Cell structure

• cell surface membrane 


  Surrounds cell and controls the exchange of materials between internal and external environment

  made of a phospholipid bilayer and is partially permeable
• cell wall 


  formed outside of cell membrane and offers structural support . in plants its made out of cellulose and in fungus it’s a chitin cell wall
• Nucleus 


  stores genetic information of the cell in chromosomes

  enclosed in double membrane called nuclear envelopes

  envelope has nuclear pores that allow mRNA and ribosomes to travel out and enzymes and signalling molecules in

  contains chromatin which chromosomes are made from

  contains histone which is the protein DNA is wrapped around
• mitochondria 


  sight of aerobic respiration and visible with light microscope

  surrounded by double membrane with a folded inner membrane cristae

  matrix formed by cristae contain enzymes for aerobic respiration producing ATP but also increases surface area

  Has smaller circular pieces of DNA and ribosomes found in matrix for replication
• chloroplast 


  sight of photosynthesis with light dependant stage occurring in thylakoids and light independent stage in stroma

  surrounded by double membrane and larger than mitochondria

  has membrane bound compartments called thylakoids which contain chlorophyll and stack to form grana structures joined by lamellae

  contain small circular pieces of DNA and ribosomes used to synthesise proteins for chloroplast replication and photosynthesis
• ribosomes 


  formed in nucleolus and sight of protein synthesis

  found freely in cytoplasm or as part of rough endoplasmic reticulum in eukaryotic cells

  id a complex of ribosomal RNA and proteins

  80s ribosomes in eukaryotic cells

  70s ribosomes in prokaryotes mitochondria and chloroplast
• rough endoplasmic reticulum 


  has surface covered in ribosomes for protein synthesis

  formed from continuous folds of membrane continuous with nuclear envelope

  processes proteins made by ribosomes
• smooth endoplasmic reticulum 


  Does not contain ribosomes

  involved in production , processing and storage of lipids carbohydrates and steroids
• Golgi apparatus 


  Flattened sacs of membrane similar to smooth endoplasmic reticulum surrounded by vesicles

  modifies proteins and lipids before packaging them into Golgi vesicles for transport around cell

  produces lysomes that are hydrolysis enzymes and put into vesicles for transport
• large permanent vacuole 


  sac in plan surrounded by tonoplast and is selectively permeable membrane

  helps storage and disposal of substances . stores food and nutrients for cell . can store waste products and add to cells rigidity

  vacuoles in animals not permanent and small
• vesicles 


  membrane bound sac for transport and storage
• lysomes 


  specialised forms of vesicles which have hydrolytic enzymes

  break down waster materials like worn out organelles and used by cells of immune system and in apoptosis (programmed cell death)
• flagella 


  tail like structure which rotates to move cell
• what DNA is in prokaryotic cells 


  circular DNA loop that is not associated with proteins

  do not have nucleuses
• plasmids 


  small loops of DNA separate from main circular DNA molecule

  contain genes that can be passed between prokaryotes
• capsule


  protective lime layer which helps cell retain moisture and adhere to other cells .
• cell wall difference in prokaryotes

  made of murein a glycoprotein
• how are nerve cells adapted

  function is the conduction of impulses

  has a cell body and more protein synthesis occurs

  extensions of cytoplasm from cell body form dendrites and axons allowing neurons to communicate with other nerve cells , muscles and glands

  axons covered with myelin sheath which is made from lipids , which speeds up nerve impulses and long for fast impulses
• how are muscle cells adapted

  function contraction for movement

  all muscle have protein filament layers which slide over each other causing contraction

  have high density of mitochondria to provide energy via aerobic respiration for contraction

  skeletal muscle cells fuse together during development to form multi nucleated cells that contract in unison
• how have sperm cells adapted

  function : reproduction to fuse with egg

  head contain nucleus that contains half number of normal chromosomes

  acrosome in head contain digestive enzymes that can break egg cell membrane to fuse haploid cells together

  packed with mitochondria to release energy for movement

  flagella rotates propelling sperm forward
• how have root hair cells adapted

  function absorb water and mineral ions

  root hair to increase surface area so rate of absorption greater

  thinner walls than other plant cells so less diffusion distance

  permanent vacuole contains sap which in more concentrated then soil water maintaining water potential gradient

  mitochondria for active transport of mineral ions

  no chloroplast
• How are xylem cells adapted

  function : transport water and dissolved ions

  no top and bottom walls between cells form continuous hollow tubes for water to move for transpiration

  cells are dead and without organelles or cytoplasm so free movement of water

  outer walls thickened by ligain which strengthens tube to withstand osmotic pressure
• How are phloem cells adapted

  Function : transport dissolved sugars and amino acids

  made of living cells which supported by companion cells

  cells joined end to end contain holes in cell wall forming tubes for substances to flow easily by translocation

  cells have very few sub cellular structures to aid flow of materials
• organisation of cells 


  specialised cells group together to form tissues

  tissues are a group of cells that work together to perform a particular function and different tissues work together to form organs
• eukaryotic vs prokaryotic 


  Prokaryotic has no mitochondria , or chloroplast .

  prokaryotic DNA is a singular loop found free in cytoplasm eukaryotic DNA Is is nucleus

  prokaryotic divide by binary fission eukaryotic divide by mitosis

  prokaryotic smaller
• viruses 


  non cellular infectious particles

  simple structure and much smaller than prokaryotic

  have a nucleic acid core and a protein coat called a capsid

  have a outer layer called a envelope formed from membrane phospholipid

  parasitic can only reproduce from infecting living cells and using organelles to build more