Biology - B4 Bioenergetics

What absorbs the energy required for photosynthesis?

Chlorophyll

In what part of the cell does photosynthesis take place?

In chloroplasts

What is the word equation for photosynthesis? 

Carbon dioxide + water —> glucose + oxygen

What is the chemical symbol equation for photosynthesis?

6CO₂ + 6H₂O —> C₆H₁₂O₆ + 6O₂

Which type of reaction is photosynthesis?

Endothermic

What 2 things can the glucose made during photosynthesis be used for?

Respiration or stored as starch for later

What is the molecular formula for glucose?

C₆H₁₂O₆

How do plants get the carbon dioxide required for photosynthesis?

It diffuses from the air into the leaves via stomata 

How do plants get the water required for photosynthesis? 

It diffuses from the soil into the root hair cells by osmosis

What 3 things make starch a useful long term storage molecule?

It is insoluble in water, it is compact, it can easily be broken down

One use of glucose is to make amino acids. What else do plants need to make amino acids?

Nitrate ions

What are the main uses of glucose in plants? (CARLS)

make Cellulose, Amino acids, respiration, lipids, starch

Which useful energy transfer or conversion happens overall in photosynthesis?

Light —> chemical

What is the role of chlorophyll?

To absorb light energy for photosynthesis

Give two reasons why plants may produce insufficient chlorophyll

They lack the required nutrients, they have a disease like TMV

List the three other environmental factors that affect the rate of photosynthesis

light intensity, amount of carbon dioxide, temperature

Given the shape of the graph, which variable(s) could be on the x axis?

light intensity, CO2 concentration

Using what you know about how different factors affect the rate of photosynthesis, which factor would give this graph?

Temperature

What is limiting the rate of photosynthesis at the point labelled in the graph? 

CO2 concentration

When a graph levels off like this we say that it has:

Plateaued

At the point indicated on the graph above, what 2 things could be limiting the rate of photosynthesis?

Temperature, CO2 concentration

Describe and explain how the rate of photosynthesis varies with temperature. (3 marks) (3 points)

Rate initially increases with temperature... because particles have more energy and move faster so react more frequently. At higher temperatures the rate decreases as bonds holding the enzyme together begin to break, and so the enzyme denatures

Farmers in cooler climates often use (?) These help trap the heat energy from (?), and so increase the temperature. They also keep out (?) which could otherwise damage the plants. 

Greenhouses, sunlight, pests

How can farmers ensure that photosynthesis takes place 24 hours a day?

Use artificial lighting

Paraffin heaters have two benefits. As the paraffin (a type of fuel) is burned it releases lots of heat, and also lots of:

CO2

Respiration is the release of energy from sugar molecules such as…

glucose

Is respiration an exothermic or endothermic reaction?

Exothermic

Which process in plants produces the glucose required for respiration?

Photosynthesis

Give four examples of how cells use the energy from respiration.

To break large molecules into smaller molecules, for muscle contraction, to maintain our body temperature, to move substances around the cell

What is metabolism?

The combination of all chemical reactions in an organism

What is the word equation for aerobic respiration? 

Glucose + oxygen —> carbon dioxide + water

What is glucose converted to during anaerobic respiration in animals?

Lactic acid

What is the word equation for anaerobic respiration in plants and fungi:

Glucose —> ethanol + carbon dioxide

What are the two reasons animals cells prefer aerobic respiration to anaerobic respiration?

It doesnt produce lactic acid which can damage cells and lead to oxygen debt. It doesn’t break down the glucose molecule completely so it releases less energy.