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biology year 1 > topic 2 : cells, viruses and reproduction of living things > Flashcards

topic 2 : cells, viruses and reproduction of living things Flashcards

1
Q

compare and contrast the ultrastructure of eukaryotic cells and prokaryotic cells

A

similarities
- both have cell membranes
- sme eukaryotes like bacteria also have cell wall
- both have cytoplasm
- both have ribosomes

differences
- eukaryotes have membrane bound organelles
- prokaryotes have plasmid DNA, eukaryotes have a membrane bound nucleus
- eukaryotes have 80s ribosomes, prokaryotes have 70s ribosomes

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2
Q

what is the ultrastructure of prokaryotic cells (eg bacteria)

A
  • cell wall : made of peptidoglycan. for strength and support
  • slime capsule : protective layer –> allow cell to retain moisture and adhere to surfaces
  • plasmid : circular piece of DNA
  • flagellum : helps the cell move
  • pili : hair-like structure –> receptors that allow plasmids to move from cell to cell
  • 70s ribosomes : site of protein synthesis
  • mesosomes : contain enzymes for respiration
  • mitochondria : energy
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3
Q

what is the ultrastructure of eukaryotic cells

A
  • nucleus : DNA
  • RER : rer has ribosomes on surface. folds and process proteins (protein synthesis)
  • SER : a system of membrane-bound sacs. The SER synthesises and processes lipids and steroids
  • golgi apparatus : processes proteins and lipids (also produces lysosomes)
  • mitochondria : site of aerobic respiration
  • centrioles : involved in cell division
  • 80S ribosomes : site of protein synthesis
  • lysosomes : contain digestive enzymes
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4
Q

difference in structure between gram positive and gram negative plants

A

Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane whilst Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.

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5
Q

how to distinguish gram positive and gram negative bacteria

A

gram staining occurs :
- crystal violet used to stain over a fixed culture, which binds to peptidoglycan cell wall.
- after, stain poured off and slide is rinsed with water.
- iodine solution added and removed
- alcohol added (lipopolysaccharides are soluble in alcohol, so gram neg membrane dissolves)
- counterstain red safranin - gram neg is pink/red, gram positive is purple (trap the stain because of thick peptidoglycan layer)

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6
Q

describe how to use a micrometer to determine how many times bigger a drawing is than the actual cell in the blood smear

A
  • measure the length of the blood cells using an eye piece/stage in micrometer
  • divide the length by the magnification of object
  • more than one measurement taken
  • divide this value into the length of the blood cells in the drawing
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7
Q

magnification equation

A

image = actual size x magnification

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8
Q

advantages and disadvantages of electron microscope

A

adv :
- better resolution (more detailed pictures)

disadv :
- expensive
- can’t look at living material
- large

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9
Q

what are the ethical implications on using or not using untested drugs

A
  • difficult to obtain informed consent
  • unknown side effects
  • may not be as effective as the currently accepted treatment
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10
Q

rna retrovirus structure

A
  • have lipid envelope
  • single strand of viral RNA : use reverse transcriptase to make viral dna
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11
Q

dna virus structure

A
  • contain viral DNA : used as direct template for new viral DNA and for mRNA to make viral proteins
  • eg. bacteriophages including lambda phage,
    eg. small pox
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12
Q

rna virus structure

A
  • much more likely to mutate
  • majority contain single strand of `RNA (ss rna)
    eg. tobacco mosaic virus, sars, polio
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13
Q

how does the rna retrovirus replicate and infect the host cell
and give some examples

A
  • viral rna enters host cell - cannot be used as MRNA
  • RNA translated to viral DNA by reverse transcriptase in cytoplasms
  • viral DNA incorporated into host DNA.
  • production of viral dna and proteins
  • viral dna remains in host so continues to make more virus particles

eg. HIV

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14
Q

difference between positive and neg ssrna

A
  • positive ssRNA : RNA acts directly as MRNA and is translated
  • neg ssRNA : RNA is transcribed and then translated
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15
Q

how to control viral infections

A

antiviral drugs

  • target receptors on virus –. prevet them from recognising host cell
  • target enzyme of host cell used to make DNA/RNA
  • inhibit protease enzyme (which allows the virus to be hidden)

vaccine : aim to provide herd immunity (dead/inactive pathogens that stimulate an immune response)

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16
Q

how to control viral infections

A

antiviral drugs

  • target receptors on virus –. prevet them from recognising host cell
  • target enzyme of host cell used to make DNA/RNA
  • inhibit protease enzyme (which allows the virus to be hidden)

vaccine : aim to provide herd immunity (dead/inactive pathogens that stimulate an immune response)

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17
Q

how to reduce viral transmissions

A
  • a lockdown
  • good hygiene/disinfection
  • distance (stop airborne viruses)
  • sterilize medical equipment
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18
Q

what is the lysogenic cycle

A
  • bacteria attach to bacterium
  • inject dna into the host cell and synthesise viral enzymes
  • viral dna incorporated in host cells
  • the viral dna replicates each time (doesnt cause damage)

REMAIN DORMANT

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19
Q

what is the lytic cycle

A

(after change in environment, cycle goes from lysogenic to lytic)
- virus DNA take over biochem of cell
- DNA (viral) replicated
- viral proteins synthesised
- the cell will lyse and virus infects other cells

20
Q

describe the stages of the cell cycle

A

G1 (interphase) : growth, proteins to make organelles
S : replication of DNA
G2 : organelles made, energy store increase and DNA checked for errors
mitosis : cell division
cytokinesis : formation of 2 cells which are genetically identical (cell membrane splits)

21
Q

what are the checkpoints in the cell cycle

A

G1 cp : check cell size, nutrients, growth factors and DNA damage
G2 cp : cell size, replication done right? DNA damage check
metaphase cp : chromosomes aligned at equator, spindle fibres form properly

22
Q

describe what happens in mitosis

A
  • interphase : growth and dna replication, spindle formes
  • prophase : centrioles move to poles, chromosomes condense, nucleolus disappears, nuclears membrane breaks down
  • metaphase: chromosomes align at the equator. spindle fibres attach to the centromeres
  • anaphase : centromere divide, sister chromatids pulls to opposite poles by spindle fibres
  • telophase : nuclear membrane reforms around 2 sets of chromatids, chromosomes re forms
23
Q

what are the products of mitosis

A

2 genetically identical diploid daughter cells.

24
Q

describe the process of meiosis

A

P1 : nuclear membrane breakdown, centrioles move to opposite poles, nucleolus disappears, chromosomes condense. HOMOLOGUS CHROMOSOMES CROSS OVER - exchange genetic information

Metaphase 1:
Chromosome pairs line up at the equator – independent assortment of chromosomes
Spindle fibres attach to the homologous chromosomes

Anaphase 1:
Chromosomes are pulled apart

Telophase 1: nuclear membrane forms around chromatids and spindle fibre disappear, chromosomes decondense

Cytokinesis: produces 2 diploid daughter cells (genetically different)

Prophase 2:
Nuclear membrane breaks down, centrioles move to opposite poles, nucleolus disappears, chromosomes condense

Metaphase 2:
Chromosomes line up at the equator – independent assortment of chromosomes
Spindle fibres attach to the centromeres

Anaphase 2:
centromeres divides chromatids are pulled to opposite poles

Telophase 2 : nuclear membrane forms around chromatids and spindle fibre disappear, chromosomes decondense

Cytokinesis: produces 4 haploid genetically different daughter cells
25
Q

how is there variation in meiosis (3 ways)

A
  • crossing over of homologus pairs : exchange of genetic information
  • recombination of alleles
  • independent assortment of chromosomes : lined up and pulled randomly
26
Q

explain the importance of meiosis in the production of gametes

A
  • provides genetic variation by crossing over
  • independent assortment
  • it halves the chromosome numbers
  • produces haploid cells so diploid number restored during fertilisation
27
Q

what is the importance of mitosis

A
  • growth and repair
  • asexual reproduction
28
Q

what is meant by the term gene mutation

A

change in base sequence of DNA

29
Q

what are the 5 types of chromosome mutations

A
  • Duplication – an extra chromosome
  • Deletion – a section of a chromosome is removed
  • Translocation – one part of a chromosome detaches and reattaches to another chromosome
  • Inversion – one part of the chromosome is flipped
  • Non-disjunction – homologous chromosomes or the chromatids fail to separate
30
Q

what are the 3 types of dna mutations

A
  • Insertion of a base – frameshift mutation. The earlier the insertion, the greater the change in the protein
  • Deletion of a base – frameshift mutation
  • Replacement of a base
    Only one amino acid will be affected
31
Q

what is non-disjunction

A
  • homologus chromosomes may not separate in anaphase 1
  • or sister chromatids may fail to separate in anaphase 2
  • gametes may end up with an estra chromosome or none at all

when these fertilise with normal gametes the zygote has either one extra chromosome (polysomy) or one mising chromosome (monosomy)

32
Q

name the type of chromosome mutation that results in down syndrome

A

polysomy/non-disjunction

33
Q

what is polysomy

A
  • non - disjunction of chromosome 21 –> zygote has 3 copies of chromosome 21
  • this is trisomy of chromosome 21, leading to down’s syndrome which affects mental and physical development

eg. down’s syndrome

34
Q

what is monosomy

A
  • non-disjunction of the sex (X and Y) chromosomes
    eg. turner’s syndrome : in females who are missing an X chromosome, this causes infertility and they cannot mature without sex hormone treatment
35
Q

describe the process of spermatogenisis

A
  • start with primordial gem cell
  • go through mitosis several times to form spermatogonia
  • growth of spermatogonia to form primary spermatocyte
  • primary spermatocyte goes through meiosis 1 to form secondary spermatocyte
  • secondary spermatocyte goes trhough meiosis 2 to form spermatids
  • these undergo differentiation to form mature spermatozoa
36
Q

describe the process of oogenisis

A
  • start with primordial germ cell
  • go through mitosis several times to form oogonia
  • forms other oogonia but they become degenerate and do not divide
  • the generate oogonia goes through meiosis 1 to form a secondary oocyte and a polar body (does not develop into gamete)
  • the secondary oocyte goes through meiosis
37
Q

what are some characteristics of the ovum

A
  • Zona pellucida: protective layer that the sperm has to penetrate – it prevents polyspermy (prevents multiple sperm fertilising the egg)
  • Cortical granules release substances to cause the zona pellucida to harden
  • The nucleus is haploid (in a human it will have 23 chromosomes)
  • Follicle cells forma further protective coating – the purpose of the follicle is to produce progesterone (to maintain the uterus lining) after ovulation
38
Q

what are some characteristics of sperm

A
  • Flagella allows the cell to move
  • Lots of mitochondria to provide energy for this movement
  • Acrosomes (head of the sperm) contain digestive enzymes to break down the zona pellucida and allow for fertilisation
  • Haploid nucleus
39
Q

describe the process of fertilisation in mammals

A
  • The acrosome comes into contact with the zona pellucida and the acrosome reaction occurs – enzymes digest the zona pellucida
  • Acrosome fuses with the cell surface membrane and allows the sperm nucleus to enter the egg cell
  • Cortical reaction causes the zona pellucida to harden and prevent polyspermy
  • Nuclei fuse together and form a diploid zygote
40
Q

describe how pollen is produced in plants (microgametogenisis)

A
  • start with a microspore mother cell.
  • this goes through meiosis twice to form a haploid cell
  • the cell with go through mitosis twice and the nuclei only divide to form a pollen tube nucleus and a generate nucleus
  • it develops a 2nd generate before going down the pollen tube
41
Q

describe how the female egg in plants is produced (megagametogenisis

A
  • starts with a megaspore mother cell
  • goes through meiosis twice to form 4 haploid cell, but 3 of them are degenerate
  • the cell grows
  • the nuclei divide by mitosis until there are 8 nuclei that are haploid
  • the top 3 nuclei are antipodal cells (– function is unclear, seem to provide a protective coating)
  • the two nuclei in the middle are polar bodies
  • there are two synergids at the bottom (used to help the generative nucleus reach the egg cell)
42
Q

how does fertilisation in plants occur?

A
  • Pollen grain is made up of the pollen tube nucleus and the generative nucleus
  • The grain sticks to the stigma where it germinates
  • Pollen Tube nucleus
    Pollen tube grows down the style by secreting digestive enzymes
    The enzymes break down surrounding tissue for nutrients
    The pollen tube grows into the embryo sac
  • The generative nucleus
    o Divides by mitosis to produce 2 sperm cells which enter the embryo sac
    o One of the sperm cells fuses with the female nucleus – forms the main embryo
    o The other fuses with the polar nuclei to produce a triploid primary endosperm nucleus – provides nutrients for the embryo
43
Q

what does totipotent mean

A

o Totipotent: can make any other kind of cell in the body

44
Q

what does pluoripotent mean

A

o Pluripotent stem cells are more limited – it can form any cell type except the placenta/umbilical cord

45
Q

what does multipotent mean

A

o Multipotent stem cells differentiate into several cell types but are limited

46
Q

describe how an embryo develops to a blastocyte

A
  • The zygote undergoes cleavage – mitosis occurs without the interphase stage. The process occurs in the oviduct
  • The product of cleavage results in the blastocyst – a small collection of cells forming embryo
  • The outer cells of the blastocyst are totipotent and can form the placenta while the inner cells will be pluripotent and they form the rest of the foetus
  • The whole process takes about a week

biology year 1 (4 decks)

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