specialisation + stem cells

Question 1

levels of organisation in multicellular organisms

Answer 1

• specialised cells
• tissues
• organs
• organ systems
• whole organism

Question 2

erythrocytes

Answer 2

• flattened biconcave shape
• inc SA:V
• essential for transp O2
• no nuclei
• inc space for Hb
• flexible
• squeeze through narrow capillaries

Question 3

neutrophils

Answer 3

• role in immune system
• multi-lobed nucleus
• easier to squeeze through small gaps to get to infection site
• granular cytoplasm has lysosomes
• contain enzymes to attack pathogens

Question 4

sperm cells

Answer 4

• male gametes
• deliver genetic info to egg
• tail/flagellum
• can move
• lots of mitochondria
• supply energy to swim
• acrosome on head contain digestive enzymes
• released to digest protective layers around voum
• allow sperm to penetrate = fertilisation

Question 5

palisade cells

Answer 5

• in mesophyll
• contain chloroplasts
• rectangular box shape
• closely packed = continuous layer
• thin cell walls
• ## inc rate of diffusion of CO2

Question 6

RHC

Answer 6

• long extension
• root hairs
• inc SA
• maximise uptake of H2O + minerals from soil

Question 7

guard cells

Answer 7

• surface of leaves
• allow CO2 into plants for photosynthesis
• when lose H2O = less swollen bc osmotic forces
• change shape
• stoma close
• prevent water loss
• CW is thicker on one side
• cell doesn’t change shape symmetrically as volume changes

Question 8

categories of tissues in animals

Answer 8

• nervous tissue : transmission of electrical impulses
• epithelial : cover body surfaces, internal + external
• muscle : adapted to contract
• connective tissue : hold other tissues togethor or transport medium

Question 9

squamous epthielium

Answer 9

• made from specialised squamous epithelial cells
• flat appearance
• very thin bc of flat cells
• one cell thick
• rapid diffusion across a surface
• lining of lungs
• rapid diffusion of O2 into blood

Question 10

ciliated epithelium

Answer 10

• cilia on one surface
• move in rhythmic manner
• lines trachea (removes mucus)
• goblet cells release mucus trapping unwanted particles
• prevents particles reaching alveoli in lungs.

Question 11

cartilage

Answer 11

• connective tissue
• outer ear , nose and end/between bones
• contain elastin + collagen fibres
• firm
• flexible
• prevents ends of bones rubbing together = damage
• composed of chondrocyte cells in extracellualr matrix

Question 12

muscle

Answer 12

• individual MF separated by connective tissue
• contracts to move bones
• types : skeletal muscle fibres
• contain myofibrils which have contractile proteins

Question 13

tissue types in plants

Answer 13

• epidermis : cover plant surface

- vascular : adapted to transport of water + nutrients

Question 14

epidermis

Answer 14

• single layer
• closely packed cells
• covered by waxy, waterproof cuticle
• reduce loss of water
• have stomata
• allow CO2/O2/H2O vapor in+out

Question 15

xylem

Answer 15

• vascular tissue
• transport of water + mineral
• elongated dead cells
• walls are strengthen by lignin
• provides structural support

Question 16

phloem

Answer 16

• vascular tissue
• transport of organic nutrients (sucrose)
• from leaves + stems (from photosynthesis)
• columns of sieve tube cells
• separated by sieve plates

Question 17

organ

Answer 17

• group of tissues

- adapted to perform a particular function in an organism

Question 18

organ system

Answer 18

• composed of organs

- work together to carry out major functions in the body

Question 19

define stem cells

Answer 19

• not adapted to a particular function
• potential to differentiate
• become any specialised cell in an organism
• renewing source of
• undifferentiated cells

Question 20

features of stem cells

Answer 20

• can undergo cell division many times
• source of new cells for growth development and repair
• once specialised, can’t divide and enter G0
• activity is strictly controlled
• if they don’t divide fast enough, tissues aren’t efficiently replaced = ageing
• if uncontrolled division can form tumours = cancer

Question 21

what is stem cell potency

Answer 21

• ability to differentiate into diff cell types

- greater number of cell types it can differentiate into = greater potency

Question 22

totipotent

Answer 22

• differentiate into any type of cell

- E.G fertilised egg eventually produce a whole organism

Question 23

pluripotent

Answer 23

• form all tissue types but not whole organisms

- in early embryos

Question 24

multipotent

Answer 24

• only form a range of cells within a certain type of tissue

Question 25

where are blood cells

Answer 25

• derived from stem cells

- in bone marrow

Question 26

sources of animal stem cells

Answer 26

embryonic stem cells

• early stage of embryo development
• totipotent
• cells are pluripotent until birth

Tissue stem cells

• present throughout life
• found in specific areas (bone marrow)
• multipotent
• umbilical cords of new babies
• plentiful supply of UC
• non invasive
• can be stored
• not rejected in a transplant to umbilical owner

Question 27

sources of plant stem cells

Answer 27

• meristematic tissue / meristems
• tips/shoots
• located between phloem + xylem tissue = vascular cambium
• pluripotent nature of stem cells continues throughout life

Question 28

uses of stem cells in research and medicine

Answer 28

• heart disease : muscle tissue in heart is damaged bc of a heart attack - treated with stem cells
• Parkinson’s : death of dopamine producing cells in the brain causes shaking + rigidity.
• Alzheimer’s : brain cells destroyed bc build up of abnormal proteins
• development biology : important areas of study - changes that occur as organisms grow - why do some things go wrong?

Question 29

ethics of stem cells

Answer 29

• religious objections of using embryos
• moral objections - life begins at conception and destruction of embryo = murder
• use of umbilical cord stem cells overcomes ethics but are only multipotent (less useful)