Cells and Tissues

• The main difference between animal and plant cells is that plant cells have the cell wall, chloroplasts and vacuoles
• a somatic cell is all cells excluding gametes and contains the whole genome of the organism
• Somatic cell functions are determined by which genes are expressed
• cell differentiation is the process where a cell changes from one cell type to another
• stem cells can differentiate to form specialised cells, such as muscle cells or nerve cells
• prokaryotic structure: circular DNA, 70S ribosomes, plasmids, cell wall, cytoplasm, pili and flagellum

  
• prokaryotic cells have cytoplasm that lacks membrane-bound organelles whereas eukaryotic cells have cytoplasm containing membrane-bound organelles
• prokaryotic cells have smaller ribosomes compared to ribosomes in eukaryotic cells
• prokaryotic cells have no nucleus whereas eukaryotic cells do have a nucleus
• prokaryotic cells have a cell wall containing peptidoglycan whereas plant cells have a cellulose cell wall
• prokaryotic cells may have one or more plasmids whereas eukaryotic cells have no plasmids
• prokaryotic cells may have a capsule surrounding the cell whereas eukaryotic cells have no capsule
• • prokaryotic cells have simple flagella
  • eukaryotic cells have more complex flagella when present
• The 3 principles of cell theory:

  • all living things are made up of one or more cells
  • cells are the most basic unit of structure and function in all living things
  • all cells are created by pre-existing cells
• The different types of cells that make up living organisms:

  • eukaryotic cells
  • prokaryotic cells
• cell surface membrane structure:

  • phospholipid bilayer embedded with proteins
  • partially permeable
• cell surface membrane function:

  • controls the exchange of materials between the internal cell environment and the external environment
• nucleus structure:

  • surround by the nuclear envelope (double membrane which has many pores)
  • contains genetic information (DNA) which is combined with proteins to form chromatin
• nucleus function:

  • nuclear pores are important channels for allowing mRNA and ribosomes to travel out of the nucleus, as well as allowing enzymes and signalling molecules to travel in
• mitochondria structure:

  • surrounded by a double-membrane with the inner membrane folded to form cristae
  • the matrix formed by the cristae contains enzymes needed for aerobic respiration, producing ATP
  • small circular pieces of DNA and ribosomes are also found in the matrix
• mitochondria function:

  • site of aerobic respiration (producing ATP)
• ribosome structure:

  • a complex of ribosomal RNA (rRNA) and proteins
  • 80S in eukaryote
  • 70S in prokaryote
  • formed in the nucleous
  • consists of a large subunit and a small subunit
• ribosome function:

  • site of translation
  • involved in protein synthesis
  • uses the information coded in an mRNA molecules to assemble the correct order of amino acids in the protein
• rough endoplasmic reticulum structure:

  • surface covered in ribosomes
  • system of membrane-bound flattened sacs
• rough endoplasmic reticulum function:

  • processes proteins made by the ribosomes
• smooth endoplasmic reticulum structure:

  • system of membrane-bound flattened sacs
  • does not have ribosomes on the surface
• smooth endoplasmic reticulum function:

  • involved in the production, processing and storage of lipids, carbohydrates and steroids
• golgi apparatus structure:

  • a stack of flattened sacs of membrane called cisternae
• golgi apparatus function:

  • modifies proteins and lipids before packaging them into golgi vesicles
• golgi vesicle structure:

  • a membrane-bound sac for transport and storage
  • formed when the end of the cisternae are pinched off
• golgi vesicle function:

  • the vesicles transport the proteins and lipids to their required destination
• centriole structure:

  • hollow fibres made of microtubules
  • two centrioles form a centrosome
• centrioles function:

  • organises spindle fibres during cell division
• lysosome structure:

  • type of vesicle that contains digestive enzymes
• lysosome function:

  • breaks down waste materials such as worn-out organelles
• chloroplasts (in plants) structure:

  • surrounded by a double membrane
  • membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
  • grana are joined by lamellae
  • contains small circular pieces of DNA and ribosomes
  • contains fluid called the stroma
• chloroplasts (in plants) function:

  • site of photosynthesis
• cell wall (in plants) structure:

  • made of cellulose
• cell wall (in plants) function:

  • structural support to the cell
• cell vacuole (in plants) structure:

  • a sac containing cell sap surrounded by the tonoplast
  • selectively permeable membrane