Specialised Cell And Stem Cells

Question 1

How are red blood cells (erythrocytes specialised?

Answer 1

Have flattened biconcave shape to increase SA:V ratio

No nuclei to increase space available for haemoglobin to carry the maximum load of oxygen.

Flexible so they can squeeze through capillaries

Question 2

How big are erythrocytes?

Answer 2

7.5 micrometers from above

2 micrometers from the side view

Question 3

How are neutrophils specialised?

Answer 3

Play an essential role in immune system.

Multi lobed nucleus to make it easier to squeeze through small gaps to get to the site of infections.

Granular cytoplasm which has many lysosomes that contains enzymes used to attack pathogens.

Question 4

How large are neutrophils?

Answer 4

10-14 micrometers

Question 5

How are sperm cells specialised?

Answer 5

Have a tail or flagellum so that they are capable of movement

Contain many mitochondria to provide the energy required for swimming.

Acrosome contains digestive enzymes which are released to digest the protective layers around the ovum and allow the sperm to penetrate leading to fertilisation.

Question 6

How are palisade cells specialised?

Answer 6

Contain chloroplasts to absorb large amount of light for photosynthesis

Rectangular box shapes so that can be closely packed together to form a continuous layer.

Thin walls to increase the rate of diffusion of carbon dioxide.

Chloroplasts can move within the cytoplasm to absorb the maximum amount of light.

Question 7

How are root hair cells specialised?

Answer 7

Long extensions called root hairs which increases the surface area of the cell to maximise water and mineral uptake from the soil.

Question 8

How large are sperm cells?

Answer 8

3 micro meters wide and 4 micrometers long

Question 9

How large are palisade cells?

Answer 9

25-75 micrometers

Question 10

How large are root hair cells?

Answer 10

20-150 micrometers

Question 11

How are pairs of guard cells specialised?

Answer 11

Control stomata opening.

Cell wall of the guard cell is thicker on one side so the cell does not change shape symmetrically as it’s volume changes.

Question 12

What are the 4 main categories of tissues in animals?

Answer 12

Nervous tissue

Epithelial tissue

Muscle tissue

Connective tissue

Question 13

How large are guard cells?

Answer 13

15-20 micrometers

Question 14

How is squamous epithelial tissue specialised?

Answer 14

Very thin due to the squat or flat cells that make it up and it’s also one cell thick.

Present in tissues where rapid diffusion across surfaces is essential.

Forms the lining of the lungs to allow for rapid diffusion of oxygen into the blood.

Question 15

What is ciliates epithelium and how is it specialised?

Answer 15

Cells have hair like structures called cilia that move in a rhythmic manner.

This lines the trachea, causing mucus to be swept away from the lungs.

Goblet cells also present to release the mucus to trap unwanted particles, preventing this bacteria from reaching the alveoli.

Question 16

What is cartilage tissue and how is it specialised?

Answer 16

Connective tissue found in the outer ear, nose and at the ends of bones.

Contains fibres such as elastin and collagen. Cartilage is a firm, flexible connective tissue.

Prevents the ends of bones from rubbing together and causing damage.

Question 17

What is muscle and how is it specialised?

Answer 17

A tissue that needs to be able to contract in order to move bones.

Different types of muscle fibres including skeletal muscles which are attached to bones.

Skeletal muscles contain myofibrils which contain contractile proteins.

Individual muscle fibres separated by connective tissue

Question 18

Importance of the epidermis in plants?

Answer 18

Single layer of closely packed cells covering the surface of plants.

Usually covered by a thick waxy cuticle to prevent water loss by transpiration.

Stomata are present here, they allow CO2 in and out and water vapour and oxygen in and out.

Question 19

Importance of Xylem tissue in plants?

Answer 19

Responsible for the transport of minerals and water throughout plants.

Composed of vessel elements which are elongated dead cells.

Walls are strengthened with lignin(pink rings on micro graphs) which provides structural support.

Question 20

What is the importance of phloem tissue?

Answer 20

Vascular tissue in plants responsible for the transport of organic nutrients and sucrose.

Transport from leaves of plants where it is made by photosynthesis to all parts of the plant where it is needed.

Composed of sieve tube cells separated by perforated walls called sieve plates

Question 21

What is an organ?

Answer 21

A collection of tissues which are adapted to perform a specific function in an organism.

Question 22

Animal examples of coordinated organ systems?

Answer 22

Digestive system - takes in food, breaks it down, absorbs nutrients, retains water and removes waste.

Cardiovascular system - moves blood around the body to provide an effective transport system for the substances it carries.

Gaseous Exchange system - brings air into the body so that oxygen can be extracted for respiration and CO2 can be expelled

Question 23

What are stem cells?

Answer 23

Undifferentiated cells which are not adapted to any particular function.

Question 24

Why are stem cells good?

Answer 24

Are a source of new cells necessary for growth, development and tissue repair.

Question 25

What is totipotency?

Answer 25

Stem cells that can differentiate into any type of cell.

Eg stem cells from fertilised egg cells or zygotes.

Can eventually divide to produce a whole organism

Question 26

What are pluripotent stem cells?

Answer 26

Stem cells can form all tissue types but not whole organisms.

Present in early embryos and are the origin of differing tissue types.

Question 27

What are multipotent stem cells?

Answer 27

Can only form a range of cells within a certain type of tissue.

Eg, haematopoetic stem cells in bone marrow are multi potent, can form various types of blood cells.

Question 28

How do blood cells reproduce?

Answer 28

Via stem cells in the bone marrow due to having a short life cycle of only 120 days.

Eg approx 3billion erythrocytes per KG of body mass per DAY to keep up with the demand.

Neutrophils - 1.6billion per kg per hour produced by stem cells

Question 29

What are the 2 sources of animal stem cells?

Answer 29

Embryonic stem cells - present at early stage of embryo development are totipotent.
After about 7days a blastocyst forms and then stem cells are pluri potent

Tissue (adult) stem cells - present in specific areas like the bone marrow and are generally multipotent. Can be stored for future use

Question 30

Where do plant stem cells come from?

Answer 30

Meristematic tissue or in meristems. This tissue is found wherever growth is occurring in plants eg. Tips of roots and shoots.

Question 31

Where is meristematic tissue found?

Answer 31

At the tips of roots and shoots

And sandwiched between the phloem and xylem tissues called the vascular cambium. Cells originating from this region can differentiate into the different cells present in the xylem and phloem tissues

Question 32

Give some examples of the uses of stem cells?

Answer 32

Parkinson’s disease - caused by death of dopamine producing cells

Treating Alzheimer’s - brain cells that are destroyed could be replaced.

Type 1 diabetes - produce insulin producing cells to replace those killed by the disease

Heart disease - replacing dead muscle tissues

Question 33

What are the ethical concerns of Stem Cell use?

Answer 33

Removal of stem cells from embryos normally results in the destruction of such embryos = religious concerns and also is it murder?