Cell Processes

Cell Processes

1. Diffusion

   • Passive transport
     • No energy required
   • semi-permeable membrane
     • Stucture
       • Hydrophilic head
       • Hydropholic tail
       • Phospholipid Layer
   • movement from area of high concentration to area of low concentration
     • down the concentration gradient
   • Example: Carbon dioxide for photosynethesis
   • Factors that effect diffusion
     • Concentration Gradient
       • Diffusion rates will be higher when there is a greater difference in concentration between the two regions
     • Diffusion Difference
       • Diffusion over shorter distances occurs at a greater rate than larger distances
     • Surface Area
       • The rate of diffusion is greater when there is a large surface area across where diffusion occurs
     • Physical Barriers
       • Thick barriers slow the rate of diffusion
       • Pores in a barrier enhance the diffusion

2. Facilitated Diffusion

   • Semi-permeable membrane
   • Passive transport
     • No energy required
   • Same as diffusion but assisted by carrier protein
   • Example: Glucose
   • Movement from an area of high concentration to an area of low concentration
     • Down the concentration gradient

3. Osmosis

   • Movement of water from area of high concentration to an area of low concentration
     • Down concentration gradient
   • Passive transport
     • no energy required
   • Example: water in the soil will move into the cell
   • Osmoregulation
     • Isotonic Solutions: no net loss or gain
     • Hypertonic Solutions: net loss
       • Animal: shrivel up
       • Plant: plasmolysed and flaccid
     • Hypotonic Solutions: net gain
       • Animal: Expand and burst
       • Plant: turgid (tugor pressure)

4. Active Transport

   • semi-permeable membrane
   • Movement from an area of low concentration to an area of high concentration
     • Against concentration gradient
   • Energy is required
   • Transport or carrier proteins are needed
   • Types
     • Sodium-potassium pump
     • Proton pumps
     • Cytosis
   • Example: use ATP energy to move h+ ions in respiration

5. Enzymes

   • Biological catalyst that speeds up specific chemical reactions
     • Lower energy barrier - activation energy
   • The lock and key model
   • Induced fit
   • Factors that effect enzyme reaction rate
     • Temperature
       • Increases until optimum temperature then decreases as the enzymes denature
         • Denature is when the weak hydrogen bonds of the active site break
     • pH value
       • optimum temperature then denature
     • Enzyme concentration
       • increases
     • Substrate concentration
       • Increases then reaches saturation point
   • Proteins
   • Poisons when in wrong part of body

6. Respiration

   • The process of breaking down food and using oxygen to produce energy in the form of ATP
   • Aerobic respiration
     • Glucose + Oxygen = carbon dioxide + water + lots of ATP
     • Efficient
   • Anaerobic respiration
     • Glucose = Carbon dioxide + lactic acid + water +little ATP
     • Lactic acid build up in muscle and causes cramp
     • Less efficient
   • Mitochondria
     • The organelle where respiration occurs
     • Outer membrane
       • semi-permeable
     • Cristae, folded inner membrane
       • increase in surface area which allows respiration to be efficient and faster as number of reactions have increased
     • Matrix, fluid
       • High concentration of enzymes
         • increase in reactions
   • Factors
     • Temperature
       • optimum temperature
     • Body's enrgy demand
       • rate of respiration will increase to maximum as the demand increases
   • Stages
     • Glycolysis
     • Krebs cycle
     • Electron transfer chain

7. Photosynthesis

   • Equation: water + carbon dioxide + sunlight+ chlorophyll= glucose and oxygen
   • Factors
     • Temperature
       • increases to optimum then denature
     • Light intensity
       • increases rate to max. then no affect
     • CO2 concentration
       • increases to max. then no affect
   • Chloroplast
     • stroma, fluid
       • clear, doesnt block sunlight
         • maxmising penetration light
     • Grana
       • stack of thylakoids
         • thin, disc shape, short diffusion distance
       • increase surface area
     • outer and inner membrane
       • transparent to allow max sunlight
   • Stages
     • light independent stage
     • light dependent stage