Unit 1: Section 3 - Cell Division, Diversity and Organisation

Question 1

What is the cell cycle?

Answer 1

The process of cell growth and division

Question 2

What are the 5 stages of mitosis?

Answer 2

Interphase
Prophase
Metaphase
Anaphase
Telephase

Question 3

What happens in interphase?

Answer 3

The cell prepares to divide
Cells DNA is unravelled and replicated, to double its genetic content
organelles replicated so it has spares
ATP content increased in preparation for cell division

Question 4

What happens in prophase?

Answer 4

Chromosomes condense, getting shorter and fatter
centrioles move top opposite ends of the cell forming a network of proteins fibres across it called the spindle
Nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 5

What happens in metaphase?

Answer 5

Chromosomes line up along the middle of the cell and become attached to the spindle by their centromere.

Question 6

What happens in anaphase?

Answer 6

Centromeres divide, separating each pair of sister chromatids.
The spindles contract, pulling chromatids to opposite ends of the cell, centromere first

Question 7

What happens in telophase?

Answer 7

Chromatids reach the oppsosite poles
They uncoil and become long and thin
A nuclear envelope forms around each group of chromosomes so there are 2 nuclei.
Cytoplasm divides to make 2 new cells (cytokinesis)

Question 8

How can you observe mitosis under a microscope?

Answer 8

Stain the chromosomes,

Question 9

How do yeast cells reproduce?

Answer 9

asexually by budding

Question 10

What are the 5 stages of budding?

Answer 10

1) A bud forms at the surface of the cell
2) The cell undergoes interphase
3) The cell undergoes mitosis
4) Nuclear division is complete - the budding cell contains a nucleus that has an identical copy of the parent cell’s DNA
5) Bud separates off from the parent cell, producing a new, genetically identical yeast cell.

Question 11

What happens when two gametes join together?

Answer 11

They form a zygote

Question 12

What happens in meiosis?

Answer 12

1) DNA replicates
2) Chromosomes arrange themselves into homologous cells
3) Chromosome pairs then swap ‘bits’ with each other
4) In the first division, these homologous pairs split up. Any one chromosome from each pair can go into either cell.
5) In the second division each chromosome splits in half
6) Four new genetically different cells are produced
7) They are genetically different.

Question 13

What are homologous pairs of chromosomes?

Answer 13

Chromosomes that have the same genes, although they could have different versions (alleles) of those genes

Question 14

What are stem cells?

Answer 14

Unspecialised cells - they can develop into any type of cell

Question 15

Where are stem cells found in adults and embryos?

Answer 15

Adults - Bone marrow (but not as flexible as in embryos)

Embryos - In the first few days of an embryos life, any of it’s cells can turn into any cell.

Question 16

What is the diploid number?

Answer 16

The number of chromosomes in the body cells of species (in humans it is 46)

Question 17

What is the haploid number?

Answer 17

The number of chromosomes in gametes in a species (half the diploid number)

Question 18

How are stem cells used in humans?

Answer 18

Adult stem cells are used to replace damaged cells e.g. new skin or blood cells

Question 19

How are stem cells used in plants?

Answer 19

Stem cells are needed to make new roots and shoots as they are constantly growing

Question 20

Where are plant stem cells found?

Answer 20

In the cambium

Question 21

How are neutrophils adapted to perform their function?

Answer 21

Neutrophils defend the body against disease, they have a flexible shape which allows them to engluf foreign particles or pathogens. They also contain lots of lysosomes in their cytoplasm which contain digestive enzymes to break down engulfed particles.

Question 22

How are erythrocytes adapted to perform their function?

Answer 22

Erythrocytes carry oxygen in the blood, their biconcave disc shape provides a large surface area for gas exchange. They have no nucleus so there’s more room for haemoglobin

Question 23

How are epithelial cells adapted to perform their function?

Answer 23

Epithelial cells cover the surface of organs, The cells are joined by interlinking cell membranes and a membrane at their base. Some epithelia (e.g. in the lungs) have cilia to move particles away. Other cells (e.g. small intestine) have microvilli (folds in the cell membrane to increase surface area)

Question 24

How are sperm cells adapted to perform their function?

Answer 24

They have flagellum so they can swim to the egg, they also have lots of mitochondria to provide energy to swim

Question 25

How are paliside mesophyll cells adapted to perform their function?

Answer 25

They do most of the photosynthesis, they contain many chloroplasts so they can absorb a lot of sunlight, they walls are thin so CO2 can easily diffuse into the cell.

Question 26

How are root hair cells adapted to perform their function?

Answer 26

absorb water and minerals from soil. Large surface area and thin, permeable cell wall. Cytoplasm has extra mitochondria to provide more energy for active transport.

Question 27

How are guard cells adapted to perform their function?

Answer 27

They line the stomata (tiny pores in the leaf used for gas exchange). In the light, guard cells take up water and become turgid. Their thin outer walls and thickened inner walls force them to bend outwards, opening the stomata.

Question 28

What is a tissue?

Answer 28

A group of cells that are specialised to work together to carry out a particular function

Question 29

What is the squamous epithelium tissue?

Answer 29

A single layer of flat cells lining a surface. Squamous epithelium tissue is found in many places including alveoli in the lungs.

Question 30

What is the xylem tissue?

Answer 30

A plant tissue with 2 jobs... 1) Transports water around the plant 2) Supports the plant It contains xylem vessel cells and parenchyma cells

Question 31

What is the ciliated epithelium tissue?

Answer 31

A layer of cells covered in cillia. It's found on surfaces where things need to be moved e.g. in the trachea.

Question 32

What is the phloem tissue?

Answer 32

Transports sugars around the plant. Arranged into tubes and is made up of sieve cells, companion cells and ordinary plant cells. Each sieve cell has end walls with holes in them so that sap can move easily through them. These end walls are called sieve plates.

Question 33

What is an organ?

Answer 33

A group of tissues that work together to perform a particular function e.g. lungs, leaves

Question 34

2 examples of an organ system

Answer 34

Respiratory system and circulatory system

Question 35

h

Answer 35

h