2.1.6 Cell division, cell diversity and cellular organisation

Question 1

list 3 ways mitosis is used

Answer 1

growth
repair
asexual reproduction

Question 2

What is produced by mitosis

Answer 2

2 genetically identical diploid cells (2n)

Question 3

what is a haploid cell

Answer 3

a cell that contains a single set of chromosomes, e.g gametes

Question 4

what are the 4 stages of the cell cycle

Answer 4

G1, synthesis, G2 (interphase) and mitosis

Question 5

describe the events that take place in G1

Answer 5

cell grows bigger
replicates organelles
high volume of protein synthesis

Question 6

describe the events that take place in synthesis phase

Answer 6

DNA replication

Question 7

describe the events that take place in G2

Answer 7

cell continues to grow
organelles and proteins needed for mitosis are produced

Question 8

when are the two checkpoints

Answer 8

before and after S phase

Question 9

what do the checkpoints do

Answer 9

check for DNA damage/errors
check DNA replication was succesfull
checks if the cell has enough nutrients, and the proteins and organelles for mitosis

Question 10

why would a cell enter G0 phase

Answer 10

conditions are not suitable for DNA replication
specialised cells that do not need to divide
senescent cells (old cells)

Question 11

What is formed after DNA replication

Answer 11

Two sister chromatids

Question 12

where are sister chromatids joined together by

Answer 12

centromere

Question 13

stages of mitosis in order

Answer 13

prophase
metophase
anaphase
telophase

Question 14

describe events in prophase

Answer 14

chromomes condense
nuclear envelope disintegrates
centrioles move to opposite poles and form spindle fibres

Question 15

describe events in metaphase

Answer 15

chromosomes align at the equator
spindle fibres attach to the centromere
(sister chromatid on either side of equator)

Question 16

describe events in anaphase

Answer 16

centromere splits
chromatids are pulled to opposite poles of the cell

Question 17

describe events in telophase

Answer 17

two groups of chromosomes decondense
nuclear envelope reforms around them
(two new nuclei)

Question 18

what happens in cytokinesis

Answer 18

the cytoplasm divides and plasma membrane pinches off
2 genteically identical daughter cells formed

Question 19

what are gametes

Answer 19

sex cells

Question 20

Hapolid cells contain…

Answer 20

They contain only one set of chromosomes
In humans, that’s 23 chromosomes (no pairs)
Half the number of chromosomes of somatic cells

Question 21

what is the fusion of nuclei between sperm and egg cells called

Answer 21

fertilisation

Question 22

What causes genetic variation in meiosis and what stage are they done at

Answer 22

• Crossing over (Prophase I) - So chromatids will have new combination of alleles
  Amount of variation depends on distance between crossover points
• Independent assortment (Metaphase I of bivalents and Metaphase II of chromatids) - so homologous chromosomes have different alleles, produces large number of allele combinations

Question 23

describe events in

Prophase I

Answer 23

chromatids condense and arrange themselves into homologous pairs called bivalent (4 chromatids)
crossing over occurs at the chiasmata, exchange of genetic material occurs
nuclear envelope disintegrates
centrioles move to opposite poles spindle fibres form

Question 24

describe events in

Metaphase I

Answer 24

bivalents align at the equator
spindle fibres attach to centromere
independent assortment occurs

Question 25

# describe events in Anaphase I

Answer 25

homologous chromosomes are pulled to oppsoite poles

Question 26

# Describe events in Telophase I & cytokinesis

Answer 26

Nuclear envelope reforms Cytoplasm divides 2 genetically different hapoid cells formed

Question 27

# describe events in Prophase II

Answer 27

chromsomes condense nuclear envelope disintegrates centrioles move to opposite poles, spindle fibres form

Question 28

# describe events in Metaphase II

Answer 28

Chromosomes align at the equator Spindle fibres attach to centromere

Question 29

# describe events in Anaphase II

Answer 29

Sister chromatids separate and are pulled to opposite poles.

Question 30

# describe events in Telophase II & cytokinesis

Answer 30

chromsomes decondense nuclear enevelope reforms cytoplasm divides

Question 31

What is produced at the end of meiosis

Answer 31

4 genetically unique Haploid cells

Question 32

what happens during crossing over

Answer 32

homologous chromosomes connect through the chiasmata genetic material is exchanged resulting in new combinations of alleles on each chromosome

Question 33

what happens during independent assortment

Answer 33

random arrangment of homologous pairs along the equator

Question 34

What are Stem cells?

Answer 34

Unspecialised cells that can divide by mitosis and differentiate into specialised cells.

Question 35

What is Stem cell Potency?

Answer 35

The ability of stem cells to undergo differentiation

Question 36

What are totipotent stem cells?

Answer 36

Have the ability to divide into any type of cell, including extraembryonic cells

Question 37

What are pluripotent stem cells?

Answer 37

Have the ability to divide into any type of cell **except the extraembryonic cells.**

Question 38

What are multipotent stem cells?

Answer 38

Can divide into a handful of different cell type An example are stem cells found in bone marrow

Question 39

What are unipotent stem cells?

Answer 39

Can only divide into **one type** of cell

Question 40

What are 2 uses of Stem cells in medicine?

Answer 40

1. Leukemia Treatment - replace destroyed bone marrow stem cells. 2. Organ Regeneration - growing whole organs from stem cells.

Question 41

Define a tissue.

Answer 41

A group of cells working together to perform a particular function

Question 42

Define an organ

Answer 42

A collection of tissues all performing a specific function

Question 43

What is the term for a group of organs that work together to perform a specific function?

Answer 43

An organ system

Question 44

Name 2 examples of organs in animals and plants

Answer 44

Heart, lungs, leaves and roots

Question 45

Describe the 6 tissues that make up the leaf

Answer 45

**Upper epidermis** - covered in waxy cuticle to prevent transpiration **Palisade mesophyll** - tighly packed cells, located towards top of leaf, lots of mitochondria & chloroplasts **Spongy mesophyll** - loosely arranged, air spaces for gas exchange **Phloem** - translocation **Xylem** - transpiration **Lower epidermis** - stomata & guard cells for gas exchange

Question 46

Describe the 3 tissue that make up the lungs

Answer 46

**Endothelium** - forms capillary walls, facilitating the exchange of gases between the blood and the alveolar air. **Squamous Epithelium** - line walls of alveoli **Fibrous connective tissue** - helps push air out of lungs.

Question 47

Describe the function and adaptations of **Erythrocytes** (red blood cells).

Answer 47

F - transports O₂ around the body and CO₂ to the lungs A - **bioconcave**=increase SA, cytoplasm contains high volume of **haemoglobin**=binds to O₂, **no nucleus**=more space for haemoglobin, max. O₂-capacity, **Elastic membrane**=flexible cell & changes shape, to fit through narrow capillaries.

Question 48

Describe the function and adaptations of **Neutrophils**

Answer 48

F - destroy pathogens by phagocytosis and secrete enzymes A- **Flexible shape**=squeeze through cell junctions in capillary walls Large no. of **Lysosomes**= digestive enzymes help to digest and destroy invading cells **Lobed nucleus**

Question 49

Describe the function and adaptations of **Sperm** cells

Answer 49

F - reproduction, fuse with egg A - Head contains a **nucleus** with **half** the no. of normal chromosomes (hapolid) **Acrosome** in head contains **digestive enzymes**=breaks down outer layer of egg cell Mid-piece **packed with mitochondria**=tail movement

Question 50

Describe the function and adaptations of **Root hair cells**

Answer 50

F: absorption of H₂O & mineral ions from soil A: **Root hair**=increase SA, rate of water uptake by osmosis is greater **Thinner walls** than other cells=short diffusion distance **Permanent vacuole** contains **more concentrated cell sap** than soil water=maintaing **water potential gradient** Mitochondria=active transport ions No chlorplasts

Question 51

Describe the function and adaptations of **Ciliated Epithelium**.

Answer 51

F: Moving (brushing) substances away from surface of tissue. A: Have **cilia** (hair-like structures)=beat to shift materials along the surfaces **Goblet cells secrete mucus**=traps dust, dirt and microogranisms, preventing them from entering vital organs.

Question 52

Describe the function and adaptations of **Squamous Epithelium**.

Answer 52

F: provide an outer layer, found on variety of organs and structures (e.g. alveoli) A: Single layer of **flattened cells** on a basement membrane **Thin cross-section**=short diffusion distance **Permeable**=easy diffusion of gases.

Question 53

Describe the function and adaptations **Palisade cells**.

Answer 53

F: Carry out photosynthesis A: Large no. of **chloroplasts** in cytoplasm to maximisde absorption of light for photosynthesis **Tall & thin** shape=allows light to penetrate deeper before encountering another cell wall.

Question 54

Describe the function and adaptations **Guard cells**.

Answer 54

F: control the opeing of stomata A: Inner cell wall are thicker while outer walls are thinner= **difference in thickness** allows **cell to bend** when turgid (filled with water), opening stomata. High density of **chloroplasts** and **mitochondria**