E5 Macronutrients: fat, protein, carbs Flashcards
state the energy values (in kcal/g) of carbohydrates, proteins, fats and alcohol
carbohydrate: 4
protein: 4
fat: 9
alcohol: 7
what are macronutrients?
- they provide energy
- things needed in the diet in large amounts
describe how much energy is given from carbohydrates and fat and if they are stored
- carbohydrates are short term
- carbohydrates are not stored very much
- 60% of energy is from carbohydrates
- fat is stored and then used when needed
describe lipids in terms of solubility
insoluble or poorly soluble in water but soluble in organic solvents
functions of lipids in the body
- fuel and energy store
- insulation
- protection
- membrane structures
- intra / intercellular signalling
- substrate for hormone and prostaglandin synthesis
- supply of essential nutrients
functions of lipids in foods
- improve flavour perception of foods
- add texture to foods
- improve palatability
describe the function of lipids: insulation
- layer of fat underneath skin
- if this layer of fat is lost due to undernutrition, you may have problems with keeping warm
given an example of how lipids act as protection in the body
fat around kidneys
give an example of how lipids act as substrates for hormone and prostaglandin synthesis
cholesterol
describe the structure of the majority of dietary fats
- 90% of dietary fats are triacylglycerols (triglycerides)
- triglycerides are made up of glycerol and 3 fatty acids
in the image, what is shown in red and white?
- whole structure = triglyceride
- red = glycerol backbone
- white = fatty acids
what are the 3 classifications for fatty acid chains?
saturated
monounsaturated
polyunsaturated
what is meant by a saturated fatty acid chain?
- no double bonds
- all single bonds in the fatty acid carbon chain
what is meant by a monounsaturated fatty acid chain?
1 double bond in the fatty acid carbon chain
what is meant by a polyunsaturated fatty acid chain?
more than 1 double bond in the fatty acid carbon chain
describe oils at room temperature
- liquid
- more unsaturated fatty acids that cause kinks in fatty acid carbon chain
- fatty acids cannot pack together as much so the substance exists as a liquid
describe the difference in fatty acid chains in fats and oils
- oils have more unsaturated chains and therefore more kinks and a lower melting point (exist as liquids)
- fats have less double bonds in their fatty acid carbon chains so there are stronger intermolecular forces between molecules and a higher melting point (exist as solids)
describe the sources of fats and oils
fats: mostly from animals
oils: mostly from fish or plants
compare and contrast vegetable oil and fish oil in terms of their fatty acids
vegetable oil
- high in polyunsaturated fatty acids
- low in saturated fatty acids
- in most vegetable oils, the omega-6 polyunsaturated fatty acid predominate
fish oil
- high in polyunsaturated fatty acids
- low in saturated fatty acids
- omega-3 polyunsaturated fatty acids predominate
what is meant by omega-6 and omega-3 in fatty acid classifications?
omega-6 (n-6)
- 1st double bond is 6 carbons from methyl terminal
omega-3 (n-3)
- 1st double bond is 3 carbons from methyl terminal
function of phospholipids
structural lipids in membranes
functions of sterols
- fluidity of membranes
- precursor to bile salts
- precursor to steroid hormones
where are sterols found? where can similar molecules be found?
- sterols only found in animal fats
- plants have phytosterols
structure and function of phytosterols. give an example
- similar structure to cholesterol
- inhibit cholesterol uptake
- eg. benecol
what are TransFats compared to cis fats?
- in unsaturated fats, double bond is in cis conformation which gives a kink and provides fluidity (oils)
TransFats
- partially hydrogenated tp convert cis bond to trans bond so that fats sit together better
- converts plant oils into plant fat
what are TransFats used for day-to-day?
used to make cakes and biscuits in the food industry
what are essential fatty acids?
- those that the body needs for normal function but can’t make on its own
- humans can’t insert double bond between any of the 1st 7 carbons of fatty acids
- required for prostaglandins, leukotrienes (examples)
- other long chain fatty acids are derived from these EFAs
describe the function of cholesterol in the diet and body
- primary component of cell membranes
- substrate for synthesis of bile acids, steroid hormones and vitamin D
describe how blood cholesterol is influenced
- dietary cholesterol has little influence on blood cholesterol
- increased dietary cholesterol leads to decreased reuptake of biliary cholesterol (body’s natural response to increased dietary cholesterol)
- type of fat influences blood cholesterol
dietary sources of cholesterol
liver
eggs
shellfish
how are cholesterol and TAGs transported around the body?
as lipoproteins (composed of lipid and apoprotein)
what are the 3 types of cholesterol?
- VLDL (very low density lipoprotein)
- LDL (low density lipoprotein)
- HDL (high density lipoprotein)
describe VLDL
- TAG rich
- transports TAG tp adipose / muscles
- bad
describe LDL
- cholesterol rich
- transports cholesterol from liver to peripheral cells
- bad
describe HDL
- removal of excess cholesterol from peripheral tissues back to the liver for metabolism
- good
what is raised LDL associated with?
CVD (increases risk)
what is the relationship between HDL and CVD?
HDL is inversely related to CVD
describe what happens when LDL levels are raised
- taken up by macrophages called foam cells
- foam cells accumulate in blood vessel walls
- hardening occurs (atherosclerosis)
describe essential amino acids and give examples
- can’t be made de novo (must be obtained from diet, can’t be synthesised)
isoleucine
lysine
methionine
phenylalanine
threonine
tryptophan
valine
(histidine)
describe semi-essential amino acids and give examples
- synthesis dependent on something else (eg. another amino acid)
cysteine
tyrosine
give examples of non-essential amino acids
glycine
proline
glutamic acid
aspartic acid
serine
alanine
arginine
what is the RNI for protein per day?
0.75 g/kg body weight
when may increased requirements of protein be needed?
- during growth, for repair (eg. post-surgery or injury)
- pregnancy
- lactation
how much extra protein should a woman get per day when pregnant?
+ 6 g/day
how much extra protein should a woman get per day when lactating?
+ 11 g/day
what are the 2 types of protein from food sources?
HBV (high biological value)
LBV (low biological value)
describe HBV proteins
- all of the essential amino acids in sufficient amounts for protein synthesis are included
- eg. animal proteins
describe LBV proteins
- lack some essential amino acids
- eg. plant proteins
- eaten in combination can make a HBV mix
state some good plant protein sources
beans
pulses
nuts
seeds
how is surplus carbohydrate stored in the body?
in the liver and skeletal muscle
food sources of sugar carbohydrates
- present in nutrient rick foods such as fruits, vegetables and milk
- a lot from added sources (eg. sweets, chocolate, soft drinks, cakes, biscuits)
what does added sugar in foods link with?
type 2 diabetes and obesity
what are the 2 types of polysaccharide complex carbohydrates?
starches
non-starch polysaccharide (fibre)
state some food sources of starchy carbohydrates and state what else these foods provide
bread
potatoes
rice
pasta
cereals
couscous
- foods also provide other essential nutrients (B vitamins, minerals, protein and fibre)
what is fibre a major component of?
- plant cell walls
- include cellulose, pectins, gluons, gums etc.
- not digestible
what are the 2 types of fibres? describe each of them giving their sources
soluble and insoluble
soluble
- fruit, vegetables, especially pulses and legumes
insoluble
- tough fibrous parts of plants
- eg. wheat and rye
sources of fibre
fruits
vegetables
wholegrains
oats
brown rice
bread
nuts
seeds
what is the recommended intake of fibre per day?
30 grams
what properties and functions does insoluble fibre have in the body?
- water-attracting properties (softens stools and increases bulk of faeces)
- reduces transit time through GIT
- some fermentation in colon
what does colonic bacteria do to soluble fibre?
- soluble NSP (non-starch polysaccharide) is fermented in the colon by colonic bacteria
- fermented into short chain fatty acids which are important for colon health and brain development
- also provides fuel to colonic bacteria
functions of soluble fibre in the body
- delays gastric emptying (feel fuller for longer)
- blunts postprandial blood glucose response by slowing digestion, slowing uptake
- binds to bile salts, decrease cholesterol reuptake
- high fibre diet can have hypocholesterolemic effect
physiological actions of fibre
- acts as substrate for bacterial fermentation in the colon
- bacteria produce SCFA that are absorbed by colonic mucosa
- bacteria produce butyric acid (important fuel for colonic mucosal cells)
- faecal bulk
- can reduce plasma cholesterol levels
what do epidemiological studies suggest about fibre?
- a diet high in fibre reduces the risk of colorectal cancer
- linear decrease in risk of colorectal cancer with increasing fibre intake
what is the glycaemic index?
- relates the concentration of glucose in the plasma after consumption of food
- measure of the amount of plasma glucose in your blood after a meal
source of fibre foods
pulses
nuts
seeds
berries
wholegrain
broccoli
sweetcorn
cabbage
potatoes plus skins
what is meant by a low and high glycaemic index level for carbohydrates?
low GI
- broken down and absorbed slowly
- eg. complex carbohydrates
- eg. beans, legumes, bran
high GI
- broken down and absorbed rapidly and rapidly increase blood plasma glucose levels
- eg. simple sugars
state the components of a balanced diet
- carbohydrate
- protein
- fat
- saturated fat
- vitamins
- minerals, trace elements
- water
