Biology

• Enzymes have an optimum pH because...

  • The pH affects the bonds holding the enzyme together
  • If it is too high or too low, the shape of the active site is changed and the enzyme is denatured
• The 5 main uses of glucose by plants are...

  • Store as starch in leaves
  • Store as fats and oils in seeds
  • Release energy from respiration
  • Build cellulose for cell walls
  • Build proteins by combining glucose with nitrates from the soil
• Phagocytosis is white blood cells engulfing pathogens and destroying them.
• The 4 human barriers to infection and how they prevent infection are...

  • Skin - dead cells on outer layer
  • Nose - hairs trap mucus
  • Stomach acid - hydrochloric acid
  • Cilia lining of airways - traps microorganisms in the respiratory system
• An enzyme is a large protein made up of chains of amino acids. They act as a biological catalyst.
• The 3 steps of drug development are...

  1. Efficacy
  2. Toxicity
  3. Dose
• White blood cells prevent disease by producing antibodies specific to the pathogen and destroying it.
• A vaccination is a small amount of dead or inactive pathogens. It stimulates the bodies defence systems and white blood cells are produced.
• A pathogen is a microorganism that causes and spreads diseases.
• The 4 pathogen types are

  • B acteria
  • V irus
  • P rotists
  • F ungi
• Pathogens can spread by

  • D irect contact
  • W ater
  • A ir
  • V ectors
• The phloem (translocation) is...

  • Columns of elongated cells
  • Small pores in end walls for cell sap to pass through
  • Transportation for food substances, mainly dissolved sugars for immediate use or storage
  • Transport is in both directions
• A xylem (transpiration) is...

  • Dead cells joined end to end with no end walls between and a hole down the middle
  • Strengthened with lignin
  • Transports water and mineral ions from roots to stem and leaves
• The equation for photosynthesis is...

  Carbon dioxide + water -> glucose + oxygen
• The equation for aerobic respiration is

  glucose + oxygen -> carbon dioxide + water
• The equation for anaerobic respiration in...

  • Animals = glucose -> lactic acid
  • Plants & yeast = glucose -> carbon dioxide + ethanol
• The 6 features of a leaf are...

  1. Waxy cuticle
  2. Epidermis
  3. Spongy mesophyll
  4. Guard cells
  5. Palisade mesophyll
  6. Stomata
• Sexual reproduction uses meiosis, introduces variation into offspring and involves 2 parents.

  Asexual reproduction uses mitosis, all offspring are clones, involves 1 parent.
• The function of adult stem cells is to produce a limited range of specialised cells.
• Active transport is the movement of a substance from an area of low concentration to high concentration. This requires energy released from respiration because it goes against the concentration gradient.
• Transpiration is the evaporation of water from a leaf.
• A plasmid is a small circular DNA loop that is found in bacteria
• Foxglove flowers produce digitalis.
• A potometer measures the rate of transpiration in plants.
• The 4 chambers of the heart are the left and right ventricle on the bottom and the left and right atrium on the top.
• To test a sample of food for...

  • Sugar - grind up food and mix with water, add benedicts solution, heat mixture in a warm bath, turns from blue to red if there is high sugar and green or yellow if there is low sugar.
  • Protein - Grind up food, add biuret solution, if protein is present it will turn purple.
  • Starch - Add iodine solution, turns dark blue/black if starch is present.
• Metabolism is the sum of all chemical reactions in a cell or body.
• Lactic acid is the product of anaerobic respiration in muscles.
• Oxygen debt is the amount of extra oxygen needed to convert lactic acid back to glucose.
• An allele is different forms of the same gene.
• A genotype is the pair of alleles that controls a characteristic.
• A phenotype is the characteristic that a gene causes.
• Heterozygous is when alleles are different. Homozygous is when alleles are the same.
• A dominant gene is a gene that always shows its effect. A recessive gene is a gene that shows its effect only when 2 copies are present.
• Meiosis is the division of 1 cell to form 4 non identical daughter cells with half the number of chromosomes. It is sexual reproduction.
• The process of meiosis...

  1. DNA is copied
  2. Cell divides to form 2 daughter cells
  3. Each daughter cell divides to form 4 gametes with a single set of chromosomes
• A genome is the entire set of genetic material of an organism.
• A chromosome is a large structure of DNA containing a large number of genes.
• A gene is a small section of DNA that codes for a characteristic. They are in an amino acid sequence.
• DNA is the chemical that chromosomes consist of. It is a double helix that is made up of two strands of nucleotides.