Chapter 6 Stem Cells

Question 1

Define differentiation

Answer 1

The process of an unspecialised cell becoming specialised to a very specific function

Question 2

How are erythrocytes adapted to their function?

Answer 2

They have a flattened, biconcave shape which increases their surface area to volume ratio
Enucleated to maximise space for haemoglobin, no mitochondria. This helps transport the most amount of oxygen around cells.
They are flexible so can squeeze through narrow capillaries
Contains carbonic anhydrase and so can transport CO2

Question 3

How are neutrophils adapted to their function?

Answer 3

Essential role in the immune system
Contain a multilobed nucleus to make it easier to squeeze through small gaps to get to the site of infections
Granular Cytoplasm contain hydrolytic enzymes to attack pathogens

Question 4

How are sperm cells adapted to their function??

Answer 4

Tail or flagellum to move through liquids
Lots of mitochondria to supply energy to allow movement
Acrosome on the head of the sperm, contains digestive enzymes to digest protective outer layers of the ovum
Haploid cells to maintain the correct number of chromosomes in the zygote

Question 5

How are palisade cells adapted to their function?

Answer 5

For photosynthesis
Rectangular box shaped so cells can me closely packed to form a continuous layer
Large vacuole to maintain turgor pressure
Thin cell walls to increase the rate of diffusion of carbon dioxide
Chloroplasts can move in the cytoplasm to absorb more light, packed full of chloroplasts to maximise photosynthesis

Question 6

How is the squamous epithelium adapted to its function?

Answer 6

Made of specialised squamous cells, giving a flat appearance
Very thin, 1 cell thick, to increase the rate of diffusion
Lining of lungs, rapid diffusion of oxygen

Question 7

What the main categories of tissues in animals and their function?

Answer 7

Nervous- support transmission of electrical impulses
Epithelial- cover body surfaces
Muscle- to contract
Connective- hold together other tissues, transport medium

Question 8

How are root hair cells adapted to their function?

Answer 8

Long extensions called ROOT HAIRS to increase the surface area (to volume ratio), maximising the rate for osmosis
Lots of mitochondria for active transport
Large vacuole containing cell sap more concentrated than soil, allowing osomosis
Thin cell walls to increase osmosis

Question 9

How are guard cells adapted to their function?

Answer 9

Change shape due to osmotic forces, opening and closing the stomata to control water loss
Thicker cell walls on the inside than outside to allow bean shape to be formed

Question 10

What is a tissue?

Answer 10

A collection of differentiated cells which group to have a specific function

Question 11

How is the ciliated epithelium adapted to its function?

Answer 11

Cells of tissue contain cilia which move in a rhythmic manner
Line the trachea, causing mucus to be sweeped away from the lungs
Goblet cells release mucus to trap unwanted particles in the air, can’t reach alveoli

Question 12

How is cartilage is adapted to its function?

Answer 12

Connective tissue which prevents bones rubbing together
Contains elastin and collagen
Firm as composed of chondrocyte cells embedded in an extracellular matrix

Question 13

How is muscle adapted to its function?

Answer 13

Needs to be able to contract, shorten in length, to move the body
Contains multiple type of fibres:
Skeletal muscle: Muscle to bone
Myofibrils: Contain contractile proteins

Question 14

What are the different plants tissues and their function?

Answer 14

Epidermis Tissue- Cover plant surfaces
Vascular Tissue- Transport of water and nutrients

Question 15

What is the epidermis?

Answer 15

Single layer of closely packed cells, covering the surfaces of plant cells
Waxy cuticle` to reduce loss of water
Stomata to allow movement of carbon dioxide

Question 16

What xylem tissue?

Answer 16

Vascular tissue responsible for movements of water and mineral ions
Composed of elongated dead cells strengthened by lignin

Question 17

What is phloem tissue?

Answer 17

Vascular tissue responsible for the transport of organic nutrients, such as sucrose
Composed of columns of sieve tube cells separated by holed walls (perforated walls) called sieve plates

Question 18

What are organs? What are organ systems?

Answer 18

Organ- A collection of tissues adapted to perform a particular function in an organism
Organ System- Composed of a number of organs working together to carry out a major function in the body such as digestion, cardiovascular…

Question 19

What are stem cells?

Answer 19

Unspecialised cells which are able to undergo mitosis, able to differentiate into specialised cells

Question 20

What are the overall uses of stem cells naturally?

Answer 20

Growth, Development and Tissue Repair

Question 21

What is stem cell potency? What does each type mean?

Answer 21

Potency is the ability for stem cells to differentiate into different cell types
Totipotent: Zygote: Into any type of cell, whole organisms, embryonic tissues
Pluripotent: Blastocyst. All types of tissues, but not whole organisms, no embryonic tissues such as placenta
Multipotent: Only differentiate into a range of cell types from the tissue they originate, Adult stem cells

Question 22

What is differentiation?

Answer 22

The process of a stem cell changing to adapt to form a specific function

Question 23

From what and where are blood cells formed from? Why do they need to be made constantly?

Answer 23

In the bone marrow from Haemapoetic stem cells
As red blood cells are enucleated and have a limited number of organelles, their life span is short

Question 24

What are some sources of human stem cells?

Answer 24

Embryonic Stem Cells- Short span=Totipotent, then Pluripotent
Adult- From tissues, throughout life

Question 25

What are some sources of plant stem cells?

Answer 25

Meristematic Tissue, where ever growth occurs, roots and shoots. Pluripotent
Cambium

Question 26

What are some uses of stem cells?

Answer 26

Repairing damaged muscle tissue as a result of heart attacks
Repair damaged pancreatic tissue destroyed by immune system in Type 1 Diabetes
Replace damage caused by death of dopamine producing cells in Parkinsons
Replace cells damaged by abnormal proteins in Alzheimer’s
Treat burns, produce new skin
Help drug trials by being tested on stem cell cultures first

Question 27

What are some ethical issues of stem cells?

Answer 27

Embryo destroyed
Arguments about when life begins
Or could be spare embryos from IVF
Money spent in experiments which could be spent into other developments to treat disease

Question 28

How are embryonic stems useful in a growing embryo?

Answer 28

Pluripotent, so can differentiate into any time of specialised cell e.g nervous, so help develop tissues
A renewable source of cells as they can undergo mitosis

Question 29

Why can’t pluripotent cells form their own organisms?

Answer 29

Can differentiate into any type of specialised cell, but cannot form embryonic tissue such as the placenta, umbilical cord

Question 30

What are disadvantages of erythrocytes being enucleated?

Answer 30

Shortened life span, become senescent so must be replenished
Cannot undergo protein synthesis
Do not contain mitochondria so must undergo anaerobic respiration only