B4- The processes of life

Question 1

What are the extra things that plant cells have?

Answer 1

• Rigid cell walls- made of cellulose. It supports and strengthens the cell.
• Vacuole- contains cell sap- a weak solution of sugar and salts.
• Chloroplasts- these are where the reactions for photosynthesis take place. They contain a green substance called chlorophyll and the enzymes needed for photosynthesis.

Question 2

What do yeast cells have?

Answer 2

• Yeast are used to make bread and wine. They have the following parts in the cell;

• Cell membrane
• Cytoplasm
• Nucleus
• Mitochondria
• Cell wall

Question 3

What do bacteria cells have?

Answer 3

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

These are the parts in their cell;

• Cell membrane
• Cell wall
• Cytoplasm
• Circular DNA molecule

Question 4

What are enzymes?

Answer 4

Enzymes are proteins that speed up chemical reactions.

The instructions for making enzymes and other proteins are found in a cells genes.

Question 5

How are enzymes specific?

Answer 5

• Chemical reactions involve things being split apart or joined together.
• A substrate is a molecule that is changed in a reaction.
• Every enzyme has an active site- the part where a substrate joins on to the enzyme.
• Enzymes usually speed up one reaction. This is because for an enzyme to work a substrate has to be a correct shape to fit into the active site.
• Thus the name “lock and key” model.

Question 6

Why do enzymes need the right temperature and ph?

Answer 6

• Enzymes need to be at a specific constant temperature to work at their optimum (when their most active).
• Changing the temperature changes the rate of an enzyme controlled reactions.
• A higher temperature increases the rate at first.
• But if it gets too hot the bonds holding the enzyme together break. This changes the shape of the enzymes active site so the substrate no longer fits. So the enzymes doesn’t work anymore. This is called denatured.
• All enzymes have an optimum Ph they work best at.
• If the Ph is too high or too low it interferes with the bonds holding the enzymes together. This changes the shape of the active site and the enzyme is denatured.

Question 7

What is respiration?

Answer 7

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

Question 8

What does the energy released help us to do?

Answer 8

The energy released by respiration is used to power some of the chemical reactions that happens in cells- they involve;

• 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- lots of large molecule (polymers) are made by joining smaller molecules together- this requires energy.

For example, glucose is joined together to make 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 9

What is aerobic respiration?

Answer 9

• “Aerobic” means “with oxygen”.
• It releases more energy per glucose molecule than anaerobic respiration.
• We use this type of respiration the most.
• Aerobic respiration takes place in animal and plant cells and in some microorganisms.

Question 10

What are the similarities between plant and animal cells?

Answer 10

• Nucleus- contains DNA which contains instructions for making proteins (e.g. Enzymes used in chemical reactions of respiration- in animal & plants cells) and photosynthesis (in plants cells only).
• Cytoplasm- A substance where proteins like enzymes are made. Some enzyme controlled reactions take place in the cytoplasm. (E.g. The reactions of anaerobic respiration)
• Cell membrane- holds the cells together and controls what goes in and out. It lets water and gases pass through freely while acting as a barrier to other chemicals.
• Mitochondria- these are where the enzymes needed for the reactions of aerobic respiration are found and where the reactions take place.

Question 11

What is the word and symbol equation for aerobic respiration?

Answer 11

glucose + oxygen → carbon dioxide + water (+ energy)

C6H12O6 + 6O2 → 6CO2 + 6H2O

Question 12

What is anaerobic respiration?

Answer 12

• “Anaerobic” means “without oxygen”.
• Anaerobic respiration takes place in animal and plant cells and some microorganisms when there’s little or no oxygen.

For example:

• when you do vigorous exercise your body can’t supply enough oxygen to your muscle cells for aerobic respiration- so thy respire anaerobically.
• if the soil a plant growing in becomes waterlogged there will be no oxygen available for he roots. So the root cells respire anaerobically.
• bacteria can get under your skin through puncture wounds caused by things like nails. There is little oxygen under your skin so only bacteria that can respire anaerobically survive.

Energy is always released during anaerobic respiration. But products of the reaction are different depending on the type of cell it happens in.

Question 13

What is the word equation for anaerobic respiration producing lactic acid?

Answer 13

In animal cells and some batterie anaerobic respiration produces lactic acid:

Glucose→ lactic acid (+energy released)

Question 14

What is the word equation for anaerobic respiration producing CO2?

Answer 14

In plants cells and some microorganisms (like yeast) anaerobic respiration produces ethanol and carbon dioxide;

Glucose→ethanol+carbon dioxide (+energy released)

Question 15

What is fermentation?

Answer 15

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

Question 16

How can humans fermentation?

Answer 16

• Biogas-a fuel used for things like heating and lighting-different microorganisms produce biogas- they ferment plant and animal waste which contains carbohydrates- biogas produced is made of CO2 and methane.
• Bread- made using yeast- the yeast ferment the carbohydrates in the flour and release CO2 this causes bread to rise.
• Alcohol- yeast ferment sugar to form alcohol (ethanol)- the sugar used in alcohol production comes from grapes (to make wine) and barley (to make barley)

Question 17

What is photosynthesis?

Answer 17

Photosynthesis is a series of chemical reactions that uses energy from sunlight to produce food.

Question 18

Facts about photosynthesis?

Answer 18

• the “food” it produces is glucose- a sugar.
• photosynthesis happens in:
• the cells in green parts of plants (e.g. Leaf cells)
• some microorganisms (e.g. Phytoplankton)
• chlorophyll is needed to make photosynthesis happen- it is the green substance which absorbs sunlight an allows energy to be used to convert CO2 and water into glucose.
• Oxygen is produced as a waste product of photosynthesis.
• Organisms that photosynthesise from the start of food chains. They make the energy from the sun available to other organisms by converting it to glucose. The energy is transferred when the photosynthetic organisms are eaten.

Question 19

Word equation for photosynthesis?

Answer 19

carbon dioxide + water (+ light energy) → glucose + oxygen

Question 20

How do plants use glucose?

Answer 20

• Respiration- plants use glucose for respiration- this process releases energy from the glucose.
• Chemicals for growth- glucose is converted to cellulose for making cell walls- glucose is combined with nitrogen (nitrates from the soil) to make amino acids which are made into proteins- glucose helps make chlorophyll.
• Stored as starch- glucose is turned into starch and stored in roots,leaves and stems. It is used at times when photosynthesis is slow (like at winter)

Question 21

Why factors affect photosynthesis?

Answer 21

• amount of light
• amount of carbon dioxide (CO2)
• temperature

Question 22

How do environmental changes affect photosynthesis?

Answer 22

• At night- light is the limiting factor.
• In winter it is the temperature.
• If it’s warm enough and bright enough the amount of CO2 is usually limiting.

Question 23

1st graph on the rate of photosynthesis?

Answer 23

• Light provides the energy needed for photosynthesis.
• As the light level is raised the rate of photosynthesis increases steadily - up to a certain point.
• Beyond that, CO2 or temperature is a limiting factor.

Question 24

2nd graph on the rate of photosynthesis?

Answer 24

• CO2 is one of the raw materials needed for photosynthesis.
• As the amount of CO2 increases so does the rate of photosynthesis. After that, the line flattens showing that CO2 is no longer a limiting factor.
• As long as light and CO2 are in plentiful supply then the factor limiting photosynthesis is temperature.

Question 25

3rd graph on the rate of photosynthesis?

Answer 25

• If temperature is a limiting factor then it’s usually too low- the enzymes needed for photosynthesis work slow in low temperatures.
• If the plant is too hot the enzymes needed for photosynthesis become denatured.
• This happens at about 45 degrees Celsius.

Question 26

What are transects?

Answer 26

• They are a way of investigating how something changes across an area.
• To set up a transect you run a tape measure between two fixed points.
• Then you start at one end of the transect and collect the data you want.
• Then move along the transect and collect the data again. You keep collecting until you reach the end of the transect.

Question 27

What is a light meter?

Answer 27

You need to measure the level of light. It’s a sensor that accurately measures light level.

Question 28

What is a quadrat?

Answer 28

To collect data more quickly and easily you could use a quadrat.

It’s a square frame divided into a grid of 100 smaller squares.

Question 29

What’s a identification key?

Answer 29

It’s a series of questions that helps you figure out what different things your investigating.

You start at question one and the answer is used to narrow down your options of what you could be investigating.

As you answer more and more questions you are left with one thing that you have discovered during the investigation.

Question 30

What is diffusion?

Answer 30

Diffusion is the passive overall movement of particles from a region of their higher concentration to a region of their lower concentration.

Question 31

What is osmosis?

Answer 31

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

• A permeable membrane only allows certain substances to diffuse through it. For example, it only allow small water molecules to pass and not large molecules like solute.
• Plants take in water by osmosis. There’s usually a higher concentration of water in the soil than there is inside plants. So water is drawn in through the roots by osmosis.

Question 32

What is active transport?

Answer 32

Active transport is the overall movement of chemicals across a cell membrane from a region of lower concentration to a region of higher concentration using energy released by respiration.