Unit 1 Section 3: Stem cells and Differentiation

Question 1

Stem cells are…

Answer 1

Unspecialised cells

Question 2

adult stem cells

Answer 2

Adult stem cells are only found in few places e.g. in bone marrow. they’re not as flexible as embryo stem cells however and can only develop into a limited range of cells. they are used to replace damaged cells.

Question 3

the process when a cell becomes specialised is called …

Answer 3

Differentiation

Question 4

MUST LEARN EXAMPLE: human bone marrow stem cells => blood cells

Answer 4

the main bones of the body have marrow in the centres. it’s here that adult stem cells divide and differentiate, replacing worn out blood cells. they can become either red or white blood cells.

Question 5

stem cells in plants

Answer 5

needed to make new shoots and roots. stem cells can differentiate into a wide variety of cells in plants.

Question 6

MUST LEARN EXAMPLE: plant stem cells =>xylem &phloem

Answer 6

stem cells found in vascular cambium in the root and shoot divide and differentiate to become either xylem or phloem.
(the vascular cambium forms a ring inside the root and shoot, the cells divide out of that ring differentiating as they move away from the cambium.

Question 7

Specialised cells

Answer 7

once a cell has differentiated it has a specific function with a structure adapted to perform that function.

Question 8

Specialised Animal Cells: Erythrocytes

Answer 8

RED BLOOD CELLS
carry oxygen to the blood

• Biconcave disc shape - large surface area for gas exchange
• No nucleus - more room for haemoglobin

Question 9

Specialised Animal Cells: Neutrophils

Answer 9

WHITE BLOOD CELLS (PHAGOCYTES)
defend the body against disease

• Flexible shape - to engulf foreign particles or pathogens
• Many lysosomes in cytoplasm - contain digestive enzymes to break down engulfed particle

Question 10

Specialised Animal Cells: Epithelial Cells

Answer 10

SURFACE OF ORGANS
Joined by interlinking cell membrane and membrane at their base

• some have Cilia - to beat particles away e.g. in the lungs
• some have microvilli - folds that increase the surface area e.g.in the small intestine

Question 11

Specialised Animal Cells: Sperm Cells

Answer 11

MALE SEX CELLS

• Flagellum tail - Swim to Egg
• Lots of Mitochondria - to provide the energy
• Acrosome at tip containes digestive enzymes - enables sperm to penetrate the surface of the egg

Question 12

Specialised Plant Cells: Paliside Mesophyll Cells

Answer 12

IN LEAVES
photosynthesis

• Chloroplasts - Absorb a lot of sunlight
• thin walls - short distance for CO2 to diffuse

Question 13

Specialised Plant Cells: Root hair Cells

Answer 13

ROOT HAIR
absorb water and minerals from soil

• large surface area - for absorption
• thin permeable wall - for easy entry of water and ions
• cytoplasm contains extra mitochondria - provides extra ATP for Active Transport

Question 14

Specialised Plant Cells: Guard Cells

Answer 14

LINE STOMATA
take up water in vacuoles and become turgid

*Thin outer walls,thick inner walls - forced to bend outwards opening stomata, allowing gas exchange