B1

Question 1

Why do some people think structures found in eukaryotic cells such as chloroplasts and mitochondria may have originally been free-living bacteria?

Answer 1

Bacteria are 1 to 2 order of magnitudes smaller than eukaryotic cells
This is about the same size as chloroplasts and mitochondria
They contain their own genetic information like bacteria cells
So can reproduce independently of the cell dividing

Question 2

What happens when water moves into a cell by osmosis and the cell expands?

Answer 2

The cell wall prevents the cell from bursting and the cell becomes turgid (swollen)

Question 3

What happens when a water diffuses out of the cell?

Answer 3

The cell shrinks and becomes flaccid. If even more water is lost, the vacuole and cytoplasm will shrink and eventually the cell membrane pulls away from the cell wall: this ix plasmolysis.

Question 4

equation for magnification

Answer 4

size of image/ size of real object

Question 5

What is the nucleus?

Answer 5

controls all the activities within a cell and contains the genes on chromosomes that carry the instructions for making the proteins needed to build new cells

Question 6

What is a ribosome?

Answer 6

Where protein synthesis takes place, making all the proteins needed in the cell

Question 7

Is bacteria a prokaryote or eukaryote?

Answer 7

Prokaryote

Question 8

adaptions of the nerve cell? (3)

Answer 8

1. lots of dendrites to make connections to other cells
2. An axon that carries the nerve impulse from one place to another
3. nerve endings or synapses are adapted to pass the impulses to another cell or between a nerve cell and a muscle in the body using neurotransmitters

Question 9

Adaptions of a muscle cell? (3)

Answer 9

1. contain special proteins that slide over eachother, making the fibres contract
2. contain many mitochondria to transfer the energy needed for the chemical reactions that take place as the cells contract and relax
3. can store glycogen

Question 10

Adaptions of the sperm cell? (4)

Answer 10

1. a long tail whips from side to side to help move the sperm through water or the female reproductive system
2. middle section is full of mitochondria, which transfer energy needed for the tail to work
3. acrosome (tip of head) stores digestive enzymes for breaking down the outer layers of the egg
4. a large nucleus contains the genetic information to be passed on

Question 11

Adaptions of the root hair cell? (3)

Answer 11

1. greatly increase surface area available for water to move into the cell
2. have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell
3. have many mitochondria that transfer the energy needed for the active transport of mineral ions into the root hair cells

Question 12

Adaptions of photosynthetic cells? (3)

Answer 12

1. contain many chloroplasts containing chlorophyll which traps light needed for photosynthesis
2. usually positioned in continuous layers in the leaves and outer layers of the stem of a plant do the absorb as much light as possible
3. large permanent vacuole the keeps the cell rigid as a result of osmosis

Question 13

Adaptions of xylem cells? (2)

Answer 13

1. alive when first formed but lignin builds up in spirals in the cell walls and the cells die to form long hollow tubes that allow water and mineral ions to move easily through them
2. spirals and rings of lignin make them very strong and help them withstand the pressure of water moving up the plant

Question 14

Adaptions of phloem cells? (2)

Answer 14

1. cell walls between the cells break down to form sieve plates that allow water carrying dissolved minerals to move freely up and down the tubes where it is needed
2. They loose a lot of their internal structures but are supported by companion cells that help keep them alive as the mitochondria on the companion cells transfer the energy needed to move dissolved food up and down the plant in phloem

Question 15

Define diffusion

Answer 15

The spreading out of particles of any substance in a solution or a gas, resulting in a net movement from an area of high concentration to an area of lower concentration, down a concentration gradient

Question 16

Describe the structure of a prokaryotic/ bacterial cell:

Answer 16

1. much smaller than eukaryotic cells
2. they have cytoplasm and a cell membrane surrounded by a cell wall
3. The genetic material is not enclosed in a nucleus
4. The genetic information is in a single DNA loop and there may be one or more strings of DNA called plasmids

Question 17

Give the steps for the microscope practical:

Answer 17

1. place side onto the stage and use the clips to hold it in place
   
   2. Select the lowest power objective lens (usually 4x)
   3. Position objective lens so it almost touches microscope slide - slowly turn coarse focusing dial
   4. Look at microscope from side when we position it
   5. Slowly turn coarse focusing dial until focuses
   6. Use fine focus dial to bring into clear focus
   7. Magnification of eye piece (10x) * lowest objective lense (4x) = 40x
   8. Can change to larger objective lens
   9. Make pencil to make clear label drawing of some cells
      Show magnification scale

Question 18

Define osmosis

Answer 18

The diffusion of water molecules, from a region where the water molecules are in higher concentration, to a region where they are in lower concentration, through a partially permeable membrane.

Question 19

If a cell is placed in an isotonic solution, what will happen?

Answer 19

The cell will stay the same size

Question 20

If a cell is placed in a hypertonic solution, what will happen?

Answer 20

Water will move out of the cell to an area of lower concentration of water by osmosis, causing the cell to become shrivelled

Question 21

If a cell is placed in a hypotonic solution, what will happen?

Answer 21

Water will move into the cell from an area of high water concentration to an area of low water concentration, causing the cell to expand and burst

Question 22

What is turgor?

Answer 22

the force within the cell that pushes the plasma membrane against the cell wall due to the vacuole swelling as water moves into the plant cell

Question 23

Does the fluid surrounding a plant cell need to be hypertonic, isotonic or hypotonic to the cytoplasm?

Answer 23

Hypotonic because water keeps moving into the cell by osmosis and the cell becomes turgid.

Question 24

What is it called when the cell wall is no longer firm and swollen due to reduced pressure on the cell walls?

Answer 24

Flaccid

Question 25

Define active transport

Answer 25

Active transport is the movement of dissolved molecules into or out of a cell through the cell membrane, from a region of lower concentration to a region of higher concentration. The particles move against the concentration gradient, using energy released during respiration.

Question 26

Give examples of two body processes that active transport enables:

Answer 26

1. plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil against a concentration gradient
2. Enables sugar molecules used for cellular respiration to be absorbed from lower concentration in the gut into the blood where the concentration of sugar is higher

Question 27

Adaptions that an animal could have to make the exchanging of materials more efficient: (4)

Answer 27

1. having a large surface area over which exchange can take place
2. Having a thin membrane or being thin to provide a short path of diffusion
3. having an efficient blood supply moves the diffusing substances away from the exchange surfaces and maintains a steep concentration gradient
4. Being ventilated (breathing)