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Biology - Grade 12 > Metabolism and Photosynthesis > Flashcards

Metabolism and Photosynthesis Flashcards

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1
Q

Enzymes and Ea wrt Metabolism

A
  • Ea is the energy input required to start a reaction
  • When enzymes bind to substrates, substrates become altered lowering Ea
  • They speed up reaction rate millions of times faster
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2
Q

Types of enzymatic reactions

A

Exergonic: reactants have more E than products, E released into system, catabolic
Endergonic: reactants have less E than products, E absorbed from system, anabolic

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3
Q

Enzyme Inhibitors

A
  • Substances that bind to enzymes to reduce activity
  • Two Types:
    Competitive: bind to active site to block substrate chemically and structurally
    Non-Competitive: Bind to anywhere other than active site, changes enzyme shape
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4
Q

End product inhibition

A
  • The product of the last rxn in a pathway inhibits the enzyme that catalyzes the first, binds to the allosteric site and changes the shape of the enzyme
  • Inhibited enzyme is called the allosteric enzyme
  • Can be reversed when the product detaches
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5
Q

Overview of Cell Respiration

A
  • Controlled release of E (ATP) from organic compounds
  • glycolysis - link rxn - krebs - ETC - chemiosmosis
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6
Q

Redox Principle

A
  • Oxidation of a molecule is linked to a reduction rxn where another molecule gains the lost e-
  • OIL RIG
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7
Q

Electron Carriers (Redox)

A
  • Molecules that accept and give up e- as needed
  • E stored in organic molecules is transferred with proteins and e- to carrier molecules
  • 2 H atoms from a molecule are oxidized
  • One of the H atoms is split in an e- and an H+
  • NAD+ accepts the e- -> NAD, H+ released
  • NAD accepts the e- and H+ of the other H atom to become NADH
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8
Q

Phosphorylation

A
  • Adding a phosphate group to an organic molecule
  • Phosphorylated molecule is unstable and will react more easily in metabolic pathways - activated
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9
Q

Glycolysis

A
  • ‘Sugar splitting’, Occurs in cytoplasm
    4 Key Events:
    1. Phosphorylation: 6C phosphorylated
    2. Lysis: 6C split into 2 3C Pyruvates
    3. Oxidation: H atoms from 3C reduce NAD+ to NADH, twice
    4. ATP Formation: ATP synthesized from E released in intermediates, called substrate level phosphorylation, 4 ATP formed (2 per 3C)
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10
Q

Substrate Phosphorylation

A

Requires an enzyme that transfers a phosphate group for a high E substrate molecule to ADP

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11
Q

Results of Glycolysis

A
  • 6C splits into 2 pyruvate molecules
  • 2 NADH reduced via oxidation 2NADH + H+
  • Net 2 ATP, 4 produced 2 used
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12
Q

Pyruvate

A

If O2 available: pyruvate moves to mitochondria where it is fully oxidized through cellular respiration
If O2 not available: Anaerobic respiration (fermentation) occurs, pyruvate turns to lactic acid in cytoplasm or ethanol and CO2 in plants

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13
Q

Link Reaction (Pyruvate Oxidation)

A
  • Pyruvate converted into acetyl and attached to coenzyme A to form Acetyl coenzyme A
  • Oxidative Decarboxylation is the splitting of CoA and CO2 by oxygen
  • Yields 2 Acetyl COA per glucose molecule
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14
Q

Cell Respiration Using FAs

A
  • CoA can oxidize the FA C chain and break it down to produce Acetyl CoA and 2 Carbons
  • Acetyl CoA then enters Krebs
  • Glycolysis not needed, but FA oxidation is slower than glycolysis
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15
Q

Kreb’s Cycle

A
  • Occurs in the mitochondrial matrix
  • 8 step process with 8 specific enzymes
  • Cyclical, begins and ends with oxaloacetate
  • SOme reactions prepare the molecule fo E harvesting later
  • Uses NAD+ and FAD (reduced to FADH2) as e- carriers to ETC
  • Net gain of 4 CO2, 2 ATP, 6 NADH and H+, 2 FADH2
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16
Q

Electron Transport Chain (metabolism)

A
  • Series of proteins in inner mitochondrial membrane that transfer e- from NADH and FADH2 to O2
  • e- pass from one complex to the nest to form H20 at the end
  • As e- is transferred, E pumps H+ across the inner membrane to the intermembrane space
  • Oxygen is the final e- acceptor forming H20
17
Q

Chemiosmosis (metabolism)

A
  • Production of ATP through the movement of ions down their electrochemical gradient through a semi-permeable membrane
  • E in ETC moves H+ into the intermembrane space
  • Creates a gradient, pH also changes, also called proton motive force
  • H+ returns to matrix via ATP synthase
18
Q

Summary of Oxidative Phosphorlation

A
  • ETC located on inner mitochondrial membrane
  • H atoms transfer to ETC by e-carriers
  • e-carriers release e-, transferred b/w complexes, E released
  • Pumps H+ across the membrane, where they accumulate
  • H+ return to matrix via ATP synthase
  • Produces ATP via chemiosmosis
  • Oxygen is final acceptor, forms H20
19
Q

Photosynthesis overview

A

6CO2 + 6H2O -> C6H12O6 + 6O2
- Consists of two stages, light-dependent and independent

20
Q

Light Dependent Reactions Overview

A
  • Takes place in the thylakoids
  • Converts light energy into ATP and NADPH
    Consists of:
    1. Photoactivation
    2. Photolysis
    3. ETC
    4. Chemiosmosis
    5. ATP synthesis
    6. Reduction of NADP to NADPH and H+
21
Q

Photoactivation

A
  • E light used to excite e- in a chlorophyll pigment
  • e- can leave the pigment molecule and move through the ETC
  • Occurs in photosystems
  • E passed inward when absorbed until it reaches the rxn centre
  • e- becomes energized and moves to a higher e- level
  • Rxn centre is oxidized
22
Q

Photolysis

A
  • breaking apart of H2O using light E to produce H+ and e-
  • e- replace e- lost during photoactivation in PSII
  • H+ build up in a gradient in the lumen used in chemiosmosis to create ATP
  • O2 is a waste prouct
23
Q

Photosystems

A
  • Large complexes of protein and pigment within the thylakoid membrane
  • two types: PSII and PSI, PSII used first, PSI second
  • both contain pigments to collect light E and a special pair of chlorophyll in the rxn centre
24
Q

ETC (photosynthesis)

A
  • series of molecules transferring e- via redox rxns, fuels pumping of H+ across a membrane
  • Creates a protein gradient in thylakoid membrane
  • Two ETC, one for each PS
  • Transfer of e- in PSII builds H+ gradient
  • Transfer of e- in PSI reduces NADP -> NADPH
25
Q

Chemiosmosis and ATP Synthesis

A
  • Movement of H+ down gradient is coupled with ATP synthesis
  • Occurs at ATP synthase, a molecule in the thylakoid membrane
  • H+ flows down into the stroma
  • ADP is joined by a P
26
Q

Reduction of NADP to NADPH and H+

A
  • Formation of e- carrier NADPH using e- from PSI at the end of PSI ETC
  • e- excited out of rxn centre, given to e- carrier NADP, become NADPH
27
Q

Cyclic e- Transport / Phosphorylation

A
  • NADP can run out, PSII will shut down
  • e- energized in PSI will return to first acceptor in ETC
  • Transfered down chain, pumps H+ across membrane re-energized by PSI
28
Q

Light Dependent Summary

A
  • Occurs in the thylakoid membrane, inside is lumen, outside is stroma
  • Light E captured by light pigments in the chloroplast
  • PSII generates ATP via Chemiosmosis
  • PSI generates NADPH
  • Splitting H2O maintains the flow of e- through PS
  • O2 released as waste
29
Q

Light Independent Reactions Overview

A
  • Enzymes in stroma synthesize carbs from CO2 using ATP and NADPH
  • 3 Steps: Carbon fixation, Reduction, Regeneration
  • 6 turns of Calvin cycle produce 1 glucose molecule
30
Q

Carbon Fixation

A
  • Adding C from an inorganic molecule to an organic
  • C from CO2 used to build carbs
  • Occurs in stomata
    1. CO2 enters plant via stomata and diffuses into stroma
    2. CO2 attaches to RuBP(5C), becoming rubisco (6C)
    3. 6C splits into two glycerate-3-phosphates (GP 3C)
  • 3 RuBP + 3 CO2 -> 6 GP
31
Q

Reduction

A
  • ATP and NADPH used to reduce GP into triose phosphate (TP) in stroma
  • e- and H+ from NADPH become part of the carb
32
Q

Regeneration

A
  • Using ATP, some Tp are used to regenerate RuBP
  • Must be regenerated so C Fixation can occur again, occurs in stroma
  • Remaining TP stay in system to enable system to prepare for more CO2
33
Q

Structure and function of chloroplasts

A

Thylakoids: volume to increase H+ gradient as H+ accumulates, a large area of light absorbing capacity
Grana: Stacks of thylakoids to increase surface
Stroma: Central cavity with enzymes for calvin cycle, surrounds thylakoids so NADPH and ATP is close to enzymes
PS: Pigments arranged in PS in the thylakoid membrane to maximize light absorption

34
Q

Melvin Calvin and the Lollipop

A
  • Supplied algae with Carbon 14 to determine which C compounds were present
  • Used chlorella algae in a glass lollipop vessel
  • Added H14^CO3
  • Killed algae at intervals by dropping it into methanol
  • Analyzed samples using 2D chromatography and Autoradiography

Biology - Grade 12 (6 decks)

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