carbs

Question 1

Glucose transporters

Answer 1

• insulin sensitive – Glut 4 – increases glucose transport in cell following insulin exposure (sk muscle/adipose)
• insulin independent- Glut 2 - in liver–

Question 2

where does glycolysis occur

Answer 2

cytoplasm

Question 3

3 types of chemical reactions in glycolysis

Answer 3

• degrade glucose –> pyruvate
• phosphorylate ADP –> ATP
• generation of NADH

Question 4

substrate level phosphorylation

Answer 4

phosphorylate ADP-> ATP during glycolysis

Question 5

oxidative phosphorylation

Answer 5

in mitochondria

Question 6

First reaciton in glycolysis

Answer 6

glucose –> G6P

• hexokinase or glucokinase mediated
• irreversible

Question 7

what does glucose phosphorylation accomplish

Answer 7

• give intermediate net charge to trap it in cell
• conserves energy
• binding of G6P phosphate to active site of next enzyme lowers activation energy

Question 8

Hexokinase I

Answer 8

• not selective
• in all cells
• low Km for sugars
• Inhibited by G6P
• more active at lower glucose concentrations(i.e. during fasting)

Question 9

Glucokinase

Answer 9

• selective for glucose
• liver, pancreatic Beta-cells
• High Km for glucose
• inhibited by F-6-P
• more active at higher glucose concentrations

Question 10

PFK1

Answer 10

catalyzes reaction of F6P -> F 1, 6 bisphosphate

• 2nd ATP investment
• rate-limiting and committed step of glycolysis
• irreversible
• allosteric enzyme

Question 11

what inhibits PFK 1

Answer 11

ATP/citrate

Question 12

what stimulates PFK 1

Answer 12

AMP

Question 13

PFK2

Answer 13

can convert F6P to F 2,6, BP

F2,6BP most potent activator of PFK1

Question 14

5 parts of cab metabolism

Answer 14

Glycolysis, TCA cycle, Gluconeogenesis, Glycogen synthesis/breakdown, Pentose Phosphate Pathway

Question 15

Km

Answer 15

concentration at which reaction is half maximal
- Low Km = substrates have strong affinity for enzyme and reaction will go at low substrate concentrations
-

Question 16

Vmax

Answer 16

maximal rate an enzyme-catalyzed reaction

- High Vmax = produce a lot of product in small period of time

Question 17

3 types of key steps

Answer 17

1- molecule changes location in cell (moves across membrane)
2 - body invests energy (often P from ATP)
3- rate-limiting step

Question 18

Key steps in glycolysis

Answer 18

• Glucose enters cell
• Glucose –> G6P
• F6P –> F1,6,BP
• PEP –> pyruvate

Question 19

significance of G6P

Answer 19

phosphorylating glucose traps it within cell due to charge

Question 20

Rate-limiting step of glycolysis

Answer 20

F6P–> F1,6BP via phosphofructokinase (PFK)

Question 21

Fate of pyruvate

Answer 21

• with O2 –> TCA cycle
• No O2 – convert to lactate and exported from cell; regenerates NAD from NADH to allow continuation of glycolysis
• pyruvate from lactate or amino acid metabolism can also enter TCA as oxaloacetate during gluconeogenesis

Question 22

where does glycolysis happen

Answer 22

cytosol of cell

Question 23

Where is the electron transport chain

Answer 23

inner mitochondrial membrane

Question 24

Key regulated steps in gluconeogenesis

Answer 24

1) Pyruvate –> PEP through oxaloacetate and malate; pyruvate carboxylase and PEP carboxykinase
2) F1,6BP –> F6F via Fructose1,6bisphosphatase
3) G6P –> Glucose: allows it to leave cell and only happens in liver/kidney (NOT muscle/adipose)

Question 25

Sources of carbon for gluconeogenesis

Answer 25

(these substrates transported to liver) - lactate from glycolysis in muscle or RBC - amino acids from protein breakdown in muscle - glycerol from triglyceride breakdown in adipose tissue

Question 26

Glycogen

Answer 26

- when excess glucose - G6P -> G1P -> UDP-glucose : key step for synthesis/breakdown - 2nd key step adds UDP-glucose to glycogen molecules with glycogen synthase (removes with Glycogen phosphorylase)

Question 27

Glycogen phosphorylase

Answer 27

removes glucose from glycogen when needing glucose

Question 28

how is glucose added to glycogen

Answer 28

- add individual glucose in 1,4 orientation | - for breakdown, glycogen broken from terminal ends until branch point -- enzyme takes apart branch point

Question 29

Functions of pentose phosphate pathway

Answer 29

- Generate NADPH for fatty acid biosynthesis, cholesterol biosynthesis, defense against oxidative stress and white cell function - generate 5 carbon sugars for nucleotide synthesis

Question 30

key regulated step in pentose phosphate pathway

Answer 30

Glucose-6-Phosphate dehydrogenase (G6P --> 6 phosphogluconolactone)

Question 31

Regulation through pathway depends on

Answer 31

- amount of substrate - levels/amount of key enzymes - allosteric regulation-- can change Km or Vmax - Covalent modification (phosphorylation)--common with hormones (insulin/glucagon)--can also change Km or Vmax

Question 32

How can the body change Km or V max of a reaction

Answer 32

allosteric regulation or covalent modification of key enzyme

Question 33

Counter-regulatory hormones

Answer 33

glucagon, catecholamines, growth hormone, cortisol

Question 34

What happens in fed state

Answer 34

Insulin high, counter regulatory hormones low, - glycolysis/glycogen synthesis active and glucose assimilated by peripheral tissues - gluconeogenesis/glycogen breakdown reduced

Question 35

fasting state

Answer 35

- Insulin low, counter-regulatory hormones high | - Gluconeogenesis/glycogen breakdown increased