Nutrition and metabolism

Define calorie and state how many kilocalories are produced from the macronutrients

A calorie is a unit of energy 1000 calories is a kilocalorie or Calorie 1 Calorie = 4.2 kilojoules

Describe the processes of protein catabolism and anabolism

As fuel, amino acids must first be deaminated (removal of NH2 amino group). The resulting intermediates (keto acids) are then converted to pyruvic acid, acetyl-CoA or other citric acid cycle intermediates.

Define basal metabolic rate and state factors that alter it

BMR is basically the amount of calories you would burn whilst doing NO activity Some factors affecting your metabolic rate include: Gender; males have higher metabolic rates than females Prolonged dieting - decreases BMR Exercise - elevated following exercise Thyroid hormone levels - decreased levels lower BMR Age - BMR decreases with age due to decreased muscle mass

Name the major minerals used by the body and state their function

Calcium - bone and teeth hardness, muscle contraction, normal heart rhythm, necessary for blood clotting Phosphorus - important for energy storage and transfer, Iron - component of heme portion of hemoglobin, component of cytochromes in electron transport chain Sodium - acts to regulate body water distribution and blood pressure, nerve transmission and muscle function Potassium - maintains intracellular osmotic pressure, repolarises membrane for proper nerve transmission and muscle function

Name the blood lipoproteins, state their functions and describe how they differ from each other

Chylomicrons form in the absorptive intestinal cells then enter lacteals and then bloodstream VLDLs are produced in the liver and transport lipids to adipocytes LDLs formed when VLDLs dump triglycerides to adipocytes HDLs produced in liver as empty protein shell, picks up lipids in blood

Glycogen metabolism; describe the synthesis and breakdown of glycogen within the body

Glycogenesis -- synthesis of glycogen stimulated by insulin (average adult contains 450 g) Glycogenolysis - the breakdown of glycogen glucose stimulated by glucagon, cortisol and epinephrine only liver cells can release glucose back into blood Muscle cells cannot convert glucose 6-phosphate into glucose as they lack the enzyme phosphatase

Define nutrient and list the six major categories of nutrients

Ingested chemical used for growth, repair or maintenance 1.proteins 2.fats 3.carbs 4.water 5.vitamins 6.minerals

Describe the hormonal and nervous regulation of each state

Insulin: increases the cellular uptake of glucose by 20-fold stimulates glucose oxidation, glycogenesis and lipogenesis but inhibits gluconeogenesis Sympathoadrenal effects: Promote glycogenolysis and lipolysis under conditions of injury, fear, anger and stress. Adipose tissue, liver cells and muscle cells are richly innervated and also respond to epinephrine from adrenal medulla.

State the function of lipids, their RDI and major dietary sources

Lipids (triglycerides) account for most of body's stored energy - 90% of resting energy needs Lipids (steroids) are used to synthesize steroid hormones (e.g. testosterone and estrogen) Lipids aid in the absorption of fat soluble vitamins (A,D,E & K) General recommendation of limiting saturated fats (10% or less of total fat intake) with total fat intake of around 30% of total energy intake

Describe the processes of lipid catabolism and anabolism

Lipogenesis = synthesizing fat from other sources amino acids and sugars are used to make fatty acids and glycerol Lipolysis = breaking down fat for fuel Glycerol enters glycolysis and the fatty acids are broken down 2 carbons at a time to produce acetyl-CoA (beta oxidation)

Carbohydrate metabolism; explain the processes in which glucose is catabolised to produce ATP

Most dietary carbohydrate is burned as fuel within hours of absorption. Carbohydrates are ultimately broken down to glucose for metabolism glycolysis (yields 2 ATP): glucose (6C) split into 2 pyruvic acid molecules (3C) Occurs in cytoplasm of cell anearobic aerobic respiration (34-36 ATP): completely oxidizes pyruvic acid to CO2 and H2O anaerobic fermentation (no O2 avail.): pyruvic acid reduced to lactic acid replenishes NAD+ so glycolysis can continue

State the function of carbohydrate, the recommended dietary intake (RDI) and some major dietary sources

Predominantly function as a fuel source (glucose) for cells to produce ATP, particularly neurons and RBCs which depend entirely on them for energy most dietary sources suggest 45-65% of total energy requirement

Describe both short term & long term regulators of appetite

Short Term: -Ghrelin (the hunger hormone): Produces sensation of hunger. ceases within an hour of eating. -Peptide YY (PYY): Sense that food has arrived in the stomach Primary effect is to signal satiety and terminate eating -Cholecystokinin (CCK): suppresses appetite Long Term: -Leptin (the satiety hormone): Level proportionate to one's own fat stores, Inhibits appetite -Insulin: Has receptors in the brain and functions, like leptin, as an index of the body's fat stores Weaker effect on appetite than leptin

State the function of fibre, its RDI and some dietary sources

Soluble fibre delays gastric emptying and hence slows down the digestion and absorption of carbohydrates insoluble fibre aids in regular bowel movements RDI is 30 g/day Dietary fibre is the indigestible parts of plant foods such as vegetables, fruits, grains, beans, legumes and oats

Name the major vitamins used by the body and state their function

Vitamin C - acts as an antioxidant, helps in the formation of collagen, enhances the absorption of iron Vitamin A - crucial for vision, involved in synthesis of photoreceptor pigments Vitamin D - activated by sunlight on the skin, increases blood calcium levels and aids in calcium absorption Vitamin E - acts as an antioxidant, reduces LDL oxidation and may aid in reducing atherosclerotic plaques Vitamin K - essential for the formation of clotting proteins, obtained in diet but also made from bacteria in the gut

State the function of proteins, their RDI and major dietary sources

muscle contraction, movement of body, cells, cell structures RDI - 0.8 grams/kg of bodyweight/day Animal proteins (meat, eggs and dairy) are complete proteins Plant sources provide incomplete proteins so must be combined in the right proportions

Define the absorptive state of metabolism and explain what happens to the macronutrients in this state

time of nutrient absorption and use for energy needs Carbohydrates: excess is converted by liver to glycogen or fat Fats: taken up by fat cells from chylomicrons in the blood, primary energy substrate for liver, fat and muscle cells Amino acids: most pass through the liver and go onto other cells in liver cells, may be used for protein synthesis, used for fuel for ATP synthesis or used for fatty acid synthesis

Define the post-absorptive state of metabolism and explain what happens to the macronutrients in this state

when stomach and small intestine are empty, stored fuels are used to ensure supply. Carbohydrates - glucose is drawn from glycogen reserves for up to 4 hours and then synthesized from other compounds Fat - adipocytes & liver cells convert glycerol to glucose free fatty acids are oxidized by liver to ketone bodies Protein metabolism - used as fuel when glycogen and fat reserves depleted