Cell Requirements

Question 1

What is an autotroph?

Answer 1

An organism that produces their own food.

Plants, algae, cyanobacteria.

Question 2

What is a heterotroph?

Answer 2

An organism that cannot produce its own food and must consume other plants/animals.

Humans, animals.

Question 3

How does the structure of chloroplast ensure that the process of photosynthesis operates efficiently?

Answer 3

Chloroplasts posess numerous membranous discs. These flattened discs increase the surface area in which photosynthesis reactions can occur.

Question 4

How does the structure of mitochondria ensure that the processes of cellular respiration operate efficiently?

Answer 4

The inner membrane of mitochondria is folded and increases the surface area in which cellular respiration can occur.

Question 5

Why is water needed in cells?

Answer 5

It is a reactant in photosynthesis, solvent where chemical reactions occur in cytoplasm. (+more).

Question 6

Why is CO2 needed by cells?

Answer 6

Required for photosynthesis in plant cells.

Question 7

Why is oxygen needed by cells?

Answer 7

Cellular respiration.

Question 8

Why is nitrogen needed in cells?

Answer 8

It is a component of amino acids, proteins and DNA.

Question 9

Why are amino acids, fatty acids and nucleotides needed in cells?

Answer 9

Protein synthesis, lipids and nucleic acids.

Question 10

How is ammonia formed?

Answer 10

• Amino acids come from protein.
• When amino acids are broken down, they produce amino groups.
• Amino groups are converted to ammonia.
  This process is energy intensive (uses a lot of energy) but urea is slightly less toxic and can be stored for longer periods of time.

Question 11

Give some qualities about ammonia.

Answer 11

1. Highly toxic.
2. Highly soluble.
3. Highly alkaline.
4. Needs plenty of water to dilute out.

Question 12

List the ways in which diff organisms excrete ammonia.

Answer 12

1. Aquatic organisms, mostly bony fish: have plently of water, can excrete as ammonia.
2. Mammals, amphibians and sharks have less water, so they excrete as urea.
3. Birds, most insects and reptiles do not have large amounts of water, so they excrete as uric acid.

Question 13

Which organ usually breaks down amino acids and produce ammonia as a waste product?

Answer 13

The liver!

Question 14

Describe how ammonia leaves the body.

Answer 14

The liver converts ammonia into urea which enters the bloodstream. Once in the bloodstream, the urea is removed by the kidneys and leaves the body via the excretory system.

Question 15

What are the key roles of the kidneys?

Answer 15

• Removing urea and toxins from blood.
• Maintaining salt and water balance.
• Maintaing the pH of the blood.

Question 16

What is the structure of the kidney?

Answer 16

The kidney structure is made up of around 1 million filtering units called nephrons, which have blood vessels wrapped around them.

Question 17

List the three other wastes, how they are produced and how they are removed.

Answer 17

1. Water - Produced through drinking and the product of metabolic reactions. Removed through urination and sweat.
2. Metabolic heat - produced as a product of metabolic reactions. Removed through the skin.
3. Oxygen (plants)- waste product of photosynthesis. Released into air through pores.

Question 18

What happens to the SA:V ratio as you increase the size of something? How can this be prevented?

Answer 18

As you increase the the size of something you are also increasing its volume, but as a result, you are decreasing the surface area to volume ratio. This can be prevented if you split the object into smaller pieces.

Question 19

Why is it a problem when the SA:V ratio is too low?

Answer 19

Because, as the cell grows, metabolic waste accumulate in the cytoplasm, the quantity of waste produced is proportional to the volume of the cell. The cell must remove its wastes by diffusion or active transport across its cell membrane. Hence the removal of waste is limited by the surface area of the cell.

Additionally, the cell also needs to take nutrients to support the growth of the cell. The uptake of nutrients, via passive and active transport is also limited by the surface area of the cell.

Question 20

What are some things that change the SA:V ratio of a cell?

Answer 20

• Having an elongated shape.
• Having extensions of the cell.
• The cell dividing up into compartments.
• Changing its shape entirely.

Question 21

Which organ systems are important for removing waste?

Answer 21

The excretory system, respiratory system and circulatory system.

Question 22

How are organ systems made?

Answer 22

Specialised cells are group together to form tissues. Tissues are grouped together to form organs. Organs with similar functions are grouped together to form organ systems.