Nutrition and Metabolism Flashcards
Nutition
Nutrients are provided by the food we eat
Metabolism
The cells use the nutrients to carry out chemical and physical reactions in order for the cells continual function and growth
3 reasons why we need nutrients
1) Growth
2) Repair
3) Maintenance
6 examples of nutrients
1) Fats
2) Proteins
3) Carbohydrates
4) Water
5) Minerals
6) Vitamins
Micronutrients
What the body requires in small amounts.
Ex = vitamins and minerals
Macronutrients
What the body requires in large amounts.
Ex = Fats, proteins, carbohydrates and water
Essential nutrients
Nutrients that the body cannot produce itself and therefore requires to be taken in from the diet.
3 main types of carbohydrates
1) Monosaccharides
2) Disaccharides
3) Polysaccharides
Monosaccharides
1) Glucose
2) Galactose
3) Fructose
Disaccharides
1) Maltose (1 glucose and 1 glucose) mag mag 2) Sucrose (1 glucose and 1 fructose) my GF sucs 3) Lactose (1 glucose and 1 galactose) LG gal
Polysaccharides1
1) Starch
2) Glycogen (small amounts in cooked meat)
3) Cellulose (important fibre source - but humans cannot digest cellulose)
3 uses of glucose:
1) Glucose is readily taken up by cells and used to produce ATP.
2) To produce Glycogen stores (any excess glucose will be converted and stored as fat)
3) Forms structural part of some molecules (e.g. glycoproteins)
2 cells which depend of glucose to form ATP:
1) Neurons
2) Erythrocytes
What is the approx. GDA for carbohydrates?
230g/day (greater requirement than other nutrients)
What is the main source of carbohydrates?
Plant material
Why are polysaccharides the best form of carbohydrate?
It requires more energy to be broken down and so allows for a stable release of glucose.
What is Fibre?
Fibre is a plant or animal carbohydrate which resists being digested by the body.
What are the 2 effects of fibre?
1) Absorbs water into the intestines which softens the stools.
2) Provides bulk - which speeds up the transit time.
What is the approx. GDA for fibre?
24g/day
What is the problem with having too much fibre?
Interfere with mineral absorption from the digestive tract into the circulation
How much of our body mass is proteins?
12-15%
Proteins are made up of
amino acids
Transamination
The process whereby an amino group from one molecule is transferred to another - in order to synthesis and degrade amino acids.
Takes place in the liver.
How many amino acids are there?
20
How many amino acids are essential amino acids?
8
What is the approx. GDA for proteins and what does it depend on?
45-60g/day (sex and age)
In what circumstances does your GDA for protein need to increase?
1) In Pregnancy
2) Growing children
3) Training for something
2 components that make up an amino acid?
1) Amino group
2) Carboxyl group
What are the 2 sources of proteinss and their definition, products and examples?
1) Complete proteins = Proteins that contain all 8 of the essential amino acids. Found in animal products (e.g. eggs, milk and animal meat)
2) Incomplete proteins = Proteins that are lacking 1 or more of the 8 essential amino acids. Found in plat products (e.g. baked bead, kidney beans and rice)
What percentage of the body is fat (male and female)?
Adult male: 15%
Adult female: 25%
What are the uses of fat?
1) Energy storage
2) Absorption of fat-soluble vitamins
3) Used to produce plasma membrane and myelin sheath
What substances are made from fats?
1) Steriods
2) Bile
3) Salts
4) Prostaglandins
5) Vitamin D
What is the approx. GDA for lipids?
70g/day (20g of which should be saturated fats)
3 sources of lipids:
1) Saturated fats (animal origin)
2) Unsaturated fats (e.g. nuts and seeds)
3) Cholesterol (important for cell membranes)
What is a fat cell called?
Adipocyte
Where do excess lipids go?
1) Under Skin
2) Around Organs
How are lipids transported in the blood?
Lipids are not water-soluble and are transported in the blood as lipoproteins
What are the components of lipoproteins (2 core components and 2 outer components)?
Core = Triglycerides and Cholestral Outer = Phospolipids and Proteins
What breaks down lipids and where is this secreted from?
Lipases break down lipids which are secreted from:
1) Pancreas and 2) Small Intensine
Lipid Profile
Whereby a sample of the blood is taken in order to work out the number/ratio of lipoproteins, tiglycerides and cholesterol.
4 different lipoproteins:
1) Chylomicron (protein coated lipid droplet)
2) Very low density lipoproteins
3) Low density lipoproteins
4) High density lipoproteins
What does the ‘density’ refer to in the different lipoproteins?
Protein/fat ratio
The higher the density, the more protein and the less fat
Which lipoproteins and good/bad for you?
Best - HDL’s
Worst - VLDL’s
What do Chylmicrons transport?
Transport cholesterol and triglycerides from the digestive tract to the liver and adipocytes.
What do VLDL’s transport?
Transport cholesterol and tryglycerides from the liver to adipocytes
What do LDL’s transport?
Transport cholesterol to tissues
What do HDL’s transport?
Referred to as ‘empty shells’
Remove cholesterol from the tissues
Function of vitamins
Act as co-enzymes in metabolic reactions
Sources of vitamins
Can either be synthesised in the body or found in vegetables or meat
Which vitamins are fat-soluble?
K, E, A, D
Which vitamins are water-soluble and what is their problem?
B and C. Need to be replaced often as they can dissolve in water and are removed by heat and moisture.
What are 6 sources of minerals?
Meat, Fish, Shellfish, Vegetables, Eggs and milk
What is the approx. GDA for sodium/what is actually needed?
6g/day
Only actually need: 2g/day
What 3 nutrients should be increased during pregnancy?
1) Protein
2) Fats in early pregnancy (for energy)
3) Fibre (as high levels of progesterone in pregnancy slows down GI tract movements)
What are the 2 types of metabolism, definition and example:
1) Anabolism (building up):
Small molecules join up to form large complex molecules. This process required energy.
Ex = Glucose is stored in the liver as glycogen.
2) Catabolism (breaking down):
Large molecules are broken down into smaller molecules. This process releases energy.
Ex = Glycogen is broken down into glucose and glucose is used to form ATP.
Energy is measured as:
Kilojoules (kJ) or Kilocalories (Kcal)
1 Kcal:
The amount of energy that is required to heat up 1 L of water by 1 oc.
Metabolic rate:
The rate in which energy is released from cells
Which hormone is involved in the metabolic rate?
Thyroxine
Basal Metabolic rate:
The amount of energy that is required to be released from cells that can support the body’s vital organs (at rest).
What is the first steps of glycolysis (whether in the presence or absence of oxygen)?
1) 1 molecule of glucose (6 carbon) is taken up into the cell via a transported protein.
2) Inside the cytoplasm, the molecule of glucose is broken down into 2 molecules of pyruvate (each 3 molecules).
This process yields 2 molecules of ATP.
What happens to the 2 pyruvate molecules (in the absence of O2)?
1) Inside the cytoplasm the 2 pyruvate molecules will convert to lactic acid
This process does NOT yield any ATP.
What happens to the 2 pyruvate molecules (in the presence O2)?
1) The 2 pyuvate molecules will move to the mitochondria
2) In the mitochondria the 2 molecules of pyruvate will be broken down in the: Kreb’s cycle and ETC (electron transfer chain)
This process yields 36 ATP molecules
How many molecules of ATP does 1 molecule of glucose yield?
38 molecules of ATP per 1 glucose.
What occurs in protein anabolism?
Amino acids form new proteins.
What occurs in protein catabolism?
Amino acids enter the TCA cycle:
1) Amino acids are deaminated - removal of the amino group.
2) Amino group is converted into ammonia
3) Ammonia is a toxic substance in the body and so is converted to urea (in the liver).
4) Urea is excreted from the body in the urine.
Which enzyme is required to break down the 2 pyruvate molecules in the krebs cycle and ETC?
Acetyl co-enzyme A
What occurs in Lipid anabolism/ lipogenesis?
Triglycerides are formed: 3 fatty acids and 1 molecule of glycerol
What occurs in Lipid catabolism/lipolysis?
Lysis of triglycerides:
Glycerol is broken down in glycolysis
Fatty acids enter the TCA cycle and are broken down using the acetyl co-enzyme A.
After eating a meal (ABSORPTION) and before eating the next meal (POST-ABSORPTION)what types of metabolism are involved?
1) Absorption =Anabolism:
When eaten a meal and up to 4 hours after. Nutrients are being absorbed and stored.
2) Post-Absorption = Catabolism:
After 4 hours since eating the last meal. The stored will be broken down for energy.
What is the normal plasma glucose level?
3.5 - 8 mmol/L
What 3 processes are involved in maintaining the normal plasma glucose levels (homoeostasis):
1) Glycogenesis = building up glycogen from glucose.
2) Glycogenolysis = breaking down glycogen to form glucose
3) Glyconeogenesis = synthesising new molecules of glucose from amino acids.
Which hormone is involved in the absorptive state?
Insulin
Which hormone is involved in the post -absorptive state?
Glucagon
Insulin
A peptide hormone which is secreted from the B cells or Islet of Langerhan cells in the pancreas when the blood glucose level is high (in the absorptive state).
What are the 4 mechanisms occurs once insulin has been secreted (due to high plasma glucose levels)?
1) Stimulates the increase of glucose co-transporters in cell membranes (to take up glucose from the plasma into the cells via facilitated diffusion).
2) Stimulates glycogenesis
3) Stimulates the synthesis of proteins and fats
4) Inhibits glyconeogenesis
Glucagon
A hormone released from the a-cells from the Islet of Langerhan in the Pancreas when plasma glucose levels are low. They will stimulate the glucose levels to increase.
What are the 3 mechanisms occurs once glucagon has been secreted (due to low plasma glucose levels)?
1) Stimulates glyconeogenesis.
2) Stimulates glyogenolysis
3) Stimulates lypolysis.
What 2 other things can increase plasma glucose levels and what mechanisms occur?
Adrenaline = released from the adrenal medulla (via the sympathetic NS)
1) Stimulates glycogenolysis
2) Stimulates lipolysis
Glucocorticcoids = released from the adrenal cortex.
1) Stimulates glyconeogenesis.
When are ketones produced?
When the plasma glucose levels is low and so there isn’t enough glucose for ATP production and so the liver utilises fat and protein stores to produce ATP.
When are ketone bodies produced?
When there is too much acetyl co-enzyme A entering the TCA cycle and it will be converted to ketone bodies.
What problems are caused due to high levels of ketones?
1) Ketones are toxic to many tissues
2) Puts pressure on the liver to utilise protein and fat stores
3) Can cause Diabetes Mellitus
4) This can result in ketoacidosis
Ketones are produced in the TCA cycle:
1) Glucose molecule is broken down into 2 pyruvate (yield = 2 ATP).
2) 2 pyruvate enter the TCA cycle and ETC
3) Too much acetyl co-enzyme A = breaks down fat and protein stores.
4) Ketone bodies are produced (yield = 36 ATP)
Symptoms of the body producing ketones
Fragrance breath (similar to pair drops)
Definition of diabetes mellitus and what is it normally associated with?
When the body is unable to balance plasma glucose levels (homeostasis) and it is normally associated with having a problem with either of the hormones involved in plasma glucose homeostatis: insulin or glucagon.
What are the 5 causes of diabetes mellitus?
1) Environment
2) Diet
3) Genetics
4) Stress
5) Viral
What are the 2 types of diabetes mellitus?
Type 1 (auto-immune problem or genetics) Type 2 (obesity)
What happens in type 1 diabetes?
The B-cells in the pancreas, that produce insulin, are destroyed and so the plasma glucose levels can not be reduced.
Treatment = insulin replacement
What happens in type 2 diabetes?
The b-cells in the pancreas may still produce insulin, however the cells become resistant to insulin and so the effects of insulin can not occur
