B1 - Cell Structure and Transport

Question 1

How do you calculate magnification?

Answer 1

magnification = size of image / size of object

Question 2

What is the role of the nucleus?

Answer 2

Controls all activities of the cell, contains genes to build proteins.

Question 3

What is the role of the cytoplasm?

Answer 3

Liquid gel where most essential reactions take place.

Question 4

What is the role of the cell membrane?

Answer 4

Controls passage of glucose, mineral ions, urea and hormones in/out of the cell.

Question 5

What is the role of the mitochondria?

Answer 5

Structures where aerobic respiration takes place.

Question 6

What is the role of the ribosomes?

Answer 6

Where protein synthesis takes place to make all the protein required in the cell.

Question 7

What is the role of the chloroplasts?

Answer 7

Contain substance chlorophyll that absorbs light so food can be made by photosynthesis.

Question 8

What is the role of the vacuole?

Answer 8

A space filled with sap, to keep cells rigid to support the plant.

Question 9

What characteristics do eukaryotic cells have?

Answer 9

A cell membrane, cytoplasm, genetic material in a nucleus.

Question 10

What characteristics do prokaryotic cells have?

Answer 10

Cytoplasm, cell membrane surrounded by cell wall, genetic material not in distinct nucleus.

Often contain rings of DNA called plasmids for specific features like antibiotic resistance.

Question 11

How are nerve cells specialised for their purpose?

Answer 11

• Lots of dendrites to connect to other cells.
• Axon is extremely long for largest possible distance travelled.
• Chemicals used to transfer information between cells.

Question 12

How are muscle cells specialised for their purpose?

Answer 12

• Special proteins slide over each other to make fibres contract.
• Contain many mitochondria to transfer energy needed to contract and relax muscle.
• Store glycogen to help transfer energy when needed.

Question 13

How are sperm cells specialised for their purpose?

Answer 13

• Long tail whips from side to side to move through reproductive system.
• Middle section full of mitochondria to power tail.
• Acrosome stores digestive enzymes for breaking down outer layers of egg.
• Large nucleus contains genetic material to be passed on.

Question 14

How are root hair cells specialised for their purpose?

Answer 14

• Have large surface area for water to move into cell.
• Have large vacuole the improves efficiency by osmosis.
• Have many mitochondria that transfer energy needed for active transport.

Question 15

How are photosynthetic cells specialised for their purpose?

Answer 15

• Lots of chloroplasts containing chlorophyll to trap sunlight and produce energy.
• Positioned in layers in the leaves so they absorb as much light as possible.
• Large vacuole keeps cell rigid to support stem.

Question 16

How are xylem cells specialised for their purpose?

Answer 16

(Carry water and mineral ions from roots to leaves)

• Cells alive but quickly die to form long hollow tubes that allow mineral ions to move easily through.
• Spirals of lignin keep tubes strong and helps withstand pressure of water moving in plant and support the stem.

Question 17

How are phloem cells specialised for their purpose?

Answer 17

(Carry food made by photosynthesis around plant body)

• Cell walls between cells break down to form sieves that allow food-carrying water to move around the plant.
• Supported by additional companion cells that keep structure in shape and provide energy to move food.

Question 18

What is diffusion?

Answer 18

The spreading out of particles from an area of high concentation to an area of low concentration, down a concentration gradient.

Question 19

What effects the rate of diffusion?

Answer 19

Difference in concentration, temperature, surface area.

Question 20

How are many cells specialised to increase diffusion rates?

Answer 20

Folds in the membrane form villi, which increase surface area and increase diffusion rate.

Question 21

What is osmosis?

Answer 21

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

Question 22

What do the terms isotonic, hypertonic and hypotonic mean?

Answer 22

Isotonic - concentrations inside and outside the cell are equal.
Hypertonic - concentrations outside cell are higher than inside cell.
Hypotonic - concentrations outside cell are lower than inside cell.

Question 23

How can osmosis be an issue for some cells?

Answer 23

If solution outside cell becomes hypertonic, water will move out of the cell, causing the cell to shrivel up.

Similarly, if solution outside cell becomes hypotonic, water will move into the cell, causing the cell to inflate and burst.

Question 24

How is osmosis utilised in plant cells?

Answer 24

Water moves into a cell by osmosis, and moves into a vacuole. The vacuole expands, eventually taking up most of the cell, to the point that water can no longer physically enter the cell.

The vacuole then supports the cell, keeping the stem and leaves of the plant rigid.

If too much water leaves the cell, the vacuole shrinks, and eventually the cell membrane is pulled away from the cell wall - plasmolysis.

Question 25

What is active transport?

Answer 25

Substances moved by a cell across a membrane against a concentration gradient - low concentration to high.

Question 26

Why is active transport needed?

Answer 26

Allows plant root hairs to absorb nutrients from soil that are required for healthy growth.

Allows sugar molecules to be absorbed in the gut to the blood, where there is high sugar concentration.

Effectively feeds itself - puts sugar into cell, sugar turned into energy, energy used on active transport.

Question 27

What adaptations do large organisms have to improve efficiency of material exchange?

Answer 27

• Using specific exchange surfaces to exchange materials.
• Large surface areas with thin walls for short diffusion distance.
• Efficient blood supply for fast diffusion.