BIOC Lecture 3: Carbohydrate

Question 1

What is the fed state?

Answer 1

the digestive system is actively breaking down fats, AA’s and sugars

Question 2

What is happening to blood glucose and insulin during the fed state?

Answer 2

Release of insulin from pancreatic beta cells, interaction of insulin with receptors

Question 3

What are insulin dependent tissues?

Answer 3

Only break down glucose when insulin is present

Question 4

What are examples of insulin dependent tissues?

Answer 4

Skeletal muscle, adipose tissue, cardiac muscle

Question 5

What are insulin independent tissues?

Answer 5

Break down glucose whether or not insulin is present

Question 6

What are examples of insulin independent tissues?

Answer 6

Brain and liver

Question 7

What is the fate of glucose in the fed state?

Answer 7

Glycogenesis and storage or glycolysis and utilisation

Question 8

What happens after the direct effects of a meal have diminished?

Answer 8

Decline in liver glycogen and blood glucose maintained

Question 9

What is the key hormone of the fasted state?

Answer 9

Glucagon

Question 10

What does glucagon do during the fasted state?

Answer 10

Synthesised and released from pancreatic islet alpha cells

Question 11

What is gluconeogenesis?

Answer 11

the process of making glucose, AA’s play a role

Question 12

Once we have exhausted our stores of glucose, how do we maintain our levels?

Answer 12

Primary precursors are amino acids, lactate is also an important precursor

Question 13

What is the gut lumen?

Answer 13

Where the food, many bacteria and digestive enzymes are

Question 14

How does the gut lumen have a high surface area?

Answer 14

Due to the folding of villi and microvilli

Question 15

What is absorption mostly through?

Answer 15

Through cells (transcellular)

Question 16

What is transcellular absorption?

Answer 16

substances move through the cells of the intestinal epithelium to be absorbed into the bloodstream

Question 17

Where does most of the blood from the gut go?

Answer 17

to the liver

Question 18

Where do fats go?

Answer 18

To the lymphatic system

Question 19

What does digesting food cost?

Answer 19

Energy

Question 20

What are the three main sources of energy?

Answer 20

proteins, CHO, fats

Question 21

Why are amino acids required in our diet?

Answer 21

We rely on other organisms to make some AA’s and also to get bioavailable nitrogen

Question 22

What can you use pyruvate to make?

Answer 22

AA’s and glucose

Question 23

What can fat be used to make?

Answer 23

fatty acids, pyruvate and acetyl CoA but not glucose

Question 24

What can all three PRO, CHO and FAT be converted into?

Answer 24

Acetyl CoA

Question 25

What are common pathways for most ATP generation?

Answer 25

Glycolysis, CAC and oxidative phosphorylation

Question 26

What is resting metabolism mostly fueled by?

Answer 26

fatty acids

Question 27

What is the primary driver of glycolysis (and glycogenesis)?

Answer 27

An increase in glucose concentration

Question 28

What is glycogen synthase?

Answer 28

Formation of glycogen

Question 29

What is glycogen phosphorylase?

Answer 29

breakdown

Question 30

Why can't RBC do oxidative metabolism?

Answer 30

They don't have mitochondria

Question 31

Even at rest, how will you still have some lactate in your blood?

Answer 31

From RBC's

Question 32

How is glycogen synthesised in the liver?

Answer 32

Glucose is converted into Glucose-6-phosphate (G6P), then G6P is converted into Glut-1-Phosphate then glycogen

Question 33

How is UDP-glucose involved in liver glycogen synthesis?

Answer 33

it serves as the immediate donor of glucose residues for glycogen chain elongation

Question 34

Muscle vs Liver Glycogen synthesis

Answer 34

Similar, in muscle G6P is not present and therefore glucose cannot be released directly to blood

Question 35

What is glycogenin?

Answer 35

A 'kernel' molecule made from protein and carbohydrate

Question 36

What are the two stages of glycogen synthesis?

Answer 36

Chain extension and branching

Question 37

What do branches increase the rate of?

Answer 37

The rate at which glucose can be added and removed - when we are well fed there will be a large and highly branched molecule

Question 38

What are the two stages of glycogen synthesis?

Answer 38

Chain shortening and debranching

Question 39

What is gluconeogenesis closely linked with?

Answer 39

Glycolysis

Question 40

What does gluconeogenesis start with?

Answer 40

Pyruvate

Question 41

What is the first stage of gluconeogenesis?

Answer 41

Pyruvate to PEP

Question 42

What is PEP converted into?

Answer 42

F1,6BP

Question 43

What is F1,6BP converted into?

Answer 43

F6P

Question 44

What is F6P converted into?

Answer 44

G6P

Question 45

What is G6P converted into?

Answer 45

Glucose

Question 46

What are the substrates for the gluconeogenesis pathway?

Answer 46

Amino and keto acids

Question 47

What does the use of AA's require the disposal of?

Answer 47

Amino groups (NH3)

Question 48

What is the primary site of the synthesis of glucose from gluconeogenesis?

Answer 48

The liver