Carbohydrate metabolism

Question 1

Carbohydrate metabolism occurs in

Answer 1

Occurs in cytoplasm
 catabolic and anabolic processes

Question 2

Sources of carbohydrates

Answer 2

Diet
 Breakdown of glycogen or glycerol
 Propionate stored in the liver (ruminants)

Question 3

Primary carb found in blood

Answer 3

Glucose

Question 4

Glucose is absorbed by all cells by

Answer 4

Facilitated diffusion
Active transport

Question 5

Diabetes mellitus

Answer 5

caused by insufficient insulin levels or decreased insulin receptor proteins
 Body cells are starved of energy because cannot absorb and use glucose

Question 6

When blood glucose levels are low

Answer 6

liver converts stored glycogen to glucose
 Can make new glucose from non-carbohydrate material

Question 7

What does liver do to glucose

Answer 7

Liver removes glucose from blood after meal
 Converted to glycogen or triglycerides for storage

Question 8

What is the key organ involved in regulating blood glucose

Answer 8

Liver

Question 9

Carbohydrate metabolism

Answer 9

Glucose enters cell
 Glucose broken down to pyruvate through glycolysis
 If adequate oxygen, aerobic respiration follows
 If not adequate oxygen in muscle cells, pyruvate is converted to lactic acid
 Causes stiff feeling in muscles

Question 10

Glycolysis occurs in

Answer 10

Cytoplasm

Question 11

Glycolysis process and net product

Answer 11

Occurs in cytoplasm
 Glucose broken down to form two pyruvate (pyruvic acid)
 Net production of energy is:
 2 NADH
 2 ATP

Question 12

Regulation of glycolysis

Answer 12

Glycolysis pathway is constantly controlled
 Regulated by three enzymes:
 Hexokinase
 Phosphofructokinase
 Pyruvate Kinase

Question 13

Hexokinase

Answer 13

Inhibited by glucose-6-phosphate
Feedback inhibition

Question 14

Phosphofructokinase

Answer 14

Inhibited by ATP and citrate
Activated by ADP and AMP

Question 15

Pyruvate Kinase

Answer 15

Inhibited by ATP

Question 16

Aerobic respiration occurs in and has two stages

Answer 16

Occurs in the mitochondria
 2 stages:
 Krebs cycle
 Electron transport chain
Enzymes and cofactors found in cristae

Question 17

Each turn of the krebs cycel produces energy carrier molecules

Answer 17

1 ATP
1 FADH2
3 NADH

Question 18

Krebs cycle

Answer 18

Pyruvate enters mitochondria through outer and inner membrane
 Before enters Krebs cycle is transformed into an acetyl group
 Acetyl group binds to coenzyme A → acetyl coA
 Acetyl coA enters Krebs cycle and binds with oxaloacetateAfter several steps citric acid is converted back to
oxaloacetate

Question 19

By product of the krebs cycle

Answer 19

CO2

Question 20

How many times does the krebs cycle run

Answer 20

Since two pyruvate were produced from one glucose, the cycle runs two times for each glucose molecule

Question 21

Regulation of krebs cycle

Answer 21

 Rate of Krebs cycle is adjusted to meet cellular needs for ATP
 Entry of acetyl-CoA into the cycle and rate at which the cycle operates are reduced by high ATP levels
 When ATP supplies are low the cycle is stimulated

Question 22

Electron transport system

Answer 22

Final stage of cellular respiration
 Produces majority of ATP for cell
 NADH and FADH2 donate high energy electrons to a chain of electron carrier molecules
 Called cytochromes
 At each step energy is used to pump protons from mitochondrial matrix into intermembrane space
Last electron acceptor is oxygen
 Oxygen joins with two hydrogen atoms to form water
 Pumping of protons across membrane establishes an electrochemical gradient
 Potential energy
 Protons flow back into matrix through ATP synthase complex
 Energy is released
 Used to combine ADP and inorganic phosphate to make ATP

Question 23

Glycogen synthesis

Answer 23

Glycogen Synthesis
 Glucose consumed in excess of immediate body needs is converted to glycogen
 Glycogen stored in liver and muscle
 Glycogenesis
 Glycogen synthase forms bonds between glucose using ATP as energy source

Question 24

Glycogen synthesis occurs in

Answer 24

Can occur in all cells but important function of liver and muscle

Question 25

Glycogenesis is

Answer 25

Synthesis of glycogen from glucose

Question 26

Glycogenolysis is

Answer 26

Breakdown of glycogen to glucose

Question 27

When does glycogen breakdown occur

Answer 27

Occurs when muscles need energy and when liver is restoring low blood sugar level to normal

Question 28

Where does glycogenolysis occur

Answer 28

Occurs in liver, kidney, and intestinal cells
 Not in muscle because enzyme for last step is missing

Question 29

What can muscle cells produce instead of free glucose during glycogenolysis

Answer 29

Muscle cells cannot form free glucose, but can produce glucose-6-phosphate which can be used in glycolysis pathway

Question 30

Gluconeogenesis is

Answer 30

Synthesis of glucose from noncarbohydrate molecules
 Synthesizes glucose from lactate, some amino acids, and glycerol
 Primarily occurs in the liver (~90%)

Question 31

What happens during the cori cycle

Answer 31

Under anaerobic conditions, lactate produced by muscles is reconverted to glucose by the liver through the Cori Cycle Pyruvate is converted to glucose by gluconeogenesis
 Glucose enters the blood and returns to the muscles

Question 32

During active exercise what does lactate do

Answer 32

lactate levels increase in muscle tissue
 lactate diffuses into the blood
 lactate is taken to liver and converted back to pyruvate

Question 33

What main hormones control carb metablsism

Answer 33

Insulin
Glucagon
Epinephrine

Question 34

Insulin does what to carbs

Answer 34

 decreases blood glucose levels
 increases absorption of glucose by cells
 increases the synthesis of glycogen, fatty acids, and proteins
 stimulates glycolysis

Question 35

Glucagon does what to carb

Answer 35

 increases blood glucose levels
 activates glycogen breakdown in liver

Question 36

Epinephrine does what in carb metabolism

Answer 36

 increases blood glucose levels
 stimulates glycogen breakdown in muscle