2.18 - 2.32 Human & Plant Nutrition

carbs

they’re the bodies main fuel for supplying our cells with energy

proteins

growth and repair of tissues

lipids

they are used as an energy store, as insulation and to make cell membranes

vitamin A

makes a light sensitive chemical in the retina of our eyes. a vitamin A deficiency could cause night blindness

vitamin A sources

fish liver oils and carrots

vitamin C

sticks together cell lining surfaces such as the mouth

vitamin C sources

fruit and veg

vitamin D

needed for growing bones

vitamin D soruces

fish liver oils and make in skin while in sunlight

mineral - calcium

used to make teeth and bones

calcium sources

dairy products

mineral - iron

part of haemoglobin, in red blood cells which helps carry o2

iron sources

red meat and eggs

water

hydration

fibre

gives the muscles of our guts something to push against as food moves through the intestine and prevents constipation

fibre sources

whole grain bread and brown pasta/rice

pregnancy and energy requirements

energy requirements increase as energy is needed to support the growth of the developing foetus as well as the larger mass the mother has to carry around

age and energy requirements

the amount of energy young people need increases towards adulthood as this energy is needed for growth. energy in adults decrease as they age

activity levels and energy requirements

the more active, the more energy required for movement as muscles are contracting more and respiring faster

mouth

food is mechanically broken apart by teeth and tongue and is mixed with saliva which contains amylase enzymes by chemical digestion

oesophagus

tube linking mouth to stomach. it has muscles in its wall which contract and relax to push the swallowed food - saliva mix (known as the bolus). this process is called peristalsis

stomach

produces gastric juice which contains HCl, killing any pathogens in the food/drink the low PH provides the optimum temperature for protease. the wall of the stomach is very muscular so therefore food is further squashed and it churns so that the gastric juice comes into contact with the bolus

liver

produces bile, which contains alkaline substances to neutralise the acidic solution from the stomach and emulsifies fat

gal bladder

stores bile and when the muscular wall of this organ contracts, bile is pushed into the first part of the small intestine which is called the duodenum

pancreas

produces digestive enzymes as well as substances which neutralise the HCl that comes from the stomach.

1small intestine: duodenum

most of the digestion takes place here

2 small intestine: ileum

where the absorption of the food molecules takes place. the ileum is lined with villi to increase the surface area over which absorption takes place and has think walls to reduce the distance of diffusion

large intestine: colon

absorbs water into the blood via osmosis

large intestine: rectum

faeces is stored here until time for egestion (pooing)

pancreatic juice contains

amylase, protease and lipase

amylase

carbs - maltose

protease

proteins - peptides - amino acids

lipase

lipids - glycerol and fatty acids

maltase

maltose - glucose

components of a balanced diet

carbs, proteins, lipids, vitamins, minerals, water and dietary fibre

photosynthesis is the conversion of light energy to

chemical energy

photosynthesis equation

6 CO2 + 6 H20 → C6 H12 06 + 6 O2

plant gets 6 CO2 as…

it diffuses into the leaf from the stomata

plants get 6 H20 as…

its taken up by the roots and transported thru the xylem and into the leaves

limiting factor is

anything that in short supply prevents photosynthesis from occurring at its max rate

limiting factors in photosynthesis are

temp, light intensity and CO2 conc

increase temp =

more ke, therefore rate of collisions between enzyme and substrate increase

more light =

faster rate, which will continue until some other factor prevents the rate of reaction from increasing further because it is in short supply

more CO2 =

faster rate

structure of a leaf includes

cuticle, upper epidermis, palisade mesophyll, spongey mesophyll, vascular bundles, lower epidermis, cuticle, guard cells, stomata

large s.a of leaf

a large s.a means its easier for co2 and absorpiton of light for photosynthesis

upper epidermis

thin and transparent for CO2 to diffuse quicker and for light to enter the palisade mesophyll underneath it

palisade mesophyll

tightly packed with chlorophyll, to absorb max light

spongey layer

air spaces to allow CO2 to diffuse through the leaf

mineral ions are needed for

plant growth

magnesium ions are needed for

chlorophyll

nitrate ions are needed for

amino acids

we can affect the rate of photosynthesis by changing the

light, chloroplast and CO2

light can be changed by

leaving plant in a dark room for 24 hours

chloroplasts can be changed by

leaving plant in boiling water and adding ethanol

CO2 can be changed by

adding potassium hydroxide to plant to remove CO2 and leaving plant in dark room for 24 hours to ensure all the starch is used up