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IB Biology > Cell Respiration and Photosynthesis > Flashcards

Cell Respiration and Photosynthesis Flashcards

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1
Q

Define cell respiration

A

Cell Respiration - the controlled release of energy from organic compounds in cells to form ATP

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2
Q

State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.

A

In cell respiration, glucose (in cytoplasm) is broken down by glycolysis into pyruvate, with small yield of ATP.

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3
Q

Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP

A
  • used by organisms living in conditions with no oxygen
  • oxygen cannot be used as final e- acceptor
    eg. E.coli (nitrate), methanogens
  • NADP+ must be regenerated (for glycolysis)
  1. Lactate fermentation (prokaryotes and muscle cells)
    - pyruvate –> lactate
    - oxidizes NADH + H+ to NAD+
    - can cause muscle cramps, stiff, sore, fatigue
    - lactate is reoxidized (prevent low pH) in liver
    - small yield of ATP
  2. Ethanol fermentation (yeast)
    - pyruvate –> ethanol and CO2 (waste products)
    - used to make alcohol, baked goods, soy sauce
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4
Q

Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP

A
  • aerobic requires oxygen and occurs in mitochondria
  • pyruvate –> H2O + CO2
  • large yield of ATP (36-38)
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5
Q

State that oxidation involves the loss of electrons from an elements, whereas reduction involves a gain of electrons, and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen

A

Oxidation - lose electrons/hydrogen, gain oxygen
Reduction - lose oxygen, gain electrons/hydrogen

(OIL RIG)

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6
Q

Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation

A

Glucose converts to:

  • 2 pyruvate (3C)
  • 2 ATP (small yield)
  • 2 NADH (e- shuttles to ETC)

A. Phosphorylation: 2 ATP increase potential energy of reactant/substrate
B. Lysis: hexose splits into two 3C molecules
C. Oxidation: transfer of e- via H atoms (2NAD+ becomes 2NADH + 2H+)
D. ATP Formation: 4 ATP produced by substrate level phosporylation (net 2 ATP)

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7
Q

Draw and label a diagram showing the structure of a mitochondrion as seen in electron micorgraphs

A

Outer Mitochondrial Membrane - separates contents from rest of cell, creating ideal conditions for aerobic respiration
Inner Mitochondrial Membrane - contains ETCs and ATP synthase for oxidative phosphorylation
Matrix - fluid inside mt with enzymes for Krebs Cycle and Link Reaction
Cristae - tubular/shelf-like projections of inner membrane increase SA available for oxidative phosphorylation
Space Between Membranes - protons pumped in by ETC, high proton concentration maintained due to small space (chemiosmosis)
- 70s ribosomes and naked DNA in matrix
- 1-2 um in length

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8
Q

Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H+, the electron transport chain and the role of oxygen

A

Link Reaction (Oxidative Decarboxylation)
E. Decarboxylation: CO2 molecule removed
F. Redox: NAD+ reduced to NADH (used in ETC), pyruvate oxidizes (lost CO2)
G. Acetyl-CoA Formation: acetyl group (CH3CO) from pyruvate attaches to coenzyme (CoA), used in Krebs cycle

Krebs Cycle
- occurs in mitochondria matrix
- reactants are acetyl-CoA joins oxaloacetate to form 6C molecule; converted to 5C, then back to 4C
- (2) CO2, (3) NADH, (1) FADH2, (1) ATP
H. Decarboxylation: forms CO2 product
I. Redox: produce NADH and FADH2
J. Substrate-level Phosphorylation: forms ATP
K. Oxaloacetate Regeneration

Oxidative Phosphorylation
- ETC is series of e- carriers in inner mitochondria membrane
- moves e- from weakest En to highest
- highly exergonic to move H+ from matrix to intermembrane space using protein pumps
L. NADH + H+ donates 2e- to NADH dehydrogenase
M. Reduction of NADH dehydrogenase is exergonic
N. 2e- passed to ubiquinone (Q)
O. NADH + H+ outside mitochondria pass 2e- to FADH2; ; passed to Q
P. 2e- move through cytochrome b-c and C to pump H+ across membrane
Q. 2e- reach cytochrome oxidase; picked up by O to form H20
R. H+ accumulates in intermembrane space; makes ATP

  • oxygen required to form H2O at end of ETC
  • e- cannot pass through
  • NADH cannot convert to NAD+
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9
Q

Explain oxidative phosphorylation in terms of chemiosmosis

A
  • H+ accumulate in intermembrane space, forming electrochemical gradient
  • H+ diffuse through ATP synthase into matrix
  • flow of H+ synthesizes ADP + Pi into ATP
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10
Q

Explain the relationship between the structure of the mitochondrion and its function

A
  • cristae/inner membrane increase SA for ETC and ATP synthase
  • intermembrane space lets H+ accumulate
  • matrix contains enzymes for Krebs Cycle
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11
Q

State that photosynthesis involves the conversion of light energy into chemical energy

A

Photosynthesis involves the conversion of light energy into chemical energy.

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12
Q

State that light from the Sun is composed of a range of wavelengths (colours)

A

Light from the Sun is composed of a range of wavelengths (colours).
- 400 to 700 nm

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13
Q

State that chlorophyll is the main photosynthetic pigment

A

Chlorophyll is the main photosynthetic pigment.

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14
Q

Outline the differences in absorption of red, blue and green light by chlorophyll

A
  • chlorophyll absorbs mostly red and blue light

- green light is reflected and transmitted (leaf appears green)

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15
Q

State that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen

A

Light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen.

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16
Q

State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules

A

ATP and hydrogen (derived from the photolysis of water) are used to fix CO2 to make organic molecules.

17
Q

Explain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by an increase of biomass

A

Production of Oxygen

  • aquatic plants release bubbles of oxygen
  • volume can be measured

Uptake of Carbon Dioxide

  • leaves take in CO2 from air/water
  • pH of water rises

Increase of Biomass
- rate of increase of biomass gives indirect measure of rate of photosynthesis

18
Q

Outline the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis

A

Temperature

  • increase in temperature = increase in rate
  • optimum temperature yields highest rate
  • steeply decrease above optimum temperature

Light Intensity

  • low/medium light = rate increases proportionally
  • at high light, rate plateaus

Carbon Dioxide Concentration

  • no photosynthesis at low CO2 levels
  • low/fairly high CO2 = rate increases proportionally
  • at very high CO2, rate plateaus
19
Q

Draw and label a diagram showing the structure of a chloroplast as seen in electron micrographs

A
  • granum (thylakoid membranes)
  • starch grain
  • lipid droplet
  • chloroplast envelope (inner and outer membranes)
  • stroma contain 70s ribosomes and naked DNA
20
Q

State that photosynthesis consists of light-dependent and light-independent reactions

A

Photosynthesis consists of light-dependent and light-independent reactions.

21
Q

Explain the light dependent-reactions

A
  1. Photoactivation - e- in chlorophyll absorbs photon of light
    - e- becomes excited (low to high PE)
    - unstable –> emits energy to return to ground state
    - chlorophyll will fluoresce (in isolation) or redox occurs
    • chlorophyll oxidizes, primary electron acceptor captures e-
  2. Electron Transport - transfer of e- through thylakoid membrane-bound e- carriers
    - results in pumping of H+ into thylakoid
    a) Noncyclic Photophosphorylation - e- flows through ETC producing NADPH and H+ gradient
    - photoactivation of PSII (P680)
    - excited e- enters primary e- acceptor
    - Z protein splits H2O through photolysis
    - 2e- replace lost e- and pass through b6-f complex, transporting H+ from stroma to lumen
    - photoactivation of PSI (P700)
    - 2e- and 2H+ passed through PSI to NADP reductase, forming NADPH + H+
    b) Cyclic Photophosphorylation - e- from PSI flows through ETC back to PSI
    - PSI to ferradoxin to b6-f to PSI
    - when NADPH levels high, low NADP+ levels slow non-cyclic flow
    - no NADPH produced, only ATP
22
Q

Explain photophosphorylation in terms of chemiosmosis

A
  • H+ collect in lumen
  • high H+ concentration (low pH) create electrochemical gradient
  • 4H+ move through ATP synthase for every ATP produced (ADP + Pi)
23
Q

Explain light-independent reactions

A
  • regenerate RuBP (ribulose bisphosphate)
  • occurs in stroma
  • synthesize carbs using ATP and NADPH + H+
  1. Carbon Fixation
    - rubisco combines 3CO2 with 3RuBP (5C)
    - resulting unstable 6C compound splits into 2GP (3C)
  2. Reduction Reactions
    - GP reduced by 6ATP and 6NADPH + 6H+
    - forms 6G3P (3C)
    - G3P synthesizes 1/2 glucose molecule
  3. Regeneration of RuBP
    - 3ATP gives energy to rearrange 5G3P into 3RuBP

To make 1 glucose requires:

  • (2) G3P
  • (2) 3CO2
  • (2) 6NADPH + 6H+
  • (2) 9ATP
24
Q

Explain the relationship between the structure of the chloroplast and its funtion

A
  • large SA of grana for increased light absorption
  • small lumen inside thylakoids for accumulation of protons
  • stroma contains enzymes for Calvin Cycle
25
Q

Explain the relationship between the action spectrum and the absorption spectrum of photosynthetic pigments in green plants

A 
Action spectrum (rate of photosynthesis) measured by shining wavelengths of light at chloroplasts and detecting O2 produced or CO2 consumed
Absorption spectrum (light absorbed) measured by how much wavelengths of light are transmitted after passing through pigment
  • high levels of absorption in red and blue-violet range means high rate of photosynthesis
  • low absorption in yellow-green = low photosynthesis
  • most yellow-green light reflected; plants appear green
  • in some plants/algae, green light harnessed by accessory pigments
  • peaks at 450 and 670 nm
26
Q

Explain the concept of limiting factors in photosynthesis, with reference to light intensity, temperature and concentration of carbon dioxide

A

Temperature

  • low: enzymes work slowly, NADPH collects
  • middle: other limiting factor
  • high: rubisco denatures, no CO2 fixation, NADPH collects

Light Intensity

  • low: shortage of NADPH and ATP, reduce G3P
  • high: other limiting factor

Carbon Dioxide Concentration

  • low/middle: no CO2 fixation, RuBP and NADPH collect
  • high: other limiting factor

IB Biology (9 decks)

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