B4 - The Processes Of Life

Question 1

What is the cytoplasm?

Answer 1

It is a gel–like substance where proteins like enzymes are made. Some enzyme–controlled reactions take place in the cytoplasm, e.g. the reactions of anaerobic respiration.

Question 2

What does the cell membrane do?

Answer 2

It holds the cell together and controls what goes in and out. It lets gases and water pass through freely while acting as a barrier to other chemicals.

Question 3

What are mitochondria?

Answer 3

These are where the enzymes needed for reactions of aerobic respiration are found, and where the reactions take place.

Question 4

What is a cell wall made of and what is its purpose?

Answer 4

It is made of cellulose. It supports the cell and strengthens it.

Question 5

What does the vacuole contain?

Answer 5

Cell sap, which is a weak solution of sugar and salts.

Question 6

What happens in chloroplasts?

Answer 6

These are where the reactions of photosynthesis take place. They contain a green substance called chlorophyll and the enzymes needed for photosynthesis.

Question 7

Name all the parts of an animal cell

Answer 7

Nucleus, cytoplasm, cell membrane, mitochondria

Question 8

Name all the parts of a plant cell

Answer 8

Nucleus, cytoplasm, cell membrane, mitochondria, cell wall, vacuole, chloroplasts

Question 9

Yeast is a single celled microorganism, name all the parts of the yeast cell

Answer 9

Nucleus, cytoplasm, cell membrane, mitochondria, cell wall

Question 10

Name all the parts of a bacterial cell

Answer 10

Cell membrane, cell wall, cytoplasm, circular DNA molecule

Question 11

In what ways are bacterial cells different to plant, animal and yeast cells?

Answer 11

They don’t have a nucleus. They have a circular molecule of DNA which floats around in the cytoplasm. They don’t have mitochondria either, but they can still respire aerobically.

Question 12

What are enzymes?

Answer 12

Proteins produced by living things

Question 13

What does the nucleus contain?

Answer 13

DNA. DNA contains the instructions for making proteins, e.g. the enzymes used in the chemical reactions of respiration.

Question 14

What do enzymes do?

Answer 14

They are proteins that speed up chemical reactions

Question 15

What is a substrate?

Answer 15

A molecule that is changed in a reaction.

Question 16

Explain the ‘lock and key’ model

Answer 16

Chemical reactions usually involve things being split apart or joined together. A substrate is a molecule that is changed in a reaction. Every enzyme molecule has an active site - the part where a substrate joins on to the enzyme. Enzymes usually only speed up one reaction because for an enzyme to work, the substrate has to be the correct shape to fit into the active site.

Question 17

How does changing the temperature affect the rate of an enzyme-controlled reaction?

Answer 17

A higher temperature increases the rate at first because the enzymes are moving faster meaning they collide with the substrates more often. But if they get too hot, some of the bonds holding the enzyme together break. This changes the shape of the enzyme’s active site and so the substrate will no longer fit and the enzyme will be unable to form the enzyme substrate complex. It is said to have denatured.

Question 18

How does changing the pH level affect the rate of an enzyme-controlled reaction?

Answer 18

All enzymes also have an optimum pH that they work best that. If the pH it too high or too low, it interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme.

Question 19

What is photosynthesis?

Answer 19

A series of chemical reactions that use energy from sunlight to produce food.

Question 20

What does photosynthesis produce?

Answer 20

Glucose (a sugar)

Question 21

Where does photosynthesis happens?

Answer 21

In the chloroplasts of plant cells. Also in some microorganisms, e.g. phytoplankton.

Question 22

What is chlorophyll?

Answer 22

A green substance which absorbs sunlight and allows the energy to be used to convert CO2 and water into glucose.

Question 23

What is the waste product of photosynthesis?

Answer 23

Oxygen

Question 24

What is the word equation for photosynthesis?

Answer 24

Light energy
Carbon dioxide + water ————-> glucose + oxygen
Chlorophyll

Question 25

What is the symbol equation for photosynthesis?

Answer 25

6CO2 + 6H2O —> C6H12O6 + 6O2

Question 26

Why are organisms that photosynthesise at the start of food chains?

Answer 26

They make energy from the sun available to other organisms by converting it to glucose. The energy is transferred when the photosynthetic organisms are eaten.

Question 27

What are the three main ways that plants use glucose?

Answer 27

Respiration, to make chemicals for growth, stored as starch.

Question 28

Happens to the glucose during respiration?

Answer 28

This process releases energy from the glucose.

Question 29

How is glucose used to make chemicals for growth?

Answer 29

Glucose is converted into cellulose for making cell walls, especially in a rapidly growing plant. Glucose is combined with nitrogen (from nitrates taken up from the soil by plant roots) to make amino acids, which are then made into proteins. Glucose is also used to help make chlorophyll.

Question 30

Where and why is glucose stored as starch?

Answer 30

Glucose is turned into starch and stored in the roots, stems and leaves. It’s used at times when the rate of photosynthesis is slower, like in the winter.

Question 31

What are the three factors that can affect the rate of photosynthesis?

Answer 31

Light intensity, CO2 concentration and temperature

Question 32

What happens to the rate of photosynthesis as the light intensity increases? Works the same way for CO2 concentration

Answer 32

As the light level is raised, the rate of photosynthesis increases steadily – but only up to a certain point. Beyond that, it won’t make any difference because then it’ll be either the temperature or the CO2 concentration which is the limiting factor.

Question 33

How does the temperature affect the rate of photosynthesis?

Answer 33

If the temperature is too low, then the rate of photosynthesis will be slower as the enzymes needed for photosynthesis work slowly at low temperatures. If the plant gets too hot, the enzymes it needs for photosynthesis will denature and the rate will drop. This happens at about 45°C.

Question 34

What is respiration?

Answer 34

A series of chemical reactions that release energy by breaking down large food molecules. It happens in every living cell.

Question 35

Give three examples of chemical reactions that happen cells which are powered by the energy released by respiration

Answer 35

Movement - Energy is needed to make muscles contract
Active transport - this process uses energy to move some substances in and out of cells
Synthesis of large molecules - large molecules (polymers) are made by joining smaller molecules together, this requires energy.

Question 36

Give two examples of the synthesis of large molecules

Answer 36

• Glucose is joined together to make things like starch and cellulose in plant cells.
• In plant cells, animal cells and microorganisms, glucose and nitrogen are joined together to make amino acids. The amino acids are joined together to make proteins.

Question 37

What are the two types of respiration?

Answer 37

Aerobic and anaerobic. Both of these types of respiration take place in animal and plant cells, and in some microorganisms.

Question 38

What is the word and symbol equation for aerobic respiration?

Answer 38

Glucose + oxygen —-> carbon dioxide + water (+ energy released)
C6H12O6 + 6O2 —-> 6CO2 + 6H2O (+ energy released)

Question 39

When does anaerobic respiration take place?

Answer 39

When there is very little or no oxygen

Question 40

Give three examples of when anaerobic respiration takes place

Answer 40

Human cells – when you do really vigourous exercise and your body can’t supply enough oxygen to your muscle cells for aerobic respiration.
Plant cells – if the soil and plants growing in becomes waterlogged there will be no oxygen available for the roots, so the root cells will have to respire anaerobically.
Bacterial cells – bacteria can get under your skin through puncture wounds. There is very little oxygen under your skin so only bacteria that respire anaerobically can survive there.

Question 41

What are the two types of anaerobic respiration and what are the word equations for them?

Answer 41

In animal cells and some bacteria anaerobic respiration produces lactic acid: glucose —-> lactic acid (+ energy released)
In plant cells and some microorganisms (like yeast), anaerobic respiration produces ethanol and carbon dioxide:
Glucose —-> ethanol + carbon dioxide (+ energy released)

Question 42

What is fermentation?

Answer 42

This is when the microorganisms break down sugars into other products as they respire anaerobically.

Question 43

Give three examples of things humans use fermentation to make

Answer 43

Biogas - MO’s ferment plant and animal waste, which contains carbohydrates, to produce methane and carbon dioxide.
Bread - yeast ferment the carbohydrates in the flour and release carbon dioxide, this causes the bread to rise.
Alcohol - yeast ferment sugar to form ethanol. The sugar used in alcohol production comes from things like grapes and barley.

Question 44

What is a transect?

Answer 44

A way of investigating how something changes across an area

Question 45

What is a light meter?

Answer 45

It’s a sensor that accurately measures light. This would be useful if you were comparing plants in areas with different levels of light.

Question 46

Is a quadrat?

Answer 46

A square frame divided into a grid of 100 smaller squares. You could use this to estimate the percentage cover of a species on the ground by counting how much of the quadrat is covered by the species – you count a square if it is more than half covered.

Question 47

What is an identification key?

Answer 47

It’s a series of questions that you can use to figure out what a plant is. You start at question one and the answer is used to narrow down the options of what the plant could be. As you answer more and more questions you’re eventually just left with one possible species your could be.

Question 48

What is diffusion?

Answer 48

The passive movement of particles from a region of their higher concentration to a region of their lower concentration.

Question 49

Give a natural example of when diffusion happens

Answer 49

When plants photosynthesise they use up CO2 from the atmosphere and produce O2. These gases pass in and out of plant leaves by diffusion.

Question 50

What is osmosis?

Answer 50

The overall movement of water from a dilute to a more concentrated solution through a partially permeable membrane.

Question 51

What is a partially permeable membrane? Give an example

Answer 51

A membrane that only allows certain substances to defuse through it. For example, it may only allow smaller molecules like water to pass through it and not larger molecules like sucrose.

Question 52

How do plants take in water?

Answer 52

Through osmosis. There is usually a higher concentration of water in the soil than there is inside the plant, so the water is drawn into the root by osmosis.

Question 53

What is active transport?

Answer 53

The overall movement of chemicals across a cell membrane from a region of low concentration to a region of high concentration using energy released by respiration.

Question 54

Give an example of active transport

Answer 54

Plants take in minerals like nitrates through their roots by active transport. The concentration of minerals in root cells is normally higher than in the soil around them. Active transport uses energy from respiration to move minerals from the soil into the root cells.