Topic 2 & Some Topic 7: Molecular Biology Flashcards

Question

# C. Proteins & Enzymes 32.Outline with examples how a protein may consist of a single polypeptide or more than one polypeptide linked together. | 4 examples. list # of polypeptides, example, and what the protein does

Answer 1

a) Lysozyme - 1 polypeptide - the enzyme in secretions like mucus and tears - kills the bacteria by digesting the peptidoglycan in the cell walls b) Integrin - 2 polypeptides - membrane protein used to make connections between structures inside and outside the cell c) Collagen - 3 polypeptides - structural protien in tendons, ligaments, skin, blood vessel limits - provides high tensile strength w/limited stretching d) hemoglobin - 4 polypeptides - transport protien in red blood cells - binds oxygen in the lungs and releases it in the tissues with a reduced oxygen concentration

Answer 2

**fibrous** location of r-group: exposed to H2O shape: long and narrow function: structural (strength/support) solubility: insoluble amino acid sequence: repetitive stability: less sensitive to changes in heat, pH etc. examples: collagen, myosin, fibrin, actin, keratin, elastin **globular** location of r-group: folded into the core of the molecule away from the water shape: rounded and spherical function: functional (catalytic, transport etc.) solubility: soluble amino acid sequence: irregular stability: more sensitive to changes in heat, pH etc. examples: catalyse, hemoglobin, insulin, immunoglobin

Answer 3

**defn**: the change to the conformation of a protein. **how**: the 3D conformation of proteins is stabilized by bonds or interactions between R-groups of amino acids within the molecule. these bonds and interactions are relativley weake and can be broken. causes: heat- vibrations can break intermolecular bonds. **pH**- changes the charges on the R-groups, breaking ionic bonds or causing new ionic bonds to be formed.

Answer 4

1. function: catalysis, ex: rubisco - self explanatory 2.function: muscle contraction, ex: actin and myosin - muscle contraction uses in locomotion and transport around the body 3.function: cytoskeletons, ex: tubulin - tubulin is a subunit of microtubules that give animal cells their shape and pull apart chromosomes during mitosis 4.function: tensile strengthening, ex: collagen - fiborus proteins give tensile strength needed for skin, tendons, ligaments, and blood vessel walls 5.function: blood clotting, ex: fibrin - forms a network that raps red blood cells and platelets **6.**function: transports nutrients and gases, ex: haemoglobin - protien in blood help transport oxygen, co2, iron and lipids **7.**function: cell adhesion, ex: integrin protiens - adhesive adjacent animal cells 8.function: membrane transport, ex: sodium channel protein - facilliatated diffusion, active transport and electron transport 9.function: hormones, ex: insulin - both protein and hormone **10.**function: receptors, ex: rhodopsin - binding sites in membranes and cytoplasm for hormones, neurotransmitters, tastes, and smells, also receptors for light in the eye and in plants **11.**function: packing of DNA, ex: histones - associated with DNA and help chromosomes condense in mitosis **12.**function: immunity, ex: immunoglobulins -most diverse group of proteins, as cells can make a huge number of antibodies. | **bold** is easy to memorize if only need to know some

Answer 5

Rubisco: - enzyme - catalyzes the reaction that fixes CO2 in the air - ex. high concent in leaves and algal cells insulin: - hormone - signals cells (ex. liver) to absorb glucose and help reduce the glucose concentration of the blood - secreted by beta cells in the pancreas and transported by blood immunoglobulins: - antibodies: protective protiens in your immune system - two antigens can bond to each 'arm' of the protein - binding sites differ greatly thus responding to a wide array of pathogens rhodopsin: - pigment: absorbs light - present in rod cells in the retina - consists of opsin polypeptode surrounding a retinal prosthetic group - retinal absorbs single photon of light -> changes shape ->change to the opsin -> rod cell send nerve impulse to the brain collagen: - rope like proteins made of three polypeptides wound together - has many different forms - ~quarter of human body is made of collagen - forms mesh of fibres in skin, blood vessel walls etc. which prevents it from tearing and increses tensile strength. - forms part of teeth and bones- helps prevents fractures and cracks spider silk: - different types and functions - dragline silk is stronger than steel and tougher than kevlar (tough fibre) - some regions seem like a disordered tangle, and when first made the polypeptide forms parallel arrays - when stretched the polypeptide gradually extends, making the silk extendable, and high tensile strength

Answer 6

genome: all the genes of a cell, tissue or organism. proteome: all the proteins of a cell, tissue or organism. enviormental factors can affect what protein should be formed and how much of it needs to be made- this affects overall proteome proteome> genome - approx. 20,000 genes in your genome code for approx 10x as many proteins

Answer 7

A globular protien that increases the rate of a biochemical reaction by acting as a catalyst. a catalyst lowers the activation energy threshold by binding the substrate to the active site, the bonds in the substrate are weakned, thus lowere Ea and are easily broken.

Answer 8

1. active site -function: after the enzyme and substrate bind on the active site it catalyzes the reaction -structure: the area on the enzyme where the substrate would bind 2. enzyme-substrate specificity: -function: only substrates and enzymes that fit exactly react- very specific. induced fit does not explain this. -structure: seen in the lock and key model, where enzyme and substrate fit exactly 3. enzyme kinetics - function: the act of collisions occuring between enzymes and substrates. - stucture: most enzyme reactions occur when substrates are dissolved in water because the molecules are able to move randomly- colliding with the enzyme. If not immobilized (ex. bound to a cell membrane) the enzyme can move too, however enzymes tend be larger than the substrate(s) and therefore move more slowly. 4. enzyme catalysis - function: when enzymes and substrates collide successfully to result in catalysis of the reaction - structure: only successful with correct orientation (active site is aligned correctly) and with sufficent energy (when binding to overcome energy barrier).

Answer 9

Lock and Key: - lock and key suggests only one enzyme would catalyze a reaction - structurally: the 3D stucture of the active site is specific to the substrate- if they dont fit, it won't react - chemically: if the substrate is not chemically attracted to the active site so they won't react. the polar regions of the amino acid (substrate) are attracted to the active site of the enzyme. Induced fit: - some enzymes can catalyze multiple reactions - structurally: as a substrate approches an enzyme it induces comformational change in active site- changes shape to fit substrate. the activation energy decreases and enzyme reverts back to original shape. - chemically: more enzymes are attracted to multiple reaction because of conformational change

Answer 10

1. Temperature - low temp= insufficient thermal and kinetic energy for activation of enzyme-catalyst reaction, which is why at low reaction rate and temp the graph is low - as temp increases the speed and KE of both the enzyme and substrate increase resulting in more frequent successful collisions. this us why the reaction rate increases from low to high temp in the x-axis - HOWEVER, there is always an optimal temperature for every enzyme to which the rate of reaction would also be high. - After this optimal temp. the graph is shown to decrease rapidly. this is because at high temperatures the enzyme stability decreases. this is because molecular vibrations by the kinetic energy will cause the H-bonds holding the enzyme to break. this then causes the enzyme (mainly polar active site) to loose shape (conformation) and denature= loss in enzyme activity - ex. optimal temperature for enzymes in human cells are usually around human body temperature (37.5 oC). 2. pH - changing the pH will alter the charge of the enzyme (R-group). this affects the protien solubility and possibily the shape of the molecule. - changing the shape will change the active site form, diminishing its ability to bind to the substrate- thus affecting enzyme function. - There is an optimal pH for each enzyme and moving outside of this range will diminish the rate of reaction. ex. pepsin has an optimal pH of 2 3. Substrate concentration - increasing the substrate concentration will increase the rate of reaction - the optimum concentration of the substrate concentration will be when all active sites are full and working at max efficency. - any increase in concentration beyond the optimum will have no added effect as there will be no free active sites for reactions

Answer 11

if an enzyme denatures, the active site will change it's shape respectively, therefore the substrate will no longer be able to bind to it.

Answer 12

enzyme immobilization: when an enzyme is attarched to a certain material so their movement is restricted three ways enzymes can be immobilized: 1. aggregate enzymes by bonding them together 2. attached to surfaces ex. in cell membranes 3. entrapped in a gas ex. alginate gel beads advantages: 1. concentration of the substrate can be increased easily as the enzyme is fixed. this will increase the rate of reaction 2. recycled enzymes can be used many times and immobilized enzymes are easy to seperate from the reaction mixture, resulting in cost saving 3. seperation of the products is straight forward/ also means reaction can be stopped at correct time 4. stability of the enzyme to changes in temp and pH is increased, thus reducing the rate of degradation- resulting in cost saving

Answer 13

1. lactase is obtained most commonly from yeast (or bacteria) 2. lactase is bound to the surface of alginate beads 3. milk is passed (repeadetly) over the beads 4. the lactose is broken doen into glucose and galactose 5. the immobilized enzyme remains are to be used again and does not affect the quantity of the lactose free milk advantages: - for lactose intolerant people - to increase the sweatness of milk negating the need for artifical sweetners - to reduce the crystilization of ice creams (glucose and galactose are more soluble than lactose) - shortneing the production of yougurts or cheese (bacteria ferment glucose and galactose more readily than lactose)

Answer 14

Lab done in class on substrate concentration

Answer 15

Hypotheses: 1. these 20 amino acids were the ones first produced by chemical processes on earth before the origin of life- so all organisms continued to use them. if there were more amino acids present then they would have been used 2. they are the ideal 20 amino acids for making a wide range of proteins, so natural selection will always favour the organisms that use them. 3. all life has evolved from a single ancestral species, which used these 20 amino acids. because of the way the polypeptides are made by ribosomes, it is difficult for any organism to change the repertoire of amino acids, either by removing existing ones or by adding new ones.

Answer 16

A ribosome condenses two amino acids into a dipeptide forming a peptide bond. multiple amino acids would create a polypeptide chain also known as a protein

Answer 17

learn to draw

Answer 18

CARBS: 1. Glucose 2. Galactose 3. Fructose 4. Ribose 1&2 hexose, 3&4 pentose 1 & 2 have the same pattern, but different dimension in space *learn how to draw glucose and ribose, learn how to identify fructose and galactose* LIPIDS: Lipids are glycerol combined with 1, 2 or 3 fatty acids, therefore triglycerides are lipids hydrocarbon tail with carboxyl group (carbonyl group C=O that has a hydroxyl group O-H attached to the carbon atom) *learn how to draw, and identify monounsaturated, polyunsaturated, and saturated* Protiens: have an amine group (NH2) and carboxyl group at opposite ends with an R group oriented at the top, bottom, left or right. *learn how to identify*

Answer 19

Metabolism describes the totality of chemical processes that occur within a living organism in order to maintain life.

Answer 20

**Anabolism** - metabolic reactions that build up complex molecules from simpler ones - The synthesis of organic molecules via anabolism typically occurs via condensation reactions - Condensation reactions occur when monomers are covalently joined and water is produced as a by-product **Catabolism** - metabolic reactions that break complex molecules down into simpler molecules - The breakdown of organic molecules via catabolism typically occurs via hydrolysis reactions - Hydrolysis reactions require the consumption of water molecules to break the bonds within the polymer

Answer 21

Hydrogen bonds are electrostatic attractions between a hydrogen atom and more electronegative elements like N, O, and F. It's FON to hydrogen bond! strongest intermolecular force!

Topic 2 & Some Topic 7: Molecular Biology Flashcards

DP2- U1: Biochem (45 cards)