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Topic 1

by jordancc, May 2016

Subjects: Biology

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What is a polymer?	A large, complex molecule composed of long chains of monomers joined together
What is a monomer?	Small, basic molecular unit
What elements do carbohydrates contain?	Carbon Oxygen Hydrogen
What is the monomer of carbohydrates?	Monosaccharides
Give three examples of monosaccharides?	Glucose Fructose Galactose
What are the two types of glucose?	alpha and beta Two types of glucose have the RHS groups reversed
What is a condensation reaction?	When two molecules join together with the formation of a new chemical bond A water molecule is released
What type of reaction joins monosaccharides together?	Condensation reaction
What type of bond joins monosaccharides together?	Glycosidic bond
What is a disaccharide?	Two monosaccharides joined together
What is the disaccharide sucrose formed from?	Glucose and fructose
What is the disaccharide lactose formed from?	Glucose and galactose
Describe a property of starch	Insoluble In water and doesn't affect water potential So doesn't cause water to enter cells by osmosis, which would make them swell So good for storage
Describe a test for starch	Iodine test Add iodine dissolved in potassium iodide solution Positive result - colour changes from browny orange to blue black
What is the function of glycogen?	Main energy storage material in animals
Describe the structure of glycogen	Polysaccharide of a-glucose Similar to amylopectin, loads more side branches, so stored glucose can be released quickly, important for energy release Very compact - good for storage
What is the function of cellulose?	Major component of cell walls in plants
Describe the structure of cellulose	Long unbranched chain of b-glucose Forms straight cellulose chains linked by hydrogen bonds to form microfibrils Cellulose provides structural support for cells
What is a triglyceride made from?	One molecule of glycerol and three fatty acids
Describe the structure of triglycerides	Fatty acid molecules have long 'tails' made of hydrocarbons The rails are 'hydrophobic' This makes lipids insoluble in water. All fatty acids have the same basic structure but the hydrocarbon tail varies
What reaction forms triglycerides?	Condensation reactions
What bond is formed when fatty acids and glycerol join together?	Ester bond
What is the disaccharide maltose formed from?	Glucose and glucose
What is saturated?	No double bonds between carbon atoms
What is unsaturated?	Have at least one double bond between carbon atoms
Describe the structure of phospholipids	One glycerol Two fatty acids One phosphate group
What is the function of triglycerides?	Mainly used as energy storage materials
What is the function of phospholipids?	Make up bilayer of cell membranes, which control what enter sand leaves the cell
Give two examples of lipids	Triglycerides Phospholipids
How does the structure of triglycerides relate to their function?	Long hydrocarbon tails contain lots of chemical energy which is released when they're broken down Insoluble, so don't affect water potential of the cell and don't cause water to enter cell by osmosis. Clump together as insoluble droplets in cells because fatty acid tails are hydrophobic
Describe how the structure of phospholipids relate to their function	Heads are hydrophilic and tails are hydrophobic, so they form a double layer with heads facing outwards Centre of bilayer is hydrophobic so water-soluble substances can't easily pass through it - membrane acts as a Barrier to those substances
Describe a test for lipids	Emulsion test Shake test substance with ethanol, then pour solution into water Any lipid will show up as a milky emulsion
What are the monomers of proteins?	Amino acids
What is a hydrolysis reaction?	The breaking of a chemical bond between monomers using a wager molecule
What is a dipeptide?	Two amino acids join together
What is a polypeptide?	More than two amino acids join together
Describe the structure of amino acids	A carboxyl group (-COOH) An amine group (-NH2) A carbon containing R group	All living things have a bank of only 20 amino acids
What type of reaction joins amino acids together to form a polypeptide?	Condensation reaction
What is the bond formed between amino acids?	Peptide bonds
What is primary structure?	Sequence of amino acids in polypeptide chain
What is secondary structure?	Hydrogen bonds form between amino acids in chain Makes it automatically coil into alpha helix or folded into beta pleated sheet
What is tertiary structure?	Coiled and folded further More bonds form eg. Hydrogen bonds, ionic bonds, disulfide bridges - when to molecules is amino acid cysteine
What is quaternary structure?	The way polypeptide chains are assembled together, proteins final 3D structure
What are the different functions of proteins?	Enzymes Antibodies Transport proteins Structural proteins
Describe a test for reducing sugars	Benedict's test Add Benedict's reagent and heat in a water bath If test is positive it will form a coloured precipitate Colour change from blue to brick red
Describe the properties and function of enzymes	Usually spherical due to tight folding of polypeptide chains Soluble and often have roles in metabolism (digestion and synthesising)
Describe the properties and function of antibodies	Involved in immune response Made up of two light polypeptide chains and two heavy chains bonded together Have variable regions
Describe the properties and function of transport proteins	Eg. channel proteins contain hydrophobic and hydrophilic amino acids, which cause protein to fold up and form a channel These proteins transport molecules and ions across membranes
Describe a test for non-reducing sugars	Get a new sample of test solution Add a few drops of dilute hydrochloric acid and carefully heat in a water bath Neutralise with sodium hydrogencarbonate Carry out Benedict's test
What is a polysaccharide?	Formed when more than two monosaccharides are joined together by condensation reactions
What is the function of starch?	The main energy storage material in plants
Describe the structure of starch	Mixture of two polysaccharides of alpha-glucose which are amylose and amylopectin
Describe the structure of amylose in starch	Long, unbranched chain of a-glucose Angles of glycosidic bonds give it a coiled structure Makes it compact and good for storage
Describe the structure of amylopectin in starch?	Long, branched chain of a-glucose Side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily Glucose can be released quickly
Describe the properties and function of structural proteins	Physically strong Consist of long polypeptide chains lying parallel to each other with cross links between them Include keratin and collagen
Describe the properties and function of structural proteins	Physically strong Consist of long polypeptide chains lying parallel to each other with cross links between them Include keratin and collagen
Describe a test for protiens	Biuret test Add a few drops of sodium hydroxide solution Add some copper (II) sulfate solution If protein is present solution goes from blue to purple
What is an enzyme?	Biological catalyst that speeds up chemical reactions Lower activation energy of a reaction
Describe main features of enzymes	Catalyse metabolic reactions Can affect structures in an organism (eg involved in production of collagen) as well as functions (respiration) Intracellular or extracellular Enzymes are proteins Have an active site, specific shape, substrate molecules bind to Highly specific due to tertiary structure
Why does the formation of enzyme-substrate complex Lowe activation energy?	Joining molecules - Substrate molecules being attached to the enzyme holds them close together, reducing repulsion so they bond more easily Breakdown reaction - enzyme fitting into active site puts strain on bonds in substrate, so breaks more easily
What are the main features of 'lock and key' model?	Substrate fits into enzyme to for enzyme-substrate complex Enzyme remains unchanged
What are the main features of 'induced fit model'?	Enzyme binds to substrate to form enzyme-substrate complex Substrate makes enzymes active site change slightly
Explain how the properties of enzymes relate to their tertiary structure	Very specific - catalyse one reaction Only one complementary substance will fit to active site Active sites shape is determined by tertiary structure (which is determined by primary structure) Primary structure of a protein is determined by a gene
What are the factors affecting enzyme activity?	Temperature pH Enzyme concentration Substrate concentration Inhibitors
Name two types of nucleic acids	DNA and RNA
What does DNA stand for?	Deoxyribonucleic acid
What is the role of DNA?	Stores genetic information
What is genetic information?	All the instructions an organism needs to grow and develop from a fertilised egg to a fully grown adult
What does RNA stand for?	Ribonucleic acid
What is the role of RNA?	Transfers genetic information from the DNA to the ribosomes
What is a nucleotide?	Monomers that make up DNA and RNA
Describe the structure of a nucleotide	Contains A pentode sugar Nitrogen containing base A phosphate group
Describe be structure of a DNA nucleotide	Pentose sugar (deoxyribose) Phosphate group Base - (adenine, thymine, guanine, cytosine)
Describe the structure of an RNA nucleotide	Pentode sugar (ribose) Phosphate group Base - (adenine, uracil, cytosine, guanine)
How does temperature affect enzyme activity?	Rise in temp makes molecules vibrate more so they're more likely to collide If temp goes above a certain level, vibration breaks some of the bonds that hold enzyme Active site changes shape and enzyme is denatured
What is a polynucleotide?	a polymer of nucleotides
What is the structure of a polynucleotide?	Nucleotides join between the phosphate group of one and the sugar of another Chain of sugars and phosphates is called sugar-phosphate backbone
What is the bond between a phosphate group and sugar called?	Phosphodiester bond
What type of reaction forms polynucleotides?	Condensation readtion
How is DNA formed?	Two DNA polynucleotide strands join together by hydrogen bonding between bases (complementary base pairing) Two antiparallel polynucleotide strands twist to form the DNA double helix
How many hydrogen bonds form between adenine and thymine?	Two
How many hydrogen bonds form between cytosine and guanine?	Three
What was believed about DNA in 1800?	- doubted it could carry genetic code as it has a relatively simple chemical composition Some argued genetic information must be carried by proteins which are much more chemically varied
What did experiments show about DNA by 1953	DNA was the carrier of genetic code Double-helix structure was determined by Watson and Crick, it helps DNA to carry out its function
How does DNA replicate?	Semi-conservative replication
How does pH affect enzyme activity?	Above and below the optimum pH the H+ and OH- ions found in acids and alkalis can break hydrogen bonds and ionic bonds that hold enzymes tertiary structure in place This makes active site change shape so enzyme is denatured
What is the role of DNA helicase in semi-conservative replication?	Breaks hydrogen bonds between bases of two polynucleotide DNA strand this makes helix unwind to form two single strands
What is the role of template strands in semi-conservative replication?	Each original strand acts as a template Free floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand
What is the role of DNA polymerase in semi-conservative replication?	Catalyses the condensation reactions that join the nucleotides of the new strands together Hydrogen bonds form between the bases of the original and new strands
What is the outcome of semi-conservative replication?	Each new DNA molecule contains one strand from the original DNA molecule and one new strand
What happens in semi-conservative replication?	Half of the strands in each new DNA molecule are from the original DNA molecule So there's genetic continuity between generations of cells
How does DNA polymerase work on DNA strands?	The active site of DNA polymerase is only complementary to the 3' end of the newly forming DNA strand This means new strand is made in a 5' to 3' direction and that DNA polymerase moves down the template strand in a 5' to 3' direction Because the strands in a doubly helix are antiparallel DNA polymerases move in opposite directions on each strand
How does enzyme concentration affect rate of reaction?	More enzyme molecules increases chances of colliding with substrate molecule and form an enzyme-substrate complex, so increases rate of reaction If amount of substrate is limited, adding more enzyme has no further effect
How does substrate concentration affect rate of reaction?	As substrate concentration increases collisions are more likely, up until saturation point where all of enzymes active sites are full Substrate concentration decreases with time during a reaction, so rate of reaction decreases Initial rate of reaction is the highest
What are the two types of enzyme inhibitors?	Competitive inhibition Non-competitive inhibition
What is a competitive inhibitor?	A molecule with a similar shape to that of the substrate They bind to the active site but no reaction takes place They block the active site so no substrate molecules can fit in
How does concentration of inhibitor and substrate affect competitive inhibition?	If there's a high concentration of the inhibitor l, it'll take up nearly all the active sites and little substrate will get to enzymes If there's a higher concentration of substrate, the substrates chances of getting to an active site before the inhibitor increase. So increasing concentration of substrate will increase rate of reaction
What is non-competitive inhibition?	Molecules bind to the enzyme away from its active site Causes active site to change shape so substrate molecules can no longer bind to it
How does increasing concentration of substrate affect non-competitive inhibition?	Won't make a difference to reaction rate - enzyme activity will still be inhibited
What are the functions of water in living organisms?	Metabolite (condensation and hydrolysis reactions) Good solvent Can buffer changes in temperature as it has a high specific heat capacity and high latent heat of vaporisation Water molecules very cohesive
What is the structure of water?	One atom of oxygen joined to two atoms of hydrogen by shared electrons Oxygen is delta negative Hydrogen is delta positive Water is a polar molecule Molecules are joined by hydrogen bonding
What is ATP?	An immediate source of energy in a cell
Describe the structure of ATP	Nucleotide base is adenine Ribose sugar Three phosphate groups
How is ATP broken down?	A hydrolysis reaction, on which a phosphate bond is broken and energy is released ATP is broken down into ADP and Pi
Where is the energy in ATP stored?	In high energy bonds between the phosphate groups It's released via hydrolysis reactions
What enzyme breaks down ATP?	ATP hydrolase
Why are phosphate ions essential in ATP and DNA?	When a phosphate ion is attached to another molecule, it's known as a phosphate group it's the bonds between phosphate groups that store energy in ATP The phosphate groups in DNA and RNA allow nucleotides to join up to form polynucleotides
Name four inorganic ions	Iron ions Hydrogen ions Sodium ions Phosphate ions
Give examples of eukaryotic cells?	Animal cells Plant cells Algae Fungi
Give an example of a prokaryotic cell	Bacteria
What are organelles?	Part of cells - each one has a specific function
What is in an animal cell?	Plasma(cell surface membrane) Rough endoplasmic reticulum Nucleolus Nucleus Smooth endoplasmic reticulum Lysosomes Ribosome Nuclear envelope Golgi apparatus Cytoplasm Mitochondrion
What is in a plant cell?	Plasma(cell surface membrane) Chloroplasts Rough endoplasmic reticulum Plasmodesma Mitochondrion Golgi apparatus Vacuole Smooth endoplasmic reticulum Cytoplasm Nucleolus Nucleus Ribosome Cell wall
What are the differences between plant cells and animal cells?	Plant cells are made with a cellulose cell wall with plasmodesmata Plant cells have a vacuole and chloroplasts
What is in algal cells?	All the same organelles as plant cells
What is in fungal cells?	Everything in plant cells except their cell walls are made of chitin and they don't have chloroplasts
Give a use of inorganic phosphate	Can be added to another compound (phosphorylation) which often makes the compound more reactive
Describe cell surface (plasma) membrane	Membrane found on surface of animal cells and inside the cell wall of other cells Made mainly of lipids and protein
What is the function of the cell membrane?	Regulates the movement of substances into and out of the cell Has receptor molecules on it which allow it to respond to chemicals like hormones
Describe the nucleus	A large organelle surrounded by a nuclear envelope, which contains many pores. Nucleus contains chromosomes (which.are made from protein bound linear DNA) and a nucleolus
What is the function of the nucleus? (Including the pores and nucleolus)	Controls the cells activities. DNA contains instructions to make proteins. The pores allow substances to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes
Describe mitochondria?	Usually oval shaped Have a double membrane - inner one folded into structures called cristae. Inside is the matrix, which contains enzymes involved in respiration
What is the function of mitochondria?	The site of aerobic respiration, where ATP is produced Found in cells that are very active and require a lot of energy
Describe chloroplasts	Small flattened structures Surrounded by a double membrane Has membranes inside called thylakoid membranes which are stacked up to form grana Grana are linked together by Lamellae
What is the function of chloroplasts?	The site where photosynthesis takes place Some parts of photosynthesis happen in the grana and other parts in the stroma (a thick fluid found in chloroplasts)
Describe Golgi apparatus	A group of fluid-filled membrane-bound flattened sacs Vesicles are often seen at the edges of the sacs
What is the function of Golgi apparatus?	Processes and packages new lipids and proteins Makes lysosomes
How is ATP re-synthesised?	A condensation reaction between ADP and Pi Happens during both respiration and photosynthesis, and is catalysed by the enzyme ATP synthase
Describe Golgi vesicles	Small fluid filled sacs in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus
What is the function of Golgi vesicles	Stores lipids and proteins made by the Golgi apparatus and transports them out of the cell
Describe a lysosome	A round organelle surrounded by a membrane, with no clear internal structure It's a type of Golgi vesicle
What is the function of lysosomes?	Contain digestive enzymes called lysozymes which can be used to digest invading cells or break down worn out components of the cell
Describe a ribosome	A very small organelle, either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum Made up of proteins and RNA Not surrounded by a membrane
Describe the function of ribosomes	The sight where proteins are made
Describe rough endoplasmic reticulum	A system of membranes enclosing a fluid-filled space Surface is covered with ribosomes
Describe the function of rough endoplasmic reticulum	Folds and processes proteins that have been made at the ribosomes	Folds and processes proteins that have been made at the ribosomes
Describe smooth endoplasmic reticulum	A system of membranes enclosing a fluid filled Space With no ribosomes
What is the function of smooth endoplasmic reticulum?	Synthesises and processes lipids
What is an ion?	An atom with an electric charge
Describe cell wall	A rigid structure that surrounds cells
What is the function of cell walls?	Supports cells and prevents them from changing shape
Describe a cell vacuole	A membrane-bound organelle found in the cytoplasm of plant cells Contains cell sap - a weak solution of sugar and salts Surrounding membrane is called tonoplast
What is the function of the cell vacuoel	Helps to maintain pressure inside the cell and keep the cell rigid. This stops plants wilting Also involved in the isolation of unwanted chemicals inside the cell
What is a cation?	An ion with a positive charge
What is an anion?	An ion with a negative charge
What is an inorganic ion?	An ion which doesn't contain any carbon They are in solution, in body fluids of organisms
How are iron ions involved in haemoglobin?	Haemoglobin is made up of four different polypeptide chains, each with an iron ion in the centre which bind to the oxygen in haemoglobin When oxygen is bound Fe2+ ion temporarily becomes Fe3+ ion until oxygen is released
How do hydrogen ions determine pH?	pH is calculated on the concentration of hydrogen ions in the environment. The more H+ present the lower the pH (and the more acidic the environment)
What is the role of sodium ions in transport?	A molecule of glucose or an amino acid can be transported into a cell alongside sodium ions through co-transport
What enzyme breaks down ATP?	ATP hydrolase
Why are phosphate ions essential in ATP and DNA?	When a phosphate ion is attached to another molecule, it's known as a phosphate group it's the bonds between phosphate groups that store energy in ATP The phosphate groups in DNA and RNA allow nucleotides to join up to form polynucleotides
Name four inorganic ions	Iron ions Hydrogen ions Sodium ions Phosphate ions
Give examples of eukaryotic cells?	Animal cells Plant cells Algae Fungi
Give an example of a prokaryotic cell	Bacteria
What are organelles?	Part of cells - each one has a specific function
What is in an animal cell?	Plasma(cell surface membrane) Rough endoplasmic reticulum Nucleolus Nucleus Smooth endoplasmic reticulum Lysosomes Ribosome Nuclear envelope Golgi apparatus Cytoplasm Mitochondrion
What is in a plant cell?	Plasma(cell surface membrane) Chloroplasts Rough endoplasmic reticulum Plasmodesma Mitochondrion Golgi apparatus Vacuole Smooth endoplasmic reticulum Cytoplasm Nucleolus Nucleus Ribosome Cell wall
What are the differences between plant cells and animal cells?	Plant cells are made with a cellulose cell wall with plasmodesmata Plant cells have a vacuole and chloroplasts
What is in algal cells?	All the same organelles as plant cells
What is in fungal cells?	Everything in plant cells except their cell walls are made of chitin and they don't have chloroplasts
Give a use of inorganic phosphate	Can be added to another compound (phosphorylation) which often makes the compound more reactive
Describe cell surface (plasma) membrane	Membrane found on surface of animal cells and inside the cell wall of other cells Made mainly of lipids and protein
What is the function of the cell membrane?	Regulates the movement of substances into and out of the cell Has receptor molecules on it which allow it to respond to chemicals like hormones
Describe the nucleus	A large organelle surrounded by a nuclear envelope, which contains many pores. Nucleus contains chromosomes (which.are made from protein bound linear DNA) and a nucleolus
What is the function of the nucleus? (Including the pores and nucleolus)	Controls the cells activities. DNA contains instructions to make proteins. The pores allow substances to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes
Describe mitochondria?	Usually oval shaped Have a double membrane - inner one folded into structures called cristae. Inside is the matrix, which contains enzymes involved in respiration
What is the function of mitochondria?	The site of aerobic respiration, where ATP is produced Found in cells that are very active and require a lot of energy
Describe chloroplasts	Small flattened structures Surrounded by a double membrane Has membranes inside called thylakoid membranes which are stacked up to form grana Grana are linked together by Lamellae
What is the function of chloroplasts?	The site where photosynthesis takes place Some parts of photosynthesis happen in the grana and other parts in the stroma (a thick fluid found in chloroplasts)
Describe Golgi apparatus	A group of fluid-filled membrane-bound flattened sacs Vesicles are often seen at the edges of the sacs
What is the function of the cell membrane?	Regulates the movement of substances into and out of the cell Has receptor molecules on it which allow it to respond to chemicals like hormones Is partially permeable so allows some molecules to get through and not others
How is ATP re-synthesised?	A condensation reaction between ADP and Pi Happens during both respiration and photosynthesis, and is catalysed by the enzyme ATP synthase
Describe Golgi vesicles	Small fluid filled sacs in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus
What is the function of Golgi vesicles	Stores lipids and proteins made by the Golgi apparatus and transports them out of the cell
Describe a lysosome	A round organelle surrounded by a membrane, with no clear internal structure It's a type of Golgi vesicle
What is the function of lysosomes?	Contain digestive enzymes called lysozymes which can be used to digest invading cells or break down worn out components of the cell
Describe a ribosome	A very small organelle, either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum Made up of proteins and RNA Not surrounded by a membrane
Describe the function of ribosomes	The sight where proteins are made
Describe rough endoplasmic reticulum	A system of membranes enclosing a fluid-filled space Surface is covered with ribosomes
Describe the function of rough endoplasmic reticulum	Folds and processes proteins that have been made at the ribosomes	Folds and processes proteins that have been made at the ribosomes
Describe smooth endoplasmic reticulum	A system of membranes enclosing a fluid filled Space With no ribosomes
What is the function of smooth endoplasmic reticulum?	Synthesises and processes lipids
What is an ion?	An atom with an electric charge
Describe cell wall	A rigid structure that surrounds cells
What is the function of cell walls?	Supports cells and prevents them from changing shape
Describe a cell vacuole	A membrane-bound organelle found in the cytoplasm of plant cells Contains cell sap - a weak solution of sugar and salts Surrounding membrane is called tonoplast
What is the function of the cell vacuoel	Helps to maintain pressure inside the cell and keep the cell rigid. This stops plants wilting Also involved in the isolation of unwanted chemicals inside the cell
What is a cation?	An ion with a positive charge
What is an anion?	An ion with a negative charge
What is an inorganic ion?	An ion which doesn't contain any carbon They are in solution, in body fluids of organisms
How are iron ions involved in haemoglobin?	Haemoglobin is made up of four different polypeptide chains, each with an iron ion in the centre which bind to the oxygen in haemoglobin When oxygen is bound Fe2+ ion temporarily becomes Fe3+ ion until oxygen is released
How do hydrogen ions determine pH?	pH is calculated on the concentration of hydrogen ions in the environment. The more H+ present the lower the pH (and the more acidic the environment)
What is the role of sodium ions in transport?	A molecule of glucose or an amino acid can be transported into a cell alongside sodium ions through co-transport
What are plasmids?	Small loops of DNA Contain genes for things like antibiotic resistance, and can be passed between prokaryotes
What is flagellum?	A long, hair like structure that rotates to make the prokaryotic cell move
What is a capsule?	Made up of secreted slime, helps to protect cell
What are plasmids?	Small loops of DNA Contain genes for things like antibiotic resistance, and can be passed between prokaryotes
What is flagellum?	A long, hair like structure that rotates to make the prokaryotic cell move
What is a capsule?	Made up of secreted slime, helps to protect cell
How is DNA stored in prokaryotes?	Floats free in cytoplasm DNA is circular and present as one long coiled up strand Not attached to any histone proteins
What are plasmids?	Small loops of DNA Contain genes for things like antibiotic resistance, and can be passed between prokaryotes
What is flagellum?	A long, hair like structure that rotates to make the prokaryotic cell move
What is a capsule?	Made up of secreted slime, helps to protect cell
How is DNA stored in prokaryotes?	Floats free in cytoplasm DNA is circular and present as one long coiled up strand Not attached to any histone proteins
What are viruses?	Nucleic acids surrounded by proteins They're smaller than bacteria They invade and reproduce inside the cells of other organisms (host cells)
Describe the structure of viruses	Contain a core of genetic material The protein coat around the core is called a capsid Attachment proteins stick out from the edge of the capsid. These let viruses cling on to suitable host cells
Describe the structure of viruses	Contain a core of genetic material The protein coat around the core is called a capsid Attachment proteins stick out from the edge of the capsid. These let viruses cling on to suitable host cells
How do prokaryotic cells replicate?	Binary fission
Describe the structure of viruses	Contain a core of genetic material The protein coat around the core is called a capsid Attachment proteins stick out from the edge of the capsid. These let viruses cling on to suitable host cells
How do prokaryotic cells replicate?	Binary fission
What happens in binary fission?	Circular DNA and plasmids replicate Cell gets bigger and DNA loops move to opposite poles of the cell The cytoplasm begins to divide It divides and two new daughter cells are produced
Which type of cell division produces genetically identical cells?	Mitosis
What happens in mitosis?	A parent cell divides to produce two genetically identical daughter cells
What happens in mitosis?	A parent cell divides to produce two genetically identical daughter cells
Why do cells undergo mitosis?	For growth of multicellular organisms For repairing damaged tissues
Outline the cell cycle	Consists of a period of cell growth and DNA replication called interphase, mitosis happens after that Interphase is divided into three septet age growth stages: Gap phase 1 Synthesis Gap phase 2
Outline the cell cycle	Consists of a period of cell growth and DNA replication called interphase, mitosis happens after that Interphase is divided into three septet age growth stages: Gap phase 1 Synthesis Gap phase 2
What happens during gap phase 1?	Cell grows and new organelles and proteins are made
Outline the cell cycle	Consists of a period of cell growth and DNA replication called interphase, mitosis happens after that Interphase is divided into three septet age growth stages: Gap phase 1 Synthesis Gap phase 2
What happens during gap phase 1?	Cell grows and new organelles and proteins are made
What happens in synthesis?	Cell replicates its DNA ready to divide by mitosis
Outline the cell cycle	Consists of a period of cell growth and DNA replication called interphase, mitosis happens after that Interphase is divided into three septet age growth stages: Gap phase 1 Synthesis Gap phase 2
What happens during gap phase 1?	Cell grows and new organelles and proteins are made
What happens in synthesis?	Cell replicates its DNA ready to divide by mitosis
What happens in gap phase 2?	Cell keeps growing and proteins needed for cell division are made
How can substances move across the cell-surface membrane?	Diffusion Active transport Osmosis
What do membranes do around organelles?	Divide the cell into different compartments Act as a barrier between organelle and cytoplasm Partially permeable - control what enters and leaves organelle
Describe the structure of cell membranes	fluid mosaic structure. Composed of lipids, proteins and carbohydrates phospholipid molecules form a continuous, double bilayer which is fluid because the phospholipids are constantly moving cholesterol molecules are present within the bilayer proteins are scattered through the bilayer eg, channel proteins and carrier proteins. some proteins are able to move sideways through the bilayer, others are in fixed position There are glycoproteins and glycolipids
what are glycoproteins?	proteins with a polysaccharide(carbohydrate) chain attached
what are glycolipids?	lipids with a polysaccharide chain attached
what is the role of phospholipids in a cell membrane?	form a barrier to dissolved substances - head is hydrophilic and tail is hydrophobic - the molecules automatically arrange themselves into a bilayer so the heads face outwards the centre of the bilayer is hydrophobic so the membrane doesn't allow water soluble substances through it
what is the role of cholesterol in the cell membrane?	gives the membrane stability - it is a type of lipid present in all cell membranes - molecules fit between phospholipids, causing them to pack more closely together. this restricts the movement of the phospholipids, making the membranes less fluid and more rigid
what affects the permeability of cell membranes?	different conditions eg temperature and solvent concentration
what can be used to investigate the permeability of cell membranes?	use beetroot cells, they contain a coloured pigment that leaks out, this higher the permeability of the membrane the more pigment leaks out of the cell
describe an experiment to find out how temperature effects beetroot membrane permeability	use a scalpel to cut five equal sized pieces of beetroot, rinse the pieces to remove any pigment released during cutting Add the 5 pieces to five different test tubes each containing 5cm^3 of water. use a measuring cylinder of burette to measure water place each tube in a water bath at a different temperature, for the same length of time. Remove the pieces of beetroot from the tubes, leaving just the coloured liquid use a colorimeter. the higher the absorbance, the more pigment released so the higher the permeability of the membrane
what is a colorimeter?	a machine that passes light through the liquid and measures how much of that light is absorbed.
what is shown to happen to membrane permeability at temperatures below 0	permeability increases as phospholipids don't have much energy so cant move very much. they're packed closely together and the membrane is rigid. but channel proteins and carrier proteins in the membrane deform ice crystals may form and pierce the membrane making it highly permeable when it thaws
what is shown to happen to membrane permeability at temperatures between 0 and 45	the phospholipids can move around and aren't packed as tightly together - the membrane is partially permeable as the temperature increases the phospholipids move more because they have more energy - increasing permeability
what is shown to happen to membrane permeability at temperatures above 45	phospholipid bilayer starts to melt and the membrane becomes more permeable. water inside the cell expands, putting pressure on the membrane. channel proteins and carrier proteins deform so they cant control what enters or leaves the cell - this increases permeability
describe an experiment that can be used to investigate water potential	serial dilution - you can use potato cylinders, to find out the water potential of plant tissue. - first you need to make up several solutions of different, known concentrations to test the cylinders in
what is the serial dilution technique?	- for making five serial dilutions of a sucrose solution, starting with an initial sucrose concentration of 2M and diluting each solution by a factor of 2 1. line up 5 test tubes 2. Add 10cm3 of the initial 2M sucrose solution to the first test tube and 5cm3 of distilled water to the other test tubes 3. using a pipette, draw 5cm3 of the solution from the first test tube, add it to the distilled water in the second tube and mix the solution thoroughly. repeat this process three more times
how do you find the scale factor for making solutions of different concentrations?	start with a solution of a known concentration (eg 1M) find the SF by dividing the concentration of this solution by the concentration of the solution you want to make transfer the amount of solution you need to a clean test tube top up the test tube with distilled water to get the volume you need
Describe an experiment used to find the water potential of potato cells	- using serial dilutions (sucrose) - use a cork borer to cut potatoes into identically sized chips, about 1cm in diameter - divide the chips into groups of three and measure the mass of each group using a mass balance - place one group into each of your sucrose solutions - leave the chips in solutions for at least 20 mins - remove the chips and pat dry gently with a paper towel - weigh each group again and record your results - calculate the % change in mass for each group - the potato chips will gain water in solutions with a higher water potential than the chips, and lose water in solutions with a lower water potential
what is immunity?	resistance to pathogens the body's defence seems to be better prepared for a second infection from the same pathogen and can kill it before it can cause any harm
Describe the human body's defence mechanisms from pathogens which involves white blood cells	- cell mediated response involving T lymphocytes - humoral response involving B lymphocytes
how does the body distinguish its own cells from foreign antigens?	each type of cell, self or non-self has specific molecules on its surface to identify it, which includes proteins. proteins have enormous variety and a highly specific tertiary structure this enables lymphocytes to distinguish one cell from another
what are antigens?	antigens are molecules on pathogens that can stimulate an immune response when detected by the body - they are recognised as non-self
what do antigens allow the immune system to identify?	pathogens non self material - such as cells from other organisms of the same species toxins abnormal body cells
how is the immune response affected in people with organ transplants?	the immune system recognises the tissue or organ transplant as non-self even though they have come from individuals of the same species it then attempts to destroy the transplant in order to reduce this, donor tissues for transplants are normally matched as closely as possible to those of the recipient
summarise defence mechanisms	defence mechanisms can either be specific or non-specific. specific includes cell mediated response (T-lymphocytes) and the humoral response (B-lymphocytes) this response is slower and specific to each pathogen non specific involves physical barrier (skin) and phagocytosis. this response is immediate and the same for all pathogens
what are the two types of white blood cell?	phagocytes lymphocytes
describe phagocytosis	A phagocyte recognises the foreign antigens on a pathogen The cytoplasm of the phagocyte moves around the pathogen, engulfing it the pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte a lysosome fuses with the phagocytic vacuole. the lysozymes hydrolyse and break down the pathogen the phagocyte then presents the pathogens antigens on its surface to activate immune response of other cells
where are lymphocytes produced?	by the stem cells in bone marrow
describe B-lymphocytes	mature in bone marrow associated with humoral immunity - immunity involving antibodies that are present in body fluids, or 'humour' such as blood plasma
describe T-lymphocytes	mature In thymus gland associated with cell mediated immunity - involving body cells
describe the cellular response (cell mediated immunity)	- a pathogen presents antigens on its cell surface - receptors on a specific helper T-cell fit exactly onto these antigens - this attachment activates the T-cell to divide rapidly by mitosis and form a clone of genetically identical cells - these cloned T-cells: develop into memory cells that enable a rapid response to future infections by the same pathogen - stimulate phagocytes to engulf pathogens by phagocytosis stimulate B-cells to divide and secrete their antibody activate cytotoxic T-cells
how do cytotoxic T-cells kill infected cells?	produce a protein called perforin that makes holes in the cell surface membrane. These holes mean the cell membrane becomes freely permeable to all substances and the cell dies as a result
describe humoral immunity	when an antigen enters the blood or tissue fluid, there will be one B cell that has a complementary antibody on its surface. the antibody therefore attaches to this complementary antigen the antigen enters the B-cell by endocytosis and gets presented on its surface T-helper cells bind to these processed antigens and stimulate this B-cell to divide by mitosis to give a clone of plasma cells (clonal selection). the cloned plasma cells produce and secrete the specific antibody that exactly fits the antigen on the pathogens surface (monoclonal antibodies) antibodies attach to antigens and destroys them some B-cells develop into memory cells
what are plasma cells?	live for a short amount of time secrete antibodies usually into blood plasma these antibodies lead to the destruction of the antigen plasma cells are therefore responsible for the immediate defence of the body against infection (primary immune response)
what are memory cells?	live for a long duration responsible for the secondary immune response they don't produce antibodies directly, but circulate in the blood and tissue fluid when they encounter the same antigen at a later date, they divide rapidly and develop into plasma cells and more memory cells. plasma cells produce the antibodies needed to destroy the pathogen, while the new memory cells circulate in readiness for any future infection
what are antibodies?	proteins with specific binding sites synthesised by B-cells
describe the structure of antibodies	made up of four polypeptide chains of amino acids, the chains of one pair are long - heavy chains, chains of the other pair are shorter - light chains. The specificity of an antibody depends on its variable regions, which form antigen binding sites. Each binding site consists of a sequence of amino acids with a unique tertiary structure that binds directly to a specific antigen. the rest of the antibody is known as the constant region. this binds to receptors on cells such as B-cells
how do antibodies assist the destruction of antigens?	they cause agglutination - an antibody has two binding sites, so can bind to two pathogens at the same time. this means pathogens become grouped together. phagocytes then bind to the antibodies and phagocytose many pathogens at once. - serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached.
what are monoclonal antibodies?	antibodies produced from a single group of genetically identical B-cells (plasma cells) they're identical in structure
give three uses of monoclonal antibodies	targeting drugs to particular cell type (Cancer cells) targeting a particular substance for medical diagnosis (pregnancy testing) using an ELISA as a HIV test
give an example of how monoclonal antibodies being used to target drugs to cancer cells	monoclonal antibodies are produced that are specific to antigens on cancer cells (tumour markers) these antibodies are given to a patient and attach themselves to receptors on their cancer cells they attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth advantage - fewer side effects
give an example of how monoclonal antibodies are used to target a particular substance for medical diagnosis	pregnancy testing - detect the hormone human chorionic gonadotropin (hCG) that's found in the urine of pregnant women - the application area contains antibodies for hCG bound to a coloured bead (blue) when urine is applied to application area and hCG will bind to the antibody on the beads, forming an antigen-antibody complex the urine moves up the stick to the test strip, carrying any beads with it. the test strip contains antibodies to hCG that are stuck in place (immobilised) if there is hCG present the test strip turns blue because the immobilised antibody binds to any hCG - concentrating the hCG antigen-antibody complex with the blue beads attached.
give an example of how monoclonal antibodies are used in the ELISA test for HIV	indirect ELISA test - HIV antigen is bound to the bottom of a well in a well plate - a sample of the patients blood plasma, is added to the well. HIV specific antibodies bind to the HIV antigen stuck to the bottom of the well. the well is washed out to remove any unbound antibodies a secondary antibody, that has a specific enzyme attached to it, is added to the well, this can bind to the HIV specific antibody. the well is washed out again to remove any unbound secondary antibody a solution is added to the well. this solution contains a substrate, which is able to react with the enzyme attached to the secondary antibody and produce a coloured product. if the solution changes colour, it indicates that the patient has HIV-specific antibodies in their blood and is infected with HIV
why are the washing steps important in the ELISA test?	they make sure unbound antibodies aren't left in the well which could affect the results
what is the difference between direct ELISA and indirect ELISA tests?	direct - uses a single antibody that is complimentary to the antigen you're testing for indirect - uses two different antibodies
what is the ELISA test used for?	(enzyme linked immunosorbent assay) allows you to see if a patient has any antibodies to a certain antigen or any antigen to a certain antibody - it can be used to test for pathogenic infections or for allergies
evaluate ethical issues with using monoclonal antibodies	production involves the use of mice - the production of tumour cells involves deliberately inducing cancer in mice - have been used successfuly in treating diseases including cancer and diabetes, saving many lives, there have also been some deaths associated with their use in treatment of multiple sclerosis. - testing for the safety of new drugs presents certain dangers - risk to volunteers
what is passive immunity?	no direct contact with pathogen the type of immunity you get from being given antibodies made by a different organism natural - a baby becomes immune due to the antibodies it receives from its mother, through placenta and in breast milk artificial antibodies - when you become immune after being injected with antibodies from someone else
what are the differences between active and passive immunity?	active takes time to develop due to activation of specific B-cells in passive production is immediate active requires exposure to antigen so plasma cells are stimulate to secrete antibody, passive doesn't require exposure to antigen active is long lasting because antibody is produced in response to complementary antigen being present in body, passive is short term because antibodies break down in active memory cells are produced, on passive they aren't
what is a vaccination?	the introduction of the appropriate disease antigens into the body, either by injection or by mouth. the intention is to stimulate an immune response against a particular disease
what factors determine the success of a vaccination programme?	a suitable vaccine must be economically available in sufficient quantities to immunise most of the vulnerable population there must be few side-effects means of producing, storing and transporting the vaccine must be available there must be a means of administering the vaccine properly at the appropriate time it must be possible to vaccinate the majority of the vulnerable population to produce herd immunity
what is herd immunity?	when a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread within that population
why may vaccinations not eliminate a disease?	vaccination fails to induce immunity in certain individuals (defective immune systems) individuals may develop disease immediately after vaccination but before their immunity levels are high enough to prevent it the pathogen may mutate frequently, so that its antigens change suddenly, this means vaccines suddenly become ineffective (antigenic variability) there may be so many different varieties of a particular pathogen
evaluate the ethics of using vaccines	involves the use of animals side effects testing and trials should vaccines be compulsory should expensive vaccination programmes continue when a disease is almost eradicated
describe vaccines	contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. antigens may be free or attached to a dead or attenuated (weakened) pathogen vaccines can be injected or taken orally
what are the disadvantages of taking a vaccine orally?	it could be broken down by enzymes in the gut or the molecules of the vaccine may be too large to be absorbed into the blood
describe how antigenic variation affects the production of vaccines to help prevent people catching influenza	the influenza (flu) vaccine changes every year because the antigens on the surface of virus change regularly, forming new strains of the virus memory cells produced from vaccination with one strain of the flu will not recognise other strains with different antigens. the strains immunologically distinct. every year there are different strains so a different vaccine has to be made
describe active immunity	your immune system makes its own antibodies after being stimulated by an antigen natural - you become immune after catching a disease artificial vaccination - you become immune after being given a vaccination containing a harmless dose of antigen
what is HIV?	human immunodeficiency virus - a virus that effects the immune system. it eventually leads to acquired immune deficiency syndrome (AIDS)
what is AIDS?	a condition where the immune system deteriorates and eventually fails. this makes someone with AIDS more vulnerable to other infections - people with HIV develop AIDS when the helper-T-cells in their body reach a critically low level
how does HIV damage the immune system?	it infects and eventually kill helper T-cells, which act as host cells for the virus. t-cells are really important in the immune response, without them the immune system is unable to mount an effective response to infections because other immune system cells don't behave how they should
what is the structure of HIV?	spherical has a core that contains genetic material (RNA) and some proteins (revers transcriptase) an outer coating of protein called a capsid an extra outer layer called an envelop sticking out from the envelope are loads of copies of an attachment protein that help HIV attach to the host helper T-cell
describe the replication process of HIV	replicates inside the host helper T-cell - the attachment protein attaches to a receptor molecule on the cell membrane of the host helper T-cell - the capsid is released into the cell, where it uncoats and releases the genetic material (RNA) into the cells cytoplasm - inside the cell reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template - from this double stranded DNA is made and inserted into the human DNA - host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA - the viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells
what are the initial symptoms of AIDS?	minor infections of mucous membranes and recurring respiratory infections
what are the middle symptoms of AIDS?	patients become susceptible to more serious infections including chronic diarrhoea, severe bacterial infections and tuberculosis
what are the symptoms of AIDS in the late stages?	serious infections such as toxoplasmosis of the brain (a parasite infection) and candidiasis of the respiratory system (fungal infection)
what factors affect the severity of AIDS?	existing infections the strain of HIV age access to healthcare
why don't antibiotics work against viruses?	viruses don't have their own enzymes and ribosomes so they use ones in the host cells, antibiotics cant inhibit them as the don't target human processes
describe anti-viral drugs	designed to target the few virus-specific enzymes that exist. eg. HIV uses reverse transcriptase to replicate, human cells don't use this enzymes so drugs can be designed to inhibit it without affecting the host cell (reverse-trancsriptase inhibitors)
what is the best way to control HIV?	reducing its spread - HIV can be spread via unprotected sexual intercourse, through infected bodily fluids and from a HIV positive mother to her fetus