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A level biology-CIE > Energy And Respiration > Flashcards

Energy And Respiration Flashcards

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1
Q

Why do living organisms need energy?

A

To Work!
Examples of work:
Anabolic Reactions for example protein synthesis, synthesis of glycogen (glycogenesis), DNA replication, polymerisation.
Active transport: for example Na+-K+ pump, movement of vesicles in exo/endocytosis.
Movement: For example muscle contraction, cilia/flagella, movement of chromosomes
Maintenance of a constant body temperature in warm blooded animals for example endotherms.
Bioluminescence/electrical discharge for example in jellyfish and electric eels.

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2
Q

What is the meaning of anabolic reactions?

A

Anabolic reactions is the building of large molecules from smaller molecules using energy.

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3
Q

What is the meaning of catabolic reactions?

A

Catabolic reaction is when a large molecule is broken down into smaller molecules and releases energy.

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4
Q

Describe the structure of ATP

A

Adenosine triphosaphate
It is a phosphorylated nucleotide.

Its structure has three components.
1) Adenine (organic, nitrogenous base)
2)Ribose sugar (Pentose sugar)
3)Three phosphate groups

1+2=adenosine (nucleoside)

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5
Q

What are the chemical properties/characteristics of ATP?

A
  • Small
  • Water-Soluble
    →Easily transported around the cell
  • Readily hydrolysed/lose phosphate to release energy
  • Small packets of energy released at one time.
  • ATP can be synthesised and broken down quickly
    →High turnover rate

This makes it ideal as an energy currency in all organisms.

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6
Q

What is the roles/functions of ATP as a universal link/intermediate energy molecule:

A

a)The universal link/Intermediate energy molecule
* Between energy-giving reactions and energy-requiring reactions.
*Examples of energy-giving reactions: aerobic respiration aka complete oxidation of glucose.
→Gives a very large quantity of energy 2870KJ per molecule.
C6H12O6+6O2→6CO2+6H2O+2870KJ
Hydrolysis of ATP→Energy
* But energy transfers are inefficient
→Excess energy is lost at different stages in the multi-step reaction.
→As thermal/heat energy

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7
Q

What is the roles/functions of ATP as the energy currency of the cell:

A

b)ATP is the energy currency of the cell
* Energy giving/yeilding-reactions are linked to the production of ATP first,then energy requiring reactions.

ATP is NOT an energy storage molecule

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8
Q

What is an energy storage molecule:

A

An energy storage molecule stores energy in the form of chemical potential energy. For example:
Short term-Glucose,Sucrose
Long term-Glycogen,starch,triglyceride

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9
Q

What is the role of ATP as an immediate donor of energy?

A

ATP is an immediate donor of energy to reactions requiring energy.
Chemical equation of ATP hydrolysis:
ATP⇌ADP+Pi+30.5KJ
Where Pi is inorganic phosphate or
ATP+H2O ⇌ ADP + H3PO4 + 30.5KJ
Reactions are reversible
ATP can be synthesized and broken down quickly
Rate of turnover/interconversion of ATP is high
For example at rest we use about 40kg of ATP in 24 hours
Removal of 1st phosphate group ATP→ADP
→30.5KJmol-1 energy released
Removal of 2nd phosphate group from ADP→AMP
→30.5KJmol-1 energy released
Removal of the last phosphate group from AMP→Adenosine
14.2 KJmol-1 energy released

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10
Q

Where is ATP synthesised from?

A

ATP is synthesized from energy yielding reactions.
For example the oxidation of glucose and cellular respiration or light dependent stage in photosynthesis.
In a series of reactions.

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11
Q

What is respiration?

A

Respiration is a process where organic molecules such as glucose amino acid glycerol or fatty acids are broken down in a series of stages.
To release energy.
Which is used to synthesize ATP.
The two types are
1) aerobic respiration
2) anaerobic respiration

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12
Q

What is aerobic respiration and what are the four stages and their location?

A

Aerobic respiration is the breakdown of organic molecules for example glucose, fatty acids, glycerol and amino acids
to release energy
which is used to synthesize ATP
in the presence of oxygen.
There are four stages in aerobic respiration of glucose:
1) Glycolysis-Cytoplasm
2)Link Reaction-Mitochondrial matrix
3)Krebs Cycle-Mitochondrial matrix
4) Oxidative Phosphorylation-Inner mitochondrial membrane/cristae

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13
Q

Why is the oxidation of glucose in cellular respiration a multi-step reaction?

A

Each step releases a small quantity of energy(ATP) to:
1) Allow precise control
2)Cells could not fully harness total energy released if all were made available in one instant.
Also, reactions do not happen easily:
because glucose is a stable substance
It requires a high activation energy for the reaction to take place.
To overcome this:
1) Usage of enzymes to lower activation energy
2)Raising energy level of glucose by phosphorylation
➝more reactive

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14
Q

What are the steps in glycolysis or the glycolytic pathway?

A

1)Glucose (6C) is phosphorylated (phosphorylation)
*By 2 ATP
*Form hexose/fructose disphosphate (6C)
*This raises chemical potential energy of glucose
*Provide activation energy for split
2)Fructose diphosphate breaks down to 2 triose phosphate (3C) (lysis)
*6C➝2x3C
3) 2 hydrogen atoms are removed
*2 reduced NAD formed
*This is a dehydrogenation/oxidation reaction
4) 4 ATP produced (ATP is synthesized through substrate-level phosphorylation)
*4 ATP-2 ATP=net gain of 2 ATP
*Chemical potential energy is released from intermediate steps.
5) 2 pyruvate (3C) produced
Initial reactants:
1 Glucose (6C)
2 ATP
4 ADP, 2 NAD
Final products per molecule of glucose:
*2 pyruvate (3C)
*2 NADH
*4 ATP➝But 4-2=net gain of 2 ATP only!
The whole process involves many enzymes at each step

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15
Q

What are the different types of hydrogen acceptor molecules?

A

They are also called hydrogen carrier molecules:
You will learn 3 types:
1. NAD-nicotinamide adenine dinucleotide (used in respiration)
2. NADP-nicotinamide adenine dinucleotide phosphate) used in photosynthesis)
3. FAD-Flavin adenine dinucleotide (used in respiration)

They are all coenzymes= a non protein complex organic substance that is required for an enzyme’s activity.

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16
Q

Describe the structure of NAD:

A

*Nictonimide Adenine Dinucleotide
*Coenzyme
*H carrier molecule in respiration
Structure:
*Two linked nucleotides
*Both have ribose sugar and a phosphate group each
* 1 has an adenine base, the other nicotinamide ring
*Nictonimade ring-Accepts H
NAD+H⇋Reduced NAD
NAD+ + H+ +2e- ⇋ NADH

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17
Q

What is the function of NAD?

A

The function of NAD is:
H Carrier molecule in respiration
Carry hydrogens from all stages of respiration (stage 1 2 3)
To take part in oxidative phosphorylation (stage 4) where most ATP is synthesized.

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18
Q

Describe the structure of NADP

A

Nicotinamide Adenine dinucleotide phosphate
Coenzyme
Hydrogen carrier molecule used in photosynthesis
Different from of NAD
Structure:
Similar to NAD
But has a phosphate group instead of H on carbon 2 on ribose ring with adenine

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19
Q

Describe the structure of hydrogen carrier molecule FAD:

A

Flavin Adenine Dinucleotide
Coenzyme
H carrier molecule in respiration
Used to carry H produced in Krebs cycle (stage 3 only)
→Then used in oxidative phosphorylation (stage 4)
Structure:
Two linked nucleotides
One nucleotide with phosphate, ribose and adenine
Another nucleotide with phosphate, ribitol and flavin.

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20
Q

What are the steps in the link reaction?

A

Occurs in the mitochondrial matrix
*Pyruvate (3C) is transported from the cytoplasm
*Into the mitochondria matrix
*When oxygen is available
*By active transport
When oxygen is available, pyruvate (3C) is
1) Decarboxylated
→To form carbon dioxide
2) Dehydrogenated
→NADH produced
3)Combined with coenzyme A (CoA)
→ To form acetyl coenzyme A (2C)

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21
Q

What is coenzyme A?

A

*Complex molecule
*Made of nucleoside (adenine+ribose) and a vitamin B5 (pantothenic acid)
Function
*Carry acetyl groups (2C) to Krebs cycle (stage 3)

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22
Q

What are the steps in the Krebs cycle?

A

The Krebs cycle aka citric acid cycle/tricarboxylic acid cycle
Occurs in the mitochondrial matrix
* Enzyme-controlled pathway
1) Acetyle coenzyme A (2C)
→Combines with oxaloacetate (4C)
→To form citrate (6C)
→CoA removed and can be used again in link reaction (stage 2)
2) Citrate goes through a series of dehydrogenation and decarboxylation
→ 7 steps, by products of each step are
1. Nothing
2. Reduced NAD and CO2
3. Reduced NAD and CO2
4. ATP (substrate-level phosphorylation)
5. Reduced FAD
6. Nothing
7. Reduced NAD
3) Oxaloacetate (4C) regenerated
→ Can combine with another acetyl CoA
→Kreb cycle continues

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23
Q

What are the final products per molecule of acetate CoA and per molecule of glucose.

A

The initial reactants are:
*1 Acetyle CoA (2C)
*1 Oxaloacetate (4C)
*1 ADP, 3 NAD and 1 FAD
Final products per molecule of acetyl CoA:
(this is 1 turn of the Krebs cycle)
* 3 NADH
* 1 FADH2
* 2 CO2 →waste gas, released
* 1 ATP
* Oxaloacetate (4C) → regenerated
But since 1 molecule of glucose (6C) oxidised into 2 pyruvate, which is converted to 2 acetyl CoA in the link reaction.
So everything is double in quantity with oxaloacetate (4C) being regenerated twice.

24
Q

Where does oxidative phosphorylation occur?

A

Occurs in the inner membranes/cristae of mitochondria
* High release of electrical potential energy here
→For the production of ATP (ADP+Pi→ATP)
*Involves a chain of electron carrier molecules in the inner membrane
→Electron transport chain (ETC)
*ATP synthesis is catalyzed by ATP synthase

25
Q

What is the first step in oxidative phosphorylation?

A

1) Hydrogen atoms removed from reduced NAD and FAD
* NADH and FADH2 are from glycolysis, link reaction, krebs cycle
* At the inner mitochondrial membrane
*Through dehydrogenation/oxidation reaction
*Catalysed by dehydrogenase enzymes
*NAD and FAD regenerated
→Can be reduced again in glycolysis, link reaction, Krebs cycle
Reduced NAD→NAD+H
Reduced FAD→FAD+2H
*Hydrogen atoms split into electrons and protons (H+ ions)
H→H+ + e-

26
Q

What is the second stage of oxidative phosphorylation?

A

2)Electrons are passed along Electron transport chain
*Passed along a series of electron carriers in inner membranes
*Electron carriers are associated with 4 types of membrane proteins
→Forms a functional unit called a respiratory complex
* Energetic electrons release energy as they pass through the ETC

27
Q

What is the third stage in oxidative phosphorylation?

A

3) Energy released is used to pump protons
*Across inner mitochondrial membrane
*From mitochondrial matrix to intermembrane space
* Since inner membrane is impermeable to protons
* And there is high [H+] in intermembrane space
→Proton gradient formed/electrochemical gradient formed

28
Q

What is the fourth stage of oxidative phosphorylation?

A

4) Protons move down electrochemical gradient
*By facilitated diffusion through ATP synthase
*Back into the mitochondrial matrix
*This provides energy for ATP synthesis
*This process is called chemiosomosis
*ATP synthase enzyme rotates
ADP+Pi→ATP
*ATP is synthesised
*Movement of 3 H+ ions back into matrix = 1 ATP molecule

29
Q

Describe ATP synthase

A

*AKA ATP synthesise/stalked particles
*Transmembrane channel protein + enzyme

Found in:
*inner membrane of mitochondria
*Thylakoid membranes of chloroplasts

Structure:
*Enzyme is connected to a part of the channel protein-able to rotate as H+ ions pass through
*3 binding sites for ADP+Pi
*As it rotates, enzymes binding sit changes structurally to allow 3 different processes to occur:
a) binding of ADP and Pi
b) Forming tightly bound ATP
c) Releasing ATP

30
Q

What are the two ways ATP can be synthesized in respiration?

A

1) substrate level phosphorylation
*During glycolysis @ cytoplasm → 2 ATP
* During Krebs cycle @ matrix →2 ATP
* 4 ATP produced by substrate-level phosphorylation in total
* Transfer of phosphate group from one molecule to another
* Chemical potential energy released
2) Oxidative phosphorylation
@ inner mitochondrial membrane/ cristae
* Requires proton/ electrochemical gradient, ATP synthase, ETC
* Electric potential energy released by chemiosmosis is used by ATP synthase to catalyse formation of ATP
* 28 ATP produced by Oxidative phosphorylation in total
Also happens in the chloroplast during photosynthesis!

31
Q

Describe the structure and function of mitochondria

A

The mitochondria is the site for
Link reaction (matrix)
Krebs cycle (matrix
-Oxidative phosphorylation (inner membrane)

*Typical rod-shaped
*Able to change shape and move in the cell
* 0.5-1.0 μm in diameter
*Double membrane
* No. Of mitochondria in a cell, no. of cristae and length of Crista in mitochondria- depends on cell

32
Q

Describe the structure and function of the mitochondrial matrix.

A

*has small, circular mitochondrial DNA
*Has 70S ribosomes
→synthesise mitochondrial proteins
* Have many enzymes in matrix for link reaction and Krebs cycle.

33
Q

Describe the structure and function of the outer membrane of mitochondria.

A

*different in composition from inner membrane
*Smooth, not folded
*More permeable to small molecules than inner membrane
*Contains transport proteins to transport pyruvate into the mitochondria for link reaction and Krebs cycle.

34
Q

Describe the structure and function of the intermembrane space of mitochondria.

A

*space between two membranes
*Allows accumulation of H+
*Lower pH than mitochondria matrix
*More acidic
→due to pumping of H+ ions from matrix by the activity of ETC

35
Q

Describe the structure and function of inner membrane/cristae.

A

*inner membranes is the site of ETC and oxidative phosphorylation
*Inner membrane holds many special proteins and electron carriers
→i.e. enzyme ATP synthase, channel for H+ ions
Linear arrangement of ETC on inner membrane
→greater efficiency
*Inner membrane/cristate is folded
→increase total surface area for ATP synthase and membrane proteins
→active cells have more folding/dense cristae
*Inner membrane impermeable to H+ ions

→maintains proton gradient
→H+ only go through channels i.e. ATP synthase
→energy released by chemosmosis used to synthesize ATP.

36
Q

Define anaerobic respiration

A

*synthesis of ATP in the absence of oxygen.
When free oxygen is not available:
*No final electron and H acceptor
*H from reduced NAD and FAD cannot be removed
→ETC stops working
→ No ATP from oxidative phosphorylation
*NAD and FAD not regenerated
→ No Krebs cycle and link reaction
→ No ATP from Krebs cycle
However,
* Glycolysis still occurs @ cytoplasm
* Only net 2 ATP made per glucose molecule by substrate-level phosphorylation
* So glucose not completely broken down without oxygen
* Pyruvate still contains energy
* 2 NADH are formed too!
But special pathways are used to regenerate NAD
* But this is not sustainable/cannot go on indefinitely
* Due to toxic byproducts

37
Q

Where does anaerobic respiration occur?

A

Anaerobic respiration occurs in:
* Yeast Cells/Plant tissues
→ethanol pathway/alcoholic fermentation
*In animals/mammalian muscles/some bacteria
→ especially when muscle activity is high and cells do not have enough oxygen to perform aerobic respiration
→lactate pathway/lactic fermentation
*These pathways are used to regenerate NAD
* But this is not sustainable/cannot go on indefinitely
*Due to toxic byproducts

38
Q

Describe the anaerobic respiration in yeast. (Ethanol pathway/alcoholic fermentation)

A
  • 2 step reaction: Pyruvate→Ethanal→Ethanol
    *Irreversible
    1) Glycolysis: Glcose→Pyruvate (3C)
    *Net gain of 2 ATP
    *2 NADH produced
    2) Pyruvate (3C) undergoes decarboxylation → Ethanal (2C)
    *CO2 produced
    3) Ethanal (2C)/acetaldehyde acts as a H acceptor
    *Reduced by receiving hydrogen from reduced NAD
    **Ethanal → Ethanol (2C)
    *Catalysed by alcohol dehydrogenase
    →This prevents H+ from lowering pH in yeast cell
    4) NAD is regenerated
    →Allows glycolysis to continue
    →To produce ATP

Ethanol is toxic
Remaining chemical potential energy in ethanol is wasted

39
Q

Describe anaerobic respiration in mammals (lactate pathway/lactic fermentation)

A

1 step reaction: pyruvate→lactate
Reversible reaction
1) Glycolysis: Glucose→Pyruvate (3C)
*Net gain of 2 ATP
* 2 NADH produced
2) Pyruvate acts as the H acceptor
*Receive H from NADH
*Pyruvate reduced to lactate/lactic acid
*Catalysed by lactate dehydrogenase
3) NAD is regenerated
→ Allows glycolysis to continue
→ To produce ATP

Lactate is toxic
Causes drop in pH/ acidic
But the reaction is reversible!

Lactate is transported by blood plasma
From muscles to be broken down in liver

40
Q

Describe what happens to lactate in the liver

A

In liver:
Lactate is converted back to pyruvate
By lactate dehydrogenase
When oxygen is present again:
Pyruvate is further broken down/oxidized in aerobic respiration
i.e. link reaction→Krebs cycle → oxidative phosphorylation
*Produce carbon dioxide + water
*Excess lactate converted to glycogen

41
Q

Describe oxygen uptake during exercise

A

During exercise:
*Oxygen demand and uptake by cells increase
*But the heart and lungs are unable to meet demand immediately
*Oxygen deficit=the volume difference between ideal and real O2 uptake
*So anaerobic respiration occurs
*Heart rate and breathing rate takes time to increase to meet O2 demand

42
Q

Describe oxygen uptake at rest

A

At rest rate of oxygen uptake is low.

43
Q

Describe oxygen uptake during recovery

A

*Breathing rate/oxygen uptake is still higher than resting levels
*To ‘pay back’ the oxygen debt
*Oxygen debt=volume of oxygen required to metabolise lactate accumulated during anaerobic respiration to CO2 and water after exercise.
Extra oxygen is also needed for:
1. For the conversion of lactate → Glycogen
2. For the reoxygenation of haemoglobin in the blood
3. To meet the high metabolic rate in organs

44
Q

What are the similarities between ethanol and lactate pathway

A
  1. Both occur when oxygen is absent/low concentration
  2. Both occur in the cytoplasm
    3.Both involve glycolysis
  3. Both produce only 2 ATP net per glucose molecule
  4. Both involve usage and regeneration of NAD
45
Q

Describe the three respiratory substrates

A

1)Glucose
*Essential respiratory substrate for neurons in the brain, RBC, lymphocytes
*Oxidized in glycolysis, link reaction, Krebs cycle
2)Lipids
*Converted to acetyl coA (2C)
*Oxidised in Krebs cycle
3)Protein
*Amino acid converted to pyruvate (3C) or acetyl coA (2C)
*Oxidised in link reaction or/and Krebs cycle

In all:
NADH and FADH2 are produced
Passed to the ETC in oxidative phosphorylation
To produce ATP

46
Q

How do we know which molecule contains the most energy?

A

Most ATP comes from oxidative phosphorylation
H needed for ATP production/chemiosmosis
Hence,
*The higher the number of C-H bonds/ H atoms in a respiratory substance
→ The more hydrogens can be carried by hydrogen carriers (NAD,FAD)
→More reduced NAD produced
→More oxidative phosphorylation/ETC
→More hydrogen ions pumped across inner mitochondrial membrane/steeper proton gradient gradient
→The more ATP made per gram of respiratory substrate
→ The greater the energy value

47
Q

Describe the energy values of lipids

A

*Most C-H bonds/no. Of H atoms per unit mass
*Compared to carbs and protein
*So releases most energy per unit mass
*High energy density
*Many more H available to reduce oxygen to water
*More water produced from metabolism of lipid
*Oxidation of lipids can only happen in the presence of oxygen.

48
Q

Describe the energy value of proteins

A

*Slightly more C-H bonds per unit mass
*Than carbohydrates
*Used during starvation/lack of fat or carbs
*Oxidation of amino acids can only happen in the presence of oxygen

49
Q

What are the energy values for carbohydrates, lipids and proteins?

A

Carbohydate-15.8
Lipid-39.4
Protein-17.0

KJ g-1

50
Q

How can we determine energy values for respiratory substrates?

A

Using calorimeter
Burning a known mass of substance
With oxygen
Measure rise in temperature
Of a known mass of water

51
Q

How do we calculate RQ?

A

RQ=Ratio of the volume of carbon dioxide produced to oxygen used per unit time

RQ=volume of carbon dioxide given out in unit time divided by volume of oxygen taken in unit time

Or from an equation; moles or molecules of carbon dioxide given out divided by moles or molecules of oxygen taken in

Different respiratory substrate, diff rat in of the volumes of oxygen used and carbon dioxide produced.

52
Q

What is the function of RQ

A

1) Shows the type of substrate being used in respiration
2)Shows if anaerobic respiration is occurring

Notes; in anaerobic respiration of glucose in yeast; ethanol pathway0
C6H12O6 → 2C2H5OH +2CO2 + energy
RQ 2/0 = infinity
In reality some respiration in yeast cells be aerobic as well so won’t reach infinity
But in anaerobic respiration of glucose in muscle cells; (lactate pathway)
No carbon dioxide produced so no RQ be calculated

53
Q

How can we determine in Anaerobic respiration is occurring by the RQ values

A

High values of RQ=Anaerobic respiration is occurring

54
Q

What is the RQ value of the respiratory substrates

A

Carbohydrates 1.0
Lipid 0.7
Protein 0.9
Anaerobic in yeast x/0=infinity
Greater than 1.0

55
Q

Describe oryza sativa

A

Oryza sativa is rice.
205 of human population’s energy source
Paddy fields- intentionally flooded
Tolerate growing in water but competitor weeds cannot

56
Q

Describe the challenges of adaptation of rice with submerged roots in water

A

Low oxygen in water, roots do not get enough oxygen
Gas diffuse much slowly through water than in air
Anaerobic respiration occurs
Toxic alcohol produced

57
Q

What are the adaptations of rice with submerged roots in water

A

1) rice tolerant to higher levels of alcohol
* rice produces high levels of alcohol dehydrogenase to break down alcohol
*can respire anaerobically for longer periods
2) Presense of aerenchyma
*Air spaces between cells in mesophyll/cortex of stem
*oxygen able to diffuse through aerenchyma from aerial tissues to roots
*this provides oxygen for aerobic respiration occurs
8Also allows for;
Escape of ethane
*buoyancy
*enables active transport in roots bus aerobic respiration produces energy
3) Grow taller in response to flooding
8So leaves, flower and spikes are above water
*O2 and CO2 can diffuse in/out through stomata on leaves
4) Leaves underwater have hydrophobic, corrugated surface
8Air trapped in between ridges
*holds thin layer of air in contact with leaf surface

A level biology-CIE (14 decks)

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