Topic 2 - Cells and Control

Question 1

List the order of the cell cycle

Answer 1

• Interphase - DNA spread out into strings and is duplicated
• Prophase - Chromosomes condense (small and fatter) and nucleus breaks down to lie free in cytoplasm-
• Metaphase - Chromosomes line up in centre
• Anaphase - Cell fibres pull chromosomes apart to opposite sides
• Telephase - Membrane forms around new cells and has divided
• Cytokinesis - The dividing of cytoplasm and cell membrane

Question 2

Why is mitosis important for organisms?

Answer 2

It replaces old or damaged cells

Question 3

How does it create genetically identical cells?

Answer 3

The daughter cells contain exactly same sets of chromosomes so they are genetically identical diploid cells

Question 4

Why do organisms rely on asexual reproduction?

Answer 4

• Lots of offspring quickly and only 1 parent needed
• Divide by mitosis (identical)
• Can reproduce when condition perfect (aphids in sumer)

Question 5

How does cancer form/occur?

Answer 5

Uncontrolled cell division by genes in the DNA. If a change in genes occurs causing a mutation, that cell starts dividing uncontrollably. Forms a mass of abnormal cells called a tumour. Cancer then damages tissues.

Question 6

Define what growth in animals entails

Answer 6

All growth in animals is through cell division/mitosis. An animal gets bigger as its number of cells increases.

Question 7

Give examples of animal cells which are specialised

Answer 7

Ciliated epitherial cells, red bllod cells (bioconcave dish)

Question 8

Why is cell differentiation important to develop specialised cells?

Answer 8

Cell differentiation is where a cell becomes specialised for its role so an organism can work more efficiently

Question 9

How does growth happen in plants?

Answer 9

Through cell elongation for height of a plant and cell division in the tips of roots and shoots (meristem). Meristems divide by mitosis and produce unspecialised cells that differentiate to any type of cell.

Question 10

Examples of specialised plant cells?

Answer 10

Root hair cells
Phloem
Xylem

Question 11

How are phloem and xylem tubes adapted?

Answer 11

Phloem - Collumned? of elongated living cells with pores at ends to let food substances through due to active transport. Translocation requires energy from respiration
Xylem - dead cells joined together in tube strengthened with lignin carry water and mineral ions from roots up

Question 12

Where are stem cells found?

Answer 12

Human embryos and bone marrow.

Question 13

What is the purpose of stem cells in plants and animals?

Answer 13

To differentiate into a specific cell for the organism so it can work more efficiently

Question 14

Compare adult stem cells and embryonic stem cells in animals

Answer 14

• In adults stem cells can be found in bone marrow. It is not as versatile as embryonic stem cells (they can’t produce any type of cell, only certain ones) adult replace damaged cells.
• Stem cells in embryos can produce any kind of cell which helps for growth and development.

Question 15

Where are stem cells used in medicine?

Answer 15

• To cure diseases such as sickle cell anaemia (transplant bone marrow)
• Create specialised cells to replace damaged ones eg new cardiac muscle

Question 16

Name some benefits of using stem cells in medicine

Answer 16

• Replace old damaged cells (tissue)

- Create specialised cells

Question 17

Name some risks of stem cells

Answer 17

• Tumour development - SC’s divide very quickly
• Disease transmission - viruses living inside cells can be passed on to recipricant of stem cells
• Rejection - transplanted cells aren’t grown using patients SC’s. Body may trigger immune response making susceptible to disease

Question 18

What is the brain made up of?

Answer 18

Billions of interconnected neurones

Question 19

What are the main parts of the brain? (and their roles)

Answer 19

• Cerebrum - (largest) 2 hemispheres, right controls muscles on left side of body, also memory, language, vision and intelligence
• Cerebellum - Muscle coordination and balance
• Medulla oblongata - unconscious activities such as breathing, heart rate

Question 20

Describe process of CT scanning

Answer 20

• X-rays used to produce brain image
• Main structures (not function)
• Shows diseased, damaged brain structure and where patient lost function

Question 21

Describe process of PET scanning

Answer 21

• Use radioactive chemicals
• More detailed than CT, shows structure and function in real time
• Studies disorders in brain eg Alzheimers

Question 22

How is brain function observed?

Answer 22

Using PET scanners

Question 23

What are the effects of spinal chord damage?

Answer 23

• Can stop neurones being transmitted around body

- Hard to reach to do treatment and could lead to permanent damage

Question 24

What damage can tumours do to the brain?

Answer 24

• Damage tissues

- Clogs arteries and stops blood flow

Question 25

What are the limitations of brain surgery?

Answer 25

Some areas cannot be accessed making it impossible to surgically remove

Question 26

What are the parts of the nervous system? (order of a stimuli)

Answer 26

``` Stimulus Receptor Sensory neurone CNS Motor Neurone Effector Response ```

Question 27

What is the structure of a sensory neurone?

Answer 27

One long dendron and a short axon and have a myelin sheath to insulate and stop impulses escaping

Question 28

Identify parts of the eye and what they do

Answer 28

Cornea - refracts light into eye Iris - controls amount of light let into eye Lens - refracts light onto retina Rods - sensitive to dim light, can't sense colour Cones - sensitive to colour, not dim light Optic nerve - electrical impulses sent to brain

Question 29

What is colour blindness?

Answer 29

Red or green cones in retina aren't working properly so hard to tell difference

Question 30

What is a cataract and how can it be corrected?

Answer 30

Cloudy patch on lens stopping light entering normally. Colours less vivid. Replace lens with artificial one.

Question 31

How can short-sightedness be corrected?

Answer 31

(Distant objects are hard to see). Concave lens used (in front)

Question 32

How can long-sightedness be corrected?

Answer 32

(Short distant is hard to see) Convex brought to focus from behind retina

Question 33

What is the structure of a motor neurone?

Answer 33

Long axon and short dendrites (can be myelinated)

Question 34

What is the structure of relay neurones?

Answer 34

Short dendrites carry impulse from sensory to cell body axon to motor neurones.

Question 35

What happens at a synapse?

Answer 35

Connection between two neurones | Nerve signal transferred by chemicals called neurotransmitters which diffuse across gap and slow due to diffusion