protein filaments.
Describe flagella.
Cellular extensions with 9 + 2 arrangement of pairs of microtubules.
Describe the cell wall.
Outer layer of cellulose or chitin, or absent.
What does a prokaryote have?
Cell capsule, cell wall, plasma membrane, ribosomes.
No membrane bound organelles
What is the makeup of the plasma membrane?
It is a a thin sheet of lipid embedded globular proteins and cholesterol which helps maintain fluidity.
What can sugar chains do to lipids and proteins?
Proteins can have added sugar chains resulting in glycoproteins.

Lipids can have a sugar chain attached instead of a phosphate group resulting in a glycolipid.
What is the difference between proteins that are peripheral and those that are integral?
Integral membrane proteins are embedded in the membrane, and peripheral proteins are associated with the surface of the membrane.
The portion of a membrane protein that extends through the bilayer (zone of fatty acid tails) would have to consist of amino acids that are also hydrophobic or hydrophilic?

Would they be polar or nonpolar?
Hydrophobic, nonpolar.
What is the function of the phospholipid bilayer?
Provides fluid matrix and imposes selective permeability barrier.
What idea does the Fluid-Mosaic model convey?
Fluid-Mosaic Model conveys the idea of the ability of lateral movement of phospholipids within the membrane with peripheral and integral proteins associated with the phospholipids.
What does the non-polar portion of phospholipid molecule consist of?
How are they oriented?
Hydrophobic fatty acid tails.

These are oriented towards each other and away from the ECF or cytosol.
What does the polar portion of phospholipid molecule consist of?
How are they oriented?
Hydrophilic head of phosphorylated alcohol.

These are oriented towards the aqueous environment of the ECF and cytosol.
The cellular membrane consist of what four component groups?
1. Phospholipid bilayer
2. Transmembrane proteins
3. Interior protein network
4. Cell-surface markers
The lipid layer that forms the foundation of a cell's membranes is a bilayer formed of ___.
What do phospholipids consist of?
Like the fatty molecules, triglycerides, a phospholipid has a backbone derived from the three carbon polyalcohol, glycerol.

However a phosphate has only two fatty acid chains attached to its backbone, unlike a triglyceride who has three.

The third carbon of the glycerol carries a phosphate group, thus the name phospholipid.
The phosphate end of a phospholipid is strongly ____, while the fatty acid end is strongly ____.
What happens when a collection of phospholipid molecules is placed in water?
The polar water molecules repel the long, nonpolar tails of the phospholipids while seeking partners for hydrogen bonding.

Because of the polar nature of the water molecules, the nonpolar tails of the phospholipids end up packed closely together, sequestered as far as possible from water.
Every phospholipid molecule is oriented with its polar head (toward/away from) water and its nonpolar tails (toward/away from) water.
The _____ interior of a lipid bilayer impedes the passage of any water-soluble substances through the bilayer.
Nonpolar, hydrophobic
Membrane fluidity can be altered by changing _____.
The membrane's fatty acid composition.
Saturated fats tend to make the membrane (less fluid/more fluid).

Unsaturated fats tend to makes the membrane (less fluid/more fluid).

*Think of how these fats are at room temperature.
Saturated makes the membrane less fluid.

Unsaturated makes the membrane more fluid.
Changes in the environment (like temperature) can cause drastic effects on the membranes of single celled organisms. What exactly are these effects?

Which enzymes do some bacteria have to counteract this?
Because increasing temperature makes a membrane more fluid, and decreasing temperature makes it less fluid, some bacteria have evolved to contain enzymes called fatty acid desaturases.

These enzymes introduce double bonds into fatty acids in membranes, making the membrane more fluid at cold temperatures, counteracting the environmental effect of reduced temperatures.
What does cholesterol do to the membrane?
Increases or decreases membrane fluidity depending on temperature, so fluidity is maintained.
What can membrane fluidity be affected by?
Membrane fluidity can be affected by changes in temperature, presence of cholesterol, and the number of double bonds in the phospholipid fatty acid tails.
Increasing degree of alignment (fewer double bonds) of tails has what effect on membrane fluidity?
Fewer double bonds means less fluidity.
What are transmembrane proteins?
Proteins that transverse the lipid bilayer
Both active (ATP used) and passive (facilitated diffusion) transport of specific molecules by transmembrane (integral) carrier proteins involves ______.
Involves change in conformation in the protein.
This can allow large, charged molecules to pass through the membrane.
What do glycoproteins/ glycolipids do?

How do they do it?
They play a role in recognition/identity signals between cells.

The 'glyco' portion of these markers are sugar chains, or carbohydrate chains, that can act as marker molecules that identify the cell type.
What are the six key functions of membrane proteins?
1. Transporters
2. Enzymes
3. Cell surface receptors
4. Cell surface identity markers
5. Cell to cell adhesion proteins
6. Attachments to the cytoskeleton
What are peripheral membrane proteins?
Proteins anchored to a phospholipid in one layer of the membrane
-possess nonpolar regions that are inserted in the lipid bilayer
-are free to move throughout one layer of the bilayer
Where are integral membrane proteins?
These proteins span the lipid bilayer (making them transmembrane proteins)

-nonpolar regions of the protein are embedded in the interior of the bilayer
-polar regions of the protein protrude from both sides of the bilayer
What is the locking mechanism for keeping proteins in bilayer?
Protein’s non-polar region locks on to non-polar region of bilayer
Diffusion moves substances from (high/low) to (high/low) concentration?
Diffusion: High to low concentration
During diffusion, once equilibrium is reached, what happens?
Upon reaching equilibrium, movement does not cease, but net change in concentration no longer changes.
What substances can cross the membrane without the presence of membrane proteins?
Hydrophobic molecules, nonpolar molecules, and small uncharged polar molecules
What is the saturation of carrier transport rate?
Point where increases in gradient can no longer increase rate of transport because finite # of carriers are all being used.

There is a fixed number of transport molecules available to carrier substrates across a cell membrane. At saturation, all the carrier sites are occupied and further increasing the concentration of solute will have no effect on the transport rate.
What is the difference between a solute and a solvent?
A solute is the substance being dissolved and a solvent is what the solute is being dissolved in.

For example, if you were to add salt into a cup of water, salt would be the solute and water would be the solvent.
What are aquaporins?
Specialized channels for water
What happens if a cell is in a hypertonic (hyperosmotic) solution?
There is a higher concentration of the solute in the solution than inside the cell.

The water will move out of the cell, from the lower concentration, to the solution, which has a higher concentration to try and make homeostasis.

Water will leave the cell, making the cell shrivel up.
What happens if a cell is in a hypotonic solution?
The cell will have a higher concentration of solute than the solution it is in.

So, water will rush from the lower concentration to the higher concentration, to dilute the concentration to try and make homeostasis.

If the water goes into the cell, the cell will expand.
What is the difference between endocytosis and exocytosis?
Endocytosis is the process of taking in particles into the cell.

Exocytosis is the reverse, as it the process of discharging materials from vesicles at the cell surface.
What are the three major types of endocytosis?

Describe each.
1. Phagocytosis: when a cell takes in a solid material and envelops around it to then engulf it to form a vacuole.

2. Pinocytosis: when a cell takes in a liquid material.

3. Receptor-mediated endocystosis: Located in clathrin coated pit, receptor protein specific to target molecule…binding of fitted target to receptor triggers endocytosis
Active transport concentrates substances by using energy to move them from where there is (high/low concentration) to where there is (high/low concentration) ?
Active transport: Low to High concentration
Besides energy (ATP), what else does active transport require?
What are the three types of carrier proteins active transport uses?

Describe each.
1. Uniporters: move one molecule at a time

2. Symporters: move two molecules in the same direction

3. Antiporters: move two molecules in opposite directions
Organisms can maintain osmotic balance in three different ways, describe each.
1.Extrusion: in which water is ejected through contractile vacuoles.

2. Isosmotic regulation: involves keeping cells isotonic with their environment.

3.Turgor pressure: to push the cell membrane against the cell wall and keep the cell rigid.
What happens when there is Low internal [Na+], relative to surroundings and High internal [K+]?
Sodium (Na+)-potassium (K+) pump (electrogenic pump) maintains extreme concentration gradients by actively pumping 3 Na+ out, and 2 K+ in, through active transport (ATP cost).
What happens during a single cycle of sodium-potassium pump?
Three Na+ (sodium) leave cell, two K+ (potassium) enter cell.
What is coupled transport?
Movement of molecules up their concentration gradient by use of energy stored in gradient of different molecule.
What are the two processes involved in bulk transport?
Endocytosis and exocytosis
What are the three types of passive processes?
Diffusion, facilitated diffusion, and osmosis
What are the two types of facilitated diffusion?

What is the net movement? (toward a high/low concentration?)
1. When there is a protein channel: polar molecules or ions move through directly.

2. When there is a protein carrier: molecule binds to carrier protein in membrane and is transported across.

Both ways the net movement is toward region of lower concentration.
What happens during osmosis?
The water diffuses across the membrane via aquaporins.
What are the two types of active transport?
Na+/K+ pump: carrier uses energy to move a substance across a membrane against its concentration gradient.

Coupled transport: molecules are transported across a membrane against their concentration gradient by the cotransport of sodium ions or protons down their concentration gradients.
What is an example of diffusion?
Movement of oxygen into cells
What is an example of facilitated diffusion with a protein channel?
Movement of ions in or out of cell
What is an example of facilitated diffusion with a protein carrier?
Movement of glucose into cells
What is an example of osmosis?
Movement of water into cells placed in a hypotonic solution
What is an example of phagocytosis?
Ingestion of bacteria by white blood cells
What is an example of pinocytosis?
Taking in a liquid
What is an example of receptor-mediated endocytosis?
Cholesterol uptake
What is an example of exocytosis?
Secretion of waste
Ions and large hydrophilic molecules (can/cannot) cross the phospholipid bilayer alone?
The rate of transport is limited by _____.
Limited by the number of carriers in the membrane.
The direction of movement due to osmosis depends on _____.
Depends on the solute concentration on either side of the membrane.
Cells in a hypotonic solution will (gain/lose) water
as opposed to cells in a hypertonic solution that will (gain/lose) water?
Cells in a hypotonic solution will gain water
Cells in a hypertonic solution will lose water.
What is the difference between coupled transport and countertransport?
In couple transport, energy is released by a diffusing molecule which is used to transport a different molecule against its concentration gradient but in the same direction.

On the other hand, countertransport is when the two molecules move in opposite directions.
Membrane fluidity depends on ____.
Depends on the fatty acid composition of the membrane.

Temperature also affects it.
What are transporters?
These are integral membrane proteins that carry specific substances though the membrane.
Where do enzymes often occur?
(Interior/ exterior of membrane)
Interior surface
What do cell-surface receptors respond to?
They respond to external chemical messages and change conditions inside the cell
Surface proteins are attached to the surface by (polar/nonpolar) regions that associate with (polar/nonpolar) regions of phospholipids.
Surface proteins are attached to the nonpolar regions that associate with the polar regions of phospholipids.
What are the different types of cell communication?
Direct contact, paracrine signaling, endocrine signaling, autocrine signaling, and synaptic signaling
What is a ligand?
A signaling molecule that binds non-covalently to receptor with high specificity resulting in a conformational change in the receptor structure thereby often involving activating or inactivating proteins (phosphorylation vs/de-phosphorylation)
What is signal transduction?
A ligand interacting with a receptor, downstream signaling steps and a response being triggered.
What are the three steps of cell signaling?
1. Receptor activation
2. Signal transduction
3. Cellular response
What happens during the first step of cell signaling, receptor activation?
The signal binds to a specific cellular protein called a receptor, which is often located on the surface of the cell.
What happens during the second step of cell signaling, signal transduction?
The binding of the signal (messenger) changes the receptor in some way, usually a change in conformation or shape. The change in receptor initiates a process of converting the signal (information) into a specific cellular response; this process is called signal transduction.
The transduction system may have one or many steps. So information is passed along, not the messenger molecule and at each step of the process, the nature of the information is converted, or transduced, into a different form.
What happens during the third and final step of cell signaling, cellular response?
The transduction system triggers a specific cellular response. The response can be almost any cellular activity, such as activation of an enzyme or altered gene expression.
What is phosphorylation?
Typical process by which enzyme receptors activate intracellular proteins.
What is a protein kinase?
An enzyme that adds a phosphate to a protein
What is a phosphatase?
An enzyme that removes a phosphate from a protein
What is the difference between autocrine signaling and paracrine signaling?
Autocrine: cells secrete signaling molecules that bind to their own cell surface or neighboring cells of the same type

Paracrine: signal does not affect the cell secreting the signal but does influence cells in close proximity.
Who does endocrine signalling?
What is an example of paracrine signaling?
Neurotransmitter signaling
What do enzymatic surface receptors do?
They are protein kinases which add phosphate groups to proteins.
How are cell surface receptors activated?
Must bind to a signaling molecule to be activated.
What do channel linked receptors do?
They are ion channels that opens in response to a ligand.
What are ion channels?
They are these gated channels can be chemically gated or voltage gated; when the correct signal is received, a conformational change will occur (gate opens) and the ions will either be allowed to pass through or will be blocked from passing.
What are G-protein-coupled receptors?

How are they characterized?
These are the largest family of cell surface receptors.

Characterized by a single polypeptide chain that is threaded back and forth through the plasma membrane in such a way as to possess seven transmembrane domains.
G-proteins bound to GDP are inactive/active?
G-proteins bound to GDP are inactive.
G-proteins bound to GTP are inactive/active?
G-proteins bound to GTP are active.
The function of the G-protein is influenced by the ______ to which it is bound.
What is the structure of a enzymatic receptor (tyrosine-kinase) characterized by?
Characterized by an extracellular ligand-binding domain and a cytosolic domain possessing tyrosine kinase enzyme activity.
A ligand binds to a receptor covalently/noncovalently?
A ligand bind to a receptor noncovalently.
Ligands alter ____.
Ligands alter receptor structure.
What is the difference between the 3 subclasses of membrane receptors?
1. Channel linked receptors: ion channel that opens in response to a ligand

2. Enzymatic receptors: receptor is an enzyme that is activated by the ligand

3. G protein-coupled receptor: a G-protein (bound to GTP) assists in transmitting the signal
What type of receptors are steroid receptors?
Intracellular receptors located inside the cell, as opposed to most cells that are on the surface of the membrane.
Steroid receptors have what 3 domains?
1. Hormone-binding domain
2. DNA binding domain
3. Domain that interacts with co-activation to affect gene expression
What is a second messenger?
Small, nonprotein, water soluble molecules or ions that are signaling molecules produced within the cell.
The substance mediating the action of epinephrine on liver glycogen breakdown is a second messenger, which is specifically called _____.
What is the present understanding of the transduction steps associated with cAMP?
1. Ligand (first message) binds to a receptor.

2. Receptor conformation changes; G-protein complex is activated.

3. The active G-protein in turn activates the enzyme, adenylyl cyclase, which is associated with the cytoplasmic side of the plasma membrane.

4. Adenylyl cyclase converts ATP to cAMP.

5. cAMP binds to and activates a cytoplasmic enzyme, protein kinase A.

6. Protein kinase A propagates the message by phosphorylating various other proteins that lead to the cellular response
What is phosphorylation?
Phosphorylation is the transferring a phosphate group from ATP to a protein substrate.
Phosphorylation is catalyzed by enzymes called ____.
Protein kinases
What are cAMP's two advantages?
Speed and signal amplification
What are the three different cell junctions?
1. Tight junctions: create sheets of cells
2. Anchoring junctions: connect the cytoskeletons of adjacent cells
3. Communicating junctions: permit small molecules to pass between cells
What are the two different types of communicating junctions?
What is the difference?
1. Gap junctions are in animal cells
2. Plasmodesmata are in plant cells
What are commonly used as tissue-specific markers?
Glycolipids are commonly used as tissue-specific markers.
What proteins are used by cells to distinguish “self” from “non-self”?
(MHC) proteins are used by cells to distinguish “self” from “non-self”
Signals binding to cell surface are (first/second) messengers?
Signals binding to cell surface are first messengers.
Once activated, the effector protein produces a ______.
Once activated, the effector protein produces a second messenger.
What is a kinase cascade?
A kinase cascade is a series of protein kinases that phosphorylate each other in succession.

This amplifies the signal because a few signal molecules can elicit a large cell response
What happens during signal transduction?
A message from outside the cell switches and becomes a message within the cell.
What are the steps in a signal transduction pathway?
It starts with a message from outside of the cell that is given to the receptors.
Then the message is transduced and given to a second messenger who delivers the message to a target cell.
Adenylyl cyclase is an example of what?

What happens when it is activated by an alpha subunit?
A protein or an inactivated enzyme, and when activated by an alpha subunit it converts ATP into cAMP, which is a secondary messenger.
What does cAMP do to a protein kinase?

What happens to the protein kinase?
cAMP targets the protein kinase, which has two catalytic subunits and two regulatory subunits.

cAMP then binds to the regulatory portions and releases the catalytic portions.

The catalytic portions of the protein kinase are phosphorolated, (pick up energy from ATP and become activated). They then can act on proteins within the cell.
When a ligand binds to the G protein receptor, what happens?
When the ligand attaches to the G protein, it causes a confirmational change in the protein, which releases an alpha sub unit that then goes to a protein nearby.

This enzyme is inactive, but once the alpha subunit is in place, the enzyme is active and will convert ATP to cAMP.
Difference between protein kinase and protein phosphatases?
Protein kinase: phosphoralates
Protein phosphatases: dephosphoralates
What are the steps involved with the enzymatic receptor (tyrosine-kinase)?
1. Ligand binding causes aggregation of two receptor units, forming receptor dimers.

2. Aggregation activates the tyrosine kinase activity on cytoplasmic domains.

3. Tyrosine kinase catalyzes transfer of phosphate groups from ATP to amino acid tyrosine contained in particular protein
All G proteins are active when bound to (GTP/GDP) and inactive when bound to (GTP/GDP).
Active: GTP

Inactive: GDP
Effector proteins are usually what?
Effector proteins are usually enzymes.
All animal cells studied thus far use ____ as a second messenger.
When a signaling molecule binds to a G protein coupled receptor (GPCR) that uses the enzyme _______ as an effector, a large amount of cAMP is produced within the cell.
Adenylyl cyclase
Receptor tyrosine kinases (RTK) are activated by what?
RTK are activated by autophosphorylation.
What is the class of enzyme that adds phosphate groups from ATP to proteins?
Protein kinase