GCSE B2 Chapter 1

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  • Created by: emma998
  • Created on: 16-03-14 14:34

Animal and plant cells

  • All living things are made up of cells
  • Cells can only be seen with powerful microscopes
  • Light microscope are used in schools, electrons microscopes magnify things thousands of times larger
  • Most cells have some structures in common
    • Nucleus - controls the cells activitiy, is where DNA is stored
    • Cytoplasm  - where most of the chemical reactions occur
    • Cell membrane - controls the movements of substances into and out of the cell
    • Mitochondria - release energy during aerobic respiration
    • Ribisomes - where protein synthesis takes place
  • Plant and algal cells also have:
    • Cell wall - made of cellulose for support
    • Permanent vacuole - containing cell sap used as a food storage
    • Chloroplasts - Containing chlorophyll for photosynthesis
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Bacteria and yeast

  • Bacteria
    • Micrscopic organisms which can only be seen with very powerful microscopes
    • Colonies of bacteria can be seen with the naked eye
    • They have a cell wall and a cell membrane surrounding cytoplasm
    • They don't have a nucleus, DNA is stored loose in the cytoplasm
    • Also have a flagella(tail), plasmids and slime capsules
  • Yeast
    • Single celled organism
    • Been useful for centuries to make bead and beer
    • They have a nucleus and cytoplasm surrounded by a cell wall and a cell mebrane
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Specialised cells

  • As a multicelluar organism matures and develops, unspeciallised stem cells differentiate into speciallised cells which have a paticular structure to carry out a specific function
  • Cells which have tails must need to move e.g. sperm cells
  • Cells which have many mitochondria must need a lot of energy e.g. muscle cells
  • Cells with lots of ribosomes must be making lots of protein e.g gland cells
  • Cells which have receptors must be able to detect stimuli
  • Cells with many chloroplasts must be photosynthesising
  • Root hair cells increase surface area for maximum absorbtion of water and mineral ions
  • Nerons are speciallised to carry impulses from the receptors to the CNS
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Diffusion

  • Molecules in gases and liquids move around randomly because of the energy they have
  • Diffusion is the spreading out of particles
  • Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration
  • The steeper the concentration gradient the faster the rate of diffusion
  • Examples of diffusion:
    • The diffusion of simple sugars and amino acids from the gut through cells membranes
    • The diffusion of oxygen from the blood into cells as the cells are respiring
    • The diffusion of carbon dioxide into actively photosynthesising plant cells
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Tissues and organs

  • During the development of multicellular organisms the cells differentiate and become speciallised to carry out a paticular function
  • A tissue is made up of a group of cells with a similar structure and function
  • Animal tissue types include:
    • Muscular tissue - can contract to bring about movement
    • Glandular tissue - produces substances such as enzymes and hormones
    • Epithelial tissue - covers parts of the body
  • Plant tissue types include:
    • Epidermal tissue - covers the plant
    • Mesophyll tissue - contains chloroplasts for photosynthesis
    • Xylem and phloem - transport substances around the body
  • An organ is a group of tissues that work together to carry out a paticular function
  • The stomach is an organ made up of epithelial tissue which covers inside and outside of the stomach, muscular tissue which churns stomach contents and glandular tissue which produces digestive juices
  • The leaves, stem and roots are plant organs
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Organ systems

  • Organ systems are groups of organs which work together to carry out a paticular function
  • The digestive system is an organ system which carries out the process of digestion (large insoluble molecules into smaller soluble molecules)
  • Digestive system is a muscular tube which contains:
    • Glands such as the pancreas and the salivary glands which produce digestive juices
    • The stomach and the small intestine which is where digestion occurs 
    • The liver which produces bile to aid digestion
    • The small intestine where the absorbtion of soluble molecules occurs
    • The large intestine where water absorbed from insoluble molecules producing faeces 
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