Photosynthesis And Respiration Flashcards
What is an autotroph?
Type of nutrition where organic molecules are synthesised from inorganic molecules
What is a heterotroph
Type of nutrition where complex organic molecules are digested into smaller molecules
What is the granum
Inner part of chloroplasts made of thylakoid membranes, where the light dependent stage of photosynthesis takes place
What is the thylakoid
Flattened membrane bound sac found inside chloroplasts, contains photosynthetic pigments and site of light dependent stage in photosynthesis
What is the stroma
Fluid filled matrix of chloroplasts, where the light independent stage takes place
What are accessory pigments
Pigments which absorb different specific wavelengths of light and trap the energy associated with light
Examples of accessory pigments
Chlorophyll A and B, carotene and xanthophyll
What is an electron carrier
Molecules which can accept one or more electrons and then donate those to another carrier. Proteins in thylakoid membrane are electrons carriers and form electron transport chain or system. Ferredoxin, NAD and NADP also electron carriers
What does NADP stand for
Nicotinamide adenine dinucleotide phosphate
What is NADP and example of
Coenzyme
What is photophosphorylation
Generation of ATP from ADP and inorganic phosphate in presence of light
What is the Calvin cycle
Metabolic pathway of light independent stage. Occurs in eukaryotic cells in the stroma of chloroplasts where co2 fixed with products of light dependent stage to make organic compounds.
Where are photosystems found
Thylakoids
What is the peak absorption of photo system 1
700nm
What is the peak absorption of photo system 2
680 nm
What is the advantage of having different photosynthetic pigments
They have different peak absorption meaning at different types of the day, photosynthesis is still efficient at different light levels
What connects granum
Intergranal lamellae
How are chloroplasts adapted
Have many grana which provides large SA for :
- distribution of photosystems which have photosynthetic pigments which trap sunlight
- electron carriers and ATP synthase enzyme needed to convert light energy to ATP
What holds the photo system in place
Proteins embedded in the thylakoid membrane
Why is the grana surrounded by stroma
So products of light dependent stage can pass to stroma to be used in light independent stage
Describe the stages in the light dependent stage
- Light energy channeled to primary pigments by accessory pigment
- Light energy excited pair of electrons in PSII
- Electrons released from PSII captured by electron carrier
- Lost electrons replaced by photolysis
- When electron reaches electron carrier it becomes reduced to Fe2+ allowing it to become oxidised Fe3+ after passes electron down to next carrier
- As electrons move down chain, energy released
- Chemiosmosis - energy used to pump protons across thylakoid membrane to thylakoid space creating a proton gradient and chemiosmotic potential
- Electrons then captured by chlorophyll A in PSI which replaces electrons lost in PSI by excitation of light energy
- Ferredoxin accepts electrons from PS1, passing to NADP in stroma
- As protons accumulate in thylakoid space, proton gradient formed
- Protons diffuse down conc gradient through special membrane channels associated with ATP synthase enzyme causing ADP and inorganic phosphate to join forming ATP
- As protons flow through channel, they are accepted with electrons by NADP which is reduced . This reduction catalysed by enzyme NADP
Describe the production of ATP by substrate level phosphorylation in different stages of respiration with reference to number of ATP molecules produced
GLYCOLYSIS
2 ATP molecules produced by glycolysis
When triose biphosphate converted to pyruvate
4 ATP made but 2 used in glycolysis so net 2 ATP made
1 ATP made per turn of krebs cycle
What is the precise location of the link reaction within cells?
Mitochondrial matrix
Explain how having a high number of proton pores in the inner mitochondrial membrane would result in a person being less likely to gain weight
Proton pores result in protons leaking into mitochondrial matrix
This disrupt the chemiosmotic gradient resulting in a lower yield of ATP
So less ATP made from oxidative phosphorylation
More energy wasted as heat
Food not converted to ATP as efficiently
Less excess energy intake in diet
Fat stores may be respired for energy
Describe 2 quantitative changes in the inter membrane space after oxidative phosphorylation
PH decreases
Becomes more positively charged due to H+ ions
Outline how ATP is produced through chemiosmosis
Occurs in mitochondria
Involves inner membrane and matrix
Involves movement of hydrogen across membrane
Uses ATP synthase
H+ ions pumped out of matrix across membrane into inter membrane space
Proton gradient created
Cristae involved
ATP synthase produces ATP from ADP+P
H+ go from high to low concentration
Draw and annotate the light independent stage (Calvin cycle)
RuBP converted to GP as it is combined with CO2 (catalysed by RuBisCo). ATP then converted to ADP and Pi and energy used for molecular rearrangement. Reduced NADP gives up its H+ ion and is oxidised to create TP. ATP then converted to ADP and Pi again to create RuBp again.
Gp is used to make amino acids and proteins and can be converted to fatty acids.
Can combine with glycerol produced by TP to create lipids
TP used to make glycerol and lipids when combined with GP
Used to make starch as well
Where does glycolysis occur
Cytoplasm
Describe the process of glycolysis
What is the role of NAD
NAD is a molecule which helps dehydrogenase enzymes carry out oxidation reactions
NAD oxidises substrate molecules during glycolysis, link reaction and Krebs cycle
What is the role of reduced NAD
Carries protons and electrons to cristae of mitochondria and delivers them to be used in oxidative phosphorylation for generation of ATP from ADP and Pi
What are the three main stages of glycolysis
Phosphorylation
Glucose gains 2 phosphates to make hexose bisphosphate
Splitting of hexose bisphosphate into triose phosphate
Split into 2x 3C molecules
Oxidation of triose phosphate to pyruvate
Dehydrogenase enzymes aided by coenzyme NAD, remove hydrogens from triose phosphate
2 molecules of NAD accept the H+ ion and become reduced
What are the products of glycolysis per molecule of glucose
2x ATP
2x reduced NAD
2x Pyruvate
What are the stages of aerobic respiration
Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation
How are the pyruvate molecules from glycolysis transported to link reaction
Active transport
What happens in the absence of oxygen after glycolysis
Pyruvate is converted , in the cytoplasm, to lactate or ethanol.
In these pathways, reduced NAD reoxidised
So glycolysis can continue to run
Generates two molecules of ATP for every glucose molecule
Where do the krebs and link reaction take place
Mitochondrial matrix
What does the mitochondrial matrix contain
Enzymes that catalyse stages of link and krebs
NAD and FAD
Oxaloacetate
Mitochondrial DNA
Mitochondrial ribosomes
What does the outer membrane of a mitochondria contain
Proteins which form channels or carriers to allow molecules like pyruvate into mitochondria
Electron transport chain
How is pyruvate (formed by glycolysis) transported across the inner and outer mitochondrial membranes
By a Symport - transport protein which transports 2 ions or molecules in the same direction and into the matrix
Briefly describe the link reaction
Carboxyl group removed (source of some of co2 in respiration)
Decarboxylation and dehydrogenation of pyruvate produces acetyl group
Acetyl group combines with CoA to form acetyl CoA
Coenzyme NAD becomes reduced
What carries the acetyl group from the link reaction to the Krebs cycle
Coenzyme A
Where does the Krebs cycle take place
Mitochondrial matrix like the link reaction
What is the role of reduced NAD and reduced FAD in Krebs cycle
Carry the hydrogen atoms to cristae’s electron carrier chain where ATP is produced
Per molecule of glucose, how many turns of the Krebs cycle is there
2
What are the products produced in the link reaction per molecule of glucose
2x Reduced NAD
2x CO2
What are the products produced in the Krebs cycle per molecule of glucose
6x reduced NAD
2x reduced FAD
4x CO2
2x ATP
(Remember there are 2x cycles of Krebs per molecule of glucose)
What is the role of other substances in respiration
Fatty acids broken down to acetate which enter Krebs cycle via acetyl CoA
Glycerol converted to pyruvate and enter Krebs through link reaction
Amino acids delaminated and enter Krebs cycle directly or changed to pyruvate or acetyl CoA
Theoretical amount of ATP per molecule in oxidative phosphorylation
30
What is the real yield closer to
28
Why is the theoretical yield rarely achieved
Some ATP used to actively transport pyruvate to mitochondria
ATP used in shuttle system that transports reduced NAD, made in glycolysis, into mitochondria
Some protons may leak out outer mitochondrial membrane
What is the final electron acceptor In oxidative phosphorylation
Oxygen
What is the equation in oxidative phosphorylation
4H+ + 4e- + O2 ——> 2H2O
What happens if oxygen is absent in respiration
Oxygen can’t act as final electron acceptor in oxidative phosphorylation. Protons can’t combine with electrons and oxygen to form water after pass through ATP synthase channel
Conc of protons increases in matrix and reduces inner membrane proton gradient
Reduced NAD and FAD can’t unload hydrogen atoms and can’t be reoxidised
Krebs and link reaction stops
What is the purpose of the fermentation pathways in anaerobic respiration
To reoxidise the reduced NAD
Where do the fermentation pathways take place
In the cytoplasm
What pathways to animals and fungi use
Animals use the lactate fermentation
Fungi use the ethanol fermentation pathway
Describe the process of the ethanol fermentation pathway
Pyruvate is converted to ethanal through decarboxylation (catalysed by ethanal decarboxylase)
Ethanal then accepts hydrogen atom from reduced NAD and becomes reduced to ethanol
What happens to the reduced NAD in the ethanol fermentation pathway
Reoxidised and available to accept hydrogen atoms from triose phosphate allowing glycolysis to continue
Where does the lactate fermentation pathway occur
In the mammalian muscle
Describe the lactate fermentation pathway
Pyruvate made in glycolysis accepts hydrogen atoms from reduced NAD (catalysed by lactate dehydrogenase) and is converted to lactate
What happens to lactate after the lactate fermentation pathway
Converted to pyruvate which will enter Krebs or link
Recycled to glucose and glycogen
What would happen if lactate was not removed from the muscle tissues
PH would be lowered, inhibiting action of enzymes in glycolysis and muscle contraction
Why are monosaccharides like fructose and galactose less effective than glucose as a respiratory substrate
Because they are monosaccharides they have to be converted to glucose by isomerase enzymes
Why are disaccharides less effective than glucose as a respiratory substrate
They have to be hydrolysed and converted to glucose before they enter glycolysis
Describe how lipids are used as a respiratory substrate
With energy from hydrolysis of ATP to AMP, each fatty acid combines with CoA
Fatty acid CoA complex transported to mitochondrial matrix where broken down into 2C acetyl groups, each attached to CoA
Beta oxidation pathway generates reduced NAD and reduced FAD
Acetyl groups released from CoA and enter Krebs cycle
Describe how proteins are used as a respiratory substrate
