Topic Two - Cells

Question 1

what are the 3 stages of interphase?

Answer 1

G1 phase
S phase
G2 phase

Question 2

what happens in the G1 phase?

Answer 2

cell organelles replicate
nutrients are provided

Question 3

What happens in the S phase?

Answer 3

chromosomes replicate

Question 4

what happens in the G2 phase?

Answer 4

preparation for mitosis

Question 5

what happens in prophase?

Answer 5

• spindle fibres form
• chromosomes condense + become visible
• nucleus + nucleolus dissolves

Question 6

what happens in metaphase?

Answer 6

• chromosomes line up at the equator
• spindle fibres attach to the chromatids

Question 7

what happens in anaphase?

Answer 7

• spindle fibres contract
• chromatids move to opposite poles
• E comes from ATP

Question 8

what happens in telophase?

Answer 8

• spindle fibres disintegrate
• nucleus, nuclear envelop + Nucleulos reform
• chromosomes are longer so not seen anymore

Question 9

what happens in cytokinesis?

Answer 9

• cell divides into 2
• 2 genetically identical cells have formed

Question 10

when does cancer form?

Answer 10

when there is no signal for the cell to stop dividing

Question 11

what does chemotherapy do?

Answer 11

blocks mitosis

Question 12

what is the structure of chromosomes?

Answer 12

• 2 chromatids
• joined at centromere
• DNA is held in position by histone proteins

Question 13

what is the process to prepare for cell fractionation?

Answer 13

place in a cold, buffered solution with the same H2O potential

Question 14

Why place in a cold, buffered, same water potential solution?

Answer 14

cold - reduce enzyme activity
buffered - so pH doesn’t change
same H2O potential - prevents shrinking/bursting from osmosis

Question 15

what is the process of cell fractionation?

Answer 15

Stage 1: Homogenisation
- cells are broken up by a homogeniser into homogenate (to release organelles) + filtered
Stage 2: Ultracentrifufication
- tube of filtrate is spun in centrifuge @ low speed
- heaviest organelles fall to bottom to form sediment
- supernatant removed + spun at faster speed
- process repeats

Question 16

At what speed are nuclei released?

Answer 16

x 1,000

Question 17

At what speed are mitochondria released?

Answer 17

x 3,500

Question 18

At what speed are lysosomes released?

Answer 18

x 16,500

Question 19

what is the equation for magnification?

Answer 19

size of image / size of object

Question 20

what is resolution?

Answer 20

the ability to distinguish between 2 points

Question 21

what happens if there is a shorter wavelength?

Answer 21

higher resolution

Question 22

how do SEM microscopes work?

Answer 22

• -directs a beam of e- onto the surface from above
• beam passes back and forth
• e- are scattered by the specimen creating an image

Question 23

how do TEM microcopes work?

Answer 23

• e- gun produces a beam of e-
• beam is focused onto the specimen by a condenser electromagnet
• beam passes through a thin segment
• some parts absorb (dark) e- other’s don’t (light)
• image produced
• image can be photographed to give a photomicrograph

Question 24

what is the definition of osmosis?

Answer 24

the net movement of water from an area of high to low concentration via a partially permeable membrane without the use of E

concentrate -> dilute

Question 25

what is the definition of diffusion?

Answer 25

the net movement of molecules from an area of high to low conc. without the use of E

Question 26

what is the definition of Active transport?

Answer 26

the movement of particles from an area of low to high conc with the use of E from ATP

Question 27

what is the definition of facilitated diffusion?

Answer 27

the net movement of particles down their conc. gradient across a partially permeable cell membrane via carrier or channel proteins

Question 28

what is the definition of water potential?

Answer 28

measure of tendency of water molecules to move from 1 area to another + describes the pressure created by the water molecules more dilute = higher water potential (less -ve)

Question 29

what is the definition of co-transport?

Answer 29

occurs when the transport of 1 substance is coupled with the transport of another across a membrane

Question 30

what is the role of extrinsic proteins on the cell membrane?

Answer 30

- at the surface - mechanical support - act as receptors along with glycoproteins

Question 31

what is the role of glycoproteins?

Answer 31

- receptor - maintains stability - helps cells attach to form tissue

Question 32

what are glycoproteins?

Answer 32

carbs covalently bonded to lipids

Question 33

what is the purpose of phospholipid bilayer?

Answer 33

- flexibility - fluid mosaic model - allows lipid soluble substances to diffuse across the membrane easily but prevents water soluble from leaving and entering the cell

Question 34

what is the role of cholesterol?

Answer 34

- adds strength - pull together fatty acid tails of the phospholipid molecules to limit movement

Question 35

what are the 2 types of intrinsic proteins?

Answer 35

- carrier - channel

Question 36

what is the role of carrier proteins?

Answer 36

- bind to ions/other molecules and change shape to move them into the membrane

Question 37

what is the role of channel proteins?

Answer 37

water-filled tubes to allow water soluble ions to diffuse across

Question 38

What happens in Binary fission?

Answer 38

1) cell replicates it's DNA 2) The membrane elongates separating DNA molecules 3) membrane pinches inwards, dividing the cytoplasm in two 4) new cell wall forms between the 2 DNA molecules dividing the original cell.