BIOC Lecture 3: Carbohydrate Flashcards

1
Q

What is the fed state?

A

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

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2
Q

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

A

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

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3
Q

What are insulin dependent tissues?

A

Only break down glucose when insulin is present

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4
Q

What are examples of insulin dependent tissues?

A

Skeletal muscle, adipose tissue, cardiac muscle

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5
Q

What are insulin independent tissues?

A

Break down glucose whether or not insulin is present

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6
Q

What are examples of insulin independent tissues?

A

Brain and liver

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7
Q

What is the fate of glucose in the fed state?

A

Glycogenesis and storage or glycolysis and utilisation

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8
Q

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

A

Decline in liver glycogen and blood glucose maintained

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9
Q

What is the key hormone of the fasted state?

A

Glucagon

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10
Q

What does glucagon do during the fasted state?

A

Synthesised and released from pancreatic islet alpha cells

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11
Q

What is gluconeogenesis?

A

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

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12
Q

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

A

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

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13
Q

What is the gut lumen?

A

Where the food, many bacteria and digestive enzymes are

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14
Q

How does the gut lumen have a high surface area?

A

Due to the folding of villi and microvilli

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15
Q

What is absorption mostly through?

A

Through cells (transcellular)

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16
Q

What is transcellular absorption?

A

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

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17
Q

Where does most of the blood from the gut go?

A

to the liver

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18
Q

Where do fats go?

A

To the lymphatic system

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19
Q

What does digesting food cost?

A

Energy

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20
Q

What are the three main sources of energy?

A

proteins, CHO, fats

21
Q

Why are amino acids required in our diet?

A

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

22
Q

What can you use pyruvate to make?

A

AA’s and glucose

23
Q

What can fat be used to make?

A

fatty acids, pyruvate and acetyl CoA but not glucose

24
Q

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

A

Acetyl CoA

25
Q

What are common pathways for most ATP generation?

A

Glycolysis, CAC and oxidative phosphorylation

26
Q

What is resting metabolism mostly fueled by?

A

fatty acids

27
Q

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

A

An increase in glucose concentration

28
Q

What is glycogen synthase?

A

Formation of glycogen

29
Q

What is glycogen phosphorylase?

A

breakdown

30
Q

Why can’t RBC do oxidative metabolism?

A

They don’t have mitochondria

31
Q

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

A

From RBC’s

32
Q

How is glycogen synthesised in the liver?

A

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

33
Q

How is UDP-glucose involved in liver glycogen synthesis?

A

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

34
Q

Muscle vs Liver Glycogen synthesis

A

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

35
Q

What is glycogenin?

A

A ‘kernel’ molecule made from protein and carbohydrate

36
Q

What are the two stages of glycogen synthesis?

A

Chain extension and branching

37
Q

What do branches increase the rate of?

A

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

38
Q

What are the two stages of glycogen synthesis?

A

Chain shortening and debranching

39
Q

What is gluconeogenesis closely linked with?

A

Glycolysis

40
Q

What does gluconeogenesis start with?

A

Pyruvate

41
Q

What is the first stage of gluconeogenesis?

A

Pyruvate to PEP

42
Q

What is PEP converted into?

A

F1,6BP

43
Q

What is F1,6BP converted into?

A

F6P

44
Q

What is F6P converted into?

A

G6P

45
Q

What is G6P converted into?

A

Glucose

46
Q

What are the substrates for the gluconeogenesis pathway?

A

Amino and keto acids

47
Q

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

A

Amino groups (NH3)

48
Q

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

A

The liver