Transpiration
The process by which weather loss from a lead draws water and dissolved minerals up the xylem inside of the plant from the roots. This creates the transpiration stream
- Plant loses about 90% of all water taken up by roots to transpiration
- Provides a transport mechanism for minerals within the plant
- Evaporation at leaf helps to cool leaf down. P/s is not very efficient at high temperature
- Water evaporates on the surface of the spongy mesophyll cells in a leaf
- Water vapour passes out of the leaf via stomata high concentration of water vapour in leaf, lower concentration in air so passes out by diffusion
- Rate of diffusion - rate of transpiration will be affected by:
- Temperature - heat speeds it up
- Humidity – drier the air the faster it is
- Wind flow -wind blows damp air away from the leaf
- Light- stomata close in dark
- Air pressure – water loss greater at top of a mountain
Mineral take up from soil
Minerals from soil water taken up mainly by root hairs
Transport of chemicals inside plant
- Xylem – carry products and mineral salts (in solution upwards from roots to all other parts of the plant
- Phloem- carry products of p/s (sugars)from p/sing leaves (+stems) upwards or downwards to all other parts of the plant (esp. roots + developing shoots, flowers etc)
Adaptation of the leaf for photosynthesis
There are three main adaptations that a leaf makes for p/s
- Leaves are thin and flat so providing a large surface area for the diffusion of gases (oxygen, carbon dioxide) and absorption of light.
- The have stomata controlled by guard cells which allow the diffusion of gases into and out of the leaf.
- Most of the chlorophyll is packed into chloroplasts in the palisade cells which are just below the upper epidermis for maximum light absorption.
Action of the guard cell
In the light when the plant is photosynthesising, it produces Glucose which increases the concentration of the cell sap and causes it to absorb water by osmosis. This increases the pressure in the guard cells and causes them to stretch and bend, thus opening the stoma. In the inflated state , the cells are said to be Turgid
In the dark , photosynthesis stops producing glucose, and the glucose already present is used up by respiration. The guard cells may lose some water by osmosis to the surrounding cells , so they become limp or flaccid.
This is the equation for photosynthesis:
Light energy
Carbon dioxide + water glucose + oxygen
Chlorophyll
Limiting factors of photosynthesis
The rate at which photosynthesis occurs is limited by the following factors:
- Water- this has and an indirect affect. Lack of water causes the stoma to close and this reduces the amount of carbon dioxide the leaves can absorb Extreme water shortage kills the plant.
- Carbon dioxide- increasing the carbon dioxide levels leads to increased photosynthesis up to a certain point after which further increase in carbon dioxide levels has no beneficial effect. It is no longer a limiting factor
- Light intensity is the same as CO2
- Light wavelength
- (colour)Plants reflect green light9 which is why they look green) and strongly absorb Blue and RED light. Plants most like orange / red.
Mineral requirements of plants
Plants require many elements form the soil e.g.
Nitrogen, Phosphorus, potassium
Nitrate
Most important chemical is nitrate is deficient = stunted growth , yellowing of the leaf.
Phosphate
Needed for reactins in respiration =+ photosynthesis forms a chemical way of handling packages of energy using ATP
If phosphate is deficient = poor root growth Younger leaves are purple
Potassium
Helps enzymes involves in respiration + p/s to work
I potassium is deficient= yellow of leaves , dead spots on leaves
Digestion of Food
The digestion of food can be summarised as
Enzymes
Food products (on to the blood system)
Proteins
Large Small
Complex Simple
Insoluble Soluble
Happens within the digestive system
Oesophagus
Mouth stomach small intestine Large intestine
Salivary glands Gall bladder Pancreas
Liver
Digestion Absorption Defecation
Mouth Mouth Mouth
Stomach Stomach Stomach
Small intenstine Small intestine Small intestine
Large intestine large intestine
(rectum + anus)
Lock and – key hypothesis- to get enzyme action
Proteins
Pepsin (stomach) Peptidase
Protein Peptide chains Amino acids
e.g. from meat
fish or dairy
products only
Lipase
Lipids small droplets of lipids Glycerol fatty acids
Bile from liver acts from pancreas is an enzyme
like a detergent
not an enzyme
Enzymes “Biological catalysts”
- They are all made of Protein
- Each living cell has over 50 different enzymes
- Enzymes are affected by:
Temperature – up to a certain point which after a certain temperature the cells get destroyed
pH- Enzymes do not do so well if conditions are too acid or alkali.
Enzymes + Substrate concentration- on increase either speeds up chemical reactions
Food types in diet
1. Carbohydrate starch
sugar e.g. sucrose(soluble)
2.Lipids- fats (solids) + oils (liquid0 for energy + building cell membranes
3.ProteinsFor growth and repair
4.Minerals- e.g. iron for red blood cells , calcium for bones
5.Vitamins (organic chemicals from plants)
e.g. vitamin A – eye pigments
vitamin C- good skin condition
- Water
- Roughage+ cellulose
Useful but not essential
The eye
SCLERA: tough outer part of the eye; keeps shape of the eye and protects it
RETINA: inner layer which contains the light sensitive cells
CONES for colour
RODS for black and white
CORNEA: clear , curved part at front of eye. Begins the focusing of light. This is protected from physical damge by the conjunctiva
LENS: this completes the focussing of the image onto the retina
IRIS/PUPIL : muscles in the iris can pull the pupil open or closed. Regulates the amount of light going into the eye.
BLINDSPOT/OPTIC NERVES: the optic nerve leaves the eye at the blind spot and carries all of the sensory nerves to the brain
FOVEA; part of the retina opposite the lens with the highest concentration of light receptors
for the most detailed images.
The heart
Arteries :carry blood to tissues
Veins: carry it back to the heart
Capillaries: allow exchange of chemicals with tissues e.g. glucose + O2
Artery
- Carrie sblood away from the heart
- blood is under high pressure
- therefore they have a tough outer coat to prevent damage
- Elastic fibres to smooth out pressure
- Circular in cross section
Veins
- Blood towards heart
- under low pressure
- Valves to prevent back flow
- Irregular in cross section
Capillary
- the vessels in which chemicals are carries in blood stream are exchanged with living tissue
- Link arteries to veins
- One cell thick – to speed up diffusion
- No valves
Blood
- Red blood cells
- Shape inportant- the shape of the red blood celss have a large surface area for maximum uptake of oxygen
- RBC’s filled with heamoglobin( even the nucleus is excluded to make more room)
Heamoglobin (hb) reacts with oxygen but can but can give up that oxygen in the tissues whereit is being usedup i.e.
Lungs
Hb +o2 Hbo2
Tissues Oxy heamoglobin