Biology Additional

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  • Created by: Amrita
  • Created on: 25-03-14 12:43
Controls cell activities
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All chemical reactions happen here
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Cell membrane
Controls what enters and leaves
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Makes proteins from amino acids
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Produces energy from respiration
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Contains chlorophyll to absorb sunlight
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Sap vacuole
Contains sugar and salts
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Cell wall
Provides strength and support
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Plant cells have a rigid cell wall made of cellulose which strengthens the cell and the plants structure
Dissolved substances can move into and out of cells by diffusion through the cell membrane
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What is diffusion?
Diffusion is when particles move from an area of high concentration to an area of low concentration e.g Oxygen moving from blood vessels into the cells
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The greater the difference in concentration, the faster the rate of diffusion, due to the steeper concentration gradient
Only relatively small molecules can diffuse through cell membranes e.g Amino acids not proteins
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What are a plant's organs?
The stem, roots and leaves
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Palisade cells contain chlorophyll and are adapted for photosynthesis
Guard cells are adapted to open and close the pores which allows gas exchange and water evaporation
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What is the epidermal tissue?
The outer layer which covers the whole plant
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What are the mesophyll tissues?
Most photosynthesis happens here. They are between the epidermal tissues
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What do the xylem and phloem do
Transport substances around the plant e.g Sugars like sucrose and glucose
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Equation for photosynthesis?
Co2 + Water > Glucose + Oxygen
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Light energy is absorbed by chlorophyll which is found in chloroplasts
The energy is used by converting Co2 and water into sugars
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What are limiting factors of photosynthesis?
Shortage of light, low temperatures, shortage of co2
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Glucose produced may be converted into insoluble starch for storage in leaves, roots and stems
To produce proteins, plants use nitrate ions that are absorbed from the soil
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Factors that affect distribution
Temperature, amount of light, availability of nutrients, water, oxygen and co2
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Random sampling with quadrats
Close your eyes and throw
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Sampling along a transect
Put down a metre string. Place quadrat at the beginning. Record presence of each plant type. Place quadrat at next point. Repeat to get reproducible results
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Protein molecules are made up of long chains of amino acids. They are folded to produce a specific shape that enables other molecules to fit into the protein. e.g Biological Catalysts
Proteins act as structural components of tissues e.g muscles. Or hormones, antibodies and catalysts
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What do catalysts do?
Increase the rate of chemical reactions
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Biological catalysts are called enzymes and they enable the vast majority of reactions in cells.
Enzymes are proteins and work best at 35-37 degrees
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Pepsin works best in acid conditions of the stomach
Carbonic hydrase works best in neutral media like the blood
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Trypsin is most effective in alkaline conditions
The higher the enzyme concentration, the faster the reaction
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Digestive enzymes are produced by specialised cells in glands and in the lining of the gut
Enzymes then pass out of the cells into the gut where they come into contact with food. They catalyse the breakdown of large molecules into smaller molecules. E.g. Large carbohydrate molecules are converted into smaller sugar molecules
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Where is amylase produced?
In the salivary glands, pancreas and small intestine
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Where is protease produced?
In the stomach, pancreas and small intestine
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Where is lipase produced?
In the pancreas and small intestine
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Starch turns into sugars using amylase
Protein turns into amino acids using protease
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Lipids turn into fatty acids and glycerol using lipase
The mouth turns starch into sugars
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The stomach turns protein into amino acids
The small intestine and pancreas turn lips into fatty acids and glycerol, starch into sugars and protein into amino acids
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What does bile do?
The bile, which is alkali, from the liver mixes with the acid from the stomach to neutralise it
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At home, why are biological detergents used?
They contain protease to digest proteins and lipase to break down fats and oils
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Baby food
Protease turns protein into pre digested protein
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Carbohydrase turns starch into sugar syrup
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Diet foods
Isomerase turns glucose syrup into fructose syrup, which is sweeter therefore you can use less
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Advantages of enzymes
Effective at low temperatures so it uses less energy, therefore it is cheaper. They can also be reused
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Disadvantages of enzymes
It is expensive to produce the enzyme and it denatures at a high temperature
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Equation for aerobic respiration
Glucose + Oxygen > Co2 + Water (+Energy)
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Where does the majority of aerobic respiration occur?
In the mitochrondria
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What is energy from respiration used for in living things?
To turn amino acids into proteins
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What is energy from respiration used for in animals?
To contract muscles
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What is energy from respiration used for in mammals/birds?
Maintain body temperature
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What is energy from respiration used for in plants?
Takes sugar and nitrates and builds them up to make amino acids which makes proteins for growth
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Equation for anaerobic respiration
Glucose > Latic Acid + Energy
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What exercise could cause anaerobic respiration?
Lifting weights
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When lactic acid is produced you..
Become fatigued and your muscles stop contracting efficiently
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What is the oxygen debt?
Oxidisation of lactic acid into carbon dioxide and water
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Blood flowing through muscles removes lactic acid
When exercising, the glycogen in the muscles breaks down which supplies glucose for respiration
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What contains genetic information?
The chromosomes
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Cells in the testes and ovaries divide to form gametes
Stem cells can be made to differentiate into many different types of cells e.g Nerve Cells. They can cure conditions like paralysis
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Sexual reproduction gives rise to variation because when gametes fuse, one of each pair of alleles comes from each parent
An allele is one version of a gene
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Chromosomes are made up of large molecules of DNA which has a double helix structure. A gene is a small section of DNA
Each gene codes for a particular combination of amino acids which make a specific protein
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What can DNA fingerprinting be used for?
Paternity and criminal identification
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What is polydactyly?
Having extra fingers or toes. It is caused by a dominant allele of a gene and can therefore be passes on by only one parent who has the disorder
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What is cystic fibrosis?
A disorder of cell membranes which must be inherited from both parents. The parents may be carriers of the disorder without having it themselves due to a recessive allele of a gene which can be passed on by parents
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Embryos can be screened for the alleles that cause genetic disorders
Evidence for early forms of life comes from fossils. Fossils are traces or remains of organisms which are found in rocks
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How are fossils formed?
Either from the hard parts of animals that do not decay easily or preserved traces of organisms e.g. Footprints
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Soft bodied forms of life like slugs decay easily therefore they have left few traces behind which were destroyed by geological activity
From fossils you can learn how much different organisms have changed as life developed on Earth
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Extinction may be caused by...
Changes to the environment over geological time. New predators. New diseases. More successful competitors.
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Genetic Variation
Each population has a wide range of alleles that control their characteristics
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Natural Selection
In each population, the alleles that control the characteristics which help the organism to survive are selected
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The populations become so different that successful interbreeding is no longer possible
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Two populations of a species become separated e.g. Geographically
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New species arise as a result of...
Isolation, Genetic Variation, Natural Selection or Speciation
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All chemical reactions happen here



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Controls what enters and leaves


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Card 4


Makes proteins from amino acids


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Produces energy from respiration


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