BIO PAPER 1

• LIGHT MICROSCOPES

  • Limited magnification
  • limited resolution
  • cheaper
• ELECTRON MICROSCOPES

  • better magnification
  • better resolution
  • expensive
  • need to be kept in special conditions
• EUKARYOTES

  • animal and plant cells
  • genetic material is enclosed in a nucleus
• PROKARYOTES

  • bacterial cells
  • Loop of DNA and plasmids
• 5 sub-cellular structures of eukaryotic cells and their functions

  • NUCLEUS - enclosed genetic material
  • CYTOPLASM - chemical reaction site
  • MEMBRANE - controls substances in and out
  • MITOCHONDRIA - site of aerobic respiration
  • RIBOSOMES - site of protein synthesis
• 3 extra sub-cellular structures of plant cells

  • CHLOROPLAST - contain chlorophyll and are sites of photosynthesis
  • CELL WALL - cellulose strengthens cell
  • VACUOLE - contains cell sap to gove plants shape
• Whats cell specialisation

  Adaptions to help cells cary out particular functions
• SPERM CELL

  • long tail to swim to ovum
  • lots of mitochondria to provide energy for swimming
• NERVE CELL

  • axon to carry electrical impulses
  • synapses that allow impulses to pass from one nerve cell to another
• MUSCLE CELL

  • mitochondria to provide energy for contraction
  • able to contract dur to protein fibres
• ROOT HAIR CELL

  • increase surface area for water and mineral uptake
  • no chloroplast because underground
• XYLEM CELL

  • thick lignin walls for support
  • no internal structures
  • cells form long, hollow tubes
• PHLOEM CELL

  • sieve plates allow dissolved sugars to move
  • companion cells with mitochondria for energy
• What's diffusion

  Spreading out of particles resulting in a net movement from a high to low concentration.
• FACTORS EFFECTING RATE OF DIFFUSION

  • CONCENTRATION GRADIENT - bigger the gradient, faster the diffusion
  • TEMPERATURE - higher temp means faster diffusion because particles have more kinetic energy and are moving faster
  • SURFACE AREA - larger surface area means faster diffusion
• Whats OSMOSIS 


  Diffusion of water from a dilute to concentrated solution through a partially permeable membrane
• example of osmosis in animals

  • if water moves into the cell it will expand and possibly burst
  • if water moves out of the cell it will shrink
• osmosis in plant cells

  • if water moves into cell, the cell wall prevents it from bursting and the cell becomes turgid
  • if water moves out of the cell it becomes flaccid
• Whats ACTIVE TRANSPORT

  moves substances from a more dilute to a more concentrated solution. Requires a lot of energy from repiration.
• MITOSIS

  1. DNA replicates to form two copies
  2. One set of chromosomes is pulled to either end of the cell
  3. the nucleus divides
  4. The cytoplasm and membrane divide to form two identical cells
• FUNCTIONS OF MITOSIS

  • essential for growth and development
  • takes place when an organism repairs itself
  • happens during asexual reproduction
• Whats a STEM CELL

  undifferentiated cell that can produce more cells of the same type and can differentiate to form other types of cells.
• Where to find stem cells

  • early embryo
  • bone marrow
• BONE MARROW TRANSPLANT

  1. patients existing bone marrow destroyed using radiation
  2. patient recieves transplant of bone marrow from donor
  3. stem cells in marrow divide and form new bone marroe that can differentiate and form blood cells
• THERAPUTIC CLONING

  1. embryo produced with same genes as patient
  2. stem cells from embryo transplanted into patient without being rejected
  3. stem cells can then differentiate into cells that aren't working

  Some ethical and religious objections but this can treat a wide range of illnesses.
• PLANT STEM CELLS

  • roots and buds contain MERISTEM which can differentiate into any type of tissue at any point
• MEIOSIS

  • copies of the genetic information are made
  • the cell divides twice to form four gametes, each with a single set of chromosomes
  • gametes are haploid
  • all gametes are genetically different from each other
• DIFFERENCES BETWEEN MEIOSIS AND MITOSIS

  • mitosis is a form of cell division which produces two identical, diploid body cells
  • meiosis is a form of cell division which produces four non-identical, haploid sex cells or gametes
• TISSUE


  group of cells with similar structure and function
• ORGAN


  group of tissues working together for a specific function
• MOUTH

  • saliva begins to breakdown starch
• STOMACH

  • begins breaking down proteins
  • hydrochloric acid
  • stomach muscles contract
• PANCREAS

  • breakdown of starch, lipids and protein
• LIVER

  • releases bile which speeds up digestion of lipids and neutralises stomach acid
• SMALL INTESTINE

  • Breakdown of lipids and proteins
  • small food molecules absorbed into bloodstream
• PROTEASE

  Breaks down protein in:

  • stomach
  • pancreas
  • small intestine

  Converts proteins back into amino acids to be absorbed by blood
• CARBOHYDRASE


  Breaks down carbohydrates

  • amylase for starch
  • produces simple sugars
  • pancreas
  • saliva
• LIPASE

  Breaks down lipids into glycerol and three fatty acids

  • pancreas
  • small intestine
• BILE

  • made in the liver and stored in the gallbladder
  • emulsifies large lipid globules into smaller ones to increase the SA for lipase
  • its alkali so it neutralises stomach acid, creating alkaline conditions in the small intestine
• how do enzymes work

  They are biological catalysts

  • The shape of the substrate is complementary to the shape of the active site, so when they bond it forms an enzyme-substrate complex