Cells, Tissues and Organs

Animal and Plant Cells
1. Most human cells, like most animal cells contain a nucleus, cytoplasm, cell membrane, mitochocondria and ribsomes.
2. Plant and algal cells contain everything in an animal cell, plus many also contain chloroplasts and a permanent vacuole filled with sap.
3. Plant cells are different because they have different functions
4. KEYWORDS
  1. Nucleus
  2. Cytoplasam
  3. Cell Membrane
  4. Mitochondria
  5. Ribsomes
    1. The site of protein synthesis in a cell
  6. Protein
  7. Algal Cell
    1. The cell of algae, single celled or simple multicellular organisms, which can photosynthesis but it is not a plant
  8. Cell Wall
    1. A rigid structure which surrounds the cells of living organisms apart from animals
  9. Chlorophyll
  10. Vacuole
Specialised Cells
1. Cells are specialised to carry out a particular function, e.g. fat cells, cone cells, root hair cells and sperm cells.
2. If a cell has many ribsomes it is making a lot of protein, e.g. Gland Cells which produce enzymes.
3. Receptor cells have special structures which enable them to detect stimuli, e.g. the cone cells in the eye are light sensetive
4. Neutrons are specialised to carry impulses from receptors to the CNS
  1. CNS = Centeral Nervous System
5. Plant cells with many chloroplasts will be photosynthesising, e.g. mesophyll cells of a leaf
6. Root hair cells increase the surface area of the root so that it can absorb water and mineral ions efficiently.
Diffusion
1. Molecules in gases and liquids move around randomly because of the energy they have
2. DIFFUSION is the spreading out of the particles of a gas, or of any substance in solution.
3. The NET MOVEMENT into or out of cells depends on the concentration of the particles on each side of the cell membrane
4. Because the particles move randomly, there will be a net (overall) movement from an area of high concentration to an area of lower concentration.
5. The difference in concentration between two areas is called the concentration gradient
6. The larger the difference in concentration, the faster the rate of diffusion
Tissues and Organs
1. A tissue is a group of cells with similar structure and function
2. During the development of multicellular organisms the cells differentiate
  1. Multicellular Organism
    1. An organism which is made up of many different cells which work together. Some of the cells are specialised for different functions in the organism
3. Animal tissues include...
  1. Muscle tissue which can contract to bring about movement
  2. Glandular Tissue, to produce substances such as enzymes or homones
  3. Epithelial Tissue, which covers some parts of the body
Organisms in the Enviroment
1. Photosynthesis
  1. Photosynthesis can only be carried out by green plants and algae
  2. Chlorophyll in the chloroplasts absorbs the Sun's light energy.
  3. The Process
    1. 1. Carbon dioxide is taken in by the leaves, and water is taken up by the roots.
    2. 2. The chlorophyll traps the light energy needed for photosynthesis.
    3. 3. This energy is used to convert the carbon dioxide and water into glucose.
  4. Oxygen is released as a by-product of photosynthesis
  5. some of the glucose is converted into insoluble starch for storage.
  6. Keywords
    1. Light Energy
      1. Energy in the form of light.
    2. Glucose
      1. A simple sugar.
    3. Variegated
      1. Having diffrent colours, e.g a green and white leaf.
  7. Making the most of photosynthesis
    1. Plant growers try to give their plants the best conditions for grwoth by controlling the enviroment
    2. Plant grwoers can atificially control the enviroment to improve plant growth
    3. It can be expensive to provide a suitable temperature, light and carbon dioxide. The grower has to compare the biomass of plants growth indoors and outdoors without these extra factors.
2. Limiting Factors
  1. Plants grow best when they have enough light, carbon dioxide and water, and are kept at a suitable temperature.
    1. If any of these conditions are not met, the rate of photosynthesis will be limited.
  2. A lack of light will slow down the rate of photosynthesis.
  3. If it is cold, then th enzymes will not work effectively and this slows down the rate of photosynthesis.
  4. Anything which puts a cap on the rate of photosynthesis is a limiting factor.
  5. Variables which need to be controlled are light, temperature and the type of plant being used.
  6. Keywords
    1. Limiting Factor
    2. Indepenent variable
    3. Dependent Variable
3. How Plants Use Glucose
  1. Plants and algal cells produce glucose during photosynthesis
  2. Glucose produced in photosynthesis can be used in a variety of ways.
  3. Plants and algae need nitrate ions to make proteins.
  4. Uses of soluble glucose
    1. Converted into insoluble starch for storage
    2. Used for respiration
    3. Converted into fats and oils for storage.
    4. Used to produce cellulose which strengthens cell walls
4. Measuring the Distribution of Organisms
  1. The distribution of living things in their natural enviroment can be measured.
  2. The data can be used to find the range, mean, median and mode of the measurements.
  3. Random sampling using a transect
  4. Sample size is important. In a large field, enough quadrats must be placed to be sure the sample is representive of the whole field.
Enzymes
1. Proteins, Catalysts and Enzymes
  1. Proteins are made up of long chains of amino acids.
  2. Enzymes are proteins which act as biological catalysts.
  3. Enzymes are large proteins and the shape of an enzyme is vital for its function.
    1. This shape has an area where other molecules can fit. This is called an active site.
  4. The substrate in a reaction can be held in the active site and can be either connected to another molecule or it can be broken down.
  5. What can an enzyme do?
    1. Build large molecules from many smaller ones
    2. Change one molecule into another one.
    3. Break down large molecules into smaller ones.
2. Factors affecting enzyme action
  1. Factors which alter the shape of the active site prevent the enzyme from working.
  2. Enzyme activity is affected by temperature and pH.
  3. Reactions take place faster when it is warmer. At higher temperature, the molecules move around quicker and collide with each other more often and with more energy.
  4. If the temperature gets too hot the enzyme stops working because the active site changes shape. We say that the enzyme becomes denatured,
3. Enzymes in Digestion
  1. Digestive enzymes are made by glands in the digestive system.
  2. Digestive enzymes work outside the body cells in the cavity of the digestive system.
  3. Specific enzymes digest each particular food type.
4. Speeding up Digestion
  1. Enzymes work best in a narrow pH range.
  2. Protease enzymes in the stomach work best in acid conditions. Glands in the stomach wall produce hydochloric acid to create very acidic conditions.
  3. Amylase and Lipase work in the small intestine. They work best when the conditions are slightly alkaline.
  4. Bile is produced in the liver and stored in the gall bladder.
    1. Bile only neutralises acid, it does not contain enzymes.

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