Notes

• What are the 2 main types of cells

  • prokaryotic
  • eukaryotic
• What type of cells are eukaryotic

  • animal cell
  • plant cell
• What is the structure of an animal cell

  • nucleus
  • cytoplasm
  • cell membrane
  • mitochondria
  • ribosomes

  
• What is the structure of a plant cell

  • cell wall
  • cell membrane
  • nucleus
  • mitochondria
  • ribosomes
  • vacuole
  • chloroplasts

  
• What types of cells are prokaryotic

  • bacteria cell
• What are the differences between prokaryotic cells and eukaryotic cells

  Prokaryotic : unicellular, no nucleus, often smaller

  Eukaryotic: multicellular, nucleus, often larger
• What is the structure of a bacteria cell

  • circular strands of DNA
  • Plasmids
  • Flagellum
  • Cell membrane
  • Cell Wall
  • ribosomes
  • Cytoplasm

  
• What is the function of the nucleus in animal and plant cells

  • contains DNA coding for a particular protein needed to build new cells
  • enclosed in a nuclear membrane
• What is the function of the cytoplasm in animal, plant and bacteria cells

  • liquid substance in which chemical reactions occur
  • contains enzymes (biological catalysts etc proteins that speed up the rate of reaction)
  • organelles are found in it
• What is the function of the cell membrane in animal, plant and bacteria cells

  • controls what enters and leaves the cell
• What is the function of the mitochondria in animal and plant cells

  • where aerobic respiration reactions occur, providing energy for the cell
• What is the functions of ribosomes in animal and plant cells

  • where protein synthesis occurs
  • found on a structure called the rough endoplasmic reticulum
• What is the function of chloroplasts in plant cells

  • where photosynthesis takes place, providing food for the plant
  • contains chlorophyll pigment (which makes it green) which harvests the light needed for photosynthesis
• What is the function of the permanent vacuole in plant cells

  • contains cell sap
  • found within the cytoplasm
  • improves cell's rigidity
• What is the function of the cell wall in plant cells

  • made from cellulose
  • provides strength to the cell
• What is the function of the cell wall in a bacteria cell

  made up of a different compound in comparison to plant cells: peptidogylcan
• What is the function of the single circular strand of DNA in a bacteria cell

  as the bacteria cell has no nucleus, this floats in the cytoplasm
• What is the function of plasmids in bacteria cells

  small rings of DNA
• How do you calculate the size or area of a sub-cellular structure

  find a shape such as a circle or rectangle that resembles it and find the area/size of that shape (length x width - for rectangle)
• how do cells become specialised

  they undergo differentiation: a process that involves the cell gaining new sub-cellular structure in order for it to be suited to its role.
• how often can cells specialise

  they can either differentiate once early on or have the ability to differentiate their whole life (these are called stem cells)
• In animals cells when do cells typically become specialised

  most cells differentiate early on and only once
• In plant cells when do cells typically become specialised

  they have the ability to differentiate their whole life
• What are some examples of specialised cells in animals

  • sperm cells
  • nerve cells
  • muscle cells
• What are some examples of specialised cells in plants

  • root hair cells
  • xylem cells
  • phloem cells
• How are sperm cells specialisedin animals

  • specialised to carry the male's DNA to the egg (ovum) for reproduction
  • streamlined head and long tail to aid swimming
  • many mitochondria (where respiration happens) which supply the energy to allow the cell to move
  • the acrosome (top of the head) has digestive enzymes which break down the outer layers of membrane of the egg cell
• How are nerve cells specialised in animals

  • specialised to transmit electrical signals quickly from one place in the body to another
  • acon is long, enabling the impulses to be carried long distances
  • having lots of extensions from the cell body (dendrites) means branched connection can form with other nerve cells
  • nerve endings have many mitochondria which supply the energy to make special transmitter chemicals called neurotransmitters which allow for an impulse to be passed from one cell to another
• How are muscle cells specialised in animals

  • specialised to contract quickly to move bones or simply to squeeze therefore causing movement
  • special proteins (myosin and actin) slide over each other, causing muscle to contract
  • lots of mitochondria to provide energy from respiration for contraction
  • they can store a chemical called glycogen that is used in respiration by mitochondria
• How are root hair cells specialised in plants

  • specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots
  • have a larger surface area due to root hairs, meaning more water can move in
  • large permanent vacuole affects the speed movement of water from soil to the cell
  • mitochondria to provide energy from respiration for the active transport of mineral ions into the root hair cell
• How are xylem cells specialised in plants

  • specialises to transport water and mineral ions up the plant from the roots to the shoots
  • upon formation a chemical called lignin is deposited which causes the cells to die. They become hollow and are joined end-to-end to form a continuous tube so water and mineral ions can move through
  • lignin is deposited in spirals which help the cell withstand the pressure from the movement of water
• How are phloem cells specialised in plants

  • specialised to carry the products of photosynthesis (food) to all parts of the plant
  • cell walls of each cell from structure called sieve plates when they break down, allowing the movement of substances from cell to cell
  • despite losing many sub-cellular structures, the energy the cells need to be alive is supplied by the mitochondria of the companion cells
• How does cell differentiation work

  to become specialised the stem cells must undergo differentiation to form specialised cells this involves their genes being switched on or off to produce different proteins allowing the cell to acquire different sub-cellular substances for it to carry out a specific function
• How does cell differentiation work in animals

  • most cells differentiate in the early stages and then lose this ability later in life
  • most specialised cells can make more of the same cell by undergoing mitosis (the process that involves a cell dividing to produce 2 identical cells)
  • other cells such as red blood cells (which lose their nucleus) cannot divide and are replaced by adult stem cells ( which retain their ability to undergo differentiation)
  • in mature animals, cell division mostly only happens to repair or replace damaged cells as they undergo little growth
• How does cell differentiation work in plants

  • many types of cells retain the ability to differentiate throughout their life
  • only when they reach their final position in the plant do they differentiate, but can still re-differentiate when it is moved to another positions
• Extremely small structures such as cells cannot be seen without microscopes, which enlarge images
• The first cells of a cork were observed by Robert Hooke in 1665 using a light microscope
• What are the features of a light microscope

  • it has 2 lenses, an objective and eyepiece
  • the objective lens produces a magnified image, which is then magnified and directed into the eye by the eyepiece lens
  • it is usually illuminated from underneath using a lamp or mirror
  • They have approximately, a maximum magnification of x2000 and a resolving power (this affects resolution: the ability to distinguish between 2 points) of 200nm (the lower the RP, the more detail is seen)
  • used to view tissues, cells and larger sub-cellular structures
• When was the electron microscope developed

  1930s
• In the 1930s the electron microscope was developed, enabling scientists to view deep inside the sub-cellular structures, such as mitochondria, ribosomes, chloroplasts and plasmids
• What are the features of an electron microscope

  • can see sub-cellular structures in more detail and closer up
  • electrons, as opposed to light, are used to form an image because the electrons have a much smaller wavelength than that of light waves
  • there are 2 types: a scanning electron microscope that create 3D images (at a slightly lower magnification) and a transmission electron microscope which creates 2D images detailing organelles
  • they have magnification of up to x2,000,000 and resolving power of 10nm (SEM) and 0.2nm (TEM)