B4

Question 1

What processes do all living things Perform?

Answer 1

1) Movement
2) Respire
3) Sense
4) Feed
5) Excrete
6) Reproduce
7) Grow

Question 2

What process creates energy for living cells?

Answer 2

• biological chemical factory in the cytoplasm of every plant cell
• takes small molecules and builds them into large molecules
• uses chemical reactions to build itself, copy itself, and repair itself
• It takes large food molecules and breaks these down to release energy in respiration

Question 3

What’s used to grow bacteria?

Answer 3

1)Large vessels- fermenter
used to grow bacteria enzymes can be harvested
2)contain a nutrient solution
conditions such as temperature, pH, and oxygen levels controlled for optimum growth
3)As bacteria grow, they release enzymes into the nutrient solution
4)When nutrients used up solution filtered to remove the bacteria
5)required enzymes can be purified from solution
6)now available for use in applications such as food industry, textiles industry, and in the home as biological washing powders

Question 4

What are enzymes made Of?

Answer 4

1) They are proteins
2) large molecules made up of long chains of amino acids
3) The amino acid chains are different in each protein, so they fold up into different shapes
4) An enzyme’s shape is very important to how it works
5) The sequence of amino acids in each enzyme is determined by instructions in a gene

Question 5

What do enzymes do?

Answer 5

Enzymes are the catalysts that speed up chemical reactions in living organisms

Question 6

How do enzymes work?

Answer 6

1) Some enzymes break down large molecules into smaller ones
2) Others join small molecules together
3) In all cases, the molecules must fit exactly
into a part of the enzyme called the active site

Question 7

What does Amylase do?

Answer 7

The enzyme amylase breaks down starch to sugar (maltose);

Question 8

What does catalase do?

Answer 8

catalase breaks down hydrogen peroxide to water and oxygen

Question 9

Why can’t catalase break down starch?

Answer 9

An enzyme has an active site.
2The reaction takes place in the active site
Only the correct molecule fits
into the active site
4The product leaves the active site
The enzyme can be used again

Question 10

Why do we need enzymes?

Answer 10

At 37 °C, chemical reactions in your body would happen too slowly to keep you alive
One way of speeding up a reaction is to increase the temperature
A higher body temperature could speed up the chemical reactions in your body
But higher temperatures damage human cells
Also, to keep your body warm you have to release energy from respiration
For a higher body temperature you would need a lot more food to fuel respiration
So, we rely on enzymes to give us the rates of reaction that we need
They can increase rates of reaction by up to 10 000 000 000 times. It is not possible to live without enzymes.

Question 11

How does temperature effect enzymes?

Answer 11

At low temperatures, enzyme reactions get faster if the temperature is increased
But above a certain temperature the reaction stops
This is because enzymes are proteins
Higher temperatures change an enzyme’s shape so that it no longer works

At 37 °C the molecule fits into the enzyme’s active site.

The active site has been changed by heating the enzyme above 40 °C.

The molecule no longer fits the enzyme, so no reaction can take place.

Question 12

Why does increasing the temperature cause enzyme reactions to stop at higher temperatures?

Answer 12

High temperatures change the shape of an enzyme. They do not destroy it completely. But even when an enzyme cools down, it does not go back to its original shape. Like cooked egg white, the protein cannot be changed back. The enzyme is said to be denatured.

Question 13

What is meant by an enzymes optimum temperature?

Answer 13

The temperature at which an enzyme works best is called its optimum temperature. Enzymes in humans work best at around 37 °C. Some organisms have cells and enzymes adapted to different temperatures.

Question 14

How does PH affect enzymes?

Answer 14

Proteins including enzymes can be damaged by acids and alkalis. The shape of an enzyme’s active site will be changed if bonds holding the protein chains together are broken. The substrate will no longer be able to fit, so the enzyme becomes denatured. Every enzyme has an optimum pH at which it works best.

Question 15

What is salivary amylases optimum PH?

Answer 15

4.8

Question 16

What is Pepsins optimum PH?

Answer 16

2.0

Question 17

What is catalaysed optimum PH?

Answer 17

7.6

Question 18

What is photosynthesis?

Answer 18

During photosynthesis, plants trap energy from sunlight and use it to make all the molecules they need for growth. These include sugars, starch, enzymes, and chlorophyll. These molecules feed other organisms along the food chain. So photosynthesis supplies food for life on Earth.

Question 19

What’s the chemical equation for photosynthesis?

Answer 19

The chemical equation for photosynthesis is:

                                  LIGHT ENERGY 6CO2  (carbon dioxide)------------>C6H12O6
\+                                  chlorophyll     glucose 6H2O (Water)      +6O2 (Oxygen)

Question 20

What is glucose made up of?

Answer 20

A glucose molecule is made up of carbon, hydrogen, and oxygen atoms. So glucose is a carbohydrate.

Question 21

Where does photosynthesis take place?

Answer 21

Photosynthesis takes place in chloroplasts. They contain a green pigment called chlorophyll. Chlorophyll absorbs light and uses the energy to kick-start photosynthesis.

Question 22

What happens during photosynthesis?

Answer 22

Energy from light splits water molecules into hydrogen and oxygen atoms. The hydrogen is combined with carbon dioxide from the air to make glucose. The oxygen is released as a waste product. It passes out of the plant into the air. Given enough raw materials, light, and the right temperature, a large tree can make 2000 kg of glucose in a day.

Question 23

What are the three ways glucose made during photosynthesis is used?

Answer 23

(1)Glucose is converted into other carbohydrates, as well as fats and proteins.Two important carbohydrates in plants are cellulose and starch. Cellulose and starch are both polymers of glucose. They are made up of thousands of glucose molecules linked together.

Question 24

What is diffusion?

Answer 24

Molecules in gases and liquids move about randomly. They collide with each other and change direction. This makes them spread out.
Overall, more molecules move away from where they are concentrated than move the other way. The molecules diffuse from areas of their high concentration to areas of low concentration.

Question 25

What are stomata's?

Answer 25

The underside of a leaf contains thousands of tiny holes called stomata. These allow carbon dioxide into the leaf and oxygen out. Diffusion drives these gases from high to low concentrations.

Question 26

What's a xylem?

Answer 26

Vessels that transport water and minerals to leaves

Question 27

What's a phloem?

Answer 27

Transports sugars made in photosynthesis to other parts of the plant

Question 28

What is osmosis?

Answer 28

Osmosis is a specific type of diffusion. It is the process that moves water molecules into and out of cells. The cell membrane is important in osmosis.

Question 29

What does partially permeable mean?

Answer 29

Cell membranes let some molecules through but block others. Tiny channels in the membrane allow small molecules, like water, to travel through them. Larger molecules are too big and cannot get through. Cell membranes are partially permeable membranes.

Question 30

What is dilute and concentrated?

Answer 30

A solution with a high concentration of water molecules that are free to move is a dilute solution. For example, if you make a dilute drink of squash, it has lots of water in it. A more concentrated solution of squash would have fewer free water molecules.

Question 31

What happens with division in plants?

Answer 31

Plants do not have skeletons to give them support. They must keep their structure by having cells that are just the right size and shape. Osmosis is important in this. It drives the uptake of water by plant roots and determines how water passes from one cell to another throughout the whole plant. If plant cells take in too much water, they bulge and become stretched. Their strong cell wall prevents them from bursting. If plant cells lose too much water, they shrink. Plant cells need to keep just the right amount of water inside their cytoplasm. Look at the two pictures on the right to see what happens to a plant if it does not have enough water.

Question 32

Why is starch needed to store glucose in plant cells?

Answer 32

Plants make glucose during photosynthesis. The glucose is transported from the leaves to other cells where it is stored until it is needed for respiration. This poses a problem for the plant cells that store the glucose. They will take in too much water by osmosis. The water would move from a dilute solution surrounding the cells into the more concentrated glucose solution in the cells. To overcome this problem, glucose is stored as starch. Large carbohydrates like starch are insoluble. They have very little effect on the concentration of the solutions in a plant cell. This makes them ideal for storing glucose. The starch does not affect the movement of water in and out of the cells. Starch is kept in small, membrane-bound bags in the cell called starch grains.

Question 33

Why is nitrogen needed to make proteins?

Answer 33

Proteins are long chains of amino acids. To make amino acids, nitrogen must be combined with carbon, hydrogen, and oxygen atoms from glucose made during photosynthesis. Most of the Earth’s nitrogen is in the air, but plants mainly take in nitrogen from the soil as nitrate ions. These nitrates are absorbed by root hair cells. Nitrates are not the only minerals that plants need. For example, they need magnesium to make chlorophyll and phosphates to make DNA. As proteins are used to build cells and make enzymes, nitrates are needed in the largest quantities. Fertilisers contain minerals such as phosphates and nitrates.

Question 34

Why do cells sometimes need to use active transport?

Answer 34

Plant roots absorb nitrate ions dissolved in water in the soil. Nitrate ions are at a higher concentration inside the root cells than in the surrounding soil. Diffusion would move the nitrate ions out of the roots and into the soil. To overcome this, the cells use a process called active transport to pump nitrates from the soil and into the roots.

Question 35

What is active transport?

Answer 35

When a cell needs to take in molecules that are in higher concentration inside the cell than outside, active transport is used. In active transport, cells use the energy from respiration to transport molecules across the membrane. An example of active transport is where nitrates are taken into plant roots against their diffusion gradient.