Fat Metabolism Flashcards
what are lipids ? (4 points)
- includes fats and oils
- composed predominantly (but not exclusively) of Carbon, Hydrogen and Oxygen atoms
- atoms are linked by non-polar covalent bonds
- lipids are non-polar and have a very low solubility in water
what are the 4 sub-classes of lipids ?
- fatty acids
- triglycerides
- phospholipids
- steroids
state 3 reasons to why fats are important
- energy storage (triglycerides –> adipocytes)
- membrane structure (phospholipids)
- hormones and signalling compounds (steroids)
what, in essence, are fatty acids ?
a fatty acid is a carboxyl group bound to a hydrocarbon
what is the difference between cis and trans fats ?
- cis double bond = both H in same orientation (side) of the bound carbon atoms
- trans double bond = H atoms are on opposite sides if the bound carbon atoms
‘triglycerides are stored in adipocytes’ - state 3 facts to describe this statement
- food intake: adipocytes synthesise and store triglycerides
- non-food intake: adipocytes release fatty acids and glycerol into the blood
- used by other cells to provide energy for ATP synthesis
state 3 facts about steroids
- four interconnected rings of carbon atoms
- insoluble in water
- examples: cholesterol, steroid hormones
state, and explain, the 3 places where fatty acids come from
- adipose tissue: fat storage cells can release fats when needed
- de novo synthesis: made from carbohydrates and some amino acids
- diet: about 30-40% of calories in the diet come from fats
what does the pancreas secrete for lipid digestion ?
the pancreas secretes digestive enzymes (including lipases) as well as bicarbonate
what does the liver secrete for lipid digestion ?
the liver secretes bile (detergent –> emulsifies lipids)
what are the following for fats in the body:
1) total bontent (kg)
2) energy content per gram
3) total body energy content (kcal)
4) percentage of total energy content
- 15.6 Kg
- 9 kcal / gram
- 140,000 kcal
- 78%
what are the following for proteins in the body:
1) total bontent (kg)
2) energy content per gram
3) total body energy content (kcal)
4) percentage of total energy content
- 9.5 Kg
- 4 kcal / gram
- 38,000 kcal
- 21%
what are the following for carbohydrates in the body:
1) total bontent (kg)
2) energy content per gram
3) total body energy content (kcal)
4) percentage of total energy content
- 0.5 Kg
- 4 kcal / gram
- 2000 kcal
- 1%
state the 3 steps of fat metabolism
- lipid mobilisation of adipose tissue
- activation and transport
- fatty acid oxidation
explain, in brief, the first step of fat metabolism (2 points)
- triglycerides are degraded to fatty acids and glycerol
2. released from adipose tissue and transited to energy releasing tissue
explain, in brief, the first second of fat metabolism
in energy requiring tissue, fatty acids are activated and transported into the mitochondria for degradation
explain, in brief, the first third of fat metabolism
fatty acid oxidation produces Acetyl CoA, which is then processed into the CTA
briefly explain the reaction, and state the enzyme, of the first reaction of fat metabolism
1) fatty acid + CoA + ATP —> Acetyl CoA + AMP + PPi
2) Acetyl CoA synthetase
briefly explain the reaction, and state the enzyme, of the second reaction of fat metabolism
1) carnitine + Acyl CoA —-> acylcarnitine + CoA
2) carnitine acyltransferase
briefly explain the reaction, and state the enzyme, of the third reaction of fat metabolism
1) Acyl CoA + E-FAD —-> Trans-Δ²-enoyl CoA + E-FADH2
2) Acetyl CoA dehydrogenases
briefly explain the reaction, and state the enzyme, of the fourth reaction of fat metabolism
1) trans-Δ-enoyl CoA + H2O —-> L-3-hydroxyacyl CoA
2) enol CoA hydratase
briefly explain the reaction, and state the enzyme, of the fifth reaction of fat metabolism
1) L-3-hydroxyacyl CoA + NAD+ —-> 3 ketoacyl CoA + NADH + H+
2) L-3-dehydroxyacyl CoA dehydrogenase
briefly explain the reaction, and state the enzyme, of the sixth reaction of fat metabolism
1) ketoacyl CoA + CoA —-> Acetyl CoA + Acetyl CoA (shortened by 2C)
2) B-ketothiolase
what are ketone bodies (2 points)
- energy rich
2. water soluble
state the cellular location of: 1) fat synthesis, 2) fat breakdown
1) cytoplasmic
2) mitochondria
state the coenzyme(s) of: 1) fat synthesis, 2) fat breakdown
1) NADP+/NADPH
2) NAD+/NADH, FAD/FADH
state the enzyme characteristics of: 1) fat synthesis, 2) fat emulsification
1) a single polypeptide chain (fatty acid synthase)
2) not covalently linked
state what the intermediaries are bound to in: 1) fat synthesis, 2) fat emulsification
1) acetyl carrier protein (ACP)
2) Acetyl CoA
state the names of the 3 steps of fatty acid biosynthesis (in order)
- carboxylation of Acetyl CoA and linkage to ACP
- elongation
- removal of ACP
