diet and digestion Flashcards
key adaptations of the villi
- large surface area (villi and microvilli)
-> increases rate of diffusion - good blood supply
-> maintain concentration gradient of blood - lacteal absorbs lipids
- long
-> lots of chance for diffusion to occur - thin/near capillary
-> short diffusion distance
what is assimition
small food molecules are used to build larger molecules (e.g. amino acids are used to synthesise proteins)
what is absorbtion
small, soluble molecules move from the small intestine to the blood
what is ingestion
food enters the digestive system via the mouth
what is egestion
removal of undigested food (faeces) from the anus
what is digestion
breakdown of large insoluble molecules into small soluble ones
what is mechanical digestion
teeth break down food into small pieces and peristalsis helps to move food along
what is chemical digestion
enzymes break down food to small soluble molecules
what is the order of digestion
mouth -> oesophagus -> stomach -> duodenum -> ileum -> colon -> rectum -> anus
function of salivary glands
produces saliva
-> helps to moisten food
-> contains enzyme salivary amylase which starts the breakdown of food
function of the mouth
food is ingested
mechanical digestion occurs here - teeth cut and crush food into smaller pieces which increases the surface area for enzymes to work
food is mixed with saliva - contains digestive enzymes (salivary amylase) to break down starch and moisten food
form a bolus of food which is pushed to the back of the mouth using the tongue
function of the teeth
involved in mechanical digestion (physical breakdown of food)
incisor - for cutting and biting
canine - for holding and cutting
premolar and molar - for crushing and chewing
function of the oesophagus
food passes down oesophagus and into the stomach
food is moved through the digestive system via peristalsis
- circular and longitudinal muscles involved to produce wave-like contractions
function of the stomach
muscular bag that stores food for several hours
secrete HCl which makes stomach very acidic - the acid kills bacteria so you don’t get food poisoning and provides optimum pH for pepsin
produces the enzyme pepsin, which breaks down proteins to dipeptides
muscles in the wall of the stomach contract and churn the food
function of the liver
filters toxins from the blood
acts like a food processing factory and will break down some molecules and build/store others
produces bile which emulsifies lipids
function of the gall bladder
stores bile and releases bile into bile duct to enter the duodenum
in the duodenum bile has two roles:
- neutralising acids
- emulsifying lipids
function of the pancreas
produces trypsin, lipase, pancreatic amylase
these are released into duodenum for chemical digestion
function of the duodenum
food is continued to be broken down here, resulting in lots of small soluble molecules that can be absorbed in the ileum
bile (neutralises HCl from stomach) creates an alkaline environment, which is ideal for the enzymes maltese and peptidase
function of the ileum
absorption of small soluble molecules into the blood stream and lacteal (absorbs fats)
villi has key adaptations to quickly and efficiently absorb soluble products of digestion
function of the large intestine
any excess water is absorbed in the first part of the large intestine, the colon
leaving the non soluble/indigestible food (cellulose, dead and living cells from the gut) to move through
function of the rectum
stores the faeces
function of the anus
expels faeces from the body (egestion - removal of indigestible material)
salivary amylase
- produced in the salivary glands
- used in the mouth
- breaks down starch
- end products are disaccharides (e.g. maltose)
- optimum pH 7-8
pancreatic amylase
- produced in the pancreas
- used in the duodenum
- breaks down starch
- end products are disaccharides (e.g. maltose)
- optimum pH is 7-8
maltase
- produced in the duodenum
- used in the duodenum
- breaks down maltose
- end products are glucose
- optimum pH 7-8
pepsin
- produced in the stomach
- used in the stomach
- breaks down protein
- end products are dipeptides
- optimum pH 1-2
trypsin
- produced in the pancreas
- used in the duodenum
- breaks down protein
- end products are dipeptides
- optimum pH 1-2
peptidase
- produced in the duodenum
- used in the duodenum
- breaks down dipeptides
- end products are amino acids
- optimum pH 1-2
lipase
- produced in the pancreas
- used in the duodenum
- breaks down triglycerides
- end products are glycerol and fatty acids
practical: effect of temperature on enzyme activity
- will use bacterial amylase to breakdown starch
- can measure the activity of the enzyme by looking at the speed at which the starch disappears
- will use iodine to work out when the reaction is finished - iodine will be blue/black
independent - temp
dependant - speed of colour change
controls - pH level, volume of starch, volume of iodine, volume of bacterial amylase
1) place single drops of iodine into depressions on a spotting tile
2) prepare a water bath for 20, 30, 40, 50, 60, 70 degrees celsius
3) place 2cm^3 of amylase into a test tube then put one in each water bath for 5 mins
4) add 2cm^3 starch into each amylase solution
5) place one drop of mixture into each drop of iodine - wait 10 seconds in between each drop
6) stop when the solution stays orange
7) each iodine drop used equals 10 seconds of reaction time
8) repeat for all temps
what elements are found in carbohydrates
carbon, oxygen, hydrogen
what elements are found in lipids
carbon, oxygen, hydrogen
elements present in proteins
carbon, oxygen, hydrogen, nitrogen, sometimes sulphur
monosaccharide example
glucose, fructose, galactose
what is formed when two monosaccharides join together
a disaccharides
disaccharides example
maltose, lactose, sucrose
what is formed when lots of monosaccharides join together
polysaccharide
polysaccharide examples
starch, glycogen, cellulose
what are lipids made of
triglycerides
what are triglycerides made of
1x glycerol
3x fatty acids
what are triglycerides made of
1x glycerol
3x fatty acids
what is the monomer of proteins
amino acids
what are two amino acids joined together called
dipeptide
what are many amino acids joined together called
polypeptide
function of vitamin a
- helps vision
- helps keep tissues healthy
vitamin a deficiency
night blindness (nyctalopia)
good food sources of vitamin a
- cod liver oil
- broccoli
function of vitamin c
- tissue repair
- keeping skins/gums healthy
vitamin c deficiency
scurvy
good food sources of vitamin c
- citrus fruits
- kiwi
- potatoes
function of vitamin d
helps absorption of calcium
vitamin d deficiency
rickets
good food sources from vitamin d
- dairy
- fish oil
- egg
calcium function
stronger bones and teeth
calcium deficiency
osteoporosis
good food source of calcium
dairy
iron function
in haemoglobin, helps carry oxygen to respiring cells
iron deficiency
anaemia
good food sources for iron
- red meat
- liver
- eggs
fibre function
helps push indigestible material through large intestine
iron deficiency
constipation
good food sources for iron
- whole mead bread/pasta/rice
- all bran
water function
all metabolic reactions occur
water deficiency
dehydration
good food sources for water
- water
- cucumber
- pepper
- celery
what is the role of bile
- neutralising stomach acids
- emulsifying lipids
what is energy content of food measured in
kilojoules (kJ)
method to investigate energy content in food
1) fill a boiling tube with 20cm^3 water + measure temp
2) measure mass of chosen food
3) light food on fire
4) immediately, place food under boiling tube
5) measure temp of water once food has stopped burning
6) repeat with other foods
7) use equation:
energy released per gram = [mass of water(g) x temperature rise x 4.2] / mass of food sample
