Unit 1 AoS1 - WHOLE REVISION

• Organelles in the cell

  • Nucleus
  • Ribosome
  • Endoplasmic reticulum
  • Golgi apparatus
  • Mitochondria
  • Cytoskeleton
  • Centrioles
  • Cell membrane
  • Lysosomes
  • Smooth endoplasmic reticulum
  • Cell wall
  • Vacuole
  • Chloroplast
  • Flagellum & Cilium
• Nucleus


  Contains DNA, codes for all cellular proteins
• Ribosome


  Reads message from DNA regarding which protein to make, strings together a protein chain
• Endoplasmic reticulum


  Modifies protein chain into functional shape, called 'rough' as studded with ribosomes
• Golgi apparatus


  Makes some changes to the functional protein & packages it into a vesicle so that it can be delivered outside cell
• Mitochondria


  Uses oxygen & glucose
• Cytoskeleton


  Microtubules which support cell's structure
• Centrioles


  Cylindrical structures involved in cell division (only visible in cell division)
• Cell membrane


  Phospholipid bilayer that surrounds the entire cell & assist the regulation of materials in and out of cell
• Lysosomes


  Contains digestive enzymes that break down waste products from the cell
• Smooth endoplasmic reticulum


  Contains enzymes involved in synthesis of molecules such as steroids & phospholipids
• Cell wall


  Surrounds cell membrane & provides the plant with shape, support & protection, made of carbohydrates (cellulose) in plants, made of peptidoglycan in prokaryotes
• Vacuole


  Filled with water & dissolved nutrients, help plants keep its shape
• Chloroplast


  Contains pigment (chlorophyll), absorbs sun energy & uses it to split water & carbon dioxide, converting it into glucose (photosynthesis), glucose used as an energy source
• Flagellum & Cilium


  Hair-like structures on the surface of cells contain arrangement of microtubules, assist with cell movement & to move substances around the cell
• Differences in Plant & animal cells

  • Plant cells have additional cell wall
  • Plant cells contain chloroplast organelle
• Plasma membrane movement


  • Passive transport (Simple diffusion, Facilitated diffusion)
  • Active transport (Active transport, Endocytosis/exocytosis)
• Passive transport


  No ATP required
• Simple diffusion


  Transport of small hydrophilic substances (lipophilic)
• Facilitated diffusion


  Transport of dissolved hydrophilic substances down concentration gradient, involved protein transporters
• Active transport


  Transport of dissolved hydrophilic substances against concentration gradient, involved protein transporters (pumps)
• Endocytosis/exocytosis


  Bulk transport of macromolecules & liquids
• Role of plasma membrane

  • Acts as a protective boundary
  • Keeps out foreign molecules
  • Allows cells to communicate with each other
  • Involved in cell recognition
• Diffusion


  Net movement of molecules from high to low concentration
• Factors affecting rate of diffusion

  • Temperature - increase in kinetic energy
  • Molecular size
  • Steepness of gradient - more difference, faster movement
• Osmosis


  Passive movement of water from a region of high water concentration to low water concentration to reach equilibrium, solutes cannot cross membrane unaided, water will move to equalise solutions
• Tonicity


  • Isotonic - no net movement, same concentration as internal & external environment
  • Hypotonic - water moves into cell, cell could burst, solution has lower concentration than intracellular environment
  • Hypertonic - water moves out of the cell, cell could shrink, solution has higher concentration of solute causing more water to move out of the cell
• Factors affecting movement of substances

  • Molecular size
  • Presence of net charge
  • Solubility in lipid solvents
  • Direction of concentration gradient
• DNA & Chromosomes


  • Chromosomes - tightly coiled DNA that forms when cell divide
  • Chromatin - a mixture of DNA & proteins that form chromosomes, comprised of protein (histones) & DNA
  • Sister chromatids - copy of DNA made during interphases, two copies of each chromosomes are called sister chromatids which split during cell division
  • Centromere - the join between sister chromatids
  • Telomere - repetitive non-coding DNA found at the end of chromosomes which protect the chromosome from damage
  • Homologous chromosomes - a set of one maternal & one paternal chromosome that pair up with each other inside the cell
• Purpose of Cell replication


  • To replace other cells that have worn out or have become damaged (maintenance)
  • To all multicellular organisms to grow
  • To repair damaged cells after injury
  • Restores the nucleus-to-cytoplasm ratio (SA:V ratio)
• Cell division & cell cycle (IPMATC)

  • Interphase (G1, S, G2, G0)
  • Mitosis (Prophase, Metaphase, Anaphase, Telophase)
  • Cytokinesis
• Interphase


  Longest stage, cell spends most of the time here
• G1


  Pre-DNA synthesis, growth stage, greatest number of new cell components are made here, formation of new cell components, if conditions are not right, cell will stop or go into G0 phase
• S


  DNA is synthesised, formation of sister chromatids, DNA is duplicated & chromosomes will be made into two sister chromatids
• G2


  Post-DNA synthesis, biggest growth phase, cell specialisation & differentiation taking place
• G0


  Resting stage if conditions are not met for cell replication, only some cells enter this stage, may result in cell-suicide (apoptosis)
• Mitosis


  The process in which one cell divides into two new cells (daughter cells), contains same genetic material as original cell
• Mitosis stages


  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• Prophase


  Nuclear membranes disappear, centrioles move to opposite poles, spindle fibres form, chromosomes condense & become visible, becoming thicker & shorter
• Metaphase


  Centromeres of highly condense chromosomes attach to spindle fibres & align with equator, spindle fibres anchor dyads (chromosomes) to equator, attached at the kinetochore (special protein complex attachment site)