2.Cell Structure

• The main features of animals:

  • They are multicellular
  • Their cells contain a nucleus with a distinct membrane
  • Their cells do not have cellulose cell walls
  • Their cells do not contain chloroplasts (so they are unable to carry out photosynthesis)
  • They feed on organic substances made by other living things
  • They often store carbohydrates as glycogen
  • They usually have nervous coordination
  • They are able to move from place to place
• The main features of plants:

  • They are multicellular
  • Their cells contain a nucleus with a distinct membrane
  • Their cells have cell walls made out of cellulose
  • Their cells contain chloroplasts (so they can carry out photosynthesis)
  • They feed by photosynthesis
  • They store carbohydrates as starch or sucrose
  • They do not have nervous coordination
• Nucleus function:

  contains DNA which controls the activities of the cell
• cytoplasm function:

  • jelly-like texture
  • supports internal cell structures
  • site of many chemical reactions including anaerobic resperation
• cell membrane function:

  • holds cell together
  • separates inside cell from outside cell
  • controls substances that enter and leave cell
• ribosome function:

  • found in cytoplasm
  • site of protein synthesis
• mitochondria function:

  • site of most reactions involved in aerobic respiration
  • where energy is released
• (plant) cell wall function:

  • made of cellulose
  • gives cell extra support
  • gives cell its shape
• chloroplasts function:

  • contains green chlorophyll pigments
  • contains enzyme needed for photosynthesis
• permanent vacuole function:

  • contains cell sap
  • used for storage for certain materials
  • helps support the cell
• cell cap is a solution of sugars and salts dissolved in water
• chlorophyll pigments absorb light energy
• bacteria have a wide variety of shapes and sizes
• bacteria all share the following biological characteristics:

  • They are microscopic single-celled organisms
  • Possess a cell wall (made of peptidoglycan, not cellulose), cell membrane, cytoplasm and ribosomes
  • Lack a nucleus but contain a circular chromosome of DNA that floats in the cytoplasm
  • Plasmids are sometimes present
  • They lack mitochondria, chloroplasts and other membrane-bound organelles found in animal and plant cells
• plasmidsare small rings of DNA (also floating in the cytoplasm) that contain extra genes to those found in the chromosomal DNA
• Some bacteria also have a flagellum (singular) or several flagella (plural). These are long, thin, whip-like tails attached to bacteria that allow them to move
• • Examples of bacteria include:
  • Lactobacillus (a rod-shaped bacterium used in the production of yoghurt from milk)
  • Pneumococcus (a spherical bacterium that acts as the pathogen causing pneumonia)
• Organelles visible in almost all cells except prokaryotes when looking at higher magnification

  • Mitochondria
  • Ribosomes
  • Endoplasmic Reticulum
  • Vesicles
• Mitochondria


  Organelles found throughout the cytoplasm
• Ribosomes


  Tiny structures that can be free within the cytoplasm or attached to a system of membranes within the cell known as Endoplasmic Reticulum
• Endoplasmic Reticulum studded with ribosomes


  Looks rough under the microscope, giving rise to its name of Rough Endoplasmic Reticulum (often shortened to R.E.R.)
• Vesicles


  Small circular structures found moving throughout the cytoplasm
• organelles visible under light microscope vs electron microscope

  in an animal cell

  
• organelles visible under light microscope vs electron microscope

  in a plant cell

  
• • The cells in your body need to be able to divide to help your body grow and repair itself
• Cells grow and divide over and over again
• New cells are produced by the division of existing cells
• Specialised cells are those which have developed certain characteristics in order to perform particular functions. These differences are controlled by genes in the nucleus
• Cells specialise by undergoing differentiation: this is a process by which cells develop the structure and characteristics needed to be able to carry out their functions
• ciliated cell specialised cell in animals
• ciliated cell function:

  movement of mucus in the trachea and bronchi
• ciliated cell adaptations:

  • extensions of cytoplasm at the surface of the cell form hair-like structures called cilia
  • cilia beat to move mucus and trapped particles up the throat
• nerve cell is a specialised cell in animals
• nerve cell function:

  conduction of impulses
• nerve cell adaptations:

  • Long so nerves can run to and from different body parts to CNS (central nervous system)
  • has extensions and branches so it can communicate with other cells, muscles and glands
  • the axon is covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse
• axon is the extension of cytoplasm away from cell body that carries impulses
• red blood cell is a specialised cell in animals
• red blood cell function: transport of oxygen
• red blood cell adaptations:

  • biconcave disc shape increases surface area for efficient diffusion of oxygen
  • contains haemoglobin which joins with oxygen to transport it
  • no nucleus to increase amount of space for haemoglobin inside the cell
• sperm cell is a specialised cell in animals