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MCAT Biology > Biochemistry > Flashcards

Flashcards in Biochemistry Deck (31):
1

What are the major identifying characteristics of lipids?

1) It is a biomolecule

2) It is hydrophobic

2

What do fatty acids look like?

A image thumb
3

What do triacylglycerols look like?

A image thumb
4

What do phospholipids look like?

A image thumb
5

What do glycolipids look like?

A image thumb
6

What are the differences between saturated and unsaturated fats?

 Saturated fatty acids have all possible hydrogens  and no double or triple bonds. When double bonds are present they can create kinks in the chain that interfere with stacking and therefore lower the melting point. This makes conceptual sense because the fat on your steak is solid at room temperature (saturated fat), whereas olive oil (unsaturated fat) is a liquid at room temperature. Saturated fats can build up in your arteries, but unsaturated fats are already liquid at room temperature so they would be well above their melting point at 98.6°F.

7

What are ampipathic compounds. Give examples of ampipathic lipids.

Ampipathic compounds have both a polar and a non-polar region. Fatty acids are amphipathic and have a charged carboxylic acid functional group plus a long non-polar tail. Triglycerides are completely hydrophobic. Phospholipids are definitely amphipathic and this fact is the primary explanation for their role in biological membranes. Glycolipids are also amphipathic with the sugar portion being hydrophilic and the lipid portion being hydrophobic

8

What are some common nucleotides?

Besides DNA and RNA, other common nucleotides include cAMP, NADH, FADH2, FMN, Coenzyme A, ATP, GTP, UTP, etc.

9

What are the two types of vitamins and examples? How do their functions differ?

Fat-soluble (A,D,E,K)

-act as antioxidants

Water-soluble (B,C)

-act as co-enzymes/co-factors

10

What are the key differences between vitamins and minerals?

 Vitamins and minerals are both essential for proper metabolic function. Vitamins are biological compounds that most often serve as coenzymes and cofactors. It is usually the water-soluble vitamins that play this role, while the fat-soluble vitamins act as antioxidants (Vitamin E), play a role in blood clotting (Vitamin K), aide in eyesight (Vitamin A) and maintain blood calcium levels (Vitamin D). Minerals are inorganic elements or compounds  necessary for bone formation (calcium and phosphate),  ion gradients  (sodium and potassium), oxygen transport (iron- containing heme), muscle contraction (calcium),  etc.—just to name a few.

11

What is the difference between a catalyst and an enzyme?

 Catalysts are molecules that speed up a reaction without being altered or consumed themselves--and enzymes are organic protein catalysts.

12

Enzymes will _____ reaction rate

increase

13

Enzymes will _____ activation energy

Lower

14

Enzymes will __ equilibrium

Not effect

15

Enzymes will ___ yield /%yield

16

What is the substrate?

“Substrate” is the term used to refer to the reactant or reactants in a reaction that is enzyme catalyzed. Specifically, the substrate is the molecule that binds to the enzyme at its active site. So, if we were looking at protein hydrolysis, for example, we would call the protein and water the “reactants.” However, when examining enzyme catalyzed protein hydrolysis we would call the protein the “substrate” because it is the molecule that binds at the active site of the enzyme

17

What is the active site?

The active site is the portion of the enzyme to which the substrate binds. This is usually a pocket formation that more closely resembles the transition state for that reaction than it does the substrate itself.

18

What is the enzyme-substrate complex?

The enzyme-substrate complex is the name given to the enzyme and the substrate once they are bound together

19

What are two theories of enzyme specificity and which is more accurate?

. Induced Fit and Lock & Key are the two theories of enzyme specificity. The lock and key theory would indicate that the active site matches the shape of the substrate and would therefore tend to stabilize it in that form. This does not match well with an examination of the energy transitions involved in the reaction. If the binding of the substrate to the active site results in the substrate being stabilized “as is,” this would lower the energy of the substrate with respect to the transition state and thereby increase the energy of activation. By contrast, if—as the induced fit model suggests--the active site more closely resembles the transition state and stabilized the substrate only as it approaches that conformation/shape, this same process would lower the energy of the transition state. On an energy coordinate diagram it is easy to see that lowering the energy of the transition state would lower the energy of activation. For these reasons, the induced fit model is favored over the lock & key theory.

20

What are coenzymes?

non-protein species not permanently attached to the enzyme but required by the enzyme to function

21

What are prosthetic groups?

non-protein species that are permanently attached to the enzyme and are required by the enzyme to function

22

What are cofactors?

a general term for any species required by an enzyme to function; includes coenzymes and prosthetic groups

23

Describe competitive inhibition

Inhibitor binds at the active site. (resembles the same shape as the substrate).

24

Describe non-competitive inhibition

Inhibitor binds away from the active site and changes the shape of the enzyme. 

25

What is feedback inhibition? Is it competitive or non-competitive?

It is a specific type of non-competitive feedback. One of the products produced from the synthetic pathway chain is an inhibitor for an enzyme earlier in the chain

26

Provide a definition and example of positive feedback

  process by which a product in a series of reactions acts as an agonist for an enzyme that catalyzes one of the previous steps in that series. Positive feedback is rare in the human body, but the luteal surge that results in ovulation is one example. LH stimulates the release of estrogen, which late in the cycle has a positive feedback effect on LH secretion-- causing the sharp spike in LH that results in ovulation

27

Provide a definition and example of zymogens

Zymogens are inactive enzyme precursors that allow enzymes to be transported without exercising their normal function along the way. For enzymes such as proteases this is particularly important. The “-ogen” ending indicates a zymogen as in: pepsin (enzyme) and pepsinogen (zymogen)

28

What do kinases do?

phosphorylate their substrates

29

What do phosphotases do?

dephosphorylate their substrates

30

What do the suffixes "ase" and "-tase" signify?

 The suffix “-ase” indicates an enzyme. Very often enzymes are named by simply adding this suffix to the name of their substrate. The suffix “-tase” is often used (but not always) to indicate an enzyme that requires ATP for its function

31

How will the rate of a reaction change if

a) pH is changed

b) temperature is increased

c) substrate is increased

d) enzyme is increased

a) depending on optimal pH value will increase or decrease

b) temperature increases rate until too high that enzyme becomes denatured

c) will increase exponentially until it levels out

d) same as C