Biology B4










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MRS GREN - Explanation

Movement - moves to maximise food source or escape predators

Respiration - Glucose (C6H12O6) + Oxygen (6O2) -> Carbon Dioxide (6CO2) + Water (6H2O) / release of energy

Sensitivity - ability to respond to change in the environment

Growth - increase in size and/or complexity

Reproduction - all organisms have to create offspring

Excretion - urine, sweat, CO2 / the removal of metabolic waste - part of a chemical reaction

Nutrition - cells need nutrients and oxygen to function / plants make their own food (photosynthesis) / animals eat other animals or plants

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Animal and Plant Cells


  • Nucleus
  • Cell membrane
  • Mitochondria
  • Cytoplasm


  • Nucleus
  • Cell membrane
  • Mitochondria
  • Cytoplasm
  • Cell wall
  • Chlorplasts
  • Vacuole
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Cell Organelles and purposes

Nucleus - contains DNA which carries the genetic code used for making enzymes which are used in chemical reactions and all other proteins

Cell Membrane - allows gases and water to move in and out of the cell freely, while presenting a barrier to other chemicals

Mitochondria - contains the enzymes for aerobic respiration

Cytoplasm - where enzymes are made and contains teh enzymes for anaerobic respiration

Cell Wall - for structure and support

Chloroplasts - contain chlorophyll and enzymes for the reactions in photosynthesis

Vacuole - filled with cellsap

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'Lock and key' theory/Factors that affect activity

  1. Enzyme (active site) + substrate -> enzyme substrate complex
  2. Products leave the active site
  3. The enzyme is unchanged and ready to join another substrate

Factors that affect enzyme activity

  • pH
  • temperature
  • enzyme concentration
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Leaf Layers/Xylem and Phloem/Glucose and Oxygen

Layers from top of leaf

  1. Waxy cuticle
  2. Upper epidermis
  3. Palisade cells
  4. Spongy mesophyll
  5. Air space
  6. Lower epidermis

Xylem - transports water and mineral salts

Phloem - transports sugars and amino acids

Glucose - stored as starch / testwith iodine solution (orange to black)

Oxygen - collect from pond plant / relights a glowing splint

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Limiting Factors

A Limiting Factor is a factor that prevents the rate of photosynthesis from increasing at a particular time

Different Limiting Factors

  • light intensity
  • temperature
  • carbon dioxide
  • water availability
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Diffusion, Active Transport and Osmosis


  • high to low concentration (down a concentration gradient)
  • affected by: temperature, air currents (gas), concentration gradient

Active Transport

  • low to high concentration
  • uses ATP
  • only in living things


  • osmosis is referring to only the movement of water
  • osmosis needs a partially permiable membrane

Lactic acid/lactate causes "pain"

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Respiration and Energy uses

Anaerobic - without oxygen

Oxygen (6O2) + Glucose (C6H12O6) -> Carbon Dioxide (6CO2) + Water (6H2O)

The energy is used for

  • movement
  • chemical reactions
  • synthesis of large molecules
  • synthesis of amino acids
  • active transport
  • generate body hear
  • glucose -> fats and oils

Starch is a storage molecule

Cellulose is in a cells walls (structural)

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