5. Photosynthesis and Cellular Respiration Flashcards
What is photosynthesis
The process in which green plants trap light energy and transform it into chemical energy.
Photosynthesis equation
6CO2 + 12H2O ➡️ (light energy and chlorophyll) C6H12O6 + 6O2 + 6H2O
Define thylakoids
Membranous fluid filled flattened discs in the chloroplast envelope
Define grana
Thylakoids that are joined into stacks
Define chlorophyll
Light trapping pigment which is embedded in the thylakoids membranes
Define stroma
Fluid inside the chloroplast that bathes the grana
What do accessory pigments do?
They absorb wavelengths of light that cannot be absorbed by chlorophyll a and b and pass on the energy to chlorophyll
What does light dependent reaction involve
Trapping of sunlight energy by chlorophyll and converting it to chemical energy
Where does light dependent reaction take place?
Thylakoids of the chloroplast
What is the process of light dependent reaction?
- When light energy strikes chlorophyll molecule it excites an electron which leaves chlorophyll and enters electron transport chain.
- Absorption of light energy also splits water molecules and electrons from the water replace electrons removed from the chlorophyll
- Oxygen produced from splitting of water is waste product and releases to outside environment or environment within the cytosol, used during cellular respiration
- Electrons move along the electron transport chain, lose their energy to produce ATP from ADP + Pi
- Electrons and a H+ transferred to NADP to produce NADPH which carries H+ to next stage of photosynthesis. NADP+ terminal electron acceptor
Where does light independent reaction take place?
Stroma of the chloroplasts
Inputs and outputs of light dependent reaction?
Inputs: light NADP h2O ADP + Pi
Outputs: NADPH O2 and ATP
What does light independent reaction involve?
The ATP formed in the light independent reaction is used as a source of energy in reaction that combines carbon dioxide and hydrogen to form glucose and water
What role does NADPH play in light independent reaction?
Source of energised elections and reducing power that reduce carbon dioxide and build it into glucose.
What are the three stages of Calvin cycle?
Carbon fixation
Reduction
Regeneration
Calvin cycle stages
- Input of carbon dioxide results in an output of glucose.
- Enzymes (RUBISCO) are involved in this reaction.
- Reduction of carbon dioxide using NADPH and ATP from light dependent reaction.
- Carbon reduction reactions begin with calvin cycle. The carbon dioxide together with H+ ions from light dependent stage become part of a 3 carbon compound, glyceraldehyde 3 phosphate (G3P)
- Reaction referred to as carbon dioxide fixation because carbon is secured in an organic compound.
- The G3P compound produced in the calvin cycle is the starting point of production of many other compounds such as glucose.
Inputs and outputs of Light independent reaction
Inputs: carbon dioxide, ATP, NADPH
Outputs: ADP + Pi, NADP, glucose
What external factors affect the rate of photosynthesis?
Intensity of radiant light Ambient temperature Concentration of CO2 Humidity Colour of light
What internal factor affect the rate of photosynthesis?
Chlorophyll content of the leaves
Surface area of leaves
Enzyme concentration
What is a limiting factor?
Light intensity, temperature and availability of carbon dioxide interact and could be a limiting factor
When the supply of the factor is in short supply such that it restricts the rate of photosynthesis
What is the purpose of cellular respiration?
To transfer the chemical energy stored in glucose into the chemical energy of ATP for use by cells for staying alive
What happens when a cell requires energy?
Endergonic reaction
Bonds attaching the last phosphate group in ATP are broken releasing stored energy
ADP is formed. ATPase is required for this reaction to proceed
Atp➡️(energy and ATPase) ADP + Pi
What happens in EXERGONIC reactions?
🔹Free energy from EXERGONIC reactions can be used to add a phosphate group to ADP from ATP
🔹ATP synthase is enzyme required for this
🔹process of phosphorylation addition of a phosphate group to an organic molecule
🔹ADP + Pi ➡️ (energy and ATP synthase) ATP
What is the chemical reaction for cellular respiration?
🔹 c6H12o6 + 6O2 ➡️ (36 ADP + 36Pi -> 36 ATP) 6CO2 + 6H2O + heat energy
What are the parts of the mitochondria?
🔹 cristae, each mitochondria has highly folded inner membrane
🔹 matrix is the fluid filled material containing DNA and ribosome
What is the process of glycolysis?
🔹 one molecule of glucose, a C6 molecule is broken down into two C3 compound, pyruvate
🔹 the electrons from hydrogen atoms in glucose are collected by acceptor molecules such as NAD+ and when acceptor molecules are carrying hydrogen they are loaded, NADH
🔹 produces two ATP molecules per glucose
Where does glycolysis occur?
🔹 in the cytosol
Where does Krebs cycle occur?
Matrix of the mitochondria
What’s the process of Krebs cycle?
🔹 pyruvate (3C) produced in glycolysis passes into mitochondrion where it’s broken down into two carbon fragments to form intermediate acetyl coenzyme A
🔹 co2 is released and H+ are gathered by acceptor molecule to produce NADH.
🔹 as the cycle proceeds acceptor molecules NAD+ and FAD become loaded with H+ and electrons to form NADH and FADH2.
What is the yield of Krebs cycle?
🔹 each pyruvate molecule, 3 Co2 molecules are released and for 2 pyruvate molecule, 6 Co2 produced
🔹 2 ATP molecules are produced from two pyruvate molecules
🔹 for each glucose molecule 6 carbon dioxide molecules are produced and the Krebs cycle must complete 2 circuits to break down two pyruvate molecules
Where does electron transport chain occur?
In the cristae of the mitochondria
What happens in the electron transport chain?
🔹 loaded acceptor molecules (NADH and FADH2) produced during glycolysis and Krebs cycle transfer electrons from one cytochrome to another and then finally to oxygen, which combines with hydrogen to form water.
🔹 electron transport releases energy which drives production of32 ATP
Inputs and output of aerobic respiration
🔹 glycolysis INPUT: glucose, 2 NAD+, ADP + Pi
OUTPUT: 2 pyruvate, 2 NADH, 2ATP
🔹 Krebs cycle INPUT: 2 pyruvate, 8 NAD, 2 FAD2-, ADP + Pi
OUTPUT: 6CO2, 8NADH, 2FADH2, 2ATP
🔹 Electron transport chain INPUTS: 6O2, 2FADH2, 10NADH, ADP + Pi
OUTPUT: 6H2O, 2FAD, 10NAD+, 32ATP
Where does anaerobic respiration occur?
Cytosol
What are the limiting factors for aerobic respiration?
Oxygen Glucose Concentration of enzymes involved in the reactions Temperature and ph Available of unloaded acceptors
