Nutrition

Question 1

Define obesity

Answer 1

An obese individual is someone with a BMI over 30

Question 2

What are the six essential chemical nutrients for a healthy diet?

Answer 2

Water Essential fatty acids Essential amino acids Fibre Carbohydrates Vitamins and minerals

Question 3

What are the three clinical forms of acute malnutition?

Answer 3

Marasmus Kwashiorkor Marasmatic kwashiorkor

Question 4

Describe the causes and features of marasmus

Answer 4

Characterised by severe wasting of fat and muscle which the body metabolises as an energy source. Caused by a rapid deterioration in nutritional status. Complications include heart failure, reduced liver, renal function, recurrent infections. Presents as skin-and-bones appearance,

Question 5

Define basal metabolic rate

Answer 5

The energy required to perform fundamental metabolic processes such as breathing, transport, cellular turnover etc

Question 6

Define factors which affect BMR

Answer 6

Age, sex, weight, trauma/disease

Question 7

Give three examples of conditional nutrients

Answer 7

Conditional nutrients are nutrients which may be required from the diet if the body is unable to produce sufficient levels on it’s own. Examples include Carnitine, Inositol, Folate

Question 8

Define the form and function of vitamins

Answer 8

Vitamins are organic compounds which are required by the body in limited amounts. Vitamins have diverse biochemical functions which cannot be synthesized by the body in sufficient amounts. Essential for normal growth and development

Question 9

what is the dietary fate or protein, carb, fat

Answer 9

Proteins are broken down into amino acids, carbohydrates into monosaccharides, fats into fatty acids and glycerols.

Question 9

What are the factors that contribute to obesity

Answer 9

Age Sex Diet Genetics Mental health Physical activity

Question 10

Name three uses of essential fatty acids

Answer 10

Required for membrane fluidity, fat metabolism and transport and synthesis of prostaglandins.

Question 11

Name the 6 essential nutrients required in the diet

Answer 11

Water Calories (carbohydrates and fat) Essential amino acids Essential fatty acids Vitamins and Minerals Fibre

Question 12

Give two examples of micronutrient deficiencies

Answer 12

Vitamin A deficiency: Vitamin A (retinol) produces retinol required for the formation of rhodopsin, also plays a role in normal growth and differentiation of cells. Deficiency is the most common cause of preventable blindness in children.

Iron defiency: Important co-factor, forms part of the protoporphryn ring of haeme, binds oxygen in Hb. Deficiency causes anaemia

Vitamin C: Important co-factor for procollagenase enzymes. Deficiency results in a lack of hydroxylation of proline and lysine, leading to poor cross-linking and instable collagen fibres. Scurvy.

Question 13

Give an example of carbohydrate intolerance

Answer 13

Lactose intolerance: Lactose broken down into glucose and galactose by lactase enzyme. Lactose intolerance is caused by the inability to sufficiently digest lactose and so it is malabsorbed. In individuals with a deficient lactase enzyme, lactose is not broken down, causing diarrohoea, bloating and flatulence. In individuals with “true” lactose intolerance have a normal lactase enzyme but galactose is not broken down. Build up in the body leads to liver impairment and cataracts. Neonates fail to thrive.

Fructose intolerance: Fructose normally enters the glycolysis pathway in cells by being phosphorylated to fructose-6P by hexokinase. When glucose concentrations are high it is metabolised in the liver by fructokinase to Fructose-1P then phophofructoaldolase to DHAP and glyceraldehyde, In fructosurea lack of fructokinase means there is no fructose uptake and it is lost in the urine. If the phophofructoaldolase enzyme is absent then F-1P accumulates in the liver and lowers the phosphate supply. This shuts off glycolysis and leads to tissue damage

Question 14

What is the main function of cholesterol?

Answer 14

Cholesterol is used for the biosynthesis of steroid hormones.

Question 15

What are the five classes of lipoprotein?

Answer 15

chylomicron

vldl

idl

ldl

hdl

Question 16

What are chylomicrons?

Answer 16

The packaged form of dietary lipids. They contain triacylglycerides,cholesterol and apoproteins.

Chylomicrons provide the main mechanism for transporting the digestion products of dietary fat the liver and peripheral tissues. Apoproteins binds to specific receptors in adipose tissue, skeletal muscle and the liver which allows liprotein lipase to remove and store the triglycerides. Cholesterol is taken up in the liver

Question 17

Describe the role of VLDLs

Answer 17

Contain most of the triglycerises synthesised endogenously by the body.

Excess fat and carbohydrate is converted into TAG in the liver, packaged into VLDLs and released into the circulation. Adipose and muscle harvest TAG for VLDLs using lipprotein lipase in the capillary endothelium. This leaves a partile called IDL.

VLDLs are the body’s main source of eneergy during prolonged fasting.

Question 18

What are IDLs

Answer 18

Intermediate density lipoproteins. Formed as triacylglycerols are removed from VLDLs.

Most IDLs bind to the liver and are broken down. Some have more TAGs removed and become LDLs

Question 19

Describe the role of LDLs in cholesterol transport

Answer 19

LDL particles are the main carriers of cholesterol and deliver it to the liver and peripheral cells.

LDL is taken up into cells by receptor mediated endocytosis. LDL paricles are then destroyed by liposomes, freeing cholesterol required for membrane synthesis. Cholesterol synthesised in the liver is then packaged into lipoproteins or oxidised into bile salts.

The number of hepatic clearance receptors (LDL-R) on the cell surface is regulated by the concentration of intracellular cholesterol. High intracellular cholesterol inhibits synthesis of the receptor, therefore reduing uptake and increasing levels of LDL in the blood.

LDL particles can then deposit lipid into the walls of the peripheral vasculature

Question 20

Describe the role of HDLs

Answer 20

HDLs are produced in the liver and intestine.

They are disc shaped, seemingly inert and contain apoproteins and phospholipids. The mature HDL particles take up cholesterol from cells in the peripheral tissues which is then esterified by an enzyme.

The HDL particle transports cholesterol away from the periphery and may transfer it indirectly to other particles such as VLDL in the circulation or deliver its cholesterol directly to the liver (reverse cholesterol transport) and steroid-synthetic tissues (ovaries, testes, adrenal cortex).

Question 21

How can high levels of LDLs lead to athersclerosis?

Answer 21

Endothelial injury or damage leads to an inflamatory response. Injury may be caused by trauma, nitcotine, high blood pressure ot high levels of LDL in the blood.

Lipoproteins (e.g. LDLs) leak across the endothelium and accumulate in the subendothelial space.

Macrophages accumulate at teh lesion and enter the subendothelial space. They ingest lipoproteins and become foam cells due to the presence of high cytoplasmic lipid droplets. Smooth muscle cells may also migrate into the subendothelial space and transition into foam cells. As foam cells die, they release harmful cellular contents that can contribute to the repturing of the plaque and development of blood clots.