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topic 5 Flashcards

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Biology 101 flashcards
1
Q

5.1
What’s cellular respiration?

A
  • Where food’s broken down and energy from food molecules is transferred to ATP
  • Cellular respiration yields ATP
  • To be used as a source of energy for metabolic reactions
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2
Q

Equation?
balanced?

A

Glucose + oxygen –> carbon dioxide + water (+ATP)
C6H12O6 + 6O2 –> 6CO2 + 6H2O (+ATP)

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3
Q

Is respiration exothermic / endothermic ?
why?

A
  • Exothermic
  • It releases energy + generates heat
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4
Q

Uses of the ATP produced from cellular respiration?

A
  • chemical reaction
  • Metabolic reactions
  • Movement
  • Anabolism
  • Cell division
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5
Q

Where does respiration occur?

A
  • In mitochondria + sometimes cytoplasm of each cell of the body
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6
Q

When doing bond energy calculations how to calculate
1. energy required to break bonds in reactants?
2. energy released when bonds in products are made?
3. energy change?

A
  1. sum of energy in reactants
  2. sum of energy in products
  3. Energy change = Reactants - Products energy
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7
Q

Hydrolysis + synthesis of ATP + ADP ?

A
  • ATP hydrolysed to ADP + Pi
  • Using water
  • Energy made available for cellular reactions.
  • ATP synthesised from ADP + Pi
  • Releases water
  • Energy is obtained from respiration
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8
Q

Catabolism reactions

A
  • Breaking down complex molecules to simpler ones
  • Exergonic ( releases energy )
  • Hydrolysis reactions
  • Oxidation reactions
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9
Q

Anabolism reactions

A
  • Building up ( synthesizing complex molecules from simpler ones )
  • Endergonic ( takes in energy )
  • Condensation
  • Reduction reactions
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10
Q

What are the different stages involved in aerobic respiration?

A

● glycolysis (in the cytoplasm)
● link reaction (in mitochondrial matrix)
● Krebs cycle (in mitochondrial matrix)
● oxidative phosphorylation (in mitochondrial inner membrane)

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11
Q

5.2
Glycolysis:

A
  • first stage of both aerobic + anaerobic
  • occurs in cytoplasm
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12
Q

Stages of glycolysis:

A
  1. Glucose (6C)
    (phosphorylated to glucose phosphate,
    2ATP –> 2ADP = energy transferred to new molecule = making it highly reactive)
  2. Glucose phosphate (6C)
    (highly reactive = splits into 2 triose phosphate)
  3. 2x Triose phosphate (3C)
    (molecules oxidised to produce 2x pyruvate.
    on EACH molecule: NAD–>NADH [reduced] + 2ADP –> 2ATP
  4. 2x pyruvate (3C)
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13
Q

Products of glycolysis:

A

2x Pyruvate

Net gain of 2 ATP

2x NADH

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14
Q

5.3
Link reaction:

A

Occurs in mitochondrial matrix

Reaction that moves products of glycolysis (Pyruvate + NADH) into krebs cycle.

Pyruvate + NADH actively transported from cytoplasm into mitochondrial matrix - for krebs cycle

link reaction occurs 2x as there are 2 pyruvate

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15
Q

Stages of the Link reaction:

A
  1. Pyruvate (3C) x2
    (-is oxidised to form acetate (2C) -loses H
    -the NAD picks up lost H+ and becomes reduced =
    NAD –> NADH + releases Co2)
  2. Acetate (2C)
    (Acetate combines with coenzyme A to form Acetyl Coenzyme A = Acetyl CoA)
  3. Acetyl CoA (2C)
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16
Q

Products of the link reaction:

A

2 pyruvate + 2 NAD + 2 CoA –>

2x CO2

2x NADH

2x Acetyl CoA

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17
Q

Krebs cycle:

A

Occurs in mitochondrial matrix

In a series of Redox reactions , Krebs cycle generates reduced coenzymes (NADH + FADH) + ATP by substrate level phosphorylation + CO2 is lost.

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18
Q

Stages of the Krebs cycle:

A
  1. Acetyl CoA (2C) combines with a 4C compound to form 6C acid (citrate).
    [the CoA is recycled back into the link reaction to bind to another acetate]
  2. 6C citrate is broken down into a 5C acid
    - NAD –> NADH (reduced)
    - CO2 released
  3. 5C acid is broken down into original 4C compound acid
    - NAD –> NADH x2
    - FAD–> FADH
    - ATP released
    - CO2 released
  4. The 4C acid combines with another acetyl CoA + cycle repeats
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19
Q

Products of the krebs cycle:

A

pr cycle:

3x NADH (reduced NAD)
1x FADH (reduced FAD)
1x ATP
2x CO2

pr glucose molecule (as 2x pyruvate pr glucose):

6x NADH (reduced NAD)
2x FADH (reduced FAD)
2x ATP
4x CO2

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20
Q

5.4
Oxidative phosphorylation:

A
  • occurs in inner mitochondrial membrane (cristae)
  • involves electron transport chain
  • movement of protons across inner mitochondrial membranes
  • catalysed by ATP synthase
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21
Q

Stages of oxidative phosphorylation:

A
  • The NADH + FADH from krebs cycle are oxidised + H+ atoms split into protons + electrons.
  • The electrons are passed along the electron transport chain (proteins embedded in inner mitochondrial membrane)
  • Each time an electron moves to next protein in the ETC, it releases enough energy to transfer a proton (hydrogen) to intermembrane space.
  • Results in an electrochemical gradient due to build up of the protons in intermembrane space.
  • Protons move down this electrochemical gradient (through facilitated diffusion) through the ATP synthase = allows for chemiosmosis
  • This catalyses phosphorylation of ADP to form ATP
  • Oxygen is a terminal electron acceptor = pick up the electrons at end of ETC + binds with H+ to form water H2O
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22
Q

Why is Oxygen important in respiration?

A
  • Oxygen is a terminal electron acceptor = pick up the electrons at end of ETC + binds with H+ to form water H2O
  • if O2 didn’t pick up those E- = no more E- would be able to move across ETC = no energy released = protons wouldn’t transfer across to intermembrane space = no gradient build up = ATP wouldn’t be synthesised
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23
Q

5.5
Anaerobic respiration?

A
  • occurs in absence of O2 to produce limited yield of ATP
  • occurs in cytoplasm only
  • different products in mammals vs plants + microbes
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24
Q

Anaerobic respiration in mammals:

A
  • Pyruvate produced in glycolysis is reduced to form Lactate ( by getting H+ from NADH which is oxidised into NAD)
  • The oxidised NAD is reused in glycolysis = to ensure more ATP is continued to be produced for anaerobic respiration.

Pyruvate (3C) —> Lactate (reduced = +H)
[ NADH –> NAD ] (oxidised = - H)

25
Q

Anaerobic respiration in plant (+ microbes)

A
  • Pyruvate produced in glycolysis is reduced to form Ethanol + Carbon dioxide
    (By getting H+ from NADH which is oxidised into NAD)
  • The oxidised NAD is reused in glycolysis = to ensure more ATP is continued to be produced for anaerobic respiration.

Pyruvate (3C) —> Ethanol + CO2 (reduced = +H)
[ NADH –> NAD ] (oxidised = - H)

26
Q

Why does lactate (by-product of anaerobic respiration) affect mammalian muscle contraction?

A

Lactate = acidic = results in muscle fatigue.

can’t respire anaerobically forever as acidic pH will denature enzymes etc

27
Q

What is the disadvantage of producing ethanol during anaerobic respiration?

A

Dissolves cell membranes so cells die when concentration is above 12%

28
Q

Compare the ATP yields per molecule of hexose glucose sugar from aerobic + anaerobic respiration:

A

Aerobic ≈ 38 molecules of ATP in ideal conditions

Anaerobic = 2 molecules from glycolysis

29
Q

Core practical 9: investigating aerobic or anaerobic respiration using a respirometer

A
  • Pressure changes in the boiling tube due to CO2 production (anaerobic experiments) or O2 consumption (aerobic experiments) cause a drop of coloured liquid to move.
  • Sodium hydroxide =Absorbs CO2 so that there is a net decrease in pressure as O2 is consumed
30
Q

5.6 [photosynthetic pigments]
Photosynthesis?

A
  • Reaction in which light energy is used to split apart the strong bonds in water molecules in a process of photolysis in order to combine hydrogen with carbon dioxide to produce fuel in the form of glucose
  • Autotrophic organisms make energy-containing compound out of CO2 + water by photosynthesis
31
Q

Equation?

A

Carbon dioxide + Water –> Glucose + Oxygen

     6Co2             +   6H20   -->  C6H12O6  +    6O2
32
Q

Absorption spectrum ?

Action spectrum ?

A

Absorption Spectrum:
- The range of different wavelengths of light that a photosynthetic pigment absorbs

Action Spectrum:
- The rate of photosynthesis at different wavelength of light absorbed
- How much photosynthesis occurs at different wavelight of light

33
Q

Why do Chloroplasts contain different photosynthetic pigments ?

A

Chloroplasts contain different photosynthetic pigments (eg chlorophyll a + chlorophyll b) which absorb different wavelengths of light

  • This means that more light can be absorbed in total = increases rate of photosynthesis
34
Q

Examples of different photosynthetic pigments:

A
  • Chlorophyll a [alpha] = (blue-green)
  • Chlorophyll b [beta] = (yellow-green)
  • Carotenoids:
  • Carotene (orange)
  • Xanthophyll (yellow)
  • Phaeophytin (grey) = breakdown product of the other photosynthetic pigments
35
Q

CORE PRACTICAL 10: Investigate the effects of different wavelengths of light on the rate of photosynthesis

METHOD ?

A
  1. Place a piece of pondweed in a beaker of water
  2. Cover 1 side of the beaker with the aluminium foil to block out the light
  3. Cover the other side of the beaker with one of the light filters
  4. Add half a spatula of sodium hydrogencarbonate to the water to provide CO2
  5. Leave for 5 minutes
  6. Place the bench lamp a set distance from the beaker
  7. Set up the photosynthometer + Leave for 5 minutes
  8. Record the volume of gas produced during this time
  9. Replace the filter with another colour of filter + repeat experiment
36
Q

Findings ?

A

● Volume of gas produced (assumed to be oxygen) is proportional to rate of photosynthesis

● The greatest volume of gas will be produced when there is no filter used = as all wavelengths of light can be absorbed

● All filters will decrease volume of gas, but a green filter will decrease it the most because chloroplasts don’t absorb much green light - it is mostly reflected, which is why chloroplasts appear to be green

37
Q

CORE PRACTICAL 11: Investigate the presence of different chloroplast pigments using chromatography

METHOD?

A
  1. Draw line in pencil around 1cm above the bottom of the filter paper used. Do not use a pen as the ink will obscure the results.
  2. Cut a section of leaf + place in a mortar. Add 20 drops of propanone + use the pestle to grind up the leaf sample + release the pigments
  3. Use a capillary tube to extract some of the pigment + blot it onto the centre of the pencil line drawn. Allow to dry + then blot again
  4. Suspend the paper in the solvent so that the level of the liquid does not lie above the pencil line + leave the paper for approximately 10 minutes/until the solvent has run up the paper to near the top
  5. Remove the paper from the solvent + draw a pencil line marking where the solvent moved up to.
    =The pigment should have separated out + there should
    be different spots on the paper at different heights above the pencil line
  6. Calculate the Rf value for each spot
    =distance travelled by solute / distance travelled by solvent
38
Q

Findings ?

A

● Pigments that travel further up the paper will have a higher Rf value

-Rf values should be compared to the Rf known values in database to identify pigment. (make sure they use the same solvent + are for paper chromatography =these variables will make results differ)

  • Factors that affect the rate of mobility:
  1. Affinity- pigments have different affinities to the chromatography paper
    =those with lower affinities will travel further up the paper
  2. Solubility- pigments that are more soluble travel faster up the paper + will end up closer to the top at the solvent front
39
Q

5.7 [ photosynthesis]
Chloroplast are sight of photosynthesis.

Describe the structure of chloroplasts

A

● Chloroplasts contain stacks of thylakoid , stacked up to form structures = grana
-which contain the photosynthetic pigments like chlorophyll
-These are arranged as photosystems ( l + ll )

● Chloroplasts contain stroma = the fluid surrounding the grana
-Stroma contains all of the enzymes required for the light-independent stage of photosynthesis

● Each granum is connected together by pieces of thylakoid membrane called lamella

● Double membrane = chloroplast envelope
(+ 3rd internal membrane system = thylakoid membrane)

40
Q

Photosynthesis got 2 stages:

  1. Light dependent stage
A
  • Occurs on the thylakoid membranes of the chloroplasts
    -split water molecules (photolysis)
  • Photon of light hits chlorophyll molecule in thylakoid membranes = energy transferred to electrons = excited + move to higher energy level in thylakoid membranes + leaves chlorophyll molecule
  • Picked up by an electron carrier to take part in cyclical or non-cyclical phosphorylation
41
Q

cyclic photophosphorylation ?

A
  1. A photon of light hits a chlorophyll molecule in photosystem 1
  2. Electrons are excited + leave chlorophyll molecule
  3. Electrons taken up by an electron acceptor
  4. Electrons passed along an electron transport chain (ETC) from 1 electron carrier to the next = produces ATP from ADP + Pi
  5. Electron return to Photosystem I in chlorophyll + can be excited again in same way
42
Q

Non-Cyclic Phosphorylation ?

A
  1. Photon of light hits chlorophyll in Photosystem II
  2. Electrons are excited + leave chlorophyll molecule
  3. Electrons taken up by electron acceptor + passed along an ETC chain to Photosystem I chlorophyll = ATP produced from ADP + Pi (Energy is released)
  4. Photolysis occurs: Splitting of water (using light energy) into hydrogen + hydroxide ions (to reduce NADP) + electrons to replace lost electrons in Photosystem II chlorophyll = restored to original state + ready to be excited again
  5. Electrons in PSI are also being excited by light + lost to an electron acceptor
  6. Electrons are carried down ETC + taken up by the electron acceptor NADP
    - The NADP also takes up H+ ion from dissociated water to form reduced NADP
    - Hydroxide ions react together to form water + oxygen
43
Q

What are the NADPH + ATP produced during non-cyclic photophosphorylation used for ?

A
  • NADPH + ATP produced during non-cyclic photophosphorylation used in the light-independent reactions (calvin cycle) to make glucose
44
Q

How does chemiosmosis produce ATP in the Light dependent stage ?

A

-⬆conc of H+ inside thylakoid
- energy generated as e- travel down ETC
- moves the H+ ions down electrochemical gradient
- from thylakoid space –> stroma (+ binds to NADP –> NADPH)
- through ATP synthase
= ATP synthase catalyses ADP + Pi –> ATP

45
Q

Photolysis of water :

A
  • Splitting of water (H2O) using light energy absorbed by chlorophyll into hydrogen + electrons
  • H20 –> 1/2O2 + 2e- + 2H+
46
Q

How + where is reduced NADP produced in Light dependent stage ?

+ what does NADP act as ?

A

NADP + 2H+ + 2e- –> NADPH

  • in stroma of chloroplast
  • NADP acts as the final electron acceptor of the electron transfer chain
47
Q

Where does light-dependent reaction take place?

Where does the light-independent reaction take place ?

A
  1. Light-dependent reaction:
    - On the thylakoids of chloroplast
  2. Light-independent reaction:
    - In the stroma of chloroplast
48
Q

The light-independent stage :

A
  • Final stage of photosynthesis (in stroma)
  • which uses ATP (source of energy) + reduced NADP (reducing power) to produce glucose
  • consists of series of reactions known as the Calvin cycle
49
Q

Calvin cycle
3 main stages:

A
  1. Carbon fixation
  2. Reduction
  3. Regeneration
50
Q

Calvin cycle :

A
  1. Carbon fixation: [as CO2 is said to be fixed]
  • CO2 (from air) combines with 5C Ribulose bisphosphate (RuBP) in chloroplast to produce an unstable 6C compound
  • Catalysed by RUBISCO enzyme
  1. Reduction:
  • 6C very unstable = immediately splits into two molecules of glycerate 3-phosphate (GP), a 3-carbon compound
  • GP is then reduced (Hydrogen added) into glyceraldehyde 3-phosphate (GALP), a 3-carbon sugar
  • using hydrogen comes from 2x NADPH + energy from 2x ATP [both from the light-dependent reaction]
  1. Regeneration:
  • Most of the GALP passes through series of steps to replace the RuBP needed in 1st step with ATP
  • Some GALP molecules used to make glucose, which is then converted to essential organic compounds such as polysaccharides, lipids, amino acids + nucleic acids
51
Q

How does the light-independent reaction result in the production of useful organic substances?

uses of GALP ?

A
  • GALP acts as raw material when 1C leaves the cycle to produce monosaccharides, amino acids & other biological molecules
  • some GALP feeds into glycolysis + krebs cycle as fuel to provide energy through ATP
52
Q

Roles of ATP & NADPH in the light-independent reaction:

A

ATP:
- reduction of GP to GALP TP
- provides phosphate group to convert RuP into RuBP

NADPH:
- coenzyme transports electrons needed for reduction of GP to GALP TP

53
Q

alternatve routes:

A
  • most plants fix carbon divride divecty into 3-c compords = called C3 plants
  • other plants produce 4-C compounds to minimise photorespiration → C4 plants
  • CAM plants fix carbon at night so that stomata co remain closed in the dark to mininise water loss but Still have enough CO2
54
Q

What’s a limiting factor ?

What are the limiting factors for photosynthesis ?

A
  • A factor that determines maximum rate of a reaction, even if other factors change to become more favourable
  1. CO2
  2. Light intensity
  3. Temperature
  4. magnesium levels (maintain normal functioning of chlorophyll)
55
Q
  1. Carbon dioxide as a limiting factor:
A
  • if there is not enough carbon dioxide available = it cannot be fixed in the Calvin cycle
  • This means light-independent stage (Calvin cycle) cannot proceed at its maximum rate
56
Q
  1. Light intensity as a limiting factor:
A
  • amount of light affects the amount of chlorophyll which is excited
  • this determines the amount of ATP + NADPH produced
  • this determines the rate of reactions in the light-independent stage
57
Q
  1. Temperature as a limiting factor:
A
  • many of the reactions in the LD and LI (Calvin) stages are controlled by enzymes = sensitive to temp
  • if the temperative is too high / too low + even if other conditions are suitable reactions will not be at their maximum rate = enzymes may denature
58
Q

Adaptations EG?

A
  • growing in height for sunlight
  • spreading leaves into a mosaic pattern
  • developing large leaves
  • seed dispersal methods mean baby plants do not grow in the shade of their parents

bio (alevel) (10 decks)

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