Biochemistry Flashcards
Fat is essential for the absorption of which vitamins?
Vitamins A,D,E and K
What is the main storage form of lipids?
Triglycerides
Polyunsaturated fats are essential fatty acids - what does this mean?
They have more than one double bond and can’t be synthesised by the body, therefore meaning they must be obtained from the diet
What is a chylomicron? What is the purpose of a chylomicron?
- lipoprotein particle
- triglycerides coated with - phospholipids, cholesterol, and proteins.
- They are important for the transport of fats around the body
The breakdown of lipids is referred to as ‘lipolysis’. Outline this process
*Fatty acids are converted into CoA derivatives (e.g Fatty Acyl CoA) - CYTOPLASM
*The carnitine shuttle transfers Acyl CoA into the mitochondrial matrix
*B oxidation occurs -4 steps-
Acyl CoA goes in, and the products for each cycle = 1 acetyl CoA, 1 FADH2, 1 NADH and H+ and Fattyl acyl CoA (shortened by 2C atoms)
Under what conditions are ketone bodies generated and where does this occur?
Fasting conditions
Liver mitochondria
By what process are ketone bodies formed?
Ketone bodies are formed from acetyl CoA as a by- product of B-oxidation
Although ketone bodies can cause problems if they accumulate, they are still important - outline some of their uses in the body
Energy metabolism for the brain, heart muscle and renal cortex
What can high levels of ketone bodies cause?
Fruity breath
Severe acidosis which causes impaired tissue function
What is meant by lipogenesis and where in the body does this occur?
The synthesis of lipids - occurs mainly in the liver and usually occurs when there has been excess energy intake
What substance is the major fatty acid precursor used to form all fatty acids?
Malonyl- CoA
Acetyl CoA is converted to Malonyl CoA which is the major precursor for fatty acid synthesis. Which enzyme catalyses this conversion?
Acetyl CoA Carboxylase
Describe the process of lipogenesis
Lipogenesis is the synthesis of lipids.
Firstly Acetyl CoA which is produced in the mitochondrial matrix by B oxidation must be transported to the cytoplasm. Citrate is used to do this. Once in the cytoplasm, Acetyl is converted to Malonyl CoA with he help of the enzyme: acetyl-CoA carboxylase. Malonyl CoA then transfers 2 C atoms to the acetyl CoA to form a fatty acid chain. This is a reductive process for which NADPH is the electron donor.
Lipogenesis will only occur when there is plenty energy available. To control this process, Acetyl CoA can be unregulated or down-regulated to determine whether the process proceeds and fatty acids are synthesised. Which substances affect Acetyl CoA?
UPREGULATION Insulin citrate DOWNREGULATION Glucagon Adrenaline Palmitoyl CoA
Triglycerides can be produced by esterifying fatty acids on to glycerol. Production of triglycerides only occurs in the fed state, what substance must be present for the process to proceed?
G-3-P from glucose, indicating a fed state
What does the breakdown of amino acids produce? Which of these products can be very toxic to the body if it accumulates?
Ammonia
Ammonium ions - toxic at high concentrations
The synthesis of urea occurs in 3 main steps. Where in the body does this occur?
Occurs in the liver
What are the 3 main steps in the synthesis of urea?
Transamination
Deamination
Urea cycle
What is maple syrup disease?
An inherited disorder in which the degradation of valine, isoleucine and leucine are blocked - this can cause mental and physical disorders but can be controlled by diet
What is phenylketonuria?
An inherited disorder in which degradation of phenylalanine is blocked, causing it to accumulate in body fluids.
Leads to severe mental retardation if untreated. It can however be controlled/ prevented by a low phenylalanine diet.
What is alcaptonuria?
An inherited disorder in which degradation of phenylalanine and tyrosine is blocked
What is glycogenesis?
The synthesis of glycogen from glucose
What enzymes are involved in glycogenesis?
Hexokinase Phosphoglucomutase UDP-glucose Phosphorylase Glycogen synthase
What is glycogenin and what is its role?
Glycogenin is the catalyst at the centre of the glycogen polymer which is the starting point to allow the glycogen polymer to be extended
What is glycogenolysis?
The breakdown of glycogen to produce glucose
What enzymes are involved in glycogenolysis?
Glycogen phosphorylase
glucose-6-phosphatase
phosphoclucomutase
What is gluconeogenesis?
The synthesis of glucose from non-carbohydrate precursors
What is glycolysis?
The breakdown of glucose
