M.1.2 Flashcards

Photosynthesis and Cellular Respiration

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1
Q

Carbon fixation

A
  • Changing of inorganic carbon molecule into organic sugars that combine to form glucose
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2
Q

Inorganic molecule

A
  • Not produced by an organism
  • Occurs readily in nature, e.g. carbon dioxide, water, oxygen, mineral salts
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3
Q

Organic molecule

A
  • Chemicals produced by an organism
  • e.g., lipids, proteins, carbohydrates, nucleic acid
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4
Q

Heterotrophs

A
  • Organisms that can’t make organic material
  • Consumes organic material for energy
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5
Q

Chloroplast

A
  • Disc shaped organelle
  • contains stacks of thylakoid (grana)
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6
Q

Mesophyll

A
  • Green tissue of the cell, where chloroplasts are located
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7
Q

Stoma(ta)

A
  • Pores in the leaf that allows carbon dioxide to enter and oxygen to leave
  • Opened/closed by guard cells on either side of it
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8
Q

Photosynthesis basic formula

A

Water + Carbon Dioxide → (in presence of sunlight through a chloroplast) Glucose + Oxygen Gas

H20 + CO2 (with sunlight) → C6H12O6 + O2

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9
Q

Light reaction

A
  • 1st stage of photosynthesis
  • Generates energy (ATP, NADPH) needed for dark reaction, oxygen and hydrogen by splitting water
  • Chlorophyll absorbs light energy, splits water to produce H+ ions
  • Oxygen released as a byproduct
  • Occurs in thylakoid membrane’s photosystem
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10
Q

Calvin Cycle overview

A
  • 2nd stage of photosynthesis
  • Produces glucose from CO2 using the ATP + NADPH energy from the light cycle
  • RuBP combines with CO2 to form G3P. One G3P is converted into glucose, the rest is converted back into RuBP for the next cycle
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11
Q

Chlorophyll

A
  • Pigment that traps light energy
  • Chlorophyll A: blue-violet and red wavelengths
  • Chlorophyll B: blue and orange wavelengths, reflects yellow-green wavelengths
  • Doesn’t capture green wavelengths
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12
Q

Obligate anaerobes

A
  • Die if exposed to oxygen, as they don’t produce enzymes necessary to detoxify reactive oxygen species.
    e.g. bacteroides (obligate anaerobic bacteria)
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13
Q

Facultative anaerobes

A
  • Can live with or without oxygen, as it produces ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent.
    e.g. e. coli and yeast
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14
Q

Guard cells

A
  • Cells surrounding the stomata, changing the size of pores by turgor pressure (due to the large vacuole in guard cells)
    Turgid: fills with water, stretching the guard cells to curve outwards, causing it to open
    Flaccid: as water leaves the vacuole, the guard cells deflate, collapsing inwards and closing the stomata.
  • If the environment is hot and dry, this causes a steeper concentration gradient for water vapour to diffuse out of the leaf. This loss of water in the guard cells cause them to become flaccid and close the stomata. This reduces further water loss.
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15
Q

Enzymes

A
  • special proteins: biological catalysts (in this case) that speeds up photosynthesis
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16
Q

Stroma

A
  • Fluid inside chloroplast surrounding thylakoid system and grana
  • Contains starch, chloroplast DNA, ribosomes, and enzymes needed for Calvin Cycle
17
Q

ATP

A

adenosine triphosphate

18
Q

NADPH

A

nicotinamide adenine dinucleotide phosphate hydrogen
- Created by adding hydrogen ions (H+) to NADP

19
Q

G3P

A
  • Glyceraldehyde-3-phosphate
  • Raw material for production of fatty acids, amino acids, glucose, nucleotides
  • Often immediately converted into glucose phosphate then starch
20
Q

Calvin Cycle steps

A
  1. CO2 + RuBP → 3PGA (3-phosphoglyceric acid)
  2. 3PGA → G3P (enzymes convert using energy from ATP and NAPDH)
  3. CO2 exits cycle as G3P sugar (carbon fixation)
  4. RuBP regenerated via rearrangement of leftover G3P molecules
21
Q

3PGA

A
  • 3-phosphoglyceric acid
  • Product of: carbon + RuBP (+ ATP and NADPH energy)
22
Q

RuBP

A
  • Ribulose biphosphate
  • 5-carbon sugar
  • Combines with carbon: CO2 + RuBP → 3PGA
  • Replenished by rearrangement of leftover G3P molecules from end of 1 Calvin Cycle
23
Q

Alcohol fermentation

A
  • Glucose → carbon dioxide + ethanol
24
Q

Lactic acid fermentation

A

Glycolysis occurs, and then if still not in presence of oxygen:
- pyruvate + NADH –> lactic acid, which can be broken down in glycolysis again to produce another 2 net ATP

glucose –> lactic acid + 2 ATP

Used for fermentation of kimchi, yoghurt.
Also in muscle cells, where after extended periods of exertion there is a shortage of oxygen in muscle cells, causing them to respire anaerobically. The presence of lactic acid causes a cramp.

25
Q

Glycolysis main idea

A
  • 1 Glucose → 2 pyruvates
  • Begins both aerobic and anaerobic respiration as does not need oxygen to occur
  • Occurs in cytoplasm
26
Q

Phosphorylation

A
  • Adding of a phosphate group to a molecule
27
Q

Krebs Cycle

A
  • Found by Hans Kreb in 1930s
  • Pyruvate converted into acetyl co-enzyme (acetyl co-A)
  • Acetyl co-A degraded to CO2 and H2O with release of ATP
  • Occurs in matrix of mitochondria
28
Q

Main stages of cellular respiration

A
  • Glycolysis
  • Krebs cycle
  • Electron transport chain (ETC)
29
Q

ETC

A
  • Occurs in inner membrane of mitochondria
30
Q

ATP production light reaction

A
  • Electrons energised by splitting of water travel down an electron transport chain to NADPH-producing photosystem
  • Chloroplast uses energy released by this electron “fall” to make ATP
31
Q

No.of ATP produced in cellular reaction

A
  • Aerobic: 32 ATP molecules/1 glucose
  • Anaerobic: 2 ATP molecules/1 glucose
32
Q

Light intensity photosynthesis

A
  • The rate of photosynthesis increases with light intensity, BUT will plateau eventually when it reaches plant’s optimum level as every chloroplast is saturated with sunlight energy, and is operating at maximum capacity.
  • Also plateaus as carbon dioxide concentration or temperature become limiting
  • Remember this is different to temperature, as temperature can result in inefficient loss of water vapour, but higher temperature is accompanied with high light intensity
33
Q

Relationship between photosynthesis and cellular respiration

A
  • Photosynthesis: inorganic molecules –> energy dense compound (anabolic reaction)
  • Cellular respiration: energy dense compound –> inorganic molecules + energy (catabolic)
  • Also cellular respiration occurs at a slower rate as it is a more complex reaction