03

Question 1

What do enzymes do

Answer 1

increase the rate of chemical reaction

rate = # in set amount of time

Question 2

Describe an enzyme

Answer 2

specific for one reaction (depends on the amino acids that make up the enzyme)

not permanently changed in these reactions

bind the substances that are reacting (substrates) and release the (productcs) once the reaaction is complete

Question 3

What are the steps to an enzyme catalyzed reaction

Answer 3

1. binding of substrate
   E+S <-> ES
2. conversion of the bound substrate into a still bound product
   ES <-> EP
3. release of the product
   EP <-> E+P

*reversible reactions

Question 4

What is the lock and key model
what are the limitations

Answer 4

enzyme and substrate fit together perfectly

this model explains the specificity of an enzyme
- not the ability of the enzyme to stablizie the transition state

Question 5

What is the induced fit model

Answer 5

most accurate model

allows for flexibility of the enzyme in binding to the substrate

binding of the substrate induces changes in the shape/conformation of the enzyme

changes allow for enzyme catalysis to take place

explains changes in protein structure that occur when a substrate bidns to an enzyme

conromational change can stress the bonds –> allows for a reaciton to take place more easily

Question 6

How do enzymes catalyze a reaction

Answer 6

lowers the activation energy needed to reach the final state
*doesn’t speed up the reaction progress, just the number of products made

Question 7

What are the strategies used by enzymes to catalyze a reaction

Answer 7

1. acid-base catalysis
2. covalent catalysis
3. metal-ion catalysis
4. catalysis by approximation
5. cofactor catalysis

enzymes can also use a combo of these

Question 8

What are co-factors and co-enzymes

Answer 8

functional groups that help facilitate the enzymatic reaction

come from the enzymes themselves (aa side chains), other non-protein molecules or minerals that are part of the active site

• can donate a function group to the reaction
• stabilize the transition state of the reaction

Question 9

What are examples of cofactors and coenzymes

Answer 9

zinc
iron
vitamin B6
Thiamine B1

Question 10

How do cofactors work

Answer 10

incomplete enzyme + mineral cofactor join together to form an active enzyme

Question 11

How do coenzymes work

Answer 11

incomplete enzyme + (vitamin + chemical group = functional coenzyme) join together to form an active enzyme

Question 12

How is the rate of an enzymatic reaction measured

Answer 12

by how many products can be made in a period of time

Question 13

What factors can impact the rate of reaction

Answer 13

pH
temp
substrate/enzyme/product concentration
inhibitors
protein modfications

Question 14

What happens to an enzyme as pH is increased

Answer 14

each enzyme has an optimal pH
- below: not functioning to slow
- at pH: aa residues in the protein structure either protonaed or deprotonated –> can have correct structure // functional groups can catalyze
- above: denatured

most enzyme’s optimal pH = physiological pH or the pH of their environment

Question 15

How does temp impact reaction rate

Answer 15

higher temp: more atoms and molecules vibrate

most human enzyme operate best at 37C

rate of reaction increases until the temperature at which the enzyme is denatured

temp increases = heat (vibrational) energy make it easier to break chemical bodns until the protein secondary and tertiary structure breaks down

Question 16

What happens if there is little substrate, what is the impact of the rate of reaction

Answer 16

no substrate = no reaction

Question 17

What happens if there is little enzyme, what is the impact of the rate of reaction

Answer 17

more enzymes = more product that can be made

enzyme concetration can be controlled by gene expression and protein degradation

Question 18

What happens if there is little concentration of product, what is the impact of the rate of reaction

Answer 18

when a lot of product –> binds to active site and prevents the reaction from occuring, or go backwards to be converted back into the substrate

Question 19

What are inhibitors

Answer 19

decrease the rate of reaction

reversible (competetive or noncompetetive or allosteric) or nonreversible

Question 20

What are irreversible inhibitors

Answer 20

compounds that covalently modify an enzyme

permanent and not reversible and the enzyme is permanently changed

enzyme must be degraded and replaced with a new enzyme

Question 21

What are reversible inhibitors

Answer 21

bind to enzymes, but not permanent

• competitve
• noncompetetice
• allosteric

Question 22

What are competitive inhibitors

Answer 22

has similar shape to one of the substrates of an enzymes –> reactions can’t occur –> product is not produced

only inhibit when they are bound in the active site, many can be displaced by increasing the concentration of substrate

slower, gradually reaches vmax

Question 23

What are noncompetetive inhibitors

Answer 23

does not compete with substrates for binding
- binds elsewhere on an enzyme

results in conformation change inthe enzyme –> prevents the substrate from binding or the reaction from preceeding

Allosteric inhbition: inhibitor binds to allosteric site, active site changes shape so substrate can’t bind

loweres the vmax

Question 24

How do you turn off an enzyme

Answer 24

Location: keep the enzyme away from its substrate to prevent the reaction from happening

inactive enzyme: some enzymes are kept in an inactive state until they are needed

enzymes cna be modified to turn on and off (ex. post-translational modifications)

Question 25

How are metabolic pathways turned on and off

Answer 25

enzymes are always part of a pathway when regulating these pathways, not every enzyme needs to be regulated (only the important ones) when these reactions are regulated, the whole pathway turns off

Question 26

Which cell does not contain a nucleus or membrane bound organelles

Answer 26

prokaryotic (bacterial cells)

Question 27

How do prokaryotic cells differ from eukaryotic cells

Answer 27

compartments allow cells to concentrate molecules and proteins, controls when and how reactions take place

Question 28

Describe the plasma membrane

Answer 28

all cells enclosed phospholipic bilayer that contains proteins and other molcules proteins embedded in the membrane and/or anchored to tje membrane allows cellular communication and transport between either side

Question 29

What are phopholipids

Answer 29

amphiphatic molecuels - hydrophillic and hydrophobic regions dual nature allows phospholipids to form a bilayer that is hydrophillic on the outsdie nad hydrophobic on the inside

Question 30

What are integral proteins

Answer 30

transmembrane proteins embedded in the membrane with hydrophobic and hydriphillic regions on either side can connect the outside and insdie of the cell channels, transporters, receptors for hormones, neurotransmitters

Question 31

What are peripheral proteins

Answer 31

attach to integral membrane proteins or to the edges of the lipid bilayer temporarily and crry out a specific function

Question 32

How are products transported across the membrane

Answer 32

using proteins establishes an electorchemical gradient - concentration gradient - charge gradiant

Question 33

What are the modes of transport

Answer 33

1. passive transport - simple diffusion - facilitative difussion 2. active transport - primary - secondary 3. bulk transport (endocytoriss)

Question 34

Describe simple diffusion

Answer 34

movement of molcules from jhigh to low concentrations no energy required small non-polar molecules small polar (water) can move, but slowly

Question 35

Describe facilitated diffusion

Answer 35

movmenet of molecules from high to low larger polar moele molecules must bind to its transport protein

Question 36

Describe active transport

Answer 36

uses a lot of energy ex. sodium potassium pump

Question 37

Describe secondary active transport

Answer 37

transports a molecue from a low to high contraction area no energy used riectly -- connects transport of on molecule to the tranport of another with its concentraction gradant

Question 38

What does the nucleus do

Answer 38

the library and command centre largest organlle has double membrane that is connected to the endoplasmic reticulum most of the NDA is in the nucleus, with small amount located in the mitochondria DNA replication and transcription of the DNA into RNA both occur in the nucleus once mRNA transcribed and processed it travels out of the nucleus through nuclear pores for translation

Question 39

Describe nuclear transport

Answer 39

proteins, RNA, nucleotides all need to move in and out of the nucleus involves the movement through nuclear pores proteins made in the cytoplasm, specific sequences on the protein direct the protein to where they are needed nuclear proteins --> nuclear localization sequences (NLS) nuclear export sequences (NES)

Question 40

What is the endoplasmic reticulum

Answer 40

the protein factory made up of smooth and rough (ribosomes attached) areas rough ER: site of translationg of proteins bound for outside the cell or within the membrane or organelles (where post-translation modifications occur) smooth ER: contains enzymes for lipid synthesis and the cytochrome P450 oxidative enzymes of drug metabolism as well as the site of glycogen storage in the liver

Question 41

What are ribosomes

Answer 41

protein synthesis factories that are found in the cytoplasm and attached to the ER

Question 42

What is the golgi complex

Answer 42

"amazon warehouse" golgi complex modifies, sorts and distributes proteins around the cell proteins translated in the rough endoplasmic reticulum move the golgi where they receive post-translational modifications and are transported to where they need to go

Question 43

What is the mitochondria

Answer 43

the powerplant sites of energy production consist of an outer and inner membrane (double membrnae) - inner membrane: site of the enzymes invovled in cellular respiration, while the TCA cycle and other oxidative pathways occur in the matrix mitochonrdria has its own DNA, seperate from the nucleus

Question 44

What are lysosomes

Answer 44

recycling depot membrnae-bound organelles containing enzymes that can breakdown molecules that can be re-used lysosomes break down: - anything the cell doesn't need - foreign invaders pH is maintained at about 5.5 so that the enzyme encolsed in the organelle can function pH maintained by transporters that use energy (ATP) to pump H+ into the lysosome

Question 45

What is cellular signaling

Answer 45

cells need to communicate iwth each other to maitain homeostasis - sharing info across different cells and cell types

Question 46

What are the steps to cellular signaling

Answer 46

1. secretion of a messenger molecule 2. binding of the messenger to a receptor outside or inside the cell 3. a change occuring in the cell 4. termination of the signal/degredation of the messenger

Question 47

What are the types of cellular signalling

Answer 47

- endocrine hormones and messengers are secreted into the blood and travel to target cells - paracrine messengers act on cells nearby - autocrine messengers bind on the same cell from which they are released - juxtacrine are direct cell to cell interactions

Question 48

What determines the type and location of a cell receptor

Answer 48

type and the location of receptor determined by the messenger molecule

Question 49

What does it mean if a cell receptor can cross the membrane or if it cannot

Answer 49

mol can cross the plasma membrane: receptor will likely be inside the cell mol cannot cross the plasma membrane: the receptor will need to be on the cell surface

Question 50

What are intracellular receptors

Answer 50

bind to messengers that can diffuse across the plasma membrane messengers need to be hydrophobic steroid/thyroid hormone superfamily of receptors are examples - diffuse through the plasma membrane, bind to their receptor in the cytoplasm and move to the nucleus where they alter gene expression

Question 51

What are extracellular receptors

Answer 51

bind to messengers that cannot diffuse across the plasma membrane usually hydrophillic and can be large bind to receptor proteins embedded in the plasma membrane causes a conformational change that starts signlaing cascade inside the cell