week 5

Question 1

What are the three main functions of calcium in the body?

Answer 1

Structural function (bones & teeth), neurotransmitter release, and muscle contraction.

Question 2

Structural function (bones & teeth), neurotransmitter release, and muscle contraction.

Answer 2

Free ionized calcium (47%), calcium bound to plasma proteins (46%), and non-ionized calcium salts (7%)

Question 3

What hormone is responsible for increasing calcium levels in the blood?

Answer 3

PTH

Question 4

What is the role of calcitonin in calcium homeostasis?

Answer 4

It lowers plasma calcium by inhibiting osteoclastic bone resorption.

Question 5

How is vitamin D activated in the body?

Answer 5

Through two hydroxylation steps—first in the liver to form 25-hydroxyvitamin D3, then in the kidney to form the active 1,25-dihydroxyvitamin D3 (calcitriol)

Question 6

What are the symptoms of hypercalcemia?

Answer 6

Kidney stones, depressed neuromuscular excitability, constipation, and cardiac arrhythmias.

Question 7

What are the common causes of hypocalcemia?

Answer 7

Vitamin D deficiency, hypoparathyroidism, renal failure, and magnesium deficiency.

Question 8

What are the three main hormones regulating calcium homeostasis?

Answer 8

What are the three main hormones regulating calcium homeostasis?

Question 9

How does PTH regulate calcium levels?

Answer 9

It increases bone resorption, enhances calcium reabsorption in the kidneys, and stimulates the production of calcitriol to promote calcium absorption in the intestines.

Question 10

What are the three main types of bone cells?

Answer 10

Osteoclasts (bone resorption), osteoblasts (bone formation), and osteocytes (mature bone cells).

Question 11

What is the main effect of calcitonin on bone?

Answer 11

It inhibits osteoclast activity, reducing bone resorption and lowering plasma calcium levels.

Question 12

How does phosphate contribute to the body’s function?

Answer 12

It plays a role in bone mineralization, buffering systems, DNA/RNA structure, cell membranes, and ATP production.

Question 13

What are common causes of hyperphosphatemia?

Answer 13

Renal failure, hyperparathyroidism, and excessive phosphate intake.

Question 14

What are the main roles of magnesium in the body?

Answer 14

Bone mineralization, enzyme activation, nerve impulse transmission, and muscle function.

Question 15

What condition is characterized by excessive osteoclastic activity leading to deformed bones?

Answer 15

Paget’s disease

Question 16

What biochemical markers indicate bone formation?

Answer 16

Serum alkaline phosphatase (ALP), bone-specific alkaline phosphatase (BAP), and osteocalcin.

Question 17

What is the function of the calcium-sensing receptor in the parathyroid gland?

Answer 17

It detects changes in plasma calcium levels and regulates PTH secretion accordingly.

Question 18

How does PTH affect phosphate levels?

Answer 18

It decreases phosphate reabsorption in the kidneys, leading to increased phosphate excretion (phosphaturia).

Question 19

What enzyme is responsible for converting 25(OH)D₃ to active 1,25(OH)₂D₃ in the kidneys?

Answer 19

1α-hydroxylase.

Question 20

What is the major cause of secondary hyperparathyroidism?

Answer 20

Chronic kidney disease or vitamin D deficiency

Question 21

What condition is characterized by vitamin D deficiency leading to defective bone mineralization?

Answer 21

Rickets in children and osteomalacia in adults.

Question 22

What role does magnesium play in calcium homeostasis?

Answer 22

It is necessary for PTH secretion and calcium transport in the body.

Question 23

What hormone inhibits osteoclast activity and reduces bone resorption?

Answer 23

Calcitonin

Question 24

How does chronic kidney disease affect phosphate levels?

Answer 24

It reduces phosphate excretion, leading to hyperphosphatemia.

Question 25

What is the recommended treatment for severe hypercalcemia (>3.5 mmol/L)?

Answer 25

Dialysis or parathyroidectomy.

Question 26

What is the main effect of vitamin D on the intestines?

Answer 26

It increases calcium and phosphate absorption.

Question 27

What condition is caused by excessive bone turnover with disorganized bone formation?

Answer 27

Paget's disease

Question 28

What is the effect of vitamin D supplementation in elderly individuals?

Answer 28

It reduces the risk of fractures and bone loss

Question 29

What is the definition of a lipid?

Answer 29

Lipids are organic molecules that are insoluble in water and function as energy stores, membrane components, steroid hormones, and fat-soluble vitamins.

Question 30

What are the four main classes of lipids?

Answer 30

Triglycerides, phospholipids, cholesterol, and fatty acids.

Question 31

What is the primary role of triglycerides?

Answer 31

They serve as the main dietary fat, an energy store, and a component of cell membranes.

Question 32

What is cholesterol used for in the body?

Answer 32

It is important for membrane structure and fluidity, is a precursor of steroid hormones (e.g., cortisol, estrogen, testosterone), and is involved in the synthesis of vitamin D and bile acids.

Question 33

Why do lipids need transport systems in the body?

Answer 33

Lipids are not water-soluble, so they must be transported in association with proteins, mainly through lipoproteins.

Question 34

What is the primary function of LDL?

Answer 34

LDL is the main carrier of cholesterol and delivers it to tissues. Excess LDL contributes to atherosclerosis.

Question 35

What is the role of HDL in lipid metabolism?

Answer 35

HDL helps remove cholesterol from tissues and transports it to the liver for excretion, playing a protective role against cardiovascular disease.

Question 36

What is hyperlipidemia?

Answer 36

A condition characterized by elevated levels of lipids (cholesterol or triglycerides) in the blood, which can increase the risk of cardiovascular disease.

Question 37

What is the primary treatment approach for hyperlipidemia?

Answer 37

Lifestyle changes (healthy diet, exercise, weight management, quitting smoking) and medications like statins or fibrates if necessary.

Question 38

How do statins work?

Answer 38

Statins inhibit HMG-CoA reductase, reducing cholesterol synthesis, increasing LDL receptor expression, and lowering LDL levels.

Question 39

What is the relationship between elevated plasma lipids and cardiovascular disease (CVD)?

Answer 39

Elevated plasma lipids contribute to atherosclerosis

Question 40

What are the major apoproteins, and what are their roles?

Answer 40

ApoA: Found in HDL, helps remove cholesterol from tissues. ApoB: Found in LDL, VLDL, and chylomicrons, aids in lipid transport. ApoC: Regulates lipoprotein lipase activity. ApoE: Important for the clearance of lipoprotein remnants by the liver.

Question 41

What is the function of apoproteins in lipoproteins?

Answer 41

Apoproteins provide structural support and regulate lipoprotein metabolism by interacting with enzymes and receptors.

Question 42

What is Lecithin-Cholesterol Acyltransferase (LCAT), and what does it do?

Answer 42

LCAT is an enzyme that converts cholesterol into cholesterol esters, facilitating cholesterol transport by HDL.

Question 43

How does LDL contribute to atherosclerosis?

Answer 43

LDL can penetrate blood vessel walls and be taken up by macrophages, forming foam cells that contribute to plaque formation.

Question 44

Hypercholesterolemia (FH)?

Answer 44

A genetic disorder characterized by high cholesterol levels due to defective or absent LDL receptors, increasing CHD risk.

Question 45

How does Familial Hypertriglyceridemia differ from FH?

Answer 45

It is characterized by high triglyceride levels due to excess VLDL production rather than defective LDL receptors.

Question 46

What are fibrates, and how do they work?

Answer 46

Fibrates stimulate lipoprotein lipase, reducing triglycerides and increasing HDL levels