cells & microbes

• All organisms fulfil every criteria of MRS H GREN,

  M - movement

  R - respiration

  S - sensitivity

  H - homeostasis

  G - growth

  R - reproduction

  E - excretion

  N - nutrition
• Eukaryotic: complex cells, multicellular OR single-celled, membrane bound nucleus e.g. animals, plants, fungi (yeast), protoctists (amoeba)
• Prokaryotic: simple cells, always single-celled, no nucleus (DNA floats around in cytoplasm) e.g. bacteria (lactobacillus)

  • substantially smaller than eukaryotic cells
  • no organelles
• Nucleus - Contains genetic material
• Cytoplasm - Where chemical reactions takes place, supports internal cell structure, gel-like substance, contains water & dissolved solutes
• Cell Membrane - Controls what goes in and out of the cell, semi-permeable membrane
• Ribosomes - Found in cytoplasm, made out of RNA and protein, site of protein synthesis
• Mitochondria - Site of aerobic respiration, releases ATP
• Cell Wall ( made from cellulose ) - Gives the cell structure and shape
• Chloroplasts - Contains chlorophyll to absorb light energy, contains enzymes needed for photosynthesis, site of photosynthesis
• Vacuole - Contains water & nutrients [cell sap]
• Fungi:

  • usually multicellular but some aren’t, e.g. yeast, mucus
  • cell wall made from chitin
  • store carbohydrates as glycogen
• Bacteria:

  • Microscopic
  • Single-celled
  • No nucleus, genetic material stored in a circular loop of DNA
• Pathogens: any microorganism that causes disease and malfunction

  1. Fungi
  2. Alive
  3. Athletes foot
  4. Bacteria
  5. Alive
  6. E-coli
  7. Viruses
  8. Not alive because not made of cells
  9. Coronavirus, HIV
  10. Protoctists
  11. Alive
  12. Malaria
• Viruses are parasitic

  • Only contain one type of nucleic acid, either DNA or RNA

  1. Latch onto cell
  2. Fuse with cell membrane
  3. Ingests genome into cell
  4. Hijacks cell
  5. Cell dies
• Organelles : “little organs” of the cell, each have specific functions
• Cells : basic structure in a living organism
• Tissues : group of cells of similar structure working together to perform a particular function
• Organs : group of different tissues working together to perform a particular function
• Organ systems : made from a group of organs with related functions working together to perform body functions within the organism
• Cell differentiation: process in which cells become specialised
• Red blood cells: transports oxygen from lungs to the rest of the body
• Specialisations of RBC: no nucleus, contains haemoglobin, bi-concave shape so large surface area, thin membrane, small and flexible as to fit through blood vessels
• White blood cells engulf & destroy pathogens
• Specialisations of WBC: irregular shape as to get to site of infection
• Nerve cells receive sensory input from the external world, carries electrical impulses from one place to another
• Specialisations of nerve cells: long axon to cover long distances, axon insulated by fatty sheath, increases speed of nerve, tiny branches called dendrons
• Ciliated windpipe cells moves microbes and debris out of the airways
• Specialisations of cilliated windpipe cells: cilla that can move from side to side
• Sperm cells carry half of genetic material needed for an embryo
• Specialisations of sperm cells: strong tail/flagellum for swimming, digestive enzymes in head, enzymes which dissolves the egg membrane, lots of mitochrondia
• Root hair cells absorbs water and mineral ions from the soil
• Specialisations of root hair cells: large surface area, thin cell wall, no chloroplasts or vacuoles
• Stem cells:

  • Cells that are at an early stage of development
  • Adapt and change to do a particular job
  • Found in embryos, baby’s umbilical cords, adult’s bone marrow
  • All stem cells can divide by mitosis
  • Can be used in regenerative medicine & cure a large range of diseases
  • Risks of stem cells: become infected, low numbers of stem cell donors, expensive, ethical issue
  • Embryonic stem cells are most useful
• Diffusion: the NET movement of particles of the substance from an area of higher concentration to lower concentration
• Osmosis: the NET movement of water molecules from an area of higher water concentration to lower water concentration through a semi-permeable membrane
• Hypertonic: rbc has higher water concentration than solution, so water moves out, shrivelled cellsrbc has lower water concentration than solution, therefore water moves in, cells burst

  Isotonic: rbc has same water concentration as solution, no net movement

  Hypotonic: rbc has lower water concentration than solution, so water moves IN, cells burst
• Passive transport: no energy used, move down concentration gradient
• Active transport: The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration against the concentration gradient using energy from respiration

  e.g. root hair cells lining surface of plant roots absorb nutrients from the soil

  glucose from gut → blood

  Respiration release ATP, required for active transport

  • Mitochondria more active in areas where ATP occurs more frequently
• Sugar molecules are used in respiration to release energy for cells to function