Biology chapter 11

Question 1

What do plants need energy for?

Answer 1

• photosynthesis
• active transport
• DNA replication
• cell division
• protein synthesis

Question 2

What do animals need energy for?

Answer 2

• muscle contraction
• maintenance of body temperature
• active transport
• DNA replication
• cell division
• protein synthesis

Question 3

What is the word equation for photosynthesis?

Answer 3

carbon dioxide + water + energy = glucose + oxygen

Question 4

What is the word equation for respiration?

Answer 4

glucose + oxygen = carbon dioxide + water + energy

Question 5

What are the 2 types of respiration and what are their differences?

Answer 5

Aerobic - respiration using oxygen

Anaerobic - respiration without oxygen

Question 6

What is ATP and what is it made from?

Answer 6

Adenosine triphosphate = the immediate source of energy in a cell made from adenine, combined with a ribose sugar and three phosphate groups

Question 7

Describe the synthesis of ATP

Answer 7

ATP is synthesised via a condensation reaction between ADP and inorganic phosphate using energy from an energy-releasing reaction. This energy is stored as chemical energy in the phosphate bond. The enzyme ATP synthase catalyses this reaction. This process is known as phosphorylation

Question 8

Describe the breakdown of ATP

Answer 8

ATP is broken down into ADP and inorganic phosphate once it’s diffused to the part of the cell that needs energy. Chemical energy is released from the phosphate bond and used up by the cell. ATP hydrolase catalyses this reaction. This process is known as hydrolysis. The ADP and inorganic phosphate are recycled and the process starts again

Question 9

What are the 6 properties of ATP?

Answer 9

1. ATP stores or releases only a small, manageable amount of energy at a time, so no energy is wasted as heat
2. It’s a small, soluble molecule so it can be easily transported around the cell
3. It’s easily broken down, so energy can be easily released instantaneously
4. It can be quickly remade
5. It can make other molecules more reactive by transferring one of its phosphate groups to them (phosphorylation)
6. ATP can’t pass out of the cell, so the cell always has an immediate supply of energy

Question 10

What is the compensation point?

Answer 10

The particular level of ______ at which the rate of photosynthesis exactly matches the rate of respiration e.g light intensity

Question 11

What are chloroplasts?

Answer 11

Small, flattened organelles surrounded by a double membrane

Question 12

What are thylakoids and how do they form grana?

Answer 12

Fluid-filled sacs which are stacked up in the chloroplast into grant

Question 13

What are lamellae?

Answer 13

Grana linked together by bits of thylakoid membrane

Question 14

What are photosynthetic pigments, where are they found and what are they attached to?

Answer 14

Coloured substances that absorb the light energy needed for photosynthesis. They are found in the thylakoid membranes and are attached to proteins (photosystem)

Question 15

What are the 2 types of photosystems and what are their differences?

Answer 15

Photosystem I = absorbs light best at a wavelength of 700nm

Photosystem II = absorbs light best at a wavelength of 680nm

Question 16

what is the stroma and what does it contain and what does it store?

Answer 16

Gel-like substance contained within the inner membrane of the chloroplast surrounding the thylakoids. It contains enzymes, sugars and organic acids. It stores starch grains (carbohydrates produced by photosynthesis and not used straight away)

Question 17

What are redox reactions?

Answer 17

Reactions that involve oxidation (lost electrons) and reduction (gained electrons)

Question 18

What is a coenzyme and how do they work?

Answer 18

A molecule that aids the function of an enzyme. They work by transferring a chemical group from one molecule to another

Question 19

What is the coenzyme used in photosynthesis and what does it do?

Answer 19

NADP. it transfers hydrogen from one molecule to another so it can reduce or oxidise a molecule

Question 20

Describe the light-dependent reaction during photosynthesis

Answer 20

It takes place in the thylakoid membranes of the chloroplasts. Light energy is absorbed by chlorophyll in the photosystems. The light energy excites the electrons in the chlorophyll, giving them more energy, which eventually causes them to be released from the chlorophyll molecule (photoionisation). The chlorophyll molecule is now a positively charged ion. Some of the energy from the released electrons is used to add a phosphate group to ADP to form ATP, and some is used to reduce NADP to form reduced NADP. ATP transfers energy and reduced NADP transfers hydrogen to the light-independent reaction. During the process water is oxidised to oxygen

Question 21

Describe the light-independent reaction

Answer 21

It takes place in the stroma of the chloroplats. Here, the ATP and reduced NADP from the light-dependent reaction supply the energy and hydrogen to make glucose from carbon dioxide

1.

Question 22

In the light-dependent reaction, what is the energy resulting from the photoionisation of chlorophyll used for?

Answer 22

1. Making ATP from ADP and inorganic phosphate (photophosphorylation) = the process of adding phosphate to a molecule using light
2. Making reduced NADP from NADP
3. Splitting water into protons, electrons and oxygen (photolysis) = the splitting of a molecule using light energy

Question 23

What does non-cyclic photophosphorylation produce?

Answer 23

ATP, reduced NADP and oxygen

Question 24

Describe non-cyclic photophosphorylation

Answer 24

1. Light energy excites electrons in chlorophyll = light energy is absorbed by photosystem II. The light energy excites electrons in chlorophyll. The electrons move to a higher energy level. These high-energy electrons are released from the chlorophyll and move down the electron transport chain and move down the electron transport chain to photosystem I.
2. Photolysis of water produces protons, electrons and oxygen= as the excited electrons from the chlorophyll leave photosystem II to move down the electron transport chain, they must be replaced. Light energy splits water into protons (H+ ions), electrons and oxygen- this is photolysis.
3. Energy from the excited electrons make ATP= the excited electrons lose energy as they move down the electron transport chain. This energy is used to transport protons (H+ ions) into the thylakoid so that the thylakoid has a higher concentration of protons than the stroma. This forms a proton gradient across the thylakoid membrane. Protons move down their concentration gradient, into the stroma, vie the enzyme ATP synthase, which is embedded in the thylakoid membrane. The energy from this movement combines ADP and inorganic phosphate to form ATP.
4. Energy from the excited electrons generates reduced NADP= light energy is absorbed by photosystem I, which excited the electrons again to an even higher energy level. finally, the electrons are transferred to NADP, along with a proton (H+ ion) from the stroma, to form reduced NADP

Question 25

What is chemiosmotic theory? (chemiosmosis)

Answer 25

The process of electrons flowing down the electron transport chain and creating a proton gradient across the membrane to drive ATP synthesis

Question 26

What does cyclic photophosphorylation produce?

Answer 26

ATP

Question 27

What does cyclic photophosphorylation use?

Answer 27

Photosystem I

Question 28

Why is cyclic photophosphorylation called ‘cyclic’?

Answer 28

because the electrons from the chlorophyll molecule aren’t passed onto NADP, but are passed back to photosystem I via electron carriers. This means the electrons are recycled and can repeatedly flow through photosystem I. This process doesn’t produce any reduced NADP or oxygen- only small amounts of ATP

Question 29

What is the light-independent reaction also known as?

Answer 29

The Calvin cycle

Question 30

What is the Calvin cycle?

Answer 30

It makes triose phosphate from carbon dioxide and ribulose bisphosphate (a 5 carbon compound). Triose phosphate can be used to make glucose and other useful organic substances. There are a few steps in the cycle, and it needs ATP and H+ ions to keep it going. The reactions are linked in a cycle which means the starting compound, ribulose bisphosphate is regenerated

Question 31

Describe the Calvin cycle

Answer 31

1. Formation of glycerine 3-phosphate= carbon dioxide enters the leaf through the stomata na diffuses into the stroma of the chloroplast. Here, it’s combined with ribulose bisphosphate (RuBP). This reaction is catalysed by the enzyme rubisco. This gives an unstable 6-carbon compound, which quickly breaks down into two molecules of a 3-carbon compound called glycerate 3-phosphate (GP).
2. Formation of triose phosphate= the hydrolysis of ATP (from the light-dependent reaction) provides energy to reduce the 3-carbon compound (GP) to a different 3-carbon compound called triose phosphate (TP). This reaction also requires H+ ions, which come from reduced NADP (also from the light-dependent reaction). Reduced NADP id recycled to NADP. Some triose phosphate is then converted into useful organic compounds e.g glucose and some continues in the Calvin cycle to regenerate RuBP.
3. Regeneration of ribulose bisphosphate= five out of every six molecules of TP produced in the cycle aren’t used to make useful organic compounds, but to regenerate RuBP. Regenerating RuBP uses the rest of the ATP produced by the light-dependent reaction.

Question 32

What are hexose sugars and how are they made?

Answer 32

Simple 6-carbon sugars made by joining two molecules of triose phosphate (TP) together

Question 33

How many times does the Calvin cycle have to run to make one hexose sugar and why?

Answer 33

6. This is because 3 turns of the cycle produces 6 molecules of triose phosphate (because 2 molecules of TP are made for every 1 molecule of carbon dioxide used). 5 out of 6 of these TP molecules are used to regenerate RuBP. This means that for every 3 turns of the cycle, only 1 TP is produced that’s used to make a hexose sugar

Question 34

6 turns of the Calvin cycle need ___ ATP and ___ reduced NADP from the light-dependent reaction

Answer 34

18

12

Question 35

How do you make carbohydrates?

Answer 35

Hexose sugars made from 2 triose phosphate molecules and larger carbohydrates (e.g starch, sucrose and cellulose) are made by joining hexose sugars together in different ways

Question 36

How do you make lipids?

Answer 36

Using glycerol, which is synthesised from triose phosphate, and fatty acids, which are synthesised from glycerine 3-phosphate

Question 37

How do you make amino acids?

Answer 37

From glycerine 3-phosphate