biology KS4 revision

cells
1. animal cells
  1. nucleus
    1. contains genetic material which controls the activities of the cell
  2. cell membrane
    1. acts as a barrier and controls what goes in and out of the cell
  3. mitchondria
    1. where most energy is released through respiration
  4. ribosomes
    1. where protein synthesis takes place
  5. cytoplasm
    1. most chemical processes take place here, controlled by enzymes
2. plant cells
  1. cytoplasm
  2. nucleus
  3. cell membrane
  4. permanent vacuole
    1. filled with cell sap to help keep the cell inflated (turgid)
  5. cell wall
    1. helps support the structure of the cell
  6. chloroplast
    1. contains chloryphyll which uses light energy for photo synthesis
3. bacteria cells
  1. single celled organisms
  2. different structure to plant and animal cells
  3. has a cytoplasm, cell wall and cell membrane
  4. genetic material is not in a distinct nucleus
4. yeast cell
  1. same as bacteria cell
  2. also has a nucleus
5. leaf cell
  1. absorbs light energy for photosynthesis
    1. regular shaped plant cell
    2. packed with chloroplasts
6. root hair cells
  1. absorbs water and mineral ions from surrounding soil
7. diffusion
  1. disolved substances have to pass through the cell membrane to get in or out of the cell
    1. diffusion allows this to happen
  2. diffusion takes place when particles go from a high concentration to a low concentration
    1. this only happens when the particles are free to move
    2. this happens often with gases ( how a smell travels from one area of the room to another)
  3. from the lungs oxygen particles move from the alvioli air space into the bood circulating around the lungsto be able to be taken around the body where they are needed
tissues, organs and organ systems
1. organs in animals
  1. multicellular organisms usually have differenciated cells that have specific functions
    1. tissues are groups of similar cells
      1. organs cosist of different tissues working together to carry out a particular a function
        organ systems consist of different organs
        different organ systems work together to create an organism
        some organs consist of a number of different tissues
    2. muscle tissue
      1. contracts, creating movement
    3. glandular tissue
      1. produces substances such as enzymes and hormones
    4. epithelial
      1. covers most parts of the body
  2. the body has several organ systems
    1. the respiritory system, the digestive system, the reproductive system, the nervous system
  3. liver
    1. produces bile
  4. stomach
    1. digests foods
  5. pancreas
    1. produces enzymes
  6. small intestine
    1. digest and absorb souluable food
  7. large intestine
    1. absorbs water from undigested foods producing feceas
2. organs in plants
  1. plants are multicellular organisms like animals
    1. they also contain differenciated cells, tissues and organs
  2. mesophyll carries out photosynthesis
  3. xylem and phloem transport substances around the plant
  4. sections of a leaf
    1. waxy cuticle
      1. protects the leaf without blocking out sunlight
    2. upper and lower epidermis
      1. protecitve layer of cells which allow more light through
    3. paliside cells
      1. absorb the light to allow ohotosynthesis to take place
    4. spongy messophyll
      1. irregular shaped layer of cells with airspaces inbetween to allow carbon dioxide to diffuse into the cell
photosynthesis
1. these sections of the leaf allow photosynthesis to take place
2. factors affecting the rate of reaction
  1. temperature
    1. on a graph the line will increase then once it has got to the limiting point the line will then fall back down
  2. carbon dioxide concentration
    1. on a graph the line will increase then level off
  3. light intencity
3. photosynthesis is a chemical change
4. carbon diocide + water -----> glucose +oxygen
  1. light intensity
5. some gluecose is used for respiration while most is converted into starch and stored
organisms and their enviroment
1. the distribution of living organisms in a particular habitat may be due to physical factors
  1. these physical factors include
    1. the temperature
    2. amount of light available
    3. availability of water
    4. availability of nutruents
    5. availability of oxygen and carbondioxide
2. enviroment
  1. all the conditions that surround a organism
3. ecosystem
  1. the comunity and the habitat which it lives in
4. habitat
  1. place where it lives
5. population
  1. all the members of a single speciece that live in that habitat
6. community
  1. population of different organisms that live together in the same habitat
7. collecting quantitive data
  1. use a quadrat to collect a sample of data
    1. this method is used as it is not always possible to collect an entire population of a particular organism in its habitat
    2. this must be placed rendomly to ensure a representative sample is taken
    3. the more results taken and put together the more reliable the results become
      1. from the results you can calculate the mean, median and mode number of organisms in that habitat
proteins and their function
1. protain molecules are long chains of smaller molecules named amino acids
  1. protein molecules are brocken down by protease
    1. protease can be used to pre digest food in baby food
  2. produced in the small intestine, stomach, pancreas
2. enzymes are biological catalysts
  1. they speed up the rate of chemical reactions
  2. they are proteins that fold up into cpmplex shapes to allow smaller molecules to fit in to them. the place where the substraits fit into the enzyme is called the active site
    1. the enzyme can break a large subsrtare down or join to small substrate molecules together
    2. enzyme molecules can become denatured if the temperature of their envioroment increases above 37degreeese c.
      1. if an enzyme has been denatured the active site has become miss shaped and therefore cannot breake down the correct molecules
3. fat molecules are broken down into glycerol
  1. produced in the pancreas and small intestine
    1. lipase is used in manurfactoring for biological detergents
4. starch molecules are broken down into sugars by amylase enzymes
  1. produced in the salivary gland, pancreas and small intestine
5. enzymes in the stomach work best in acidic conditions the acid in the stomach is hydrochloric acid
6. enzymes in the small intestine work best in alkali conditions. to nutralise the food so that it can becom an alkali once it has left the stomach the liver produces a substancece called bile that is stored in the call bladder
respiration
1. aerobic
  1. respiration with the use of oxygen to produce energy
  2. oxygen + glucose --> carbon dioxide+ water ( +energy)
2. anaerobic
  1. respireation with the absence of oxygen
  2. glucose--> lactic acid (+ little energy)
    1. this lactic acid can lead to muscle fatigue ( state of total mental and physical exahusion due to extreme exercise)
  3. incomplete breakdown of glucose
  4. oxygen dept
    1. the amout of oxygen needed to oxydise lactic acid into carbon dioxide and water
    2. this happens because the breakdown of glucose is incomplete
3. respiration releces energy for cells from glucose
4. energy is produced from glucose
  1. cells store glucose as glycogen and can be turned back into glucose during exercise
5. during exercise the muscles cells respire more rapidly than they would when at rest
  1. now, oxygen and glucose must be delivered to the cells more quickly
  2. and the waste product carbon dioxide must be removed more quickly
  3. to solve this the hart rate increases to increase the blood flow around the body. and the breathing rate increases to increase the rate of gaseous exchanges in the body
cell division and inheritance
1. DNA and Cell division
  1. DNA
    1. large and complex meolecules
    2. carry the ginetic code that determins the charicteristics of living organisms
    3. each persons DNA is uniqu
  2. Genes
    1. this is a short section of DNA
    2. each gene codes for a specific protein by specifying a particular order in which amino acids need to be joined together
  3. Chromosomes
    1. the cells nucleus contains chromosomes made from long DNA molecules
      1. 23 pairs of chromosomes in a body cell
  4. body cells divide by a process called mitosis
    1. the genetic information is copied and the cell spits into two daughter cells, this process then repeats
      1. mitosis occurs during growth, and to produce replacement cells
  5. gametes are sex cells, they contain one set of genetic information
    1. the type of cell division that produces gametes is mieosis
      1. when the male gametes and femail gametes join together in fertilisation the two single sets of chromosomes join together to greate 23 pairs of chromosomes which provide the genetic information needed
        cells divide twice to form four gametes
  6. most animal cells are specialised for a particular function and these functions cannot be changed
  7. stem sells
    1. stem cells can be made to differenciate to form different types of cells, such as nerve cells
    2. human stem cells can also be used from embryos and bone marrow
2. genetic variation and genetic dissorders
  1. there are two types of alleles, dominant and ressessive
speciation

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biology KS4 revision

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