3.2.1.

• Cell Surface Membrane

  Controls the exchange of materials between internal and external environment.

  • Partially permeable.
  • Phospholipid bilayer.
• Nucleus

  An organelle that stores the genetic information of the cell

  • Contains Chromosomes; protein-bound linear DNA
  • May have more than one nucelolus
• Nucleolus

  Contains all genetic information; chromasomes

  • Site of ribosome production
• Nuclear Envelope

  Double membrane surrounding the nucleus.
• Nuceloplasm

  Granular jelly-like material

  • Makes up the bulk of the nucleus
• Rough Endoplasmic Reticulum

  Processes proteins made by ribosomes

  Large surface area

  • Surface covered in ribosomes
  • Continuous folds of membrane connected to the nuclear envelope
• Nuclear Pores

  Allows molecules in and out of the nucleus
• Smooth Endoplasmic Reticulum (ER)

  Does not have ribosomes on the surface 

  • Production, processing and storage of lipids, carbohydrates and steroids.
• Mitochondria

  Site of aerobic respiration within eukaryotic cells

  • Surrounded by double membrane
• Cristae (Mitochondria)

  The folded inner membrane

  • Forms the matrix
• Matrix (Mitochondria)

  Contains enzymes needed for aerobic respiration

  • Produces ATP
  • Contains small circular pieces of DNA (mitochondrial DNA)
  • Contains ribosomes (needed for replication)
• Chloroplast

  Site of photosynthesis

  • Larger than mitochondria
  • Double membrane
  • Membrane-bound compartments
• Nucleus Structure

  • Surrounded by nuclear envelope; semi-permeable double membrane
  • Nuclear pores allow substances to enter/exit
  • Dense nucleolus made of RNA & proteins assembles ribosomes
• Function of nucleus

  • Contains DNA coiled around chromatin into chromosomes
  • Controls cellular processes; gene expression determines specialisation and site of mRNA transcription, mitosis, semi-conservative replication
• Mitochondrion structure

  • Surrounded by double membrane
  • Folded inner membrane forms Cristae; site of electron transport chain
  • Fluid matrix; contains mitochondrial DNA, respiratory enzymes, lipids, proteins
• Chloroplast structure

  • Vesicular plastid with double membrane
  • Thylakoids; flattened discs stack to form grana; contains chlorophyll
  • Lamellae; tubes attaching thylakoids to adjacent grana
  • Stroma; fluid in matrix
• Function of mitochondria

  Site of aerobic respiration to produce ATP
• Chloroplasts

  Site of photosynthesis to convert solar energy to chemical energy.
• Golgi apparatus function

  • Modifies and packages proteins for export
  • Synthesises glycoproteins.
• Lysosome Function

  • Digests contents of phagosome
  • Exocytosis of hydrolytic enzymes
• Ribosome structure

  • Formed of protein & rRNA
  • Free in cytoplasm or attached to ER
• Ribosome function

  Site of protein synthesis via translation

  • Large subunit; joins amino acids
  • Small subunit; contains mRNA binding site
• Endoplasmic Reticulum (ER) Structure

  Cisternae; network of tubules & flattened sacs extended from cell membrane through cytoplasm & connects to nuclear envelope
• Endoplasmic Reticulum (ER) Function

  • Rough ER; many ribosomes attached for protein synthesis and transport
  • Smooth ER; lipid synthesis
• Cell wall (Plant) Structure

  Made of Cellulose Microfibrils

  • Plasmodesmata; allows molecules to pass between cells
  • Middle lamella; a boundary between adjacent cell walls
• Cell wall (Bacteria) Structure


  Made of the polysaccharide murein
• Cell wall Function

  • Mechanical strength and support
  • Physical barrier against pathogens
  • Part of apoplast pathway (plants) to enable easy diffusion of water
• Cell vacuole Structure

  • Surrounded by single membrane
  • Tonoplast; contains cell sap, mineral ions, water, enzymes, soluble pigments.
• Cell vacuole Function

  • Controls turgor pressure
  • Absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm.
• Role of plasmids in prokaryotes

  • Ring of DNA that carries non-essential genes
  • Can be exchanged between bacterial cells via conjugation
• Role of Flagella

  Rotating tail propels

  • Corkscrew motion
• Role of the capsule

  Polysaccharide layer

  • Provides mechanical protection
  • Sticks cells together
• Cell wall (Fungi)

  Chitin
• Viruses

  Acellular & non-living

  • No cytoplasm
  • Cannot self-reproduce
  • No metabolism
• Viral particle structure

  • Linear genetic material (DNA or RNA) & viral enzymes e.g. reverse transcriptase
  • Surrounded by capsid (protein coat made of capsomeres)
  • No cytoplasm
• Structure of enveloped virus

  • Simple virus surrounded by matrix protein
  • Matrix protein surrounded by envelope derived from cell membrane of host cell
  • Attachment proteins on surface
• Role of capsid on viral particles

  • Protects genetic material
• Role of attachment proteins on viral particles

  Enable viral particles to bind to complementary sites on host cell

  • Entry via endosymbiosis
• How to prepare a temporary mount of tissue for an optical microscope

  1. Obtain thin section of tissue
  2. Place plant tissue in a drop of water
  3. Stain tissue on a slide to make structures visible
  4. Add coverslip using mounted needle at 45 degrees to avoid trapping air bubbles.
• Optical Microscope

  + Colour Image

  + Can show living structures

  + Afforable

  — 2D

  — Lower resolution than EM