Unit 6b - Carbohydrate Metabolism

Question 1

Where does carbohydrate metabolism occur? What are the processes involved?

Answer 1

It occurs in the cytoplasm, involves catabolic and anabolic processes

Question 2

What are the sources of carbohydrates?

Answer 2

From the diet
Breakdown of glycogen or glycerol
propionate stored in the liver (in ruminants)

Question 3

Give a brief explaination of the carbohydrate pathway. Arrow to arrow

Answer 3

From the intestines + H20 + polysaccharides (glycogen) -> Hydrolysis -> Monosacc (glucose) -> EITHER = 2 ATP for Cytoplasm OR glycolysis to = 2 pyruvate to EITHER make lactic acid (if o2 not abundant) -> Acetyl CoA (if o2 abundant) -> krebs cycle to make 2 ATP, or electron trans system to make 34 ATP and H20

Question 4

What is the primary carb found in the blood?

Answer 4

Glucose

Question 5

What carb is absorbed by all cells? How?

Answer 5

Glucose - Facilitated diffusion or active transport

Question 6

Where do RBC and brain cells derive energy from?

Answer 6

Glucose, cannot derive energy anywhere else

Question 7

Where do skeletal muscles derive energy from

Answer 7

Ketones + Fatty acids

Question 8

What is diabetes mellitus?

Answer 8

Caused by insufficient insulin lvls or decreased insulin receptor proteins

body cells are starved of energy bc they cannot absorb and use glucose

Question 9

Which organ is vital in regulating blood glucose lvl? When does it regulate it and how?

Answer 9

The liver, removes glucose from blood after meals and converts it to glycogen or triglycerides for storage

Question 10

What happens when blood glucose lvls are low?

Answer 10

Liver convertes stored glycogen to glucose
can make new glucose from non-carb material

Question 11

Explain carbohydrate metabolism. What is the chain of events?

Answer 11

Glucose enters cell -> broken down to pyruvate thru glycolysis -> either aerobic process or anerobic to make lactic acid

Occurs in cytoplasm where glucose is broken down to form pyruvate. Net prod. of energy is 2 NADH and 2 ATP

Question 12

What three enzymes regulate glycolysis? What are the inhibited or activated by?

Answer 12

Hexokinase - inhib by glucose-6-phosphate + feedback inhibition
Phoshpfructokinase - inhib by ATP and citrate + activated by ADP and AMP
Pyruvate Kinase - inhib by ATP

Question 13

Where does Aerobic respiration occur? How many stages are there?

Answer 13

In mutochondria
2 stages - krebs + E trans chain
enzymes + cofactors found in cristae

Question 14

How is carb metabolism related to the Kreb’s cycle? What is the chain of events?

Answer 14

Pyruvate enters mitochondria thru outer + inner membrane
b4 enters krebs cycle -> acetyl group
Acetyl group binds to coenzyme A -> acetyl CoA
Acetly CoA enters krebs -> oxaloacetate to form citric acid
Coverted back to oxaloacetate.

CO2 is a byproduct

Each turn = 1 ATP, 1 FADH2, 3 NADH

Question 15

How is the krebs cycle regulated?

Answer 15

Adjusts its rate to meet cellular needs for ATP
Entry of Acetyl-CoA into cycle and rate at which the cycle operates are reduced by high ATP levels
when ATP is low, cycle is stimulated

Question 16

Explain the relation betwen Carb metab and e trans system

Answer 16

Produces majority of ATP for cell
NADH and FADH2 donate high energy electrons to chain of e carrier molecules called cytochrome
each step is used to pump protons from mitochondrial matrix into intermembrane space
Last e acceptor is oxygen to = h20

Question 17

What is the summary of energy production from one glucose molecule? What makes what and where?

Answer 17

Cytoplasm (glycolysis) = 2 ATP
Mitochrondria
From glycolysis = 2 NADH + 6 ATP
From Cellular Respire
Pyrivic acid-acetyl CoA = 2 NADH + 6 ATP
Krebs = 6 NADH + 2 FADH + 24 ATP

Total 38 ATP

Question 18

What energy carrier molecules are produced by the Krebs cycle

Question 19

Does glycolysis require oxygen?

Question 20

What is the product of glycolysis

Question 21

What is glycogen synthesis?

Answer 21

Glucose consumed in excess of immediate body needs is converted to glycogen which is stored in the liver and muscle

Question 22

What is glycogenesis?

Answer 22

The synthesis of glycogen from glucose.
Occurs in all cells but important in liver + muscle
Glygocen synthase forms bonces btw glucose using UTP as energy source

Question 23

What is Glycogenolysis

Answer 23

Breakdown of glycogen to glucose, occurs when muscles need energy and when liver is restoring low blood sugar level to normal
occurs in liver, kidney and intestinal cells (not in muscle bc enzyme for las step is missing)
muscle cels cannot form free glucose but can prod glucose-6-phosphate for glycolysis pathway

Question 24

What is gluconeogenesis?

Answer 24

The synthesis of glucose from noncarb molecules
synthesizes glucose from lactate, some amino acids and glycerol
occurs in like (~90%)

(lactate, some amino acids, glycerol) -> pyruvate -> Glucose

Question 25

What is the cori cycle? What happens during active exercise?

Answer 25

Anaerobic conditions, lactate prod by muscles recoverted to glucose by liver via cori cycle

Lactate lvls inc. in muscle tissue
lactate diffuses into blood
lactate -> liver -> pyruvate
pyruvate -> glucose via gluconeogenesis (synthesis of noncarb molecules like lactate)
glucose enters blood and returns to muscles

Question 26

What 3 main hormons control carbohydrate metabolism?

Answer 26

Insulin, glucagon, epinephrine

Question 27

Explain how insulin works with carb metab?

Answer 27

dec blood glucose lvls
inc absorption of glucose by cells
inc synthesis of glycogen, fatty acids and proteins
stimulates glycolysis

Question 28

Explain how glucagon works with carb metab?

Answer 28

Inc blood glucose lvls
activates glycogen breakdown in liver

Question 29

explain how epinephrine works with carb metab?

Answer 29

Inc blood glucose lvls
stims glycogen breakdown in muscle