Energy For Biological Processes✅ Flashcards
Define photosynthesis and respiration
Photosynthesis: the process by which plants harness light to produce complex organic molecules from CO2 and H2O
Respiration: breakdown of complex organic molecules to produce ATP
What is the purpose, reactants, products of photosynthesis
Purpose: conversion of light energy to chemical energy in organic molecules, 6CO2+6H2O—->C6H12O6+6O2
Reactants: CO2+ H2O
Products: glucose and oxygen
What is the type of reaction, ATP production, use of coenzymes for photosynthesis
ToR:Endothermic
ATP production: produced in light-dependent stage and used in light independent stage
Use of coenzymes: NADP Carries H atoms between the 2 stages of photosynthesis
What is the purpose, reactants, products of respiration
Purpose: conversion of chemical energy in organic molecules to chemical energy in ATP C6H12O6+6O2—>6CO2+6H2O
Reactants: glucose and oxygen
Products: CO2 and H2O
What is the type of reaction, ATP production and use of coenzymes for respiration
ToR: exothermic
ATP production: an end product
Coenzymes: NAD and FAD carry H atoms to electron transport chain
Describe the steps of chemiosmosis
1: electrons are raised to a higher energy level (ie excited electrons)
2: the high energy electrons pass along an electron transport chain
3: energy is released as the electrons are passed to lower energy levels
4: the energy is used to pump H+ ions across a membrane
5: a proton gradient is established across the membrane
6: protons move down the concentration gradient through channel proteins linked to ATP synthase
7: the flow of protons provides kinetic energy to enable ATP synthesis by ATP synthase
For chemiosmosis in photosynthesis:
Where do high energy electrons come from, where is location of ETC, what is name given to ATP production
Light absorbed by chlorophyll
Thylakoid membrane (in chloroplasts)
Photophosphorylation
For chemiosmosis in respiration:
Where do high energy electrons come from, where is location of ETC, what is name given to ATP production
Electrons are released from chemical bonds in glucose
Inner mitochondrial membranes
Oxidative phosphorylation
What are grana
Singular (granum), are flattened membrane compartments (thylakoids), which are sites of light-dependent stage of photosynthesis
What is the stroma
A fluid-filled matrix, which is the site of the light-independent stage of photosynthesis
What are the adaptations of chloroplast and the purpose
Thylakoid membrane are stacked: large SA over which light-dependent reactions can occur
Photosynthetic pigments are organized into photo systems: efficiency of light absorption is maximized
Grana are surrounded by stroma: products of light-dependent reactions (reduced NADP+ATP) can pass directly to enzyme catalyzing the light-independent reactions
Chloroplast contain their own DNA and ribosomes: photosynthetic proteins can be produced inside chloroplasts rather then being imported
The inner chloroplast membrane is embedded with transport proteins and is less permeable than outer membrane: control over which substances that can enter the stroma from cell cytoplasm
What are photosystems
Light-harvesting complexes of pigments found in thylakoid membranes
What are accessory pigments
Chlorophyll B and carotenoids (and xanthophylls) absorb photons of light and funnel this energy to a reaction center at the heart of the photo system
What are chlorophyll A pigments
Located in reaction center, ‘special pair’
Electrons from chlorophyll A are excited and passed to electron acceptors at beginning of ETC
What is the purpose of the light-dependent stage
Light energy is absorbed and enables ATP production
Hydrogen from water is used to reduce NADP
Describe the Light- dependent stage of photosynthesis
1: electrons from reaction center in photosystem II are excited
2: the excited electrons are passed along an ETC (and ATP is produced)
3: the electrons from photolysis replace those lost from photosystem II
4: electrons from reaction center in photosystem I are excited
5: more ATP is produced via a second ETC
6: the electrons that left photosystem II replace those lost from photosystem I
7: the electrons from photosystem I and H+ ions from photolysis of water combine to reduce NADP
Describe the Calvin cycle
1: enzyme RuBisCo catalyses the reaction between RuBP and CO2 to produce two molecules of GP
2: ATP and NADPH are used to reduce GP to TP
3: 1 in every 6 TP used to make glucose, the rest continue the cycle by adding ATP to produce RUBP
What are the uses of triose phosphate (TP)
Can be converted into:
6-Carbon sugars (eg glucose and fructose)
Fructose and glucose can react to produce disaccharide sucrose
Glucose molecules can react together to form polysaccharides such as amylose, amylopectin and cellulose
A single TP molecule can be converted into glycerol
TP can act as the starting point for the synthesis of amino acids
How does light affect photosynethic rate
Light intensity determines the rate at which ATP and reduced NADP are produced in the light dependent reactions, can cause a build up of GP
How does CO2 concentration affect photosynthetic rates
Low CO2 concentrations slow the rate of GP formation
How does temperature affect photosynthetic rates
Low temperatures limit the kinetic energy of molecules involved in photosynthetic reactions. High temps can cause enzymes such as RuBisCo to denature
State 3 similarities between the processes of photosynthesis and respiration (3 marks)
Use of ETC
Use of consented (eg NaD in respiration and NADP in photosynthesis)
Some of same intermediates formed (eg GP)
Starting materials are regenerated in both
Both use chemiosmosis to produce ATP
Describe the energy conversions and transfers that occur between light and being absorbed by chlorophyll in plant leaves and heat being radiated form organisms (3 marks)
Light energy (photons) converter to chemical energy in organic molecules in photosynthesis
Respiration converts chemical energy in organic molecules into chemical energy in inorganic molecules (ATP)
Movement of H+ ions drives ATP production via chemiosmosis
Chemical energy is converted to thermal energy via metabolic reactions
State 2 differences between chemiosmosis in respiration and photosynthesis (2 marks)
Excited electrons have different origins (ie light absorption in photosynthesis, organic reactions in respiration)
Locations differ (thylakoid in membranes in photosynthesis, inner mitochondrial membranes in respiration)
Describe how a proton gradient is established across a thylakoid membrane during photosynthesis
Excited electrons are passed along ETC
Energy is released as electrons are passed to lower energy levels
Energy is used to pump protons ; from the storms to the thylakoid space/lumen
Name 2 useful molecules that can be produced from TP and describe one way in which a plant can use each molecule (4marks)
Glycerol
Triglycerides/ phospholipids/plasma membrane production
Glucose/ fructose
Respiratory substrates, polysaccharides formation
Amino acids
Protein/enzyme formation
Explain why the Calvin cycle will stop after a plant has been placed in the dark for a period of time (2marks)
ATP and NADPH are both produced in light dependent reactions
Both molecules required for reactions in the Calvin cycle
Suggest 3 reasons why plants cannot use the ATP produced in the light independent stage of photosynthesis as their only source of ATP (3 marks)
Photosynthesis only occurs in the light
The rate of production is insufficient to supply the plant with the concentration of ATP required
Some plant cells lack chloroplast and would be unable to generate ATP
Suggest why temperature changes have a greater impact on the rate of light-independent reactions than light dependent state of photosynthesis (2 marks)
Temperature affects the rate of enzyme activity
More enzymes are involved in the light-independent stage than the light-dependent stage
Where does light independent and dependent stages of photosynthesis occur
Independent: thylakoids of chloroplasts
Dependent: stroma of chloroplasts
What happens in the electron transfer chain for photosynthesis
Electrons released from chlorophyll move down carrier proteins embedded in thylakoid membrane
