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GCSE AQA Biology > Unit 4 - Bioenergetics - Photosynthesis > Flashcards

Unit 4 - Bioenergetics - Photosynthesis Flashcards

(50 cards)

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1
Q

Word equation for photosynthesis

A

carbon dioxide + water —-> glucose + oxygen

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2
Q

Symbol equation for photosynthesis

A

6CO2 + 6H2O ——> C6H12O6 + 6O2

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3
Q

What is the source of energy that drives photosynthesis?

A

light energy (via chlorophyll)

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4
Q

What type of reaction is photosynthesis?

A

endothermic

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5
Q

what is an endothermic reaction?

A

reaction that takes in energy from surroundings

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6
Q

what is an exothermic reaction?

A

reaction that releases energy to the surroundings

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7
Q

What is photosynthesis an example of?

A

a metabolic pathway

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8
Q

what is a metabolic pathway

A

metabolism
controlled by enzymes

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9
Q

How does the plant obtain carbon dioxide?

A

Air diffuses into the leaf (site of gas exchange) through stomata, through the air spaces in the spongy mesophyll

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10
Q

How does the plant obtain water?

A

from the soil, via osmosis
by root hair cells
moves by the transpiration stream, up the plant

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11
Q

What happens to oxygen made by the plant?

A

may be used in **respiration **
diffuses out of leaf through stomata

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12
Q

What happens to glucose made by the plant?

A

used as a chemical energy source (food)
used to make:
* starch (energy store)
* cellulose
* proteins
* lipids (amino acids)
can be used in respiration to release energy

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13
Q

Why is starch, cellulose, proteins and lipids needed by the plant?

A

to grow

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14
Q

What is the unique **feature **of the upper epidermis?

A

it has no chloroplasts

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15
Q

Where is the main site of photosyntheis?

A

in the** palisade mesophyll**
it contains many chloroplasts

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16
Q

How is a broad leaf shape useful for photosynthesis?

A

provides a large surface area to absorb light for photosynthesis

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17
Q

How is a thin leaf useful for photosynthesis?

A

short diffusion distance for gases
(e.g. CO2 diffuses in)

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18
Q

How are **veins **useful for photosynthesis?

A

*Xylem: *transports water + mineral ions
Phloem: transports sugars made in photosynthesis away from leaf to rest of the plant (transported as sucrose)

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19
Q

How are long, thin palisade mesophyll cells useful for photosynthesis?

A

they contain many chloroplasts/chlorophyll
this allows the leaves to absorb more light for photosynthesis

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20
Q

How are spongy mesophyll cells with air spaces useful for photosynthesis?

A

allows gases to diffuse more easily through the leaf
CO2 into cell, O2 away from cell

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21
Q

How are guard cells that open/close useful for photosynthesis?

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A

they control the opening + closing of stomata, helping to regulate gas exchange

22
Q

How are mesophyll cells with lots of chlorophyll useful for photosynthesis?

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A

absorbs more light for photosynthesis

23
Q

What** factors** affect the rate of photosynthesis?

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A
  • light intensity
  • temperature
  • carbon dioxide concentration
  • chlorophyll levels
24
Q

How does light intensity affect the rate of photosynthesis?

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A

Increase in light intensity, the rate of photosynthesis **increases. **
No light = 0 light intensity, no photosynthesis
Brighter the light, the greater the rate of photosynthesis

25
How does **temperature** affect the rate of photosynthesis?
Photosynthesis is **controlled by enzymes** **Increase** in temperature, the rate of photosynthesis **increases. ** More KE, more collisions, more enzyme-substrate complex = more reactions. Above optimum temperature -- **enzyme is denatured, which decreases the rate of photosynthesis**
26
How does **carbon dioxide concentration** affect the rate of photosynthesis?
This is the most common limiting factor in the wild, especially on a sunny day As CO2 concentration **increases**, the rate of photosynthesis **increases**. CO2 concentration increases at night but do not photosynthesise
27
How does **chlorophyll levels** affect the rate of photosynthesis?
**Less chlorophyll**, less light absorbed, **less photosynthesis** This can be linked to **low Mg** in soil = less chlorophyll
28
Show the trend of light intensity in a graph
29
Show the trend of temperature in a graph
30
Show the trend of carbon dioxide concentration in a graph
31
Describe the **pondweed experiment** (used to determine how light intensity affects the rate of photosynthesis
Cut up a piece of pondweed Use forcepts to place the pondweed in a tube of water carefully. Make sure that you don't damage the pondweed, or cause the liquid to overflow. Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results. Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.
32
What is the **independent variable** in the pondweed experiment?
light intensity distance of lamp
33
What is the **dependent variable** in the pondweed experiment?
volume of O2 produces number of bubbles
34
What are some **control variables** in the pondweed experiment?
type of plant temperature of water same lamp/bulb time
35
Why is the pondweed experiment** repeated at each distance?**
to calculate a mean and spot anomalies this **increases reliability**
36
Why is the weed left for 5 mins if the lamp has been moved in the pondweed experiment?
to give time for the pondweed to **equilibrate**
37
Define equilibrate
to get used to the light intensity
38
What are the **limitations** of the pondweed experiment?
* lamp could heat up the beaker/pondweed (if it is not a LED lamp) * it would be difficult to count all the bubbles * It is difficult to measure the volume of each bubble
39
How can we** improve** the pondweed experiment?
* IF LED bulb is not used, use a LED bulb * IF bubbles are collected, use a measuring cylinder (measure volume more accurately) * IF measuring cylinder is used, use gas syringe * IF no repeats, repeat + calculate a mean * IF only measure for a short time (e.g 30s), measure for a longer time (e.g 2 mins)
40
what is the **inverse square law**
i = 1/d² e.g double the distance between light and pondweed (20 to 40), the number of bubbles per minute falls by 1/2² (1/4).
41
define **absoprtion spectrum**
a graph that shows **how many different photosynthetic pigments** absorb light of different wavelength
42
define **action spectrum**
a graph that shows **how effective** different wavelengths of light are for photosynthesis
43
how would you change wavelength of light
using different coloured filters/bulbs
44
what are the **uses** for glucose
For respiration To make cellulose, starch, lipids and amino acids (proteins)
45
How is **cellulose** used in a plant
to **strengthen** their cell walls
46
How are **lipids** used in a plant?
lipids are fats/oils used as an **energy store** they are sometimes used in cell walls to strengthen they are an energy store in seeds
47
How are **amino acids** used in a plant?
they are **made by combining sugars with nitrate ions** + other mineral ions they are then **built up into proteins** to be used in many ways (e.g enzymes) plants** need mineral ions** to survive
48
How is **starch** used in a plant?
they are **stored** they are insoluble in water they are the **main energy store** in plants + found in cells all over a plant they are **kept in special storage areas** in plants (e.g tubers/bulbers) -- potatoes and onions
49
How would you **test a leaf for the presence of starch?**
1. Place the leaf in boiling water to kill the leaf and stop any chemical reactions. 2. Add leaf to boiling ethanol in a water bath *(do not do it with a turned on bunsen burner as ethanol is highly flammable!)*This removes the green colour of the leaf, so that it is easy to see the change of colour. 3. Wash the leaf to rehydrate and place it on a white tile. 4. Add iodine solution to the leaf with a pipette. **If starch is present** ---> colour changes to blue-black If no starch present ---> colour changes to yellow/orangey brown
50
Why does a Venus fly trap eat insects? What sort of soil does this plant live in?
It lives in **nitrate deficient soil** Insects are a **source of protein** (source of nitrogen)

GCSE AQA Biology (8 decks)

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