Topic 5A - Photosynthesis and Respiration Flashcards
What biological processes do PLANTS need energy for?
- Photosynthesis
- Active transport (to take in minerals via the roots)
- DNA Replication
- Cell Division
- Protein synthesis
What biological processes do ANIMALS need energy for?
- Muscle contraction
- Maintaining internal body temperature
- Active transport
- DNA Replication
- Cell Division
- Protein synthesis
What would happen if a plant/animal didnt receive any energy?
Biological processes would stop and the plant would die
What is photosynthesis?
Photosynthesis is a process where energy from light is used to make glucose from H20 and CO2
- light energy is converted to chemical energy in the form of glucose
What is the photosynthesis equation?
6C02 + 6H20 + energy ——– C6H1206 + 602
Where is energy stored after photosynthesis takes place?
It is stored in the glucose until it is released/used up in respiration
How do animals obtain glucose?
Animals obtain glucose by eating plants (or other animals)
What are the 2 types of respiration?
- Aerobic respiration
2. Anaerobic respiration
What is the equation for aerobic respiration?
C6H1206 + 602 —— 6C02 + 6H20 + energy
What does anaerobic respiration produce in:
1- plants?
2- animals?
- In plants + yeast, it produces C2H50H (ethanol) + CO2
2. In animals, it produces lactate
What are 6 useful properties of ATP?
- Stores/releases small,manageable amount of energy at a time, so no energy wasted as heat
- Small and soluble so easily transported around cell
- Easily broken down so energy released instantly
- It can be quickly re-made
- Can Make compound more reactive - phosphorylation
- Can’t pass out cell - immediate energy supply
Define these 4 key words:
- Metabolic Pathway?
- Phosphorylation?
- Photophosphorylation?
- Photolysis?
- Metabolic Pathway - series of small reactions controlled by enzymes e.g. respiration/photosynthesis
- Phosphorylation - Adding phosphate to molecule
- Photophosphorylation - Phosphorylation using light
- Photolysis - Splitting of a molecule using light energy
Define these next 3 key words:
- Photoionisation?
- Decarboxylation?
- Dehydrogenation?
- Photoionisation - When light energy excites electrons in an atom, giving them energy so that they are released
- Decarboxylation - Removal of CO2 from a molecule
- Dehydrogenation - Removal of H2 from a molecule
- Hydrolysis - splitting of a molecule using water
What are co-enzymes?
A coenzyme is a molecule that aids the function of an enzyme
How do co-enzymes work?
They work by transferring a chemical group from 1 molecule to another
What enzyme(s) is used in photosynthesis and what is its role?
NADP - transfers H2 from 1 molecule to another so that they can reduce or oxidise a molecule
What enzyme(s) is used in respiration and what is its role?
NAD, FAD and coenzyme A
- NAD + FAD transfer hydrogen from 1 molecule to other
- Coenzyme A transfers acetate between molecules
What are photosynthetic pigments and where are they found?
They are coloured substances that absorb light energy needed for photosynthesis (chlorophyll a/b, carotenes)
- They are found in the thylakoid membraned of chloroplasts
What is a photosystem?
The protein and pigment (attached together) in the thylakoid.
What is the main difference between the 2 photosystems used by plants to capture light energy?
Photosystem I (PSI) - absorbs light best at wavelength 700nm
Photosysem II (PSII) - absorbs light best at wavelength 680nm
What does the stroma contain?
The stroma contains enzymes, sugars and organic acids
Where exactly are starch grains stored?
They are stored in the stroma
Name the 2 stages that make up photosynthesis AND where they take place?
(DIAGRAM TO SHOW HOW LIGHT DEPENDENT AND INDENDENT REACTION ARE CONNECTED)
- The light-dependent reaction - thylakoid membranes
2. The light-independent reaction/the calvin cycle/CO2 fixation (as carbon is ‘fixed’ into an organic molecule) - stroma
The energy resulting from the photoionisationof chlorophyll, in the light independent reaction, is used for 3 things. What are they?
- Making ATP during PHOTOPHOSPHORYLATION
- Making reduced NADP from NADP
- Splitting water into protons (H+ ions), electrons and oxygen during PHOTOLYSIS
What are electron carriers?
Proteins that transfer electrons and link the 2 photosystems together
What is an electron transport chain (ETC)?
A chain of electrons through which excited electrons flow
Describe step 1 of non-cyclic photophosphorylation?
DIAGRAM
LIGHT ENERGY EXCITES ELECTRONS IN CHLOROPHYLL
- Light absorbed by PSII, exciting chlorophyll electrons
- Electrons move to higher energy level
- High-energy electrons released from chlorophyllto move down ETC to PSI
Describe step 2 of non-cyclic photophosphorylation?
DIAGRAM
PHOTOLYSIS OF WATER PRODUCES H+, ELECTRONS & O2
- As excited electrons leave PSII, they must be replaced
- Light splits water into H+, electrons, and O2
- REACTION: H20 —- 2H+ + 1/202
Describe step 3 of non-cyclic photophosphorylation?
DIAGRAM
ENERGY FROM EXCITED ELECTRONS MAKES ATP
- Excited electrons lose energy as they move down ETC
- This energy is used to transport H+ into thylakoid, so that thylakoid has higher conc of H+ than stroma. This forms H+ gradient across thylakoid membrane
- H+ move down conc gradient into stroma, via enzyme ATP synthase, which is embedded in thylakoid membrane.
- Energy from this movement combines ADP and Pi to form ATP
Describe step 4 of non-cyclic photophosphorylation?
DIAGRAM
ENERGY ALSO MAKES REDUCED NADP
- Light absorbed by PSI, exciting electrons to even higher energy level
- Electrons transferred to NADP, along with H+ from the thylakoid (during photolysis), to form reduced NADP
How is cyclic photophosphorylation different to non-cyclic photophosphorylation?
(DIAGRAM)
Cyclic photophosphorylation:
- only uses PSI
- is ‘cyclic’ so chlorophyll electrons are passed onto NADP, but back to PSI via electron carriers (so electrons are recycled and can repeatedly flow through PSI)
- Doesnt produce reduced NADP/O2, only little ATP
Briefly name the products of the calvin cycle?
- Triose Phosphate from CO2 (which is used to make glucose and other useful organic substances)
- Ribulose Bisphosphate (RuBP) - a 5 carbon compound
Describe Step 1 of the Calvin Cycle
DIAGRAM
CO2 combines with RuBP to form 2 molecules of GP
- CO2 enters leaf through stomata and diffuses into stroma of chloroplast
- Here, it’s combined with RuBP. (catalysed by Rubisco)
- This gives unstable 6-carbon compound, which quickly breaks down into 2 molecules of a 3-carbon compound called glycerate 3-phosphate (GP)
Describe Step 2 of the Calvin Cycle
DIAGRAM
ATP and reduced NADP (from light dependent reaction) are needed to reduce GP to TP
- Hydrolysis of ATP provides energy to turn GP into a different 3-carbon compound, TP
- Reaction also needs H+ ions, which comes from reduced NADP. Reduced NADP is recycled to NADP.
- Some TP is then converted into useful organic compounds (e.g. glucose) and some stays in cycle to regenerate RuBP
Describe Step 3 of the Calvin Cycle
DIAGRAM
RuBP is regenerated
- 5/6 molecules of TP produced in the cycle are used to regenerate RuBP (so there’s always enough RuBP ready to combine with CO2 taken in from atmosphere)
- Regenerating RuBP uses the rest of the ATP produced by the light-dependent reaction
How does the calvin cycle produce carbohydrates?
- hexose sugars (e.g. glucose): made by joining 2 TP molecules together
- largers carbohydrates (e.g. sucrose, starch, cellulose): made by joining hexose sugars together in different ways
How does the calvin cycle produce lipids?
Lipids are made using glycerol, which is made from TP, and fatty acids, which are made from GP
How does the calvin cycle produce amino acids?
Some amino acids are made from GP
Why does the Calvin Cycle need to run 6 times to make a Hexose Sugar?
DIAGRAM
- 3 turns of cycle produces 6 molecules of TP
- 5/6 TP molecules are used to remake RuBP
- So for 3 turns of the cycle, only 1 TP is made that is used to make sugar
- Hexose has 6 carbons so 2 TP molecules are needed
- Therefore, cycle must turn 6 times to make 2 TP molecules, in order to make sugar
** How many ATP and Reduced NADP are needed for 6 turns of the Calvin Cycle?
ATP: 18
Reduced NADP: 12
Name the 3 optimum conditions for photosynthesis.
- High light intensity of a certain wavelength
- Temperature around 25 degrees
- CO2 at 0.4%
- Sufficient amount of water
How is high light intensity an optimum condition for photosynthesis?
- Light is needed in Light-dependent reaction - higher the light intensity, the more energy it provides
- Only certain wavelengths of light are used for photosynthesis .
- Photosynthetic pigments only absorb red and blue light in sunlight (green light is reflected , which is why plants look green)
How is a good temperature an optimum condition for photosynthesis?
- Process involves enzymes (Rubisco, ATP synthase).
- If temp falls below 10, enzymes become inactive, but if over 4, they may start to denature - Also, at high temps stomata close to avoid losing too much water. This causes photosynthesis to slow down as less CO2 enters the leaf
How is a good CO2 level an optimum condition for photosynthesis?
- CO2 makes up 0.04% of the gases in the atmosphere
2. Increasing this to 0.4% gives a higher rate of photosynthesis, but any higher and the stomata start to close
How is a sufficient water amount an optimum condition for photosynthesis?
Plants need a constant supply of water - too little and photosynthesis has to stop but too much and the soil becomes waterlogged (reducing the uptake of minerals like magnesium, which is needed to make chlorophyll a)
What is a limiting factor (photosynthesis) and name 3 of them?
DIAGRAM
A factor that can limit the rate of photosynthesis if too high or too low
- Light intensity
- Temperature
- CO2 concentration
Define ‘saturation point’.
Where a factor is no longer limiting the reaction - something else has become the limiting factor
How do growers manage the limiting factors in a glasshouse? (CO2 ONLY)
CO2 = CO2 is added to the air e.g. by burning a small amount of propane in a CO2 generator
How do growers manage the limiting factors in a glasshouse? (LIGHT ONLY)
Light = light can get in through glass (lamps provide light at night)
How do growers manage the limiting factors in a glasshouse? (TEMP ONLY)
Temp = glasshouses trap heat energy from sunlight, which warms the air
- Heaters and cooling systems can also be used to keep a constant optimum temp
- air circulation systems ensure that temp is even throughout glasshouse
Why is it an advantage for plants to have loads of pigments? (in regards to absorbing max amount of light)
Each pigment absorbs a different wavelength of light, so having more than 1 type of pigment increases the range of wavelengths of light that a plant can absorb
Do all species of plants contain the same mixtures/proportions of pigments?
No
What two categories of plants pigments are there?
- Photsynthetic pigments
2. Non-Photosynthetic pigments with other roles (e.g. protectig leaves from excessive UV radiation
What are the main similarities/differences between aerobic and anaerobic respiration?
SIMILARITIES
- Both produce ATP
- Both start with the process of glycolysis
DIFFERENCES
- . Aerobic requires oxygen whilst aerobic doesnt
- Anaerobic respiration produces less ATP
- The stages after glycolysis for both types of respiration differ
In 1 sentence, state what glycolysis involves and where it happens?
It involves splitting a molecule of glucose (6C) into 2 smaller molecules of pyruvate (3C), without the use of (anaerobic process)
- It takes place in the cytoplasm of cells
Name the 2 stages of glycolysis
- Phosphorylation
2. Oxidation
Describe stage 1 of glycolysis
DIAGRAM
PHOSPHORYLATION OF GLUCOSE TO TP
1) Glucose is phosphoryated using a molecule of ATP. This creates 1 molecule of glucose phosphate and 1 molecule of ADP
2) ATP then used to add another phosphate , forming hexose bisphospate
3) Hexose Bisphosphate is split into 2 molecules of TP
Describe stage 2 of glycolysis.
DIAGRAM
OXIDATION OF TP TO RELEASE ATP
1) TP is oxidised (loses H2) forming 2 molecules of pyruvate
2) NAD collects the H2 ions, forming 2 reduced NAD
3) 4 ATP are produced, but 2 were used up in stage 1, so thereds a net gain of 2 ATP
What happens after glycolysis during AEROBIC respiration?
- The 2 molecules of reduced NAD go to oxidative phosphorylation
- The 2 pyruvate molecules are actively transported into the matrix of the mitochondira for the link reaction
What happens after glycolysis during ANAEROBIC respiration?
DIAGRAM
The pyruvate produced is converted into ethanol (in plants and yeast) and lactate (in animal cells and some bacteria) using reduced NAD
- In Alcoholic fermentation, pyruvate will release CO2 to become ethanal, and then reduced NAD would turn it into ethanol
How can the production of ethanol/lactate keep glycolysis going?
DIAGRAM
The production of ethanol/lactate regenerates oxidised NAD, so glycolysis can continue even if there isnt much oxygen around.
- *This will therefore allow ATP to be produced to keep some biological processes going as ATP is also synthesised during glycolysis
What is the 1st thing that happens when pyruvate enters the matrix in aerobic respiration?
DIAGRAM
THE LINK REACTION CONVERTS LACTATE TO ACETYL COENZYME A
1- Pyruvate is decarboxylated (1 carbon atom is removed in the form of CO2)
2- Pyruvate is oxidised (*loses H2) to form acetate and NAD is reduced to form reduced NAD
3- Acetate is combined with Coenzyme A to form Acetyl CoA.
4- No ATP is produced in this reaction
How many times does the link reaction and the Krebs cycle happen for each glucose molecule and why?
Twice as 2 pyruvate molecules are made for every glucose molecule and only one pyruvate can go through the link reaction/Krebs Cycle at a time
For each glucose molecule:
1- How many times does the link reaction and the Krebs cycle happen?
2- How many molecules of Acetyl coenzyme A enter the Kreps Cycle?
3- How many molecules of CO2 are released as a waste product of respiration?
4- How many molecules of Reduced NAD are formed and move onto the last stage? (Oxidative phosphorylation)
1- Twice
- Two
- Two
- Two
What does the Krebs Cycle produce?
Reduced Coenzymes and ATP
Describe step 1 of the Krebs Cycle.
DIAGRAM
- Acetyl CoA combines with 4 carbon molecule (oxaloacetate) to form a 6-carbon molecule (citrate)
- CoA goes back to the link reaction to be used again
Describe step 2 of the Krebs Cycle.
DIAGRAM
- The 6C citrate molecule is converted to a 5C molecule
- Decarboxylation occurs, where CO2 is removed
- Dehydrogenation also occurs, where H2 is removed
- The H2 is used to produce reduced NAD from NAD
Describe step 3 of the Krebs Cycle.
DIAGRAM
- The 5C molecule is converted to a 4C molecule (some intermediate compounds are also formed here)
- **Decarboxylation & Dehydrogenation occur, producing 1 molecule of reduced FAD and 2 of reduced NAD
- ATP is made by the direct transfer of a phosphate group from an intermediate compound to ADP. (substrate-level phosphorylation). Citrate has now been converted into oxaloacetate
What is ‘substrate-level phosphorylation’?
When a phosphate group is directly transferred from 1 molecule to another
Describe what happens to these substances after being produced in the Krebs cycle?
- 1 Conzyme A
- Oxaloacetate
- 2CO2
- 1 Co enzyme A = Reused in the next link reaction
- Oxaloacetate = Regenerated for use inthe next Krebs cycle
- 2CO2 = Released as a waste product
Describe what happens to these substances after being produced in the Krebs cycle?
- 1 ATP
- 3 reduced NAD
- 1 Reduced FAD
- 1 ATP = Used for energy
- 3 reduced NAD = To oxidative phosphorylation but reused in Krebs cycle
- 1 Reduced FAD = To oxidative Phosphorylation but reused in Krebs cycle
What is oxidative phosphorylation? (just briefly state in a sentence)
The process where energy carried by electrons,from reduced coenzymes (reduced NAD/ FAD) is used to make ATP
Describe steps 1-3 of oxidative phosphorylation?
DIAGRAM
- H2 atoms are released from reduced NAD/FAD as they’re oxidised to NAD/FAD. The H atoms split into H+ and electrons
- Electrons move down ETC, losing energy at each electron carrier
- This energy is used by carriers to pump H+ from mitochondrial matrix into intermembrane space (space between inner & outer mitochondrial membranes)
Describe steps 4-7 of oxidative phosphorylation?
DIAGRAM
- Conc of H+ is now higher in intermembrane space than matrix, forming an electrochemical gradient (a conc gradient of ions)
- Protons them move down this gradient, back across inner mitochondrial membrane and into the matrix, via ATP synthase (which is embedded in innrer mitochondrial membrane). This movement drives synthesis of ATP from ADP and Pi. (chemiosmosis)
- In the matrix, at the end of the ETC, the H+ , electrons and 02 from blood combine to form water. O2 is said to be the final electron acceptor
Name the 4 stages of aerobic respiration
- Glycolysis
- Link reaction
- Krebs cycle
- Oxidative phosphorylation
How much ATP is made from:
- 1 reduced NAD
- 1 reduced FAD
1 reduced NAD: 2.5
1 reduced FAD: 1.5
How many ATP molecules in total are made during one cycle of respiration?
32
How can mitochondrial diseases lead to high lactate concs in the blood?
- As they affect the functioning of mitochondria, they can affect how proteins involved in oxidative phosphorylation/ the krebs cycle function, reducing ATP production
- This may cause anaerobic respiration to increase, to try and make up for the ATP shortage
- This results in lots of lactate being produced, which can cause muscle fatigue and weakness
- Some lactate will diffuse into the blood, leading to high lactate conc in blood.
How is the structure of a chloroplast adapted to its function in photosynthesis?
- The disc shape of a chloroplast gives it a large SA for light absorption.
- Permeable membrane allows diffusion of gases
- Stroma contains enzymes for light independent reaction.
- Membranes provide surface for attachment of electron acceptors.
