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OCR BIOLOGY (MODULE 5) > PHOTOSYNTHESIS > Flashcards

PHOTOSYNTHESIS Flashcards

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1
Q

Define photosynthesis

A

|using light energy to synthesis large organic molecules from smaller inorganic ones
Light energy –> chemical energy

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2
Q

Autotroph

A

Able to form organic substances from inorganic substances

Self feeding

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3
Q

Chemoautotrophs

A

Synthesise complex organic molecules using energy from exogenic chemical reactions
E.g. nitrifying bacteria

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4
Q

Photoautotrophs

A

Organisms that photosynthesise

Use energy from sunlight to produce complex organic molecules from water + carbon dioxide

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5
Q

Heterotrophs

A

Other feeding
Digest complex organic molecules into simple soluble ones
Cannot make their own food

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6
Q

Word equation

A

Carbon dioxide + water –> glucose + oxygen

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7
Q

Symbol equation

A

6CO2 + 6H20 –> C6h2O6 + 6O2

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8
Q

Light dependent stage

A

Light energy converted to chemical energy
Photolysis of water occurs splitting it into H+ ions and oxygen
Produces reduced NADP + ATP

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9
Q

Light independent stage

A

Products of light reactions are used to reduce CO2 to sugars + organic molecules

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10
Q

Importance of photosynthesis

A

Plants, animals and microorganisms rely on it to produce carbohydrates and oxygen

  • oxygen required for aerobic respiration
  • carbohydrates produce energy stores
  • control green house effect
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11
Q

How photosynthesis and respiration interrelate

A

Plants respire all the time, only photosynthesise in the light
In photosynthesis, ATP is synthesised using light energy- ATP then used to build organic compounds such as glucose
In respiration, organic molecules (e.g. glucose) are broken down to release energy

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12
Q

What is the compensation point

A

During photosynthesis and respiration there is no net gain or loss of oxygen or carbohydrates

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13
Q

How is a leaf adapted for photosynthesis

A

Large SA- absorb maximum sunlight
More chlorophyll on top of the leaf
Waxy cuticle reduces water loss
Guard cells close stomata pores (reduces water loss)

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14
Q

Structure and function of chloroplast envelope

A

Double membrane
Selectively permeable

Outer membrane is permeable to small ions, inner membrane is less permeable
Contains transporter proteins

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15
Q

Structure and function granac(chloroplast)

A

Stack of thylakoids

Provide SA for chlorophyll + other pigments to attach to (photosystem II)
Enzyme ATP synthase

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16
Q

Structure and function of inter-granal lamellae (chloroplast)

A

Thylakoids between grana

Contains photosystem I pigments

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17
Q

Structure and function of stroma (chloroplast)

A

Fluid filled matrix

Contains enzymes for light independent reactions for photosynthesis

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18
Q

Structure and function of DNA (chloroplast)

A

No histones, circular

Codes proteins (e.g. enzymes for photosynthesis)

19
Q

Structure and function of ribosomes (chloroplast)

A

18nm

Protein synthesis

20
Q

Function of starch grains

A

insoluble storage molecule

21
Q

Function of lipid droplets

A

Maintain membranes (phospholipid bilayer)

22
Q

What is a photosynthetic pigment

A

absorbs certain wavelengths of light

23
Q

What is the colour of the pigment due to

A

The wavelength of light which is reflected

24
Q

Chlorophyll

A

Collection of green pigments
Porphyrin like ring structure head (contains magnesium)
Hydrocarbon tail- embeds itself in membrane of thylakoids
Head remains on surface

25
Q

Two forms of chlorophyll a

A

P680 + P700

26
Q

Carotenoids

A

Includes carotene and xanthophyll
Ranges in colour (red, orange, yellow)
Absorb wavelengths of light not efficiently absorbed by chlorophyll a
Protect chlorophyll from high light intensities

27
Q

Phycobillins

A

Red seaweed contains additional pigments

Allows them to absorb blue/green light (shorter wavelength of light penetrates water)

28
Q

Explain the distribution of bacteria in response to the absorption spectrum

A

Congregation of oxygen seeking bacteria surrounding blue and red area of spectra
Suggesting algae is absorbing the light and photosynthesising to produce oxygen
Little to no bacteria absorbing green light, no photosynthesis, no oxygen

29
Q

Describe and explain the relationship between the absorption and action spectra

A

Both peak at the blue and red light (increased photosynthesis)- most light absorbed
Action spectra shows some photosynthesis occurs at green and yellow regions- shows carotenoids and other pigments are involved in photosynthesis

30
Q

What is a photosystem

A

Pigment molecules arranged in clusters in the thylakoid membrane
Contain hundreds of chlorophyll a + b and carotenoids

31
Q

Explain a photosystem

A

One chlorophyll a molecule (primary pigment) acts as a reaction centre for each photosystem
Remaining pigments, (accessory pigments) absorbs light and funnel the energy to the reaction centre
Act as light harvesting systems (aka antennae complex)

32
Q

Photosystem I

A

Contains chlorophyll with an absorption peak at 700nm at its reaction centre (P700)
Mainly found in inter-granal lamellae

33
Q

Photosystem II

A

Contains chlorophyll a with an absorption peak at 680nm (P680)
Mainly found on granal lamellae

34
Q

Light dependent reactions

A

Take place in thylakoid

Photolysis- PSII contains enzymes to split water, hydrogen to NADP + ATP

35
Q

Light independent reactions

A

Takes place in stroma

Uses ATP + reduced NADP from light dependent

36
Q

Stages of Calvin cycle

A
  1. CO2 diffuses into stroma
  2. CO2 combines with ribulose bisphosphate (RuBP)
  3. rubisco= catalyst
  4. this product 6C compound which is unstable + immediately splits into 3C compounds
  5. two 3C compounds= gylcerate phosphate (GP)
  6. each GP reduced + phosphorylated to triode phosphate
  7. ATP + reduced NADP (from light dependent) provides phosphate, energy + hydrogen
  8. 5/6th of TP regenerated to RuBP
  9. requires ATP from light dependent
37
Q

Uses of products from Calvin cycle

A

Pairs of TP combine to form hexose (6C) sugars (e.g. glucose + fructose)
Join to form disaccharides (e.g. sucrose)
Polymers may also form (e.g. starch= storage)

38
Q

Factors affecting rate of photosynthesis

CO2 concentration

A

CO2 air conc= 0.04%
Concs lower in dense vegetation
Often limiting factor as essential factor for Calvin cycle
Concs in stroma lower than air

39
Q

Factors affecting rate of photosynthesis

Temperature

A

Temp may affect light independent
Increased temp= increased KE (hence enzyme controlled Rea actions in Calvin cycle)
Increased temp= enzymes denature
Above 25 degrees rubric changes to catalysing RuBP with O2 instead of CO2= photorespiration

40
Q

Factors affecting rate of photosynthesis

Water stress

A
  1. plant roots produce absicic acid- translocated to leaves
  2. causes stomata to close, reduces availability of CO2
  3. rate of photosynthesis reduces
    IF roots cant take up water fast enough to replace water lost from transpiration= cells plasmoylsed
41
Q

Limiting factors + Calvin cycle

Light intensity

A

Low= products of light dependent (ATP + reduced NADP) will be in short supply
Limits conversion of GP to TP + regeneration of RuBP
GP still made

42
Q

Limiting factors + Calvin cycle

CO2 concentration

A

Low= conversion of RuBP to GP will be slow as less CO2

Less CO2 to combine with RuBP

43
Q

Limiting factors + Calvin cycle

Temperature

A

All stages of Calvin cycle catalysed by enzymes (rubisco)
Low temps= cycle= slower
High temp= enzymes denature + photorespiration may occur

OCR BIOLOGY (MODULE 5) (7 decks)

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