Structure of Animal + Plants Cells
Animal Cells + Plant Cells have...
a nucleus- holds the genetic information + controls cell activity
cytoplasm- needed for chemical reactions
a cell membrane- controls substances leaving/entering the cell
ribosomes- where protein synthesis takes place
mitochondria- release energy during respiration
BUT plant cells also have...
a cell wall- strenghtens the cell
chloroplasts- make food in photosynthesis
a permanent vacuole- filled with cell sap in the cytoplasm
Substances Entering + Leaving Cells
There are 3 ways substances can get in + out of cells.
Diffusion- when particles of gas or liquid are spread out.
It is the net movement of particles from an area of high concentration to an area of a lower concentration. Net movement explains which direction particles have moved.
Osmosis- the movement of water from an area of high concentration to an area of low concentration across a semi-permeable membrane.
- an isotonic solution is the same concentration as the cytoplasm inside the cell, so when added the cell is not affected
- a hypotonic solution has a greater concentration than the cell and more water moves into the cell than out
- a hypertonic solution has a lower water concentration than the cell, causing more water to move out than in
Active Transport- against the concentration gradient
carbon dioxide + water (+light energy) ---> glucose + oxygen
the cells in the leaves of plants contain chloroplasts, which contain chlorophyll. during photosynthesis, light energy is absorbed by chlorophyll and this energy is used to convert carbon dioxide (in the air) and water into glucose. the chemical reaction also produces oxygen which is released into the air.
Plants are perfectly adapted for a number of reasons:
most leaves are broad, larger surface area for light to fall on
they have air spaces to allow carbon dioxide in and oxygen out
they have veins which bring water to the leaves of the plant
Limiting Factors of Photosynthesis
Light Intensity- brighter the light = faster the rate of photosynthesis
Carbon Dioxide Levels- plants need Co2 to photosynthesise and produce glucose
Temperature- photosynthesis is controlled by enzymes which work best at 40 degrees and are denatured if the temperature becomes too high
Water Availability- right amount of water must be available
Use Of Glucose + Nutrients
plants use glucose for..
respiration- breakdown of glucose using oxygen to provide energy for their cells
transport + storage- food must be transported to keep a constant supply of the food made
2 types of transport systems in a plant
phloem- made of living tissue. transports sugars made by photosynthesis around the plant (in all directions)
xylem- carries water + mineral irons from the soil around the plant (only upwards). made from what used to be living tissue
Nitrate Deficiency- wil not grow very big.
Magnesium Deficiency- yellow leaves, Mg needed to make chlorophyll
In photosynthesis, green plants use some light energy from the sun and some is stored in the substances that make up the cells of the plant. This new plant material adds to the biomass (the living material in an animal or plant). All biomass originates from the sun.
Pyramid of Biomass- PYRAMID!
Pyramid of Numbers- size of section represents the number of organisms that there are in a particular food chain
Biomass is lost as the food chain goes up
although the biomass an animal eats is a source of energy, not all the energy can be used.
Energy is lost in...
Excretion- faeces, urine.
Respiration- in the cells
Movement- muscles contract
Warmth- keeping constant body temperature
Sankey Diagram can be used to show the loss of energy
Detritus Feeders- animals that feed on dead animals. worms
Decay Organisms- fungi, bacteria
process of decay- detritus feeders eat dead animals/plants producing waste- decay organisms break down the waste and the dead plants and animals
decay is faster when the conditions are warm and wet. all of the produced materials from the waste are recycled.
Things that affect the levels of carbon dioxide going in and out of the atmosphere...
Photosynthesis- removes CO2
Respiration- releases CO2
Decay- releases CO2
Burning- releases CO2
Structure of Enzymes
an enzyme is a biological catalyst (speed up reactions). an enzyme is a protein and each one has its own shape. an enzyme has room for other molecules to fit in- active site. the shape of an active site changes with high temperatures and this means that the enzyme can no longer function (becomes denatured)
Limiting Factors of Enzyme Action
general reactions are quicker in warmer conditions where the molecules vibrate more violently + enzymes are able to further speed up reactions (up to a certain point). temperatures above 40 degrees tend to denature enzymes.
a subject that is too acidic or too alkaline will also change the shape of the active site.
glucose + oxygen ---> carbon dioxide + water (+energy)
the site where respiration takes place is in the mitochondria. energy is produced in the process. this energy released is used for..
building up larger molecules from smaller ones
enabling muscle contraction in animals
maintaining a constant body temperature in mammals/birds
building nitrates, sugars and other nutrients in plants which are turned into amino acids and later into proteins
digestion requires breaking down large insoluble molecules to smaller soluble molecules. enzyme action assists this. there are a number of carbohydrases (enzymes) which are involved in the digestive system.
Amylase- produced in the salivary glands, pancreas, small intestine. catalyses the digestion of starch into sugars in the mouth and small intestine.
Lipase- produced in the pancreas, small intestine. catalyses the breakdown of lipids (fats) into fatty acids and glycerol. amylase and lipase work best with alkaline conditions so the liver produces bile which is stored in the gall bladder. bile is squirted into the small intestine which neutralises stomach acid, making the conditions slightly alkaline.
Protease- produced in the stomach, pancreas, small intestine. catalyses the breakdown of proteins into amino acids in the stomach and small intestine. protease enzymes in the stomach work best under acidic conditions. glands in the stomach produce hydrochloric acid to make it very acidic. this speeds up digestion.