respiration and photosynthesis

• Mitochondria structure?

  • Outer membrane 
  • Intercellular space
  • Inner membrane 
  • Cristae: foldings of inner membrane, large surface area and have enzymes involved in krebs cycle, involved in oxidative phosphorylation 
  • matrix:  holds genetic information 
  • Ribosomes: for protein synthesis 
• ATP

  • Molecule that provides energy when it is broken down via hydrolysis 
  • It can be formed via respiration 
  • Components: adenine, ribose sugar, phosphate 
  • Functions + benefits:- quick and easy to access to break down- can be recycled - soluble in water - released in small amounts- can be used for muscle contraction, active transport, and respiration itself 
• AEROBIC RESPIRATION:

  A process used to form ATP for energy to use in biological processes 

  • Uses oxygen 
  • Full breakdown of glucose
• Glycolysis 

  This process is anaerobic and does not require oxygen 

  • Glucose C6H12O6 is phosphorylated into 2x 3C (triosphosphate) substrate level phosphorylation
  • This happens by using phosphate from ATP
  • 2 atp are used in total
  • The 2x 3C is now oxidised, loses 2 H’s
  • 2 H’s = taken up by 2 NAD coenzymes, which will then play a role in oxidative phosphorylation later on 
  • The 2x 3C becomes 2x Pyruvate, which is transported to the matrix of mitochondria 
  • For every glucose molecule: 2 atp used, 2 atp made 
• Link reaction

  convert pyruvate into acetyl coenzyme A 

  This process is aerobic and is used to

  1: Decarboxylate pyruvate (REMOVE CO2)

  2: Oxidise 2x Pyruvate, turns into acetate (2C)

  3: Reduce NAD, turns into 2x reduced NAD 

  4: 2 Acetate + 2 coenzyme A = 2 Acetate-coenzyme A

  5: This happens two times (because 2 pyruvate molecules were formed)
•  KREBS CYCLE!

  This is where oxidative phosphorylation occurs 

  ATP is produced via a series of reduction reactions in a cycle 

  1: Coenzyme is removed , goes back to link reaction 

  2: 2C acetate + 4C molecule -> 6C molecule 

  3: 6C molecule is decarboxylated

  4: 6C molecule is dehydrogenated

  5: hydrogen - 2 reduced NAD and 1 reduced FAD

  6: Energy is used to form ATP using substrate level phosphorylation 

  7: Reduced NAD AND FAD go to oxidative phosphorylation stage 

  8: cycle repeats TWO TIMES  
• Oxidative phosphorylation


  1. Reduced NAD/FAD is oxidised (H is removed)

  2. H is split into electrons and protons

  3. Electrons passed down at decreasing energy levels on carriers on the transport chain, energy formed

  4. Protons passed through concentration gradient: inner membrane -> matrix of mitochondria using ATP synthase

  5. Chemiosmosis: movement of protons forms energy which is then used to synthesise ADP + Pi -> ATP

  6. O2 from blood is the terminal electron acceptor

  Protons + Electrons + Oxygen = water
• What would happen if Oxygen was not the terminal electron acceptor during oxidative phosphorylation?


  The flow of electrons in the electron transport chain is interrupted

  The proton gradient is also disrubted

  ATP synthesis can not occur sufficiently
• aerobic respiration equation!

  C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy
• define respiration 


  use of glucose to release energy for biological processes
• define photosynthesis 


  energy from light is used to make glucose, so that energy can be stored in glucose until it is released via respiration

  equation:

  6CO2 + 6H2O + Energy -> C6H12O6 + 6O2
• chloroplast structure 


  found in plant cells

  double membrane

  thylakoid: flattened sacs, stacked up into grana

  • have large surface area
  • sight of electron transfer chain

  chloroplast: has proteins + pigments that make up 2 photosystems

  stroma: contains enzymes, sugars, starch granules

  • involved in light independant reactions
• Outline light dependant photo phosphorylation (non-cyclic)

  PHOTOYSTEM 2

  • Light is absorbed by chlorophyll
  • Electrons are excited
  • Electrons pass down transport chain into thylakoid
  • This is to establish concentration gradient

  USING ENERGY FROM ELECTRON TRANSFER…

  • Protons travel from thyroid to stoma
  • Using ATP synthase

  USING ENERGY FROM PROTON TRANSFER

  • ADP and phosphate combined to form ATP

  TO REPLACE LOST ELECTRONS FROM PHOTOSYSTEM 2

  • Water undergoes photolysis
  • Protons , electrons , oxygen
• PHOTOSYSTEM 1 non cyclic

  • Light is absorbed by photosystem one
  • electrons are transferred to NADP to produce reduced NADP
  • Oxygen is present
  • ATP + NADP reduced is transferred to light independent stage
• cyclic photo phosphorylation


  Only uses photosystem one

  Electrons are not passed onto NADP

  Back to Photos system one using electron carriers

  Electrons are recycled

  No NADP or oxygen is produced
• light independent reaction (Calvin cycle)


  Occurs in the stroma of chloroplast

  Uses reduced NADP and ATP light dependent reaction to create organic compounds

  • CO2 diffuses into leaf through stomata
  • CO2 combines with ribulose biphosphate using enzyme RuBisCO
  • Produces 2 glycerate-3-phosphate
  • 2 GP is reduced using NADP into trios phosphate using energy from hydrolysis of ATP
  • Trios phosphate is used to convert into useful organic compounds e.g glucose
  • Some trios phosphate is used to regenerate ribulose biphosphate
• What is a photosynthetic pigment?

  Something that absorbs light, creates energy

  • Chloroplast

  Absorb red, blue, violet

  Reflect green

  Contains magnesium

  Deficiency in magnesium: plant turns yellow

  • Carotenoids

  Absorb blue, violet

  Reflect yellow, brown, orange

  Pass light to chlorophyll

  Protect from excess light + oxidation

  Masked by chlorophyll
• Law of limiting factors 


  Ideal conditions needed for photosynthesis:

  1. Light
  2. Water
  3. Temperature for optimum enzyme activity
  4. Carbon dioxide

  Factors too high or too low can limit photosynthesis
• C3 plants

  • These are the most common type of plants.
  • They use the Calvin cycle to fix carbon dioxide into a three-carbon compound (hence the name "C3").
• C4 plants


  Light-dependent reactions and Calvin cycle are physically separated, with light-dependent reactions in mesophyll cells and Calvin cycle in bundle-sheath cells
• C4 carbon fixation


  1. CO2 fixed with 3C compound Phosphoenolpyruvate (PEP) in mesophyll cells to form 4C Oxaloacetate

  2. Oxaloacetate converted to Malate and transported to bundle-sheath cells

  3. Malate breaks down in bundle-sheath cells, releasing CO2 which is fixed by Rubisco
• PEP carboxylase


  Non-Rubisco enzyme that fixes CO2 in C4 plants, has no tendency to bind O2
• CAM plants


  Separate light-dependent reactions and CO2 use in time, not space
• CAM carbon fixation


  1. At night, stomata open and CO2 diffuses into leaves, fixed into oxaloacetate by PEP carboxylase, converted to organic acid and stored

  2. In day, stomata closed but organic acids released from vacuoles, broken down to release CO2 which enters Calvin cycle
• This controlled release of CO2 maintains a high concentration around Rubisco in CAM plants
• What is the stroma?


  The fluid-filled space inside the chloroplast that contains enzymes, DNA, ribosomes, and starch granules
• What is the function of the stroma?

  Site of the Calvin cycle (dark reactions of photosynthesis)
• What are grana?


  Stacks of thylakoids that increase the surface area for light absorption
• What are thylakoids?


  Flattened, membrane-bound sacs within the chloroplast that are the site of light-dependent reactions