17+18 - Energy for biological processes & respiration Flashcards
1
Q
The need for energy
A
Growth, response, make/find food, reproduce, predation……
These all require metabolic activities:
Active transport (uptake of nitrates by plants, loading sucrose into sieve tube cells and conduction of nerve impulses)
Anabolic reactions (building polymers like proteins, polysaccharides)
Movement (cillia, flagella or contractile filaments in muscles)
2
Q
photosynthesis
A
carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
Occurs in 2 stages
3
Q
Aerobic Respiration
A
glucose + oxygen → carbon dioxide + water + ATP
C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
Occurs in 4 stages
4
Q
energy and bonds
A
- energy is used to break bonds
- energy is released when bonds are formed
5
Q
how does respiration release energy
A
- large organic molecules break down to form small inorganic molecules
- the energy to break the bonds is less than the energy released in the formation of al the bonds in the smaller inorganic products
- excess energy released is used to synthesis ATP
6
Q
explain how breaking down glucose & fatty acids can release energy when bond breaking is an endothermic process.
A
- carbon and hydrogen are equal in EN, so have non-polar bonds
- so bond doesn’t require lots of energy to break
- C and H break and form new bonds with oxygen, releasing energy
7
Q
How does ATP release its energy?
A
- ATP has 3 phosphate groups, so is fully “charged”
- A small amount of energy is used to break the 3rd phosphate from the ATP
- A large amount of energy is released due to interactions involving the products (especially the phosphate making new bonds)
-ADP can be “recharged” via respiration by adding another phosphate group back
8
Q
Chemiosmosis:
A
-Diffusion of protons from a region of high concentration to a region of low concentration through a partially permeable membrane.
Uses a PROTON (H+) concentration gradient
-> The movement of protons as they flow down CG releases energy that is used for attachment of ADP + Pi ATP
9
Q
How is the proton gradient created? in chemiosmosis
A
The energy needed to create the gradient comes from high-energy electrons – excited electrons.
Electrons are raised to higher energy levels in 2 way:
-> Electrons in pigments e.g. chlorophyll are excited by absorbing sunlight.
-> High energy electrons are released when chemical bonds are broken in respiratory substrates e.g. glucose.
The excited electrons pass into an electron transport chain in the mitochondria and are used to generate a proton gradient.
10
Q
Electron transport chain
A
- Series of electron carriers (protein complexes), each causing electrons to drop to lower energy levels.
- As high energy electrons move down energy levels, energy is released.
- This is used to pump protons across the inner membrane, from the matrix into the intermembrane space, creating a concentration gradient.
11
Q
ATP synthase
A
- Protons can only move back through membrane channels linked to the enzyme ATP synthase. (facilitated diffusion)
- The flow of protons through the channels provides energy to synthesise ATP.
- This whole process, including the ETC, is called “Oxidative phosphorylation”
12
Q
explain the importance of ATP to living organisms
A
-Universal energy currency
-energy transfer is, quick/immediate
-energy is in, small/usable, quantities
-(energy transfer) is quick,
-(energy transfer) in quantities that can be used
-ATP can be resynthesised
13
Q
describe the properties of cell membranes necessary for the formation of a proto gradient
A
-Impermeable to, ions/protons
-idea that there can be different concentrations of protons on each side of a membrane
-contains, embedded / integral, proteins
e.g., ATP synthase
enzyme responsible for synthesis of ATP
14
Q
what type s diffusion is proton movement at ATP synthase and explain the role of ATP synthase
A
Facilitated diffusion
-ATP synthase provides hydrophilic channel for diffusion of protons
- catalyses the synthesis of ATP (1); lowers activation energy
15
Q
Most ATP is produced in mitochondria by chemiosmosis.
Outline how ATP is produced in mitochondria by chemiosmosis
A
idea of establishment of H+ ion gradient
-> pumping protons into intermembranal space’
H+ ions, flow down a concentration gradient /
from intermembrane space to matrix
through ATP synthase
energy, provided / AW, to join ADP and Pi ( to form ATP)
16
Q
Heterotroph
A
Organisms that acquire nutrients by the ingestion of other organisms
17
Q
Autotroph
A
Organisms that synthesise complex organic molecules from inorganic molecules. (they make their own food)
18
Q
Photoautotrophs
A
Organisms that can photosynthesise – use energy from sunlight to make complex organic molecules from inorganic molecules (CO2 and H2O)
19
Q
structure and function of chloroplasts
A
- PHS is here
- large network of membrane = large SA for maximum absorption of light
- flattened thylakoids stack to form grana, joined by lamellae
-light is absorbed by complexes of pigments which are embedded in thylakoid membrane - fluid in the chloroplast is called stroma and is the site of chemical reactions
20
Q
Photosynthetic pigments
A
Molecules that absorb light energy.
Found embedded in the thylakoid membrane.
Each pigment absorbs a range of wavelengths in the visible region and has its own distinct peak of absorption.
Other wavelengths are reflected or transmitted.
Chloroplast’s main pigment is chlorophyll a
They however also contain accessory pigments.
These include chlorophyll b, carotenoids like carotene, and xanthophylls to broaden their effectiveness in absorbing visible light
21
Q
How do pigments work?
A
Pigments are arranged in photosystems.
Photosystems can be divided into 2 regions, The antennae complex (or light harvesting complex) & the reaction centre.
Accessory pigments in the antennae complex transfer light energy to the primary pigments in the reaction centre.
22
Q
chlorophyll a
A
Chloroplast’s main pigment
There are 2 types of chlorophyll a – P680 and P700 named so because of their absorption peaks.
Each have a different photosystem:
Photosystem I (PSI)
Photosystem II (PSII)
23
Q
Photosystem II (PSII)
A
chlorophyll a - P680
primary pigment absorbs light at 680nm so is known as P680
24
Q
Photosystem I (PSI)
A
primary pigment absorbs light at 700nm so is known as P700
25
a chlorophyll a - P680 and P800 different chlorophyll molecules
They contain IDENTICAL chlorophyll a molecules. It is their association with different proteins which affects their electron distribution in the chlorophyll molecules and accounts for the slight differences in light absorbing properties.
26
Stages of photosynthesis
- what it needsm where to and what is it doing
Light dependent reactions
->Needs light
->Takes place in the thylakoid membranes
->Light energy is converted to chemical energy - ATP (using the photosystems) and NADPH2
Light Independent reactions
->Does not use light directly
->Takes place in the stroma
-> Where glucose is made using the ATP and NADPH2 from the light dependent reaction
27
Non-cyclic Photophosphorylation
1. Light travels in parcels of energy called call ‘photons’
2. When a photon hits chlorophyll in PSII, two electrons become excited
3 Excited electrons are captured by electron acceptors and passed along a series of electron carriers within the thylakoid membrane
4. Energy is released as the electrons are pass along the electron transport chain
5. This pumps H+ ions across the thylakoid membrane into the thylakoid lumen – creating a concentration gradient
6. The H+ ions flow down a gradient across channels associated with ATP synthase enzymes
7. ATP synthase drives the formation of ATP from ADP and Pi
8.This is called chemiosmosis
28
Photolysis of water
The electrons lost from the chlorophyll in PSII must be replaced to continue the flow of electrons along the electron transport chain.
Within the thylakoid space, an enzyme splits water (photolysis) using energy from the Sun, to give oxygen gas, hydrogen ions and electrons.
The electrons replace those that were emitted from the reaction centre of PSII.
The hydrogen ions contribute to the proton gradient across the thylakoid membrane
The Oxygen gas is released by the plant as a waste product
29
Reduction of NADP
Electrons are excited again by light at PSI and electrons pass along another (very short) electron transport chain (This does not pump any H+ across the membrane, it is just used to transfer the electrons to the next stage).
Ultimately, they combine with the coenzyme NADP and hydrogen ions from the water to form reduced NADP (aka NADPH).
30
Cyclic Photophosphorylation
If ATP is needed, but not NADH, thylakoids can carry out “Cyclic Photophosphorylation”.
In this process electrons leave PSI, moved to the second electron transport chain, then returned to the first ETC.
The Electrons are used to pump H+ ions across the membrane before being returned to PSI where they are excited by light again. This process repeats, generating the H+ gradient that allows ATP to be produced, but prevents NADPH from being generated.
31
Light independent reaction
Photolysis of water
Non-cyclic Photophosphorylation
Reduction of NADP
32
Describe two ways in which the structure granum is adapted to its function.
contain, (named) pigment (molecules) / photosystems;
contain, (named) electron carriers / ETC / ATP synth(et)ase;
idea that has a large surface area (in a small volume) for, light absorption / light dependent reaction(s) / light dependent stage / electron transport;
33
Name the primary photosynthetic pigment in photosystems I and II.
chlorophyll, a / A;
34
Name an accessory pigment.
chlorophyll b / xanthophyll(s) / carotenoid(s) / (β / beta-) carotene;
35
State the advantage to the plant of having a range of accessory pigments in photosystems.
able to, absorb / use,
a range of / different / more / other,
(light) wavelengths / λ
36
Name the compound that is synthesised in the light-dependent stage as a result of the generation of an electrical and pH gradient across the thylakoid membrane.
ATP
37
Limiting factors
a factor that limits the rate of a process when at a lower level
38
Light Intensity – explaining to A level standard
1. As light intensity increases, the rate of photosynthesis will increase (as long as other factors are in adequate supply)
2 As the rate increases, eventually another factor will come into short supply and increase in rate of PHS slows
3 Eventually, even if light intensity is increased, rate of PHS doesn’t change (plateau)
Low light levels mean less ATP and reduced NADP. This slows down the Calvin cycle (conversion of GP to TP and RuBP).
No light = none of this.
Light is also needed for photolysis
Increased light means more ATP and reduced NADP, meaning more photolysis, more LDR and therefore more LIR
39
Temperature - explaining to A level standard
Affects rate of enzyme controlled reactions... each step in PHS is dependent on enzymes (ATP synthase, NADP reductase, RuBisCO...)
At lower temp, substrate molecules have less kinetic energy which means there will be fewer successful collisions and a slower rate of reaction... lower conc of GP, TP, RuBP. Slower enzymes mean a slower Calvin cycle.
At a certain point, enzymes will be denatured (irreversible) and PHS will ultimately stop! Hot temperature stop the Calvin cycle.
However, the rate of photorespiration also increases above 25oC, meaning that even if enzyme is not denatured, rate of PHS might be limited by an increase in photorespiration!
High temperatures also cause more water loss from stomata, leading to the stress response of closing. Less carbon dioxide can then access the plant… closely linked to CO2 as a limiting factor
40
plant Uses of glucose
Used in respiration
Converted to starch; storage tubers
To make complex carbohydrates; xylem phloem, cell walls
To make amino acids. Enzymes
Build fats and oils eg nuts
41
The Calvin Cycle
The cyclical light independent reactions of photosynthesis
42
Carbon fixation
The incorporation of CO2 into organic molecules
43
RuBisCO
An enzyme used in photosynthesis, carries out carbon fixation in the Calvin cycle (very inefficient, thought to be the most abundant enzyme in the world). Short for “Ribulose bisphosphate carboxylase/oxygenase”.
44
Ribulose Bisphosphate (RuBP)
A 5-carbon organic molecule.
45
Glycerate 3-Phosphate (GP)
A 3-carbon organic molecule.
46
Triose Phosphate (TP)
A 3-carbon organic molecule.
47
outline the Light-independent stage
(the Calvin Cycle)
Second and final set of reactions
Occurs in the stroma – the fluid matrix inside chloroplasts
Requires CO2
Synthesises organic molecules from CO2
Uses ATP & NADPH produced during the light dependent stage
Does not need light in order to occur
BUT reactions will not continue for very long without the presence of light
Products of the light dependent stage are required. ATP & reduced NADP (NADPH)
48
Light-independent stage
(the Calvin Cycle)
1) Ribulose bisphosphate (RuBP) (5C) combines with carbon dioxide to form an unstable 6C intermediate
2) 6C intermediate immediately splits into 2 3C glycerate 3-phosphate (GP)
3) GP is reduced and phosphorylated to triose phosphate (3C) What molecules would be needed for this?
- NADPH is oxidised to NADP
- ATP to ADP + Pi
4) Some of the triose phosphates (3C) combine to form glucose (6C) – or amino acids or lipids
5) Others regenerate RuBP – ATP to ADP here
49
why is 6 turns of the calvin cycle needed
2 TP molecules contain enough carbon to make one glucose molecule, but with none remaining to regenerate the RuBP.
(remember 5 of those carbon atoms came from the RuBP).
As glucose is a 6 carbon molecule, the Calvin cycle requires the addition of 6CO2 for every molecule of glucose produced.
This ensures the RuBP is not consumed without being replaced.
6 turns of the Calvin cycle are needed to take in 6CO2 & produce 12TP.
2TP are used to make glucose (6 carbons).
10TP are used to regenerate the 6RuBP (30 carbons).
50
Products of the Calvin Cycle
- Two molecules of TP can combine to form a hexose sugar (glucose) and such structures can polymerise to form starches, sugars and cellulose
Other (non-sugar) products of the Calvin Cycle
-Molecules of GP can also be used to form amino acids and fatty acids
-TP can also be used to form glycerol, combined with fatty acids made by GP to form various lipids
-Other molecules formed are nucleic acids, growth factors, vitamins, hormones and pigments
51
RuBisCO - what is bad ?
= enzyme which adds a carboxyl group to the RuBP molecule
Ribulose bisphosphate carboxylase / oxygenase
BUT...
Oxygen can also fit into the complex
This results in a reaction called photorespiration
Oxygen combines with RuBP in the place of CO2 to produce a toxic two carbon molecule phosphoglycolate
52
The light-independent stage of photosynthesis used to be referred to as the ‘dark reaction’.
Explain why this is both an accurate and an inaccurate way to describe the light-independent stage
accurate because:
does not require , photons / light energy
inaccurate because:
needs , ATP / reduced NADP , produced in light-dependent stage
53
Name the enzyme responsible for fixing CO2 in the light-independent stage
ribulose bisphosphate carboxylase / RuBisCO
54
During the light-independent stage of photosynthesis, triose phosphate (TP) is synthesised in the chloroplasts of plant cells.
State two possible uses of this molecule within the plant.
Synthesis of:
(named) carbohydrate (1)
hexose sugars (1)
amino acids (1)
lipids (1)
ALLOW regeneration of RuBP
55
From which molecule is TP synthesised during the light-independent stage?
GP / glycerate-3-phosphate
56
Photosynthesis occurs in two stages: the light-dependent stage and the light-independent stage. The light-independent stage is affected by temperature more than the light-dependent stage.
Explain why temperature has a greater effect on the rate of the light-independent stage.
Light-independent stage is) controlled by (named) enzymes
idea that higher temperature will increase, kinetic energy of enzyme molecules / number of successful collisions /ESCs formed / ora
enzymes may be denatured at high temperatures / described
57
2 ways to “recharge” ADP to ATP
Substrate level phosphorylation
Simple attachment of Pi to ADP
Inefficient (not much ATP made at any one time)
Oxidative Phosphorylation (using chemiosmosis)
Uses a PROTON (H+) concentration gradient
58
Aerobic Respiration:
glucose + oxygen → carbon dioxide + water
C6H12O6 + 6O2 → 6CO2 + 6H2O
Produces ATP (38 ATP per glucose molecule)
Occurs in 4 stages
59
4 stages of aerobic respiration
Glycolysis
Link reaction
Krebs cycle
oxidative phosphorylation
60
overview of glycolysis
Occurs in cytoplasm
Is an anaerobic process
Glucose + 2NAD + 2ATP + 2ADP + 2Pi 2Pyruvate + 4ATP + 2NADH
Net production of 2 Pyruvate, 2 NADH, & 2 ATP
(2ATP had to be used to in the reaction)
61
steps of glycolysis
1- phosphorylation
2- Lysis
3- phosphorylation
4- Dehydrogenation & ATP synthesis.
62
step 1 of glycolysis
phosphorylation.
2 ATP molecules attach phosphate groups to the glucose, producing Hexose Bisphosphate
63
Step 2 of glycolysis
Lysis
Hexose Bisphosphate is unstable, so it splits into 2 Triose phosphate molecules
64
step 3 of glycolysis
phosphorylation
Inorganic phosphate ions in the cytoplasm attach to the triose phosphate molecules (1 each) producing 2 Triose bisphosphate molecules
65
step 4 of glycolysis
Dehydrogenation & ATP synthesis
Hydrogen atoms are removed and transferred to NAD, reducing it to NADH. Simultaneously the 2 phosphate groups are removed and used to synthesise ATP. What’s left of the triose bisphosphate becomes pyruvate.
66
Through glycolysis, 1 glucose molecule has been used to produce:
2NADH
2ATP (why only 2?)
2 Pyruvate (C3H4O3)
67
overview of link reactions
Occurs in mitochondrial matrix of the cell.
Links glycolysis (the anaerobic step of respiration) which occurs in the cytoplasm, to the aerobic steps of respiration which take place in the mitochondria.
68
steps of link reaction
- Pyruvate is a three-carbon compound that is derived from glycolysis
- Pyruvate Decarboxylation: each pyruvate molecule undergoes decarboxylation. This involves the removal of a carboxyl group (-COOH), resulting in the release of carbon dioxide (CO2) as a waste product.
- Formation of Acetyl CoA: The remaining two-carbon molecule is acetyl group (CH3CO-), combines with coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA).
- NADH Production: During the conversion of pyruvate to acetyl CoA, a pair of electrons and a hydrogen ion (H+) are transferred to the coenzyme NAD, forming NADH. -> ->This NADH will later be used in the electron transport chain to generate ATP through oxidative phosphorylation.
the production of acetyl CoA, it acts as a substrate for the next stage of cellular respiration, the citric acid cycle (also known as the Krebs cycle).
69
glycolysis overview
Glycolysis is the initial step in cellular respiration, occurring in the cytoplasm. It is a series of enzymatic reactions that converts one molecule of glucose (a six-carbon compound) into two molecules of pyruvate (each a three-carbon compound). The process involves the investment of two ATP molecules and ultimately produces a net gain of two ATP molecules, two NADH molecules, and two molecules of pyruvate.
70
reactant of glycolysis
Glucose (C6H12O6)
2 ATP molecules
2 NAD molecules
2 Pi ions
2 ADP molecules
71
products of glycolysis
4 ATP molecules (net gain of 2 ATP)
2 NADH molecules
2 molecules of pyruvate (each with 3 carbons)
72
key steps in glycolysis
Phosphorylation: Glucose is phosphorylated by ATP to form Hexose bisphosphate.
Lysis: Hexose bisphosphate is rearranged and split into two molecules of Triose phosphate.
Phosphorylation: Triose phosphate is phosphorylated using Pi ions, producing Triose bisphosphate.
Dehydrogenation & ATP synthesis: For each Triose bisphosphate, the 2 phosphate groups are removed and combined with ADP to make ATP. Simultaneously an H+ ion is removed and used to reduce NAD to NADH. The remaining 3 carbon molecule with no phosphates is called pyruvate.
73
Link reaction overview
Link Reaction: Following glycolysis, pyruvate molecules undergo the link reaction, which occurs in the mitochondrial matrix. The primary function of the link reaction is to prepare pyruvate for entry into the Krebs cycle. During this process, each pyruvate molecule is decarboxylated, producing acetyl CoA, NADH, and carbon dioxide.
74
link reaction reactant
2 molecules of pyruvate (each with 3 carbons)
2 molecules of coenzyme A (CoA)
2 molecules of NAD
75
products of link reaction
2 molecules of acetyl CoA
2 molecules of NADH
2 molecules of carbon dioxide
76
key steps in link reaction
Decarboxylation: 1 carboxyl group is removed from each pyruvate molecule. This releases carbon dioxide which is excreted & hydrogen which is used to reduce NAD to NADH.
Formation of Acetyl CoA: The two-carbon fragment (the Acetyl group) combines with coenzyme A (CoA) to form acetyl CoA.
77
where does krebs cycle occur
mitochondrial matrix
78
Overview of krebs cycle
Each molecule of Acetyl-CoA formed during the link reaction enters the Krebs Cycle, which takes place in the mitochondrial matrix.
For every molecule of glucose that undergoes glycolysis, two Acetyl-CoA are made in the link reaction, and therefore two rounds of the Krebs Cycle occur (one for each molecule of acetyl-CoA).
79
Stages of Krebs Cycle
The acetyl group is released from CoA. CoA is used to transport acetyl from the link reaction to the Krebs cycle. As soon as the Krebs cycle begins, acetate is unloaded.
acetyl joins with oxaloacetate. acetyl (2C) combines with oxaloacetate (4C), forming a 6C molecule called citrate.
Citrate is decarboxylated and dehydrogenated. Citrate (6C) loses a carboxyl group and forms a 5C molecule, releasing CO2 in the process. It also loses two hydrogens, which are accepted by NAD to form reduced NAD.
The 5C molecule is decarboxylated and dehydrogenated forming a 4C molecule. Again, NAD accepts the lost hydrogen, forming another reduced NAD.
The first 4C molecule is converted to a second 4C molecule. In the process the original 4C molecule gives a phosphate group to ADP, leading to production of ATP. This is substrate-level phosphorylation, as the 4C compound (substrate) is phosphorylating ADP during the reaction.
The second 4C molecule is converted to a third 4C molecule. Two hydrogens are released, and accepted by FAD, making FADH2.
The third 4C is dehydrogenated. This re-forms the oxaloacetate, completing the cycle. Another pair of hydrogen atoms are released, making reduced NAD.
80
substrate-level phosphorylation
the 4C compound (substrate) is phosphorylating ADP during the reaction.
81
Products of Krebs Cycle
Per molecule of glucose (and hence per 2 molecules of acetyl-CoA) Kreb’s cycle produces:
2 ATP – some energy is produced in the form of ATP.
6 reduced NAD – just like the reduced NAD from the previous two steps, the reduced NAD from the Krebs cycle goes to oxidative phosphorylation.
2 reduced FAD – the reduced FAD joins reduced NAD in going to oxidative phosphorylation.
1 coenzyme A – this goes back to the link reaction where it can be used to transport another acetate to the Krebs cycle.
82
Oxidative Phosphorylation - 2
Electron transport chain (ETC) – this is a chain of electron carriers in the inner mitochondrial membrane. They use the electrons from reduced NAD and FAD, and move them along the ETC.
Chemiosmosis – electrons release energy as they pass through the ETC. This energy is used to actively pump H+ from the mitochondrial matrix into the intermembrane space. The H+ then diffuses back out via ATP synthase, which drives ATP synthesis. The flow of H+ ions is called chemiosmosis.
83
state Oxidative Phosphorylation steps
- electron transport chain
- chemiosmosis
84
Stages of Oxidative Phosphorylation
Reduced NAD and reduced FAD from the previous steps release hydrogen atoms in the mitochondrial matrix, and in the process they become NAD and FAD again
Hydrogen atoms break up into protons and electrons. The hydrogen atoms split up into both H+ ions and electrons. The H+ stay in the matrix.
The electrons are taken up by the electron carriers in the ETC. The electrons move along the ETC, from carrier to carrier, and at each carrier the electrons release energy.
The released energy at each carrier is used by the electron carriers to pump H+ from the mitochondrial matrix into the intermembrane space. This forms an electrochemical gradient – there is a higher H+ concentration in the inter-membrane space than in the matrix.
Protons diffuse down the gradient. Protons diffuse from the inter-membrane space to the matrix, down the electrochemical gradient. This movement of protons is chemiosmosis.
Protons are unable to diffuse through the phospholipid bilayer, so instead go through the enzyme ATP synthase. Proton movement provides potential energy, which rotates a section of ATP synthase, and causes phosphorylation of ADP (ADP + Pi → ATP).
Water is formed. The electrons leave the last electron carrier and pass into the matrix, where and are accepted by oxygen. H+ also joins, forming water – a product of respiration
85
Total products made from electron transport chain in oxidative phosphorylation:
6 molecules of H2O (water)
34 ATP molecules
86
Describe the production of ATP by substrate-level phosphorylation in different stages of respiration with
reference to the number of ATP molecules produced.
2 (ATP molecules per glucose) from,
glycolysis / (breakdown of) triose
(bis)phosphate ✓
(when) triose (bis)phosphate / TP,
converted / broken down, to pyruvate ✓
ref to net yield of 2 (ATP) / 4 (ATP) made
but 2 used up ( in glycolysis) ✓
1 ATP (produced) per, (turn of the) Krebs
cycle / acetyl (coA) ✓
when 5-carbon compound is converted to,
4-carbon compound / oxaloacetate ✓
87
What properties of the mitochondrial inner membrane allow chemiosmosis to occur
What properties of the mitochondrial inner membrane allow chemiosmosis to occurmostly) impermeable to H+
ions / protons
✓
large surface area ✓
presence of, ATP synthase / stalked
particles ✓
88
Describe two quantitative changes in region inter-membrane space which occur as a result of oxidative phosphorylation.
pH decreases
AND
becomes more positive(ly charged) ✓
89
) Why does aerobic respiration yield fewer molecules of ATP than the theoretical maximum?
1 some ATP used to (actively) transport
pyruvate (into the mitochondrion);
2 some ATP used to (actively) transport
H(+) from (reduced) NAD, formed in
glycolysis / into the mitochondrion;
3 some energy released in ETC, is not
used to transport H+(across inner membrane) / is released
as heat;
4 not all the H+ movement (back across
membrane), is used to generate ATP /
is through ATP synth(et)ase;
5 not all the, reduced NAD / red NAD /
NADH, is used to feed into the ETC;
90
State one advantage of using ATP to provide energy for biological processes.
idea that it is an immediate energy source;
small molecule;
soluble;
can be easily regenerated / can be rephosphorylated;
releases energy in, fixed / small, quantities;
91
Can eukaryotes Anaerobically respire
cells CAN respire anaerobically, but it is more of a “temporary”/ “emergency” measure if there is not enough oxygen around. They cannot survive long term without oxygen.
-> however Anaerobic produces 2 ATP molecule but aerobic produces 38
92
Obligate anaerobes
require anaerobic conditions i.e. cannot survive in the presence of oxygen. Almost all are prokaryotes but also some fungi
93
Facultative anaerobes
use aerobic respiration if oxygen is present, but can switch to anaerobic respiration in the absence of oxygen e.g. yeast
94
Obligate aerobes
can only synthesise ATP in the presence of oxygen – i.e. mammals
certain cells in mammals could be described as facultative anaerobes as they are able to employ anaerobic respiration in low oxygen concentrations, but this is only sustainable for a short time
95
In the absence of oxygen, what happens to the stages of aerobic respiration?
NO oxygen to accept e- at the end of the ETC
Flow of electrons along ETC backs up and eventually stops
Synthesis of ATP by chemiosmosis stops
Reduced NAD and reduced FAD accumulate as they can no longer supply electrons to the ETC
This means no NAD / FAD is recycled for the Krebs cycle, which stops as well.
Glycolysis would also stop due to the lack of NAD if fermentation did not provide a route for a small amount of NAD to be recycled...
96
So in the absence of oxygen plant and animal cells
Plant cells convert pyruvate to ethanol and carbon dioxide
Animal cells convert pyruvate to lactic acid
To regenerate NAD from NADH
97
FERMENTATION
- a form of aerobic respiration
the process by which complex organic compounds are broken down into simpler inorganic compounds, without the use of oxygen or the involvement of an ETC
BUT involves incomplete breakdown of glucose so a small quantity of ATP produced, substrate level phosphorylation only
98
fermentation in mammals
- lactate fermentation in mammals
- Producing lactic acid from pyruvate regenerates oxidised NAD and allows glycolysis to continue
- reaction from pyruvate to lactic acid is catalysed by lactate dehydrogenase
- a reversilble process
99
what happens to the products of fermentation in mammals
- Absorbed into blood stream and taken to the liver
-Converted back to glucose – but this requires oxygen.
Contributes to the “oxygen debt” after exercise – one reason we need to breathe more heavily after exercise
100
2 reasons anaerobic respiration in muscle cells cannot continue indefinitely?
Not enough ATP produced to maintain vital processes
Accumulation of lactic acid => fall in pH ==> denaturing of proteins (e.g. enzymes and muscle fibres)
101
fermentation in yeast and many plants
- Alcoholic fermentation
- Producing ethanol from pyruvate regenerates oxidised NAD and allows glycolysis to continue
- not reversible
- reaction from pyruvate to ethanal is catalysed by pyruvate decarboxylase (this reaction is losing CO2)
- reaction from ethanal to ethanol is catalysed by alcohol dehydrogenase
- ethanol is toxic and yeast are unable to survive if this accumulates
102
Relative amount of energy released per gram or respiratory substrate
lipids > carbohydrates > alcohol
proteins
103
What are respiratory substrates?
give all examples
any organic molecule that can be broken down to release energy for the synthesis of ATP
triglycerides, glycogen/glucose, amino acids, lactate and ketone bodies
104
triglycerides as a respiratory substrate
- hydrolysed to fatty acids and glycerol
- fatty acids entre the krebs cycle as acetyl Coa. they undergo beta oxidation
- glycerol is converted to pyruvate then undergoes oxidative carboxylation to form an acetyl group. Combines with CoA to form. acetyl CoA
- fatty acids can form 50 acetyl CoA, which can synthesis 500 ATP molecules
105
proteins as a respiratory substrate
- first hydrolysed into amino acids
- AA deaminated (remove amine group)
- entre respiratory pathway by pyruvate
- theses steps require ATP, reducing net production of ATP
106
RQ-respiratory qutient
the ratio of carbon dioxide produced to oxygen used in respiration
107
RQ for protein
0.9
108
RQ for lipids
0.7
109
RQ for glucose
1
-> ^O2 used 6CO2 produced
110
RQ formula
= CO2 produces/ O2 used
111
112
why does lipid produce more ATP than carbohydrates
- conatina a greater proportion of C-H bonds
- this requires more oxygen to break them down, and release less CO2
- so RQ is less than one for lipids
