Lipids

Question 1

B-oxidation

Answer 1

Metabolic pathway that occurs in the mitochondria of cells and liver cells
Involved in the breakdown of fatty acids to generate Acetyl-coa
Acetyl-coa undergoes a series of 4 enzymatic reactions, which results in the removal of 2 carbons.
Involves oxidation, hydration, oxidation & thiolysis
Acetyl-coa produced enters the citric acid cycle, where its oxidised to generate ATP

Question 2

Exercise to maximise lipid metabolism

Answer 2

Low-moderate intensity endurance exercise
Long distance running/swimming, relies on aerobic metabolism where fatty acids are the predominant fuel source
Body uses stored fat as a source of energy

Question 3

High density lipoproteins (HDL)

Answer 3

High level of protein & phospholipids
Transport cholesterol back to the liver for excretion in a process known as reverse cholesterol transport
Helps remove excess cholesterol from tissue’s & arteries, reducing risk of CVD

Question 4

Ketone body formation

Answer 4

Also known as ketogenesis
Occurs in the liver under conditions where there is low carbohydrate availability or fasting
Fatty acids are oxidises via B-oxidation to produce acetyl coa & catalysed by thiolase

Question 5

Low-density lipoproteins (LDL)

Answer 5

Rice in cholesterol, with small amounts of triglycerides & phospholipids
Transport cholesterol from the liver to peripheral tissues, used for membrane synthesis & hormone production
Delivers cholesterol to cells throughout body
Elevated levels of LDL are a major risk of CVD, as it accumulates in the walls of arteries

Question 6

Lipoproteins - Chylomicrons

Answer 6

Longest & least dense
Composed of triglycerides & dietary cholesterol
Formed in the intestine following absorption of lipids in the small intestine
Transport dietary lipids from the intestine to various tissues incl muscle & liver for storage
Also transport fat soluble vitamins

Question 7

Explain the effect of diabetes on ketone body formation

Answer 7

-Insulin levels are insufficient, and extrahepatic synthesis.
Therefore malonyl-coa cannot be formed.
Malonyl-coa normally inhibits carnitine acetyltransferase 1
- excess B-oxidation of fatty acids results in ketone body formation. High levels of ketone bodies lead to diabetic ketoacidiosis.