CV System Biochem 1

Question 1

In carbohydrate metabolism in the heart, what is the key regulatory enzyme that catalyzes the 1st committed step (i.e. the phosphorylation of fructose 6-phosphate to fructose 1,6-bisphosphate) in the glycolytic pathway?

Answer 1

Phosphofructokinase 1

Question 2

From what source is NAD+ derived from?

Answer 2

Niacin. NAD stands for nicotinamide adenine dinucleotide.

Question 3

What is the relationship between hexokinase and glucokinase?

Answer 3

They are isozymes. Isozymes are enzymes with the same function but different chemical structures.

Question 4

What transporters bring glucose into cardiac cells?

Answer 4

GLUT 1 and GLUT4. These are the 2 main glucose transports for the heart specifically.

Question 5

What mechanism maintains a relatively constant ATP pool in the heart mitochondria?

Answer 5

Phosphocreatine shuttle. This shuttle is the intracellular energy shuttle that transports phosphates from the mitochondria.

Question 6

Which apolipoproteins (i.e. A, B, or C) are associated with which diseases?

Answer 6

Apo-A-V with hypertriglyceridemia

Apo-B100 with hypobetalipoproteinemia

Apo-C-II with hyperchylomicronemia

Apo-C-III with hypertriglyceridemia

Question 7

What are the 3 major substrates for cardiac metabolism?

Answer 7

Fatty acids

Glucose

Glycogen breakdown

Glucose and glycogen are used in glycolysis. Fatty acids are used in fatty acid beta oxidation. Both pathways produce NADH which the electron transport chain then uses to make ATP

Question 8

What are the 3 minor substrates for cardiac metabolism?

Answer 8

Lactic acid

Ketones

Intramuscular triglycerides

These 3 substrates can all create Acetyl CoA (which enter the TCA cycle and oxidation phosphorylation to make ATP).

Question 9

Insulin and myocardial ischemia cause what?

Answer 9

An up regulation of GLUT4 transporters. Insulin signals glucose uptake by binding to insulin membrane receptors that causes a cascade effect. This eventually leads to GLUT4 being expressed on the plasma membrane.

Question 10

What is the major limitation of energy metabolism by myocardium?

Answer 10

Coronary blood flow delivering oxygen to the myocardium

Question 11

What 2 factors determine oxygen consumption by myocardium?

Answer 11

(1) Wall tension in the heart that must be overcome e.g. during isovolumic contraction

(2) Isotonic contraction to eject the blood

Question 12

Does the heart generate ATP from aerobic or anaerobic means?

Answer 12

Both. Cardiac tissue usually relies on aerobic respiration. However, during times of insufficient oxygen, the heart can also utilize anaerobic respiration. 98% of ATP is derived from oxidative means

Question 13

ATP is used in the heart for what?

Answer 13

60-70% of ATP is used for contraction and 40% is used for ion pumps

Question 14

Why would hypophosphatemia result in muscle weakness and impaired cardiac function?

Answer 14

Without a proper supply of both ADP and phosphate, then the Krebs Cycle cannot produce ATP

Question 15

Besides raising LDL, triglycerides, and lipoprotein-a, what other affects do trans-fatty acids have on the cardiovascular system?

Answer 15

They promote inflammation, endothelial dysfunction, insulin resistance, visceral adiposity, and arrhythmias

Question 16

Which minerals are associated with lowering blood pressure?

Answer 16

Magnesium, calcium, and potassium. These minerals help vasodilate to lower blood pressure.

Question 17

B vitamin deficiency is associated with what cardiovascular disease?

Answer 17

Cardiomyopathy

Question 18

What polyphenol is associated with lowering blood pressure and has anti-oxidant, anti-platelet, and anti-inflammatory properties?

Answer 18

Flavonoids. They have been shown to decrease reactive oxygen species.