NUTR1023 Lecture 4: NUTR1023 Lecture 4 and Readings
4.1 Carbs
Monday, 18 December 2017
10:04 pm
CARBOHYDRATES VIDEO:
Functions of carbohydrates:
• Provide energy (esp. during high intensity exercise)
• Regulate fat and protein metabolism
• Are the only source of energy in the nervous system
• Are synthesised into glycogen in the liver and muscles
• Sourced from grains, fruit, vegetables, milk and sweets/confectionary
Classified as:
• Monosaccharides (glucose, fructose, galactose)
• Disaccharides (sucrose, lactose)
◦ Maltose = two glucose units
◦ Sucrose = glucose + fructose
◦ Lactose = galactose + glucose
• Condensation reactions = forming a disaccharide
• Hydrolysis = breaking disaccharide apart
• Polysaccharides (starch, glycogen)
◦ Glycogen = very branched
◦ Starch has two forms;
• Amylopectin (highly branched) -- absorbed more rapidly
• Amylose (long straight-chain molecule)
Fibres = carbohydrates that we can't digest
• Don't provide us with energy, BUT provide us with some bulk that aid in
moving food through our digestive system
• Once in the large intestine, can also bind to potentially
dangerous/harmful chemicals and remove them via defecation
Cellulose = similar to starch, but can't be digested due to the type of bonds
between glucose molecules in cellulose
Carbs ultimately absorbed in the small intestine as individual monosaccharide
units (either gluc, fruc or galac)
• These then go to the liver
• Galac and fruc converted to gluc
• Glucose released to bloodstream
To measure glycaemic index, compare blood glucose response to a reference
food (e.g. 50g glucose) vs the test food (which MUST contain 50g of glucose)
Glycaemic index = measure of the blood glucose response to a particular food
• Rank from 0-100 (pure glucose = 100)
• Low < 55
• Moderate 56-69
• High > 70
Protein content, fat content, fibre content of food all affect the GI (plus also
affected by other foods eaten with it)
4.1 Proteins
Tuesday, 19 December 2017
3:59 pm
PROTEINS VIDEO:
Proteins
• Make up cell structures
• Help develop, repair and maintain tissues
• Produce haemoglobin, enzymes and many hormones
• Maintain normal blood osmotic pressure
• Form antibodies
• Can be used as an energy source (prefer using fats and carbs)
• Break down into amino acids, to be used by the body (often to synthesise
new proteins)
Sources:
• Cheese, milk
• Eggs
• Meat, fish
• Beans, nuts, seeds
16% of body weight = protein
43% of total body protein is found in the skeletal muscle
26% found in internal organs
The rest is in the skin and blood
Protein contains nitrogen, oxygen, hydrogen and carbon (most macronutrients
don't have nitrogen)
Essential amino acids: body cannot produce these, need dietary intake
Nonessential amino acids: can be produced from essential amino acids, or via
dietary intake
Protein structure:
• AA linked via peptide bonds (through condensation reactions)
• Primary, secondary, tertiary and quaternary structures
Denaturation of a protein occurs when the structure is disrupted and the protein
uncoils and loses shape
• This process occurs in the stomach acid
• Can cause phase change/structure change
Protein digestion in stomach
• Involves hydrochloric acid (HCl) denaturing proteins
• Also conversion of inactive precursor Pepsinogen, to active Pepsin
Protein digestion in small intestine
Document Summary
Cellulose = similar to starch, but can"t be digested due to the type of bonds between glucose molecules in cellulose. Carbs ultimately absorbed in the small intestine as individual monosaccharide units (either gluc, fruc or galac: these then go to the liver, galac and fruc converted to gluc, glucose released to bloodstream. To measure glycaemic index, compare blood glucose response to a reference food (e. g. 50g glucose) vs the test food (which must contain 50g of glucose) Glycaemic index = measure of the blood glucose response to a particular food: rank from 0-100 (pure glucose = 100, low < 55, moderate 56-69, high > 70. Protein content, fat content, fibre content of food all affect the gi (plus also affected by other foods eaten with it) Sources: cheese, milk, eggs, meat, fish, beans, nuts, seeds. 43% of total body protein is found in the skeletal muscle. The rest is in the skin and blood.
