biology

• metabolism


  all of the chemical reactions that take place within a cell
• metabolic pathways


  pathways of enzyme catalysed reactions within a cell
• anabolic pathways


  build up large molecules from smaller molecules and requires energy
• catabolic pathways


  breakdown large molecules from smaller molecules and releases energy
• pores


  they allow larger molecules required for metabolic pathways into the cell
• pumps


  they pump specific ions into the cell and requires ATP
• enzymes


  they are embedded in the membrane catalyse steps in a metabolic pathway
• anabolic pathways


  the build up large molecules from smaller molecules and require energy
• catabolic pathways


  the breakdown of large molecules from smaller molecules and releases energy
• induced fit


  the active site of the enzyme changes shape to ensure a close fit with the substrate
• competitive inhibitors


  they bind at the active site, preventing the substrate from binding and can be reversed by increasing substrate concentration
• non-competitive inhibitors


  they bind away from the active site but change the shape of the active site, preventing the substrate from binding and cannot be reversed by increasing substrate concentration
• feedback inhibition


  when the end product in the metabolic pathway reaches a critical condition, the end product inhibits an earlier enzyme, blocking the pathway which prevents further synthesis of the end product
• cellular respiration


  the breakdown of molecules to release energy and generate ATP
• phosphorylation


  the addition of phosphate to a substance
• location of glycolysis


  cytoplasm
• location of citric acid cycle

  central matrix of mitochondria
• location of electron transport chain

  inner matrix of mitochondria
• energy investment phase


  2 ATP used up
• energy pay-off phase


  4 ATP produced and an overall net gain of 2 ATP
• dehydrogenase enzymes


  they remove hydrogen ions and electrons and pass them to coenzyme NAD, forming NADH
• gylcolysis


  the breakdown of glucose to pyruvate
• citric acid cycle (5)

  - in aerobic conditions

  - pyruvate is broken down to an acetyl group from acetyl coenzyme A

  - acetyl CoA combines with oxaloacetate to form citrate

  - CO2 is released

  - takes place in central matrix
• electron transport chain (5)

  - hydrogen ions and electrons from NADH are passed here

  - electrons are passed along the electron transport chain releasing energy

  - this energy allows hydrogen ions to be pumped along the inner membrane

  - hydrogen ions pump through ATP synthase, resulting in the production of ATP

  - hydrogen ions and electrons combine with oxygen to form water
• location of fermentation


  cytoplasm
• fermentation in animal cells

  pyruvate is converted into lactate in a reversible reaction
• fermentation in plant and yeast cells

  pyruvate is converted into ethanol and CO2 in an irreversible reaction
• metabolic rate


  the amount of energy an animal consumes in a given period of time
• ways to compare metabolic rate in different organisms (3)


  - oxygen consumption

  - CO2 production

  - energy production
• mammal circulatory system (4)

  - complete double

  - 2 atria and 2 ventricle

  - no mixing of oxygenated and deoxygenated blood

  - more efficient oxygen delivery to cells
• reptile circulatory system (3)


  - incomplete double

  - 2 atria and 1 ventricle

  - mixing of oxygenated and deoxygenated blood
• fish circulatory system (3)


  - single

  - 1 atria and 1 ventricle

  - deoxygenated blood only
• types of microorganisms


  archea, bacteria and some eukaryotes
• environmental conditions to grow microorganisms (4)


  - sterility

  - control of temperature

  - oxygen levels

  - pH
• lag phase (2)


  - no increase

  - cells adjust to growth medium to increase metabolism
• log phase


  cell grows and reproduces at the maximum rate until there is no limiting factor
• stationary phase (3)


  - nutrients begin to run out

  - toxic metabolites begin to build up

  - rate of production of new cells is equal to the death rate
• death phase


  nutrients run out
• total cell count


  both alive and dead cells
• viable cell count


  only counts alive cells