Cell Biology

• Eukaryotic cells


  Contain a nucleus and other organelles that are bound by membranes.
• Prokaryotic cells


  do not have a nucleus or other membrane-bound organelles
• Parts of an animal cell

  Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
• Function of nucleus

  directs all the cells activities; contains the cells DNA
• Function of cytoplasm

  where chemical reactions take place
• Function of cell membrane

  regulates what enters and leaves the cell and holds the cell together
• Function of mitochondria

  where aerobic respiration takes place
• Functions of ribisomes

  where proteins are made in the cell
• Parts of a plant cell

  Chloroplast,

  Vacuole, Cell membrane, Cytoplasm Nucleus, Mitochondria, Cell wall
• Function of a cell wall

  Supports the cell and strengthens it
• Function of vacuole

  Stores materials such as water, salts, proteins and carbs; helps plants support heavy structures like leaves
• Function of chloroplasts

  carries out photosynthesis
• Function of sperm cells + how is it specialised

  - To get the male DNA to the female DNA.

  
  

  - It has a long tail and a streamlined head to help it swim to the egg.

  
  

  - It has a lot of mitochondria in the cell to provide energy needed.

  
  

  - It carries enzymes in its head to digest through the egg cell membrane
• Function of nerve cells + how is it specialised

  - To carry electrical signals from

  one part of the body to the other.

  
  

  - These cells are long to cover more distance

  
  

  - Has branched connections at the their ends to connect to other nerve cells and form a network throughout the body.
• Function of muscle cells + how is it specialised

  - To contract quickly

  
  

  - These cells are long so they have more space to contract

  
  

  - Has lots of mitochondria to generate the energy needed for contraction
• Function of root hair cells + how is it specialised

  - To absorb water and minerals

  
  

  - Has long hairs that stick out into the soil which gives the plant a big surface area for absorbing water and minerals
• Function of phloem + xylem cells

  -Transports substances such as food and water around plants

  
  

  - Xylem cells are hollow + phloem cells have very sub-cellular structures so stuff can flow through them
• Differentiation

  process in which cells become specialized in structure and function
• What happens when cells change?

  - They develop different subcellular structures and turn into different types of cells.

  
  

  - This allows them to carry out specific functions.
• When do most animal cells differentiate?

  in an early stage of development, then lost after they become specialised
• When do plant cells differentiate?

  throughout their whole life
• How is cells in mature animals used?

  For repairing and replacing cells e.g skin and blood cells
• How has electron microscopes increased understanding of sub-cellular structures?

  - Has much higher magnification + resolving power than a light microscopes

  
  

  - TMT it can be used to study cells in finer detail

  
  

  - Allows biologists to see/understand sub-cellular structures
• What does a nucleus cell contain?

  It contains genetic material

  in the form of chromosomes
• Chromosomes


  coiled up lengths of DNA molecules
• What do chromosomes carry?

  A large number of genes
• What are chromosomes found in?

  They are found in body cells and in pairs.

  
  

  - One from the organism's mother and one its father
• Mitosis

  The stage of the cell cycle when the cell divides
• Use of mitosis


  growth and repair for cells that have been damaged
• Stages of mitosis

  prophase, metaphase, anaphase, telophase

  
• Cell cycle


  series of events that cells go through as they grow and divide
• Stem cell


  cell that can divide for long periods of time while remaining undifferentiated
• Function of stem cells in embryos

  Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
• Functions of stem cells in adults

  Can form into many types of cells e.g.blood cells
• Function of meristems

  Can differentiate into any type of plant cell throughout the life of a plant
• Therapeutic cloning


  The production of embryonic stem cells for use in replacing or repairing damaged tissues or organs, diabetes, nerve cells for people paralysed by spinal injury
• Arguments against stem cell research

  - unethical as the embryo is destroyed, potential life lost

  -against its human rights as it cannot give permission

  
  

  -research is time consuming and expensive time and money should be spent perfecting other conventional treatments

  
  

  - can transfer viral infections as stem cells grown in the lab may become contaminated
• Arguments for stem cell research

  Curing existing patients who are suffering is more important than the rights of embryos
• What can meristems be used for?

  - To produce identical clones of plants quickly and cheaply

  
  

  - To grow more plant of rare species

  
  

  - To grow crops with desired features, e.g. disease resistance
• Diffusion


  Movement of molecules from an area of higher concentration to an area of lower concentration.