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SNAB A Level Biology > Topic 3: Voice of the Genome > Flashcards

Topic 3: Voice of the Genome Flashcards

1
Q

what are the differences between eukaryotic and prokaryotic cells?

A

eukaryotic
- contains membrane-bound organelles (nucleus, mitochondria, ER)
- 80s ribosomes

prokaryotic
- no membrane-bound organelles (circular DNA instead of nucleus)
- 70s ribosomes

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2
Q

name all the components of an animal cell (12)

A
  • centrosome and centrioles
  • lysosome
  • mitochondria
    -rER
  • sER
  • nucleus
  • nucleolus
  • cytoplasm
  • CSM
  • ribosomes
  • golgi apparatus
  • microvilli
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3
Q

what is the function of the nucleolus?

A

ribosome synthesis

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4
Q

what is the function of the lysosome

A

contains digestive hydrolytic enzymes to digest invading cells or break down cell components and to break down waste materials such as worn-out organelles,
Lysosomes are used by cells of the immune system and in programmed cell death, known as apoptosis

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5
Q

what is the function and structure of the cell surface membrane?

A

controls the exchange of materials
partially permeable
phospholipid bilayer

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6
Q

what is the function and structure of the nucleus?

A
  • contains chromatin (material that makes chromosomes)
  • separated from the cytoplasm by the nuclear envelope (a double membrane with pores)
  • nucleolus in the nucleus = site of ribosome production
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7
Q

what is the function and structure of the mitochondria

A
  • site of aerobic respiration
  • surrounded by cristae (double membrane w folded inner membrane)
  • matrix of mitochondria contains enzymes to produce ATP
  • mitochondrial DNA and ribosomes also found in the matrix
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8
Q

what is the function and structure of the ribosomes

A

site of translation in protein synthesis
- can be found as free organelles or on the rER
- each ribosome is a complex of rRNA and proteins
- 80s ribosomes = eukaryotic
- 70s ribosomes = prokaryotic, mitochondria and chloroplasts

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9
Q

what is the function and structure of the rER

A
  • role = to process proteins made on the ribosomes
  • formed from folds of membrane continuous with the nuclear envelope
  • covered in ribosomes
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10
Q

what is the function and structure of the sER

A
  • role = involved in the production, processing and storage of lipids, carbs and steroids
  • formed from folds of membrane
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11
Q

what is the function and structure of the golgi apparatus

A

role = to modify proteins and lipids before packaging them into golgi vesicles
consists of flattened sacs of membrane - looks like a WiFi symbol

  • at the top is the cis face where the incoming vesicle attaches
    and at the bottom is the trans face where vesicles are secreted
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12
Q

centrioles

A

made of microtubules - which are filaments of protein that can be used to move substances around inside the cell

centrosome = 2 centrioles at right angles to each other. centrosome organises the spindle fibres during cell division

not found in plants and fungi

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13
Q

what is the process of protein transport - involving the rER and the Golgi Apparatus

A
  1. the nucleolus manufactures ribosomes for protein synthesis in the rER
  2. the nucleus manufactures mRNA
  3. the ribosomes in the rER make proteins
  4. the rER processes the proteins which are then sent in vesicles to the golgi body
  5. the golgi body further processes the proteins and sends them in vesicles to the plasma membrane
    6.Cells exit the Golgi in a vesicle. Extracellular enzymes are secreted by exocytosis.
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14
Q

what additional structures do prokaryotes have (7)

A
  • plasmids
  • capsule
  • flagellum
  • pilus
  • mesosomes
  • circular DNA
  • 70s ribosomes
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15
Q

what is the function of pili

A

thread-like structures that help prokaryotes stick to other cells and can be used in the transfer of genetic material

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16
Q

what is the function of the slime capsule

A

final outer layer that protects bacteria from drying out and from attacking cells
not present in all prokaryotes

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17
Q

structure and function of mesosomes

A

inward folds in the plasma membrane.
aerobic respiration, cell wall formation and DNA replication

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18
Q

what is the function of plasmids

A

small loops of DNA that contain genes that can be passed between prokaryotes

not present in all prokaryotes

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19
Q

what is the function of the flagellum

A

a ling, hair-like structure that enables the prokaryote to move

not present in all

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20
Q

what is the circular DNA in prokaryotes

A

the genetic material of prokaryotic cells mainly consists of a single circular strand of DNA that is not contained in a membrane-bound nucleus

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21
Q

What is the difference between magnification and resolution

A

mag = increase in image size of an object
res = ability to distinguish between two separate points or objects

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22
Q

What is the maximum resolution and magnification of a light microscope and an electron microscope

A

light = res - 200nm
mag = x1500- x2000

electron = res - 0.5nm
mag - 50,000,000x

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23
Q

What are the principal differences between transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs)?

A

TEMS = use transmitted electrons passing through a thin sample to show internal structures
SEMS = use scattered electrons from the surface to show surface details and topography

24
Q

How do you calibrate an eyepiece graticule suing a stage micrometer?

A

place the micrometer on the microscope stage, view it through the eyepiece, and align the graticule with the micrometer scale.
Then, determine the magnification factor by counting the number of graticule divisions that correspond to a known distance on the micrometer

25
what are 1. tissues 2. organs 3. organ systems
1. a group of cells of similar structure working together to perform a particular function 2. made from a group of diff tissues working together to perform a particular function 3. made from a group of organs w related functions working together to perform body functions within the organism
26
what are the phases of the cell cycle
G1 S G2 M phase
27
what happens during phase G1
a signal is received telling the cell to divide again, the DNA in the nucleus replicates cells make the RNA, enzymes, and other proteins required for growth
28
what happens during the S phase
synthesis of DNA
29
wha happens during the G2 phase
cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired
30
what stages of the cell cycle make up the interphase
G1 + S+ G2
31
what are the 4 phases of mitosis
prophase metaphase anaphase telophase
32
what happens during prophase
- chromosomes condense - now visible when stained - chromosomes consist of 2 identical chromatids = sister chromatids that are joined at the centromere - the 2 centrosomes - replicated in G2 - move towards opposite poles - spindle fibres begin to emerge from the centrosomes - nuclear envelope breaks down
33
what happens during the metaphase
- centrosomes reach opposite poles - spindle fibres continue to extend from centrosomes - chromosomes line up @ equator of the spindle so they are equidistant to the 2 centrosome poles - spindle fibres reach the chromosomes and attach to the centromeres - each sister chromatid is attached to a spindle fibre from opposite poles
34
what happens during anaphase
- the sister chromatids separate at the centromere - spindle fibres begin to shorten - sister chromatids, now called chromosomes, are pulled to opposite poles by the spindle fibres
35
what happens during telophase
-chromosomes arrive @ opposite poles and begin to decondense - nuclear envelopes begin to reform around each set of chromosomes - the spindle fibres break down
36
what happens during cytokinesis
whole cell divides, creates 2 genetically identical daughter cells
37
what is mitosis used for
growth repair asexual reproduction
38
how do u calculate mitotic index
number of cells w visible chromosomes / total number of cells
39
how is an egg specialised to its function
- much larger bcoz most of their internal space contains nutrients for a growing embryo - have zona pellucida (jelly-like glycoprotein layer) that forms an impenetrable barrier after fertilisation
40
how are sperm cells adapted for their function
- flagellum - enables to swim to egg - enzymes in acrosome - to digest through zona pellucida - many mitochondria - provide energy to swim
41
describe the process of fertilisation
- sperm cell membrane fuses with egg cell membrane - acrosome releases enzymes that digest through ZP - cortical granules release contents into zona pellucida - contents of cortical granules react with the zona pellucida and the ZP thickens - the haploid nuclei fuse
42
what is the cortical reaction
when the chemicals contained within the cortical granules cause the zona pellucida to rapidly thicken preventing any more sperm cells from entering
43
what is the acrosome reaction
when the acrosome releases enzymes that digest a path through the zona pellucida allowing the sperm to pass through the egg cell membrane
44
describe the process of meiosis
- chromosomes replicate before meiosis - during meiosis, the homologous pairs of chromosomes split up to produce 2 haploid nuclei - then the chromatids that make up each chromosome separate to produce 4 haploid nuclei - each chromosome now consists of a single chromatid
45
what are the two factors that create genetic variation
mutations sexual reproduction
46
What is crossing over of chromatids?
process where non-sister chromatids exchange alleles 1. homologous chromosomes pair up - called bivalents 2. the non-sister chromatids can cross over and get entangled 3. these crossing points are called chiasmata 4. the entanglement places stress on the DNA molecules, as a result of this, a section of chromatid from one chromosome may break and rejoin w the chromatid from the other chromosome
47
why is the swapping of alleles significant
it can result in a new combination of alleles on the two chromosomes crossing over is more likely to occur further away from the centromere
48
what is the independent assortment of chromosomes
random alignment of homologous chromosome pairs during meiosis, leading to diff allele combinations in daughter cells 1. homologous chromosomes pair up and move to the spindle equator 2. each pair aligns randomly, with either chromosome on top 3. the orientation of one pair is independent of others 4. homologous chromosomes are then separated and pulled to opposite poles
49
what is a totipotent cell?
can differentiate into any cell type zygote and cells up to 16-cell stage are totipotent
50
what is a pluripotent cell
can differentiate into any embryonic cell type cannot form placenta or umbilical cord found in embryonic stem cells
51
what are stem cells
an undifferentiated cell that can divide by mitosis an unlimited number of times
52
what is potency
the ability of stem cells to differentiate into more specialised cell types
53
where do plants have stem cells
shoots and roots
54
what are some examples of adult multipotent stem cells
bone marrow skin liver brain umbilical cord blood
55
how are EMBRYONIC stem cells used in medicine?
totipotent if taken 3-4 days after fertilisation pluripotent if taken on day 5 embryos used are often waste fertilised embryos from IVF
56
how are ADULT stem cells used in medicine
- only able to differentiate into a limited range of cell types - need to be a close match for blood type and antigens
57

SNAB A Level Biology (5 decks)

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