Glycogen & glycolysis

Question 1

give examples of monosaccharides and disaccharide

Answer 1

Mono = glucose, galactose
Di = lactose, sucrose

Question 2

what does glucose & galactose make?

Answer 2

Lactose

Question 3

what does glucose and fructose make?

Answer 3

Sucrose

Question 4

how do we store carbohydrates?

Answer 4

Glycogen - a multi-branched polysaccharide of glucose

Question 5

why do we need to store carbohydrates?

Answer 5

energy storage, structural components, enzyme components, DNA replication

Question 6

what are the 2 major sites of glycogen storage?

Answer 6

liver & skeletal muscle (more is stored in muscle but its more concentrated in liver)

Question 7

what happens if a problem enzyme is involved in glycogen breakdown? (disorder)

Answer 7

then will have low glucose levels in body - hypoglycaemia

Build up of glycogen in muscles and liver

Question 8

what if a problem enzyme regulates glycogen synthesis?

Answer 8

reduced amounts of normal glycogen, abnormal glucose

Question 9

symptoms of glycogen storage disorders?

Answer 9

type I - low blood sugar (Sweat, confusion, drowsiness)
enlarged liver 
weaker muscles 
obesity
kidney issues
bleeding/clotting

Question 10

what enzyme breaks down glycogen into glucose-1-phosphate?

Answer 10

Glycogen phosphorylase

Question 11

what are the 3 types of bonds in glycogen?

Answer 11

Alpha-1,6 BRANCHES

alpha-1,4 links

Question 12

as alpha-1,6 glycosidic bonds can’t be broken down by glycogen phosphorylase - what happens?

Answer 12

we need to use alpha-1,6-glucosidase which has transferase and debranching activity

Question 13

what does alpha-1,6-glucosidase do?

Answer 13

enzyme that takes off the alpha-1,6 branches - then releases a glucose

Question 14

How do we process glycogen breakdown products?

Answer 14

Glucose-1-phosphate (major) and glucose is converted to glucose-6-phosphate via phosphoglucomutase enzyme. This is then processed into glucose

Question 15

how do skeletal muscle use glycogen breakdown products?

Answer 15

Glucose-6-phosphate into glycolysis pathway to generate ATP

Question 16

How does liver use glycogen breakdown products?

Answer 16

Glucose-6-phosphate converted to glucose and sent to the brain for blood glucose

Question 17

how is glycogen synthesised?

Answer 17

Glucose is converted to glucose-6-phosphate (hexokinase)
Glucose-6-phosphate converted to glucose-1-phosphae (phosphoglucomutase)
Glucose-1-phosphate converted to UDP-glucose (UDA-glycose phosphorylase)
UDP- glucose + glycogen via glycogen synthase = glycogen and UDP

Question 18

what is UDP-glucose?

Answer 18

building block of glycogen - activated form of glucose

Question 19

Enzymes involved in glycogen synthesis (4)

Answer 19

• hexokinase
• phosphoglucomutase
• UDP- glycose phosphorylase
• Glycogen synthase

Question 20

MAIN enzymes in- glycogen breakdown & synthesis

Answer 20

Glycogen breakdown - glycogen phosphorylase

Synthesis - glycogen synthase

Question 21

what does insulin do?

Answer 21

(insulin is released when we have high blood sugar levels promotes glycogen synthesis in liver and muscle

Question 22

what does glucagon do?

Answer 22

released when we have low sugar levels = promotes glycogen breakdown in liver

Question 23

HOW does glucagon stimulate glycogen breakdown?

Answer 23

increases cAMP and PKA+ which stimulates conversion of glycogen phosphorylase kinase to glycogen phosphorylase kinase (p)
- stimulates a cascade to break down

Question 24

what are the key points of glucagon stimulated glycogen breakdown?

Answer 24

1. amplification - single glucagon molecule activates many glycogen phosphorylase molecule
2. Reverse covalent modifications - enzymes activated by phosphorylation amino acid residues.
3. Receptor mediates- single molecule glucagon activates many cAMP molecules and so on

Question 25

how does glucagon prevent glycogen synthesis?

Answer 25

Increases cAMP and PKA+ but coverts the active glycogen synthase into inactive form

Question 26

how is glycogen breakdown stimulated in active muscle (exercise)

Answer 26

adrenaline, AMP, Ca2+ ions
AMP binds to inactive glycogen phosphorylase and promotes formation of the active

Ca2+ levels increase in exercise which promotes glycogen phosphorylase kinase activity

Question 27

what is glycolysis?

Answer 27

regulated reaction that converts glucose into 2 pyruvate and 2 ATP

Question 28

if there is high ATP - is enzyme inhibited or activated?

Answer 28

activated as we want to change it into ATP

Question 29

what are the 3 key points of regulation in glycolysis?

Answer 29

1. phosphofructokinase
2. hexokinase
3. pyruvate kinase

Question 30

what is the most important enzyme in glycolysis?

Answer 30

phosphofructokinase - converts fructose-6-phosphate into fructose-1,6-bisphosphate

Question 31

what is phosphofructokinase regulated by?

Answer 31

1. ATP - activity is inhibited by ATP binding to an allosteric site as it lowers the affinity of it for fructose-6-phosphate
2. Fructose-2,6-bisphosphate - it is an activator of phosphofructokinase - binds to allosteric site and enhances the affinity of it for fructose-6-phosphate
3. Citrate - it enhances the inhibitory effect of ATP

Question 32

what is hexokinase regulated by?

Answer 32

glucose-6-phosphate. FEEDBACK INHIBITION - If phosphofructokinase is inhibited, glucose-6-phosphate levels rise and this feeds back into the pathway to prevent the unnecessary conversion of glucose to glucose-6-phosphate

Question 33

what is pyruvate kinase regulated by?

Answer 33

fructose-1,6-bisphosphate -