revision

• Cells are the basic unit of life!
• Cells


  Structural and functional unit of all living organisms
• The human body is composed of trillions of cells, with their own specialised functions
• Eukaryotic cell


  • Complex
  • Multicellular
  • Organism
• Cell membrane


  Double-layered membrane composed of lipids (45-50%), proteins (45-50%), and carbohydrates (4-8% - outer surface only)
• Cell membrane functions


  • Barrier (selective permeable)
  • Regulates transport
  • Regulates reactions (maintain homeostasis)
  • Communicates with the environment
  • Detects signals and responds to those
  • Cell recognition (cell identity)
  • Cell adhesion (communication)
• Cell transportation


  1. Endocytosis: move particles into a cell by enclosing them in vesicle made out of plasma membrane

  2. Exocytosis: Material from inside to outside of the cell in vesicles that fuse to cell membrane
• Cytoskeleton


  • Enables the cell to move and change shape
  • Organises the contents of the cell
  • Connects the cell physically and biochemically to the external environment
• The cytoskeleton is not so rigid, but very dynamic!
• Cytoskeleton composition


  Similar to Lego - multiple copies of key pieces that fit together to form larger structures, assembled into a wide range of structures, and disassembled and reassembled into different shapes
• Parts of the cytoskeleton

  • Microtubules
  • Actin/microfilaments
  • Intermediate filaments
• Microtubules


  Dimers of α- and β-Tubulin that form polymer sheets rolled into a tube, hollow but able to withstand some compression
• Microtubule structure


  1. Growing steadily

  2. Rapidly shrinking

  3. Microtubules can switch between two states
• Microtubule-organising centre (MTOC)


  Dynamic end that organises the mitotic and meiotic spindle apparatus during cell division
• Microtubules during mitosis


  1. Aster/Astral

  2. Interpolar

  3. Kinetochore
• Microtubules can serve as extensive highways for motor proteins moving vesicles and creating transport networks for the cell
• Microtubules are critical for neuronal survival
• Microfilaments (actin filaments)


  Double helix of actin (globular) subunits that bind together to form a polymer, much less rigid than microtubules, smaller at 7 nm, primarily involved in cell movement and highly dynamic (assemble and disassemble)
• Functions of microfilaments (actin filaments)

  • Form a contractile ring around the 'waist' of the cell to aid in cell division
  • Coordinate with microtubules to regulate biological functions
• Intermediate filaments


  Most flexible of the cytoskeleton polymers, can cross-link to each other, microtubules and microfilaments, not as dynamic as microtubules or microfilaments, provide structural support and cell integrity, often formed in response to mechanical stresses, important for cell adhesion
• Types of intermediate filaments

  • Type I and type II keratins (largest group)
  • Nails and hair
  • Epithelial cells
• Eukaryotic cell


  Packed full of membranes including mitochondria, endoplasmic reticulum, and Golgi apparatus
• Mitochondria


  The "powerhouse" of the cell, size 1-2um, with an outer membrane, inner membrane (cristae), intermembrane space, and matrix
• Mitochondria are remnant bacteria
• How ATP provides energy

  It's all in the covalent bond between the 2nd and 3rd phosphate - a lot of energy, some energy, a little energy. The gamma phosphate "hates" ATP and wants to leave it!
• ATP and ADP cycling

  ATP = Adenosine triphosphate, ADP = Adenosine diphosphate, the gamma phosphate is released to provide energy
• Eukaryotic cell


  Packed full of membranes
• Membrane-bound organelles in eukaryotic cells

  • Mitochondria
  • Endoplasmic reticulum
  • Golgi apparatus
• Mitochondria


  • Double-membrane organelles
  • The "powerhouse" of the cell
  • Size = 1-2um
  • Outer membrane
  • Inner membrane (Cristae)
  • Intermembrane space
  • Matrix
  • Remnant bacteria
• How ATP provides energy

  1. Covalent bond between the 2nd and 3rd phosphate

  2. A lot of energy

  3. Some energy

  4. A little energy

  5. The gamma phosphate hates ATP and wants to leave it
• ATP


  Adenosine triphosphate
• ADP


  Adenosine diphosphate
• ATP and ADP cycling in the cell


  1. Constantly cycling

  2. Reversible reaction

  3. Full charge

  4. Releases energy

  5. Requires energy
• Mechanisms of how energy from ATP is used

  • Causes conformational changes in proteins and molecules
  • Activates molecules by phosphorylating them
  • Places stresses on molecular bonds
• Cells cannot store ATP, but can make it
• How cells make ATP

  1. Glucose

  2. 2 Pyruvate

  3. Glycolysis

  4. 2 ATP

  5. 2 NADH

  6. Fermentation

  7. Kreb's cycle and electron transport chain in the mitochondria
• Mitochondria


  • Organelle present in all eukaryotic cells
  • Has double membrane
  • Main function is ATP synthesis in the inner membrane
• Endoplasmic reticulum


  • Rough ER: Synthesis of lipids and proteins
  • Smooth ER: Metabolises carbohydrates, aids in detoxification, secretes proteins
• If proteins need to be secreted from the cell

  1. mRNA export from nucleus

  2. mRNA binds ribosome

  3. Protein starts to be produced on ribosome

  4. Secreted proteins have a secretion signal

  5. Signal recognition particle binds protein and delivers it to ER translocon
• Golgi apparatus


  • Looks like a stack of pancakes
  • Has a cis side and a trans side
  • Receives transport vesicles containing protein from the rough ER
  • Modifies the proteins, e.g. glycosylation
  • Sends proteins to various places in the cell