2.2 - 2.3 prokaryotic cells & mitosis

Question 1

Gram positive bacteria is made of ..

Answer 1

-Thick layer peptidoglycan in their cell walls
-Teichoic acid trapped in thick layer

Question 2

Gram negative bacteria is made of ..

Answer 2

-Thin layer peptidogylcan between 2 layers of membrane
-no teichoic acid
- outer membrane contains lypopolysaccharides

Question 3

2 main types of bacteria can be distinguished by

Answer 3

Gram staining

Question 4

How does gram staining work ?

Answer 4

1. Add purple crystal violet / iodine complex all cells appear purple as they take in stain
2. Add alcohol to decolorisation , only GN bacteria loose colour as layer of lipopolysaccharides is dissolved & can’t hold stakn
3. Add red safranin counterstain to stain GN bacteria red. counterstain not seen on gram- positive bacteria because of the darker crystal violet stain.

Question 5

Other than gram staining how else can bacteria be classified

Answer 5

Shape
Respiratory requirements

Question 6

Respiratory requirements:
Obligate aerobes
Facultative aerobes
Obligate anaerobes

Answer 6

Need oxygen for respiration
Use oxygen if available but can manage without
Can only respire in absence of oxygen

Question 7

How does the beta lactam (penicillin) antibiotic work
Why are they more affective against gram pos

Answer 7

It attacks gram positive bacteria by inhibiting the formation of cross links in the peptidoglycan layer of cell wall
- water moves into cell my osmosis , cell bursts

They have thick pep layer so the cell wall can be affected

Question 8

How does the Glycopeptide antibiotic work

Answer 8

-They’re large polar molecules
- affective against gram positive
- difficult to penetrate outer membrane layer of gram neg
-

Question 9

How does polypeptide antibiotics work?

Answer 9

• rarely used as can have serious side effects
• affective with - as they interact w phospholipids of outer membrane

Question 10

What happens during the g1 interphase stage of mitosis?

Answer 10

Duplication of organelles like mitochondria
- cell growing in size and making of proteins

Question 11

What happens in the s phase of interphase (mitosis)?

Answer 11

• chromosomes replicate becoming double stranded chromatids

Question 12

What happens in the G2 phase of interphase (mitosis)?

Answer 12

Organelles and other materials needed for cell divisions are synthesised

Question 13

When a cell starts to actively divide …

Answer 13

The chromosomes become shorter and denser allowing them to take up stains easier and be identified

Question 14

When dna condenses (becomes shorter and denser ) how is it packaged efficiently ?

Answer 14

Dna winds around histones to produce nucleosomes
These intercatc o produce more coiling then they super coil

Question 15

The cell cycle is controlled by …

Answer 15

Cyclins which attach to enzymes called cyclin dependent kinases

Question 16

what takes place in the prophase phase of mitosis?

Answer 16

-dna condenses , chromsomes become visible
-nuclear membrane breaks down
-as centrioles divide and move to either pole spindle fibres form

Question 17

what takes place in the metaphase phase of mitosis?

Answer 17

spindle fibres attach to centomeres
Chromosomes are lined up at cell equator by sf

Question 18

what takes place in anaphase phase of mitosis?

Answer 18

centromeres separated , sc pulled apart, sister chromatids move to opp poles,

Question 19

telpohase?

Answer 19

-nuclear envelopes form around 2 sets of chromosomes
-nucleoli reforms
- chromosomes decondense , lengthen can’t see

Question 20

cytonkinesis?

Answer 20

2 identical daughter cells formed

Question 21

what is assexual reproduction

Answer 21

reproduction involving one parent and produces genetically identical offspring

Question 22

these methods of assexual reproduction rely on mitosis:

binary fission

producing spores

Answer 22

used by bacteria, splitting of one individual to form 2 new ones, causes exponential growth

fungi, plants, production of assexual spores that can grow into new individuals , spread over large distances

Question 23

these methods of assexual reproduction rely on mitosis:

regeneration

producing buds

Answer 23

lizards, starfish, fungi – use of mitosis to regrow a body part that has been lost

yeast cells, hydra – an outgrowth from a parent organism which produces a smaller but genetically identical individual

Question 24

these methods of assexual reproduction rely on mitosis:

vegatative propagation

parthogenesis

Answer 24

Producing identical plants from part of a plant

unfertilised egg cell develops into new indiviudal

Question 25

the structure of viruses is composed of..

Answer 25

capsid coat which is made of repeating units called capsomeres
-a lipid enevelope derivered from host cell membranes
-nucleic acid

Question 26

how do viruses attach to host cells..
why dont viruses attach to all cells

Answer 26

through virus attachment particles
viruses attach to specific molecules on cells surface

Question 27

how can types of viruses be classified

Answer 27

1. dna viruses
2. rna viruses (+ and - ssRNA)
3. rna retroviruses

Question 28

DNA viruses -

RNA retroviruses -

Answer 28

viral dna acts as template for cell to make mRNA then viral proteins

ssRNA, makes enzyme called reverse transcriptase converts rna to dna , cell makes mrna , cell makes viral protein

Question 29

ssRNA viruses:

positive
negative

Answer 29

+ = rna used as mRNA for cell to directly make viral proteins
- = ssRNA , rna transcribed to form mRNA, cell makes viral protein

Question 30

lambda phage -

tobacco mosaic virus -

Answer 30

-dna no envelope
- positive ssRNA, no envelope

Question 31

ebola
HIV

Answer 31

• positive ssrna, lipid envelope
• rna retovirus, lipid envelope

Question 32

how does the lytic pathway work

Answer 32

• attachment using vaps
• entry of viral gm
  -replication of vgm and production of viral prot
  -assmebly of new viral particles/viruses
  -lysis of host cell

Question 33

how does the lysogenic cycle work?

Answer 33

attachement (vaps)
-entry of vgm which is inserted into bacterial nucleoid
-replication of vgm every time bac cell undergoes binary fission
- if the amount of reperessor protein falls , dna forms own circle entering lytic cycle

Question 34

why cant viruses be treated with antibiotics?

antiviral drugs target virus replication by :

Answer 34

they arent living cells

1. targetting receptors by which viruses recognise their host cell
2. targetting enzymes that help translate / replicate viral dna or rna

Question 35

vaccinations develop..

Answer 35

immunity to a disease
gloves, facemasks, vaccines

Question 36

Why are viruses not affected by antibiotics

Answer 36

• viruses aren’t living cells
• viruses don’t have cell wall

Question 37

Define growth

Answer 37

The permanent increase in the mass of an organism

Question 38

Why can measuring mass be difficult ?

Answer 38

The water content of cells can vary greatly
- animals can also be carrying varying amounts of faecal matter in their bodies

Question 39

What’s the most accurate way of measuring growth

Answer 39

Measuring dry mass , it shows the amount of biological material present

Question 40

Growth in plants

Answer 40

Meristems where mitosis takes place
Cells differentiate
Elongation of cells