Cell Organisation,Diversity,Specialisation

Question 1

what are the stages in the cell cycle?

Answer 1

1. Interphase (G1, S, G2 phase)
2. Mitosis
3. Cytokinesis

Question 2

What happens in the G1 phase?

Answer 2

cell growth

Question 3

What happens in the s-phase?

Answer 3

DNA synthesis

Question 4

What happens in G2 phase?

Answer 4

cell growth continues and special proteins are synthesised.

Question 5

What is G0 also known as?

Answer 5

cell death

Question 6

Outline the first stage of mitosis

Answer 6

Prophase

. Chromosomes become visible.

. Centrioles split and move to opposite ends of the cell.

. The nuclear envelope disintegrates

Question 7

outline the second stage of mitosis

Answer 7

Metaphase

. Spindle formed, and a near broken nuclear envelope.

. The nuclear envelope is completely gone.

. The spindle fibres attach to the chromosomes

. The chromosomes line up at the equator.

Question 8

third stage of mitosis

Answer 8

Anaphase

. The chromosomes break apart at the centromere.

Question 9

fourth stage of mitosis

Answer 9

Telophase

. The chromatids reach opposite poles of the cell.

. The nuclear envelope reforms around the chromosomes.

. The cell prepares to split the cytoplasm and its contents.

Question 10

what is the final step of mitosis?

Answer 10

Cytokinesis

. Cytokinesis is the final step of mitosis.

. Each daughter cell will be identical to each other and their parent cell.

Question 11

why is mitosis significant in life cycles?

Answer 11

1. growth
2. repair tissue
3. aesexual reproduction

Question 12

what happens in interphase for meiosis?

Answer 12

1. S phase – DNA replication
2. Growth phase (G1 + G2) – new proteins and organelles are made

Question 13

what happens in meiosis I ?

Answer 13

. Two diploid daughter cells.

. Crossing over occurs in meiosis I.

. Two diploid daughter cells are produced.

Question 14

what happens in prophase II ?

Answer 14

If the nuclear envelope was re-made after telophase I, it will break down again.

The nucleolus disintegrates, the chromosomes condense and spindles are made.

Question 15

what happens in metaphase II ?

Answer 15

The chromosomes line up in the centre (equator) and bind to the spindle fibres at the centromeres.

The chromatids of each chromosome are independently assorted (see later).

Question 16

what happens in anaphase II ?

Answer 16

The spindle fibres pull the chromatids to opposite ends of the cell. The centromere divides.

Question 17

outline how to prepare a root tip cell squash?

Answer 17

1. Warm hydrochloric acid.
2. Cut 1-2 cm of root tip from a growing root.
3. Wash the root tips.
4. Transfer the root tip to the warm acid.
5. Remove from acid, and wash the root tips.
6. Place the root tip on a slide.
7. Stain the root tip.
8. Break open the root tip.
9. Cover with a coverslip over the stained root tip.
10. View the tips using a microscope.

Question 18

what happens in telophase II ?

Answer 18

In each cell, two nuclear envelopes will develop to form two haploid nuclei.

The two cell divide by cytokinesis to produce four haploid daughter cells.

Question 19

why is meiosis significant in life cycles ?

Answer 19

1. Production of haploid cells
2. Genetic variation by independent assortment and crossing over.

Question 20

what is the structure + function of the xylem?

Answer 20

. transport water and minerals

. structural support.

. long cylinders made of dead tissue with open ends

. lignified

. parenchyma, fibres and vessels and are produced by meristem cells which produce smaller cells that elongate

Question 21

what is the structure + function of the phloem?

Answer 21

. tubes made of living cells which are involved in translocation

. sieve plates

. companion cells

. movement of assimilates upwards and downwards in the tubes.

Question 22

what is the structure + function of the epithelial?

Answer 22

. sheet of cells that lines/cover a surface

. two types, squamous and ciliated epithelium

. move the mucus produced by goblet cells along

Question 23

Give 3 other types of tissues other than xylem, phloem and epithelia

Answer 23

1. Connective - providing support and hold structures together, example: cartilage and bone
2. Muscle - movement through contraction
3. Nervous - impulse conduction

Question 24

What are stem cells?

Answer 24

undifferentiated cells which are genetically identical and have the ability to develop into any of the various kinds of cells.

Question 25

how are stem cells used in research and medicine?

Answer 25

repair of damaged tissues, treatment of neurological disorders such as Parkinson’s and Alzheimer’s as well as studying development.

Question 26

explain stem cells in bone marrow

Answer 26

. differentiate into erythrocytes neutrophils

. erythrocytes transport oxygen in the blood , constantly destroyed and created

. neutrophils are involved in attacking and destroying foreign microorganisms in the process of phagocytosis.

Question 27

explain stem cells in the plant

Answer 27

found in meristems.

Dividing meristem cells are known as the cambium and give rise to xylem and phloem tissue.

Question 28

give other specialised cells

Answer 28

1. sperm cells - adapted to reach, penetrate and fertilise the ovum
2. palisade cells - contain many chloroplasts and are specialised for photosynthesis
3. root hair cells - increases surface area and maximising the contact with water which contains essential mineral ions which are absorbed through the roots.
4. guard cells - controlling the opening and closing of stomata