L.1 CHO metabolism

Question 2

What are carbohydrates composed of?

Answer 2

Carbon, hydrogen, and oxygen.

Question 3

What is the primary energy source for cell processes derived from carbohydrates?

Answer 3

Glucose.

Question 4

Name two sources of carbohydrate energy.

Answer 4

• Dietary sources (vegetables, fruits, grains, dairy)
• Endogenous sources (glycogen in liver and skeletal muscle).

Question 5

What is hypoglycaemia?

Answer 5

Low blood glucose (under 4mmol/L).

Question 6

What is hyperglycaemia?

Answer 6

High blood glucose (over 7mmol/L).

Question 7

What factors control plasma glucose concentrations?

Answer 7

• Glucose entering cells from plasma
• Glucose leaving cells to enter plasma.

Question 8

List the hormones involved in glucose metabolism.

Answer 8

• Insulin
• Glucagon
• Growth Hormone
• Glucocorticoids
• Adrenaline.

Question 9

What happens to plasma glucose levels following food intake?

Answer 9

Plasma glucose levels increase.

Question 10

What is the role of insulin after food intake?

Answer 10

Insulin is released from beta-cells in the pancreas and promotes uptake of glucose into cells.

Question 11

What triggers glucagon release from the pancreas?

Answer 11

Decreases in plasma glucose concentration.

Question 12

Fill in the blank: The energy stored in the body from carbohydrates is primarily in the form of _______.

Answer 12

Glycogen.

Question 13

What is the state of metabolism that builds up glycogen stores?

Answer 13

Anabolic

Occurs post-prandial and is controlled by insulin.

Question 14

What is the state of metabolism that breaks down glycogen stores?

Answer 14

Catabolic

Occurs following exercise and is controlled by glucagon, cortisol, adrenaline, and growth hormone.

Question 15

Which hormone primarily controls the anabolic state of metabolism?

Answer 15

Insulin

Question 16

Which hormones are involved in controlling the catabolic state of metabolism?

Answer 16

• Glucagon
• Cortisol
• Adrenaline
• Growth hormone

Question 17

What are GLUTs?

Answer 17

Proteins that help move glucose across cell membranes.

Question 18

Why can’t glucose diffuse through the cell membrane?

Answer 18

Because it is a large, polar molecule.

Question 19

Where is Glut1 found?

Answer 19

In blood and blood-brain barrier (insulin-independent).

Question 20

Where is Glut2 found?

Answer 20

In liver, pancreas, and small intestine (insulin-independent).

Question 21

Where is Glut3 found?

Answer 21

In brain, neurons, and sperm (insulin-independent).

Question 22

Where is Glut4 found?

Answer 22

In skeletal muscle, adipose tissue, and heart (insulin-dependent).

Question 23

What does activation of the insulin receptor (IR) promote?

Answer 23

Incorporation of the GLUT transporter into the cellular membrane

Question 24

What are the two types of glands?

Answer 24

• Endocrine: chemicals delivered into bloodstream
• Exocrine: secrete chemicals into a ductal system to an epithelial surface

Question 25

Where is the pancreas located?

Answer 25

In the abdomen

Question 26

What type of gland is the pancreas?

Answer 26

* Exocrine: pancreatic juices excreted through ducts into gastrointestinal tract * Endocrine: Islet of Langerhans

Question 27

What percentage of the pancreas by weight do the Islet of Langerhans represent?

Answer 27

1-2%

Question 28

What do α-cells in the Islet of Langerhans secrete?

Answer 28

Glucagon

Question 29

What do β-cells in the Islet of Langerhans secrete?

Answer 29

Insulin

Question 30

What do δ-cells in the Islet of Langerhans secrete?

Answer 30

Somatostatin

Question 31

What is insulin classified as?

Answer 31

Polypeptide hormone

Question 32

How many amino acids are in insulin, and in what form is it initially synthesized?

Answer 32

51 amino acids synthesized as proinsulin

Question 33

What is the relationship between insulin and C-peptide?

Answer 33

Insulin is attached to C-peptide

Question 34

What happens to C-peptide during insulin processing?

Answer 34

C-peptide is cleaved in the endoplasmic reticulum

Question 35

What percentage of the body's total energy does the brain consume?

Answer 35

≈ 20%

Question 36

What percentage of body weight does the brain represent?

Answer 36

Around 2%

Question 37

What is the primary fuel of the brain?

Answer 37

Glucose

Question 38

Why can't the brain store glucose like the liver and muscles?

Answer 38

It depends on a constant supply from the blood

Question 39

Why can't fatty acids serve as a primary fuel for the brain?

Answer 39

They are too large and cannot cross the blood-brain barrier (BBB) easily

Question 40

What is the issue with using other fuel pathways (like breaking down fats or proteins) for the brain?

Answer 40

They are too slow to meet the brain’s fast energy needs

Question 41

When can ketones be used by the brain?

Answer 41

During prolonged fasting or starvation when glucose is very low

Question 42

What is GLUT1 and where is it found?

Answer 42

GLUT1 is found in the blood-brain barrier and helps move glucose from the blood into the brain tissue

Question 43

What is GLUT3?

Answer 43

GLUT3 is a glucose transporter found in neurons that has a very high affinity for glucose.

Question 44

What is the role of GLUT3 in neurons?

Answer 44

GLUT3 allows neurons to efficiently take up glucose even when blood sugar levels are low.

Question 45

What is glycogenesis?

Answer 45

Glycogenesis is the storage of glycogen in the liver.

Question 46

What is glycogenolysis?

Answer 46

Glycogenolysis is the breakdown of glycogen in the liver.

Question 47

What is gluconeogenesis?

Answer 47

Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources.

Question 48

What are examples of non-carbohydrate sources used in gluconeogenesis?

Answer 48

Examples include lactate, glycerol, and amino acids.

Question 49

What is the kidney's role in glucose metabolism?

Answer 49

The kidney contributes to gluconeogenesis, glucose reabsorption, and glucose excretion.

Question 50

During prolonged fasting, what percentage of gluconeogenesis can the kidney contribute?

Answer 50

The kidney can contribute up to approximately 40% of gluconeogenesis.

Question 51

What happens to glucose above the renal threshold?

Answer 51

Glucose is excreted by the kidneys.