Text book The Cell Cycle

Question 1

M phase

Answer 1

• checkpoint triggers condensation of chromatin
• Metaphase CP ensures mitosis
• cell growth stops
• PMAT
• Cytokinesis

Question 2

G0

Answer 2

• triggered early in G1
• apoptosis; differentiation; senescence
• epithelial cells in gut don’t have/ neurones indefinitely

Question 3

G1

Answer 3

• checkpoint ensures can enter S phase
• cells grow
• transcription of RNA
• biosynthesis - make enzymes needed in DNA rep
• organelles duplicate

Question 4

S-phase

Answer 4

• DNA rep
• P53
• rapid as base pairs are exposed to mutagenic agents
• active housekeeping genes replicated first

Question 5

G2

Answer 5

• chemical stimulated proteins involved in making spindle to ensure ready to undergo mitosis
• cells grow

Question 6

Why cant palisade mesophyll cells undergo mitosis

Answer 6

differentiated and have a large vacuole and rigid cell wall

Question 7

Centriole
Centrosome
Chromosome
Centromere

Answer 7

• bundle of microtubules that form the spindle in nuclear division
  -the area of cell cytoplasm where the centriole is
  – a molecule of DNA wrapped around histone proteins
  – region where a pair o sister chromatids attach

Question 8

Why is mitosis necessary

Answer 8

• Growth
• Repair of tissues
• Replacement of cells
• A sexual reproduction

Question 9

Where does meiosis produce genetic variation

Answer 9

crossing over during Prophase 1

– by shuffling alleles in metaphase 1/anaphase 1 of chromatids also again in metaphase 2/ anaphase 2

Question 10

Stem cell

Answer 10

undifferentiated cells unable to express it genes and divide by mitosis

Question 11

Erythrocytes

Answer 11

To carry oxygen from lungs/gaseous exchange surface to respiring cells; they are small and flexible to squeeze through narrow capillaries; they are flattened and have a large SA/V ratio, so oxygen can diffuse through the cell surface membrane and reach all the haemoglobin molecules; there are few organelles and little cytoplasm, so more haemoglobin molecules can be present, each one able to combine with oxygen

Question 12

Neutrophils

Answer 12

Neutrophils ingest and kill invading bacteria and some fungi. They are attracted to and can move towards a site of infection. They can engulf a pathogen by phagocytosis (their cytoskeleton threads enable them to move and carry out phagocytosis). They have a nucleus, ER and ribosomes – they can synthesise toxic chemicals to kill pathogens and also make proteins that can pierce and rupture the pathogen cell membrane

Question 13

Why do plants die if there roots become waterlogged

Answer 13

there air spaces become filled with water Therefore, roots cannot take in oxygen for aerobic respiration, and so cannot produce enough ATP to transport in mineral ions, or for any other metabolic activities

Question 14

Guard cells

Answer 14

vital in regulating plant gaseous exchange. They have chloroplasts that can produce ATP and so they can actively transport potassium ions into the cell, lowering water potential and causing water to enter by osmosis. As the guard cells swell, the stoma between them opens, allowing gaseous exchange

Question 15

Mitochondria in root hair cells

Answer 15

Lots of mitochondria as need to carry out active transport if potassium ions that needs ATP a product of respiration

Question 16

How to predict the amount of stomata on the lower surface of a leaf:

Answer 16

determine the area (A) of the field of view on low or medium power of a microscope by focusing on a piece of graph paper and counting the squares (mm2 ). Strip a piece of epidermis from the lower side of the leaf, mount in distilled water on a microscope slide and observe on low power. Count all stomata (N). Now you know how many stomata per area of field of view, so find number of stomata per mm2 by dividing N/A. Draw around the leaf on a piece of graph paper and find the area of the leaf (L). Number of stomata on the underside of the leaf = A N × L.

Question 17

Elastic cartilage
Fibrous cartilage
Hylaine cartilage

Answer 17

– outer ear
– disc in knee joints
– ends of long bones

Question 18

Types of mammal tissues

Answer 18

Epithelial - lining
connective - hold structures together and provide support
muscle- made of cells that are specialised to contract and cause movement
nervous - made of cells specialised to conduct electrical pulses

Question 19

How cartilage receive nutrients

Answer 19

chondroblasts are immature and can divide by mitosis; they secrete the extracellular matrix of cartilage. Once the matrix has been secreted, the chondroblasts become less active, mature cells called chondrocytes

Question 20

mammalian muscle

Answer 20

• skeletal
• muscle
• cardiac

Question 21

How does vascular tissue in plants and animals differ

Answer 21

In plants vascular tissue doesn’t transport O2 and CO2

Question 22

Where is lignin found

Answer 22

xylem vessels and sclerenchyma cells

Question 23

Stem cells

Answer 23

undifferentiated; pluripotent; able to express all there genes

Question 24

Why is suing embryonic stem cells controversial

Answer 24

ethical issue some people may object to the use of using live embryos (regarded as potential humans

Question 25

Sources of stem cells

Answer 25

Embryonic stem cells - present in early embryo formed when the zygote begins to divide Stem cells in umbilical cord blood

Question 26

Why would patient derived ips cells not be useful for treating mitochondrial-disease blindness

Answer 26

4) The patient-derived iPS cells would have the faulty mitochondria in them and the differentiated cells derived from them would also have the faulty mitochondria. (Could discuss idea of removing mitochondria from such an iPS cell and implanting other mitochondria, before letting the iPS cell divide to give cell line.)

Question 27

Process of mitosis

Answer 27

Prophase – DNA supercoils/chromatin condenses//chromosomes shorten and thicken; nuclear envelope breaks down; centriole divides and spindle forms; Metaphase – pairs of/sister chromatids join to equator of spindle; by centromeres; Anaphase – centromere splits; motor proteins walk along tubulin threads pulling chromatids with them; chromatids pulled to opposite poles; Telophase – separated chromosomes reach poles; new nuclear envelopes reform

Question 28

structure of xylem

Answer 28

elongated tubes and vessels; lignification of walls; waterproofs and strengthens the dead cells; prevents collapse inwards of tubes/vessels as water moves upwards; lignin gives support to plant.

Question 29

Structure of phloem

Answer 29

sieve tubes, living but have little cytoplasm and few organelles; sieve plates between one sieve tube and next; transports dissolved products of photosynthesis/named product from leaves/storage organ/source, to other parts/sinks/named part; companion cells carry out metabolic functions/provide ATP to sieve tubes.

Question 30

Structure of cartilage

Answer 30

connective tissue; much non-living extracellular matrix; collagen/elastin/hyaluronic acid (polysaccharide that traps water); matrix separates living cells and enables tissue to withstand weight/forces; chondroblasts divide by mitosis and secrete matrix; named example of location: embryonic skeleton/ends of adult long bones/nose/pinna/trachea/larynx/disc between vertebrae/epiglottis