A2 - Unit 1 - Photosynthesis Flashcards

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1
Q

What are autotrophs?

A

Organisms that use light energy or chemical energy and inorganic molecules (carbon dioxide and water) to synthesise complex organic molecules

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2
Q

What are heterotrophs?

A

Organisms that ingest and digest complex organic molecules, releasing the chemical potential energy stored in them

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3
Q

What is photosynthesis?

A

The process whereby light energy from the Sun is transformed into chemical energy and used to synthesise large organic molecules from inorganic substances

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4
Q

What equation summarises photosynthesis?

A

6CO2 + 6H2O (+light energy) —> C6H12O6 + 6O2

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5
Q

What equation summarises aerobic respiration?

A

C6H12O6 + 6O2 —> 6CO2 + 6H2O (+ energy, some as ATP)

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6
Q

Where does photosynthesis take place?

A

Photoautotrophs have special organelles within their cells called chloroplasts

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7
Q

What are photosynthetic pigments?

A

Molecules that absorb light energy
Each pigment absorbs a range of wavelengths in the visible region and has its own distinct peak of absorption
Over wavelengths are reflected

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8
Q

What is the structure of a chloroplast?

A

Vary in shape and size but most are disc-shaped and between 2-10 um long
Each is surrounded by a double membrane - an envelope
Intermembrane space between the inner and the outer membrane
Outer membrane permeable to many small ions
Inner membrane less permeable and had transport proteins embedded in it, folded into lamellae which are stacked up like piles of pennies
Each stack of lamellae called a granum

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9
Q

What are the two distinct regions inside each chloroplast?

A

Stroma

Grana

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10
Q

What is the stroma in a chloroplast?

A

A fluid-filled matrix.
The reactions of the light-independent stage of photosynthesis occur in the stroma where necessary enzymes are located
Within the stroma are starch grains and oil droplets, as well as DNA and prokaryote-type ribosomes

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11
Q

What are the grana in chloroplasts?

A

Stack of flattened membrane compartments, called thylakoids
These are sites of light absorption and ATP sysnthesis during the light-dependent stage of photosynthesis
The thylakoids can only be seen using an electron microscope

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12
Q

Give 7 thing which help the chloroplasts be adapted for their role

A

Inner membrane with its transport proteins
Many grana
Photosynthetic pigments
Proteins embedded in the grana
Fluid-filled stroma contains enzymes
Grana are surrounded by the stroma
Chloroplasts can make some of the proteins they need

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13
Q

How is the inner membrane of a chloroplast adapted for its role?

A

With its transport proteins can control entry and exit of substances between the cytoplasm and the stroma inside the chloroplasts

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14
Q

How does having many grana help a chloroplast perform its function?

A

Many grana, consisting of stacks of up to 100 thylakoid membranes provide a large surface area for the photosynthetic pigments, electron carriers and ATP synthase enzymes, all of which are involved in the light-dependent reaction

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15
Q

How are the photosynthetic pigments in chloroplasts adapted for their role?

A

They are arranged into special structures called photosystems, which allow maximum absorption of light energy

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16
Q

How do proteins in the grana help chloroplasts be adapted for their role?

A

The proteins hold the photosystems in place

17
Q

Why do the chloroplasts have a fluid-filled stroma?

A

It contains the enzymes needed to catalyse the reactions of the light-independent stage of photosynthesis

18
Q

Why are the grana surrounded by the stroma in the chloroplasts?

A

So the products of the light-dependent reaction, which are needed for the light-independent reaction, can readily pass into the stroma

19
Q

How can chloroplasts make some of the proteins they need for photosynthesis?

A

Using the genetic instructions in the chloroplast DNA, and the chloroplast ribosomes to assemble the proteins

20
Q

What happens when light hits chlorophyll?

A

Causes a pair of electrons associated with the magnesium to become excited

21
Q

What are the two forms of chlorophyll a and what colour do they appear?

A

P680 and P700
Yellow-green
Each absorbs red light at a slightly different wavelength

22
Q

What is the primary pigment reaction centre?

A

The pigment which is found in the centre of a photosystem, which is chlorophyll A (P680 or P700)

23
Q

Which photosystem is P680 found in?

A

Photosystem II

Its peak of absorption is light at a wavelength of 680nm

24
Q

Which photosystem is P700 found in?

A

Photosystem I

Its peak of absorption is light at a wavelength of 700nm

25
Q

What light does chlorophyll a absorb?

A

Blue light, of wavelength around 450nm

26
Q

What light does chlorophyll b absorb?

A

Blue-green light of wavelength between 500nm and 640nm

27
Q

What is a carotenoid?

A

An accessory pigment, it is not directly involved in the light-dependent reaction however absorbs light wavelengths that chlorophyll cant pick up and passes the energy associated with that light to the chlorophyll a at the base of the photosystem

28
Q

Give an example of two carotenoids

A

Carotene (orange) and xanthophyll (yellow)