Energy for biological process Flashcards
Specification reference:5.2.1 + 5.2.2
Examples of metabolic reactions
- Active Transport
- Anabolic reactions
- Movement
Active Transport
- Essential for the uptake of nitrates by root hair cells
- Loading sucrose into sieve tube cells
- Selective re absorption of amino acids and glucose
- Conduction of nerve fibres
Anabolic reactions
Building polymers (proteins, polysacchrides) and nucleic acids) for growth and repair
Movement
Brought by cillia, flagella and contractile filaments in muscle cells
What do metabolic reactions require?
Energy
What is used to fuel metabolic reactions?
Radiation from the sun keeps organisms alive
Respiration
The process of breaking down organic molecules to form inorganic molecules like water and carbon dioxide
The energy stored in the organic molecules can synthesis…
ATP
Photosynthesis Equation
6CO2 + 6H20 C6H12O6 + 6O2
Respiration Equation
C6H12O6 + 6O2 -> 6CO2 + 6H20
What are the reactants of Respiration
Glucose and oxygen
What are the products of Respiration?
Water and Carbon dioxide
What is the purpose of Respiration?
Release Energy
What are the reactants of Photosynthesis?
Water and Carbon dioxide
What are the products of Photosynthesis?
Glucose and oxygen
What is the purpose of Photosynthesis?
To Trap energy
Endothermic
Takes in energy
Exothermic
Releases energy
What do organic molecules contain lots of?
Carbon-Hydrogen Bonds
Carbon-Hydrogen Bonds
Carbon and Hydrogen share electrons between them resulting in non-polar bonds
Carbon-Hydrogen Bonds
Carbon and Hydrogen share electrons between them resulting in non-polar bonds which doesn’t require a lot of energy to break
Explain why it is incorrect to say that energy is produced? (2 marks)
Energy cannot be created (or destroyed) energy is transferred (1) ATP is produced (1)
Explain why ATP is not a good energy storage molecule but why organic molecules like lipids and carbohydrates are. (4 marks)
ATP is not very stable (1); easy to remove phosphate group (1); organic molecules are (more)
stable (1); idea that organic molecules are more energy dense (1)
Explain the interrelationship between respiration and photosynthesis in organisms? (5 marks)
In photosynthesis light energy is converted into chemical energy (1); inorganic molecules are
converted into organic molecules (1); water and carbon dioxide are converted to glucose (and oxygen) (1); respiration uses oxygen produced in photosynthesis (1); organic molecules are broken
down into inorganic molecules (1); energy released is used to synthesise ATP (1); carbon dioxide
produced is used in respiration (1)
ATP
The universal energy currency in cells
What does Bond Energy in ATP do?
Drives Metabolic reactions
ATP in terms of photosynthesis
Light provides energy to build organic molecules.
Energy is used to form chemical bonds in ATP which are then broken to release energy needed to make bonds (glucose is formed)
ATP in terms of respiration
Organic molecules are broken down and the energy is used to synthesize ATP. ATP is then used to supply energy needed to break bonds in metabolic reactions
ATP that produced in both photosynthesis and respiration is synthesized by what process
Chemiosmosis
Chemiosmosis
Diffusion of protons from a high concentration to a low concentration via a partially permeable
What does chemiosmosis depend on…
Chemiosmosis depends on the creation of a proton concentration gradient. This energy comes from excited electrons
Electrons are excited in which two ways?
- Electrons present in a pigment molecule (chlorophyll) are excited by radiation from the sun
- High energy electrons are released when chemical bonds are broken in respiratory substrate molecules
What do excited electrons pass into?
An electron transport chain which is used to generate a proton gradient
What is an electron transport chain made of?
Electron carriers
Electron carriers
- Have progressive energy levels
- Electrons move from one carrier to another releasing energy
What are electron carriers used for?
They pump protons across a membrane creating a concentration across the membrane which is therefore a proton gradient is formed
How is a proton gradient maintained?
The impermeability of the membrane to hydrogen ions
How can protons move back through the membrane?
Protons move down the concentration gradient through the hydrophillic membrane channel linked to the enzyme ATP synthase. The flow of these protein channels provides the energy used to synthesis ATP (from ADP and P1)
What does ATP synthase do?
Catalyses the formation of ATP
Describe a way to remember an electron transport chain?
The flow of water through an hydroelectric power station causing turbines to spin, generating electricity. Both chemiosmosis and hydroelectric power generation result in energy in a usable form
Explain the importance of ATP in organism (3 marks)
Universal energy currency (1); energy transfer is, quick/immediate (1); energy is in, small/usable,
quantities (1); (energy transfer) is quick, (energy transfer) in quantities that can be used; ATP can be
resynthesised (1)
Describe the properties of cell membranes necessary for the formation of a proton gradient (5 marks)?
Impermeable to, ions/protons (1); idea that there can be different concentrations of protons on each
side of a membrane (1); contains, embedded / integral, proteins (1); e.g., ATP synthase (1); enzyme
responsible for synthesis of ATP (1).
Name the type of diffusion which enables protons to move through ATP synthase and explain the role of ATP synthase in the production of ATP (4 marks)
Facilitated diffusion (1); ATP synthase provides hydrophilic channel for diffusion of protons (1); catalyses the synthesis of ATP (1); lowers activation energy (1).
Photosythesis
The process by which energy in the form of light is used to produce organic molecules
What type of energy is used?
Light energy is transformed into chemical energy trapped in the bonds of organic molecules produced
Autotrophic
Organisms that can photosynthesise
Examples of Autotrophic organisms
Plants and Algae
Hetertrophic
Organisms that obtain complex organic molecules by eating
Example of Heterotrophic organisms
Animals
Autotrophic and Heterotropic organisms in terms in respiration
These organisms break down organic molecules during the process of respiration to release the energy needed to drive metabolic processes
Outer Membrane of a chloroplast
It is a semi-porous membrane and is permeable to small molecules and ions, which diffuses easily. The outer membrane is not permeable to larger proteins.
Intermembrane space of a chloroplast
It is usually a thin intermembrane space about 10-20 nanometers and it is present between the outer and the inner membrane of the chloroplast.
Inner membrane of the chloroplast
The inner membrane of the chloroplast forms a border to the stroma. It regulates passage of materials in and out of the chloroplast. In addition of regulation activity, the fatty acids, lipids and carotenoids are synthesized in the inner chloroplast membrane.
Stroma
Stroma is a alkaline, aqueous fluid which is protein rich and is present within the inner membrane of the chloroplast. The space outside the thylakoid space is called the stroma. The chloroplast DNA chlroplast ribosomes and the thylakoid sytem, starch granules and many proteins are found floating around the stroma.
Function of the stroma
Site of chemical reactions resulting in the formation of complex organic molecules
Lamellae
Membranous channels
Thylakoid system
The thylakoid system is suspended in the stroma. The thylakoid system is a collection of membranous sacks called thylakoids. The chlorophyll is found in the thylakoids and is the sight for the process of light reactions of photosynthesis to happen. The thylakoids are arranged in stacks known as grana. Each granum contains around 10-20 thylakoids.
Function of a chloroplast
Produces food (glucose ) and stores food energy
Pigment molecules
Absorb light of different wavelengths and reflect others
What is the primary pigment in photosynthesis?
Chlorophyll A
Chlorophyll A
Absorbs red and blue light and reflects green light
Examples of other pigments
- Chlorophyll B
- Xantrophylls
- Carotenoids
What is the reason for different shades and colours of leaves?
Different combinations of pigments
Which pigments are embedded in the thylakoid membrane?
- Chlorophyll B
- Xantrophylls
- Carotenoids
Light harvesting system (Antennae Complex)
It is used to absorb and harvest light energy of different wavelengths and transfers the energy to the reaction centre
Where is Chlorophyll A located?
In the reaction centre
Reaction centre
Where reactions of photosynthesis take place
Photosystem
Light harvesting system + reaction centre
What are the 2 stages of photosynthesis?
- Light dependent stage
2. Light independent stage
Light dependant stage
Energy from the sun is absorbed and used to form ATP. Hydrogen is used to reduce the NADP to form reduced NADP
Light independent stage
Hydrogen from reduced NADP and carbon dioxide is used to build organic molecules. ATP supplies the required energy
What are the three steps involved in the light dependent stage?
- Non-cyclic photo phosphorylation
- Photolysis
- Cyclic photo phosphorylation
Non cyclic photo phosphorylation : Step 1
Excited electrons are released form PS2 and are passed through an electron transport chain. As a result ATP is produced via chemiosmosis
How are some of the excited electrons from PS2 replaced?
They are replaced from the water molecules broken down by the energy from the sun
Non cyclic photo phosphorylation : Step 2
Excited electrons are released from the reaction centre at PS1. The excited electrons pass through another electron transport chain. ATP is produced via chemiosmosis
How are some of the excited electrons from PS1 replaced?
They are replaced by the electrons that travelled along the first electron transport chain (PS2)
Non cyclic photo phosphorylation : Step 3
Electrons leaving the electron transport chain at PS1 are accepted (along with hydrogen ions) by the coenzyme NADP forming reduced NADP.
Reduced NADP provides the hydrogen or reducing power in the production
Photolysis
The process of splitting water molecules into hydrogen ions, electron and oxygen molecules using energy from the sun
What do the electrons in photolysis do?
They replace the electrons lost at the reaction centre PS2. Which is why water CO2 and light are raw materials
Photolysis Equation
H20 –> 2H+ + 2e- + 1/2 O2-
What is the oxygen evolving complex used for?
It is apart of the PS2 which catalyses the breakdown of water.
What is the by product of the reaction?
Oxygen gas
What is released from the membrane?
Protons are released into the lumen of the thylakoids increasing the proton concentration across the membrane. As they move down the membrane they go down an electrochemical gradient so more ATP is produced.
What do hydrogen ions do when they return in the stroma?
They combine with NADP and an electron from PS1 to form reduced NADP
Cyclic photophosphorylation
Synthesis of ATP with only the use of PS1
How can ATP be formed with only PS1
The electrons after PS1 can be returned back to PS1 instead of being used to form reduced NADP. So no electrons are being supplied from PS2.
Where does the light independent reaction take place?
The stroma of the chloroplasts.
What is used a raw material in the light independent stage?
Carbon dioxide
What products from the light dependant reaction are used?
ATP and reduced NADP
What are the products of the light independent reaction?
Glucose, lipids and amino acids
How is glucose, lipids and amino acids produced?
In the calvin cycle
Calvin Cycle: Fixation
- Co2 enters the spongy mesophyll by diffusion from the atmosphere to the stomata.
- CO2 combines with RUBP (5 carbon molecule)
- The carbon in CO2 is then fixed in the molecule
What catalyses the calvin cycle
RUBISCO
It is competitively inhibited to oxygen
Calvin Cycle: Reduction
Rubisco catalyses the reaction and an unstable intermediate is formed GP (6 carbon molecule)
GP is then reduced to TP
How is GP reduced to TP
From the products from the light dependent reaction. (Using an hydrogen atom from reduced NADP and ATP)
Calvin Cycle: Regeneration
Some TP is returned to RUBP and the other TP is used for the synthesis of lipids, amino acids, nucleic acids and proteins
Regeneration of RUBP
For one glucose molecule to be produced 6 carbon glucose molecule to be produced 6CO2 molecules must enter the calvin cycle. So 6 turns of the cycle (12 TP molecules, where 2 are used to form glucose)
- 10 TP molecules = 30 carbons (6 x five carbon RUBP)
Explain the meaning of the term of photophosphorylation? (2 marks)
Synthesis of ATP/addition of phosphate group to ADP (1); using energy from light (1)
Explain why photosynthesis stops when plants are exposed to green light? (3 marks)
Green light is reflected/not absorbed (1); no energy for light-dependent stage (1); no ATP and
reduced NADP for light-independent stage (1).
Explain what is meant by fixation? (2 marks)
Inorganic carbon (1); added to organic molecule (1)
The calvin cycle used to be called a ‘dark reaction’ explain why this is incorrect? (1 marks)
Calvin cycle happens during the light as well (1)
Explain why the alternative name of the Calvin Cycle, the light dependent stage is not completely accurate? (3 marks)
Calvin cycle requires ATP (1); and reduced NADP (1); supplied from light-dependent stage (1)
Suggest the possible benefits of cyclic photo phosphorylation? (4 marks)
ATP produced and reduced NADP not produced (1); electrons not required from PSII/photolysis (1);
less ATP used in Calvin cycle (1); more ATP available for other metabolic processes (1).
Describe how RUBP is regenerated from TP in the calvin cycle? (4 marks)
10 molecules of TP every six turns of cycle (1); using ATP (1); 6 molecules of RuBP formed (1); reference to (3/5) carbon shuffle (1); reference to individual steps/named (1); light (1); enzymes (1); coenzymes/named (1); ATP (1); carbon dioxide does not combine directly with water (1).
What are plants affected by?
Temperature and availability of raw materials
Name the three limiting factors that affect the rate of photosynthesis?
- Light intensity
- Carbon dioxide concentration
- Temperature
What is a limiting factor?
When one of the factors of needed for a plant to photosynthesise are in short supply
Light intensity
Light is needed as an energy source . As light intensity increases ATP and reduced NADP are produced at a higher rate
Carbon dioxide concentration
CO2 is needed for carbon for carbon fixation in the calvin cycle so there is an increase of TP
Temperature
This affects the enzyme controlled reactions. As the temperature increases the rate of enzyme activity increases until the proteins denature
Why is water never considered a limiting factor?
For water potential to have become low never
Why is water never considered a limiting factor?
For water potential to have become low enough limit the rate of photosynthesis the plant will have already closed its stomata and ceased photosynthesis.
Law of limiting factors?
The rate of physiological process will be limited by the factor which is in the shortest supply
Investigating the factors that affect the rate of photosynthesis
Data loggers are used to record physical properties (light intensity, temperature, pressure, PH and humidity)
The effect of reducing light intensity on the Calvin cycle?
Reducing light intensity will reduce the rate of the light dependent stage of photosynthesis. This reduces the quantity of ATP and reduced NADP which is needed to turn GP to TP.
Photo-respiration
Process where oxygen competes with carbon dioxide for the active site of the enzyme RUBISCO
