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Biology > 2: Cells, Viruses, Reproduction > Flashcards

2: Cells, Viruses, Reproduction Flashcards

(75 cards)

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1
Q

What is the nucleus surrounded by?

A

Double membrane with nuclear pores that control exit of substances.
e.g mRNA leaving nucleus to get to ribosome in cytoplasm

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2
Q

Describe interior of nucleus

A

Interior is called nucleoplasm and it’s full of chromatin (DNA).

Nucleoplasm is where all chemical reactions for nucleus happen.

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3
Q

Where are ribosomes made?

A

Nucleolus

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4
Q

What is the job of ribosomes?

A

Site of protein synthesis.
They put amino acids together to form polypeptides

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5
Q

What is a ribosome comprised of?

A

2 subunits: rRNA and proteins

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6
Q

How are eukaryotic ribosomes different from prokaryotic ones?

A

Eukaryotic are 80s so larger

Prokaryotic are 70s

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7
Q

Where are ribosomes found?

A

Free in cytoplasm or attached to Rough Endoplasmic Reticulum

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8
Q

Describe RER’s appearance and function

A

RER is studded with ribosomes which gives a rough appearance.

RER folds up polypeptide chains at ribosome to turn them into proteins.

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9
Q

What does SER do?

A

Makes lipids needed by the cell

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10
Q

What is the Golgi Body? Give it’s job as well

A

Is a smooth membrane bound organelle.

It packages molecules into vesicles to transport them to the cell membrane.

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11
Q

What is exocytosis?

A

When the vesicles fuse with the cell membrane to release their contents.

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12
Q

Draw and label a mitochondria.
Explain how it’s adapted for it’s function.

A

Is site of aerobic respiration.
It’s surrounded by a double membrane.
The inner membrane is highly folded into cristae - gives a larger surface area.
Matrix is where enzyme controlled reactions take place.

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13
Q

What are lysosomes?

A

Small membrane bound vesicles containing hydrolytic enzymes

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14
Q

Describe centrioles and their function.

A

Always 2 found near nucleus. They are cylindrical. Always occur 90 degrees to each other.
Used in cell division to make spindle fibres that pull chromosomes apart.

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15
Q

What is the vacuole and what is it full of?

A

A membrane bound sac containing cell sap. Cell sap contains mineral ions.

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16
Q

What is the job of the vacuole?

A

Helps maintain pH of cytoplasm so enzymes that work in chemical reactions there don’t denature.

Gives cell turgidity.

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17
Q

Give the name of the membrane surrounding a vacuole

A

Tonoplast

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18
Q

Draw and label a choloroplast

A

Lamella are cytoplasmic bridges between thylakoid stacks.
Stroma is cytoplasm of organelle

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19
Q

What are plant, fungal, bacterial and algal cell walls made out of?

A

Plant - cellulose
Fungal - chitin
Bacterial - peptidoglycan
Algal - glycoprotein

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20
Q

What are the 2 types of prokaryotic cell wall? How are they different?

A

Gram Positive - have a thick peptidoglycan cell wall.

Gram negative - thin peptidoglycan cell wall. More complex structure. Have a layer of lipopolysaccharides on outer membrane which resists enzymes & antibiotics.
So gram negative are harder to kill

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21
Q

Outline steps of gram staining method

A
  1. Add crystal violet to sample. More peptidoglycan means more crystal violet absorbed.
  2. Then add iodine which binds to crystal violet to trap it in cell wall.
  3. Alcohol is added to wash away excess crystal violet.

Gram negative turns colorless as it has a thinner peptidoglycan wall so hasn’t absorbed much crystal violet.

  1. Add safranin which turns gram negative pink.
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22
Q

What is magnification?

A

How much an image has been enlarged to compared to the real thing.

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23
Q

What is resolution?

A

The distance at which 2 points can be distinguished.

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24
Q

Give advantages and disadvantages of light microscopes.

A
  • are simple and cheap
  • can use living cells
  • BUT it has a low magnification and resolution
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25
Give advantages and disadvantages of electron microscopes.
- have a very high resolution and magnification - can see subcellular structures e.g ribosomes - are very big and expensive - uses a vacuum so specimen is always dead
26
What are the steps to setting up a microscope?
1. Turn on light source 2. Start with low power so you can find specimen 3. Lower stage and place microscopic slide with specimen on 4. Adjust course focus to find specimen in field of view 5. Change objective lens to increase magnification 6. Adjust fine focus to have high resolution
27
How do you use an eyepiece graticule?
1. Calibrate E.P.G using stage micrometer 2. Align stage micrometer with E.P.G 3. Work out how many divisions = certain number of micrometers
28
Describe phospholipids
Composed of 1 glycerol molecule, 2 fatty acids and a phosphate group. Fatty acid chains are non polar and hydrophobic Phosphate head is polar and hydrophilic
29
What do phospholipids form in water?
Phospholipid monolayer
30
What do phospholipids form when SHAKEN in water?
Micelle
31
Name the 2 types of proteins in a cell membrane
Transmembrane (intrinsic) Peripheral (extrinsic)
32
What are the 4 types of peripheral proteins?
1. receptor proteins 2. enzymes 3. glycoproteins 4. structural
33
Give definition of osmosis
Net movement of water from high water potential to low water potential across partially permeable membrane
34
What is the water potential and osmotic potential of pure water? How does it differ to the w.p of other solutions?
Pure water has a highest w.p and o.p of 0 Impure solutions must have a w.p of lower than 0 (negative values)
35
What is turgor pressure?
Hydrostatic pressure caused by cell's contents pushing against cell wall.
36
Describe what happens in a HYPERTONIC cell
Water moves from inside cell to outside as the w.p is higher inside than out. Turgor pressure is 0 as no water is pushing against cell wall from inside
37
Describe an ISOTONIC cell
Same w.p inside and out So no net movement overall
38
What is osmotic potential?
Is the potential of water to move out of solution across a partially permeable membrane due to dissolved salts.
39
Which virus uses reverse transcriptase
HIV
40
Which viruses have a lipid membrane
HIV and Ebola
41
Which virus has a helical capsid shape
Tobacco Mosaic Virus
42
What is the host cell for a bacteriophage and what is the capsid shape of a bacteriophage
E Coli capsid shape is complex
43
Which virus has double stranded DNA
Baceriophage
44
Describe lytic cycle of virus
1. Virus attaches to host ell and injects genetic material into it 2. viruses assemble from proteins 3. lysis of host cell releases new viruses
45
During latent phase, what does the virus do?
viral DNA is replicated along with host cell DNA every time host cell divides Virus doesnt cause any harm and is not disease causing
46
What kind of pathogens are viruses and how are they spread?
Communicable pathogens = spread from person to person THROUGH direct contact, aireborne, bodily fluids.
47
What do viruses have that allows them to attach to cells
they use attachment proteins which bind to receptors on host cell
48
How can we stop viral infections
develop drugs that block attachment proteins on virus or receptors on host cell isolate infected individuals develop drugs that target viral enzymes
49
What is the difference between an epidemic and pandemic?
epidemic is an infectious disease that spreads faster and wider than usual pandemic is when an epidemic spreads across continents
50
How do ebola and HIV leave their host cells?
BUDDING they collect lipid envelopes from the hot cell's membrane then virus particles are released by budding.
51
How does Bacteriophage leave host cell (E Coli)
1. double stranded DNA injected by bacteriophage 2. it's DNA is incorporated into host cell's - now in latent phase 3. a trigger will cause transcription and translation to make new viruses 4. bacteriophage leaves by cell lysis.
52
which 3 stages does the cell cycle compose of and what does the cell cycle produce
interphase mitosis cytokinesis produces 2 identical daughter cells
53
state what happens in interphase
interphase: G1 (cell growth, nutrients) S (DNA replication G2 (prep for mitosis)
54
state what happens in each stage of mitosis then cytokinesis
Prophase - chromosomes condense and become visible. Centrioles move to opposite poles of cell. Spindle fibres begin to form. Metaphase - spindle fibres attach to centromere of chromosome. Chromosomes line up in middle of cell. Anaphase - chromatids are pulled to opposite ends of cell by spindle fibres shortening. Telophase - chromosomes de-condense. 2 new nuclei form. Cytokinesis - cytoplasm divides and 2 nuclear membranes form around new cells.
55
In complex organisms, how are cells organised
Into tissues, organs and organ systems
56
why is staining specimens important in microscopy and suggest how we can stain
stain using iodine to make subcellular structures VISIBLE
57
what are the ethical implications of using untested drugs during epdemics
patient consent may cause more harmful side effects instead of benefits vulnerable populations should not be exposed to risks without proper reason
58
outline stages of meiosis and where it happens
happens in zygotes PROPHASE 1: nuclear envelope disappears. DNA condenses so chromosomes become visible. Bivalents pair up . Crossing over happens. Spindle fibres begin to form. METAPHASE 1: bivalents line up in middle of cell. Spindle fibres attach to centromere of each chromosome. ANAPHASE 1: spindle fibres shorten so CHROMOSOMES are pulled apart. TELOPHASE 1: new nuclear envelope forms around each set of chromosomes. PROPHASE 2: centrioles move around by 90 degrees METAPHASE 2: spindle fibres attach to centromere of chromosomes. Chromosomes line up horizontally across cell ANAPHASE 2: spindle fibres shorten pulling CHROMATIDS apart TELOPHASE 2: 4 new nuclear membranes form around each set CYTOKINESIS: results in 4 haploid genetically unique cells
59
How does meiosis result in genetic variation
CROSSING OVER (prophase 1) - chromosomes get so close they interwine slightly. Chiasmata is the section where they overlap. A gene from each chromatid attaches to the other. This ensures variation INDEPENDENT RANDOM ASSORTMENT (prophase 1) - where bivalents randomly pair up.
60
what are chromosome mutations eg translocations
only for NON HOMOLOGOUS pairs. translocation can change phenotype so embryo may not develop.
61
How can non-disjunction lead to polysomy (down's syndrome) and monosomy (turner's syndrome)
non-disjunction is when chromosomes don't separate properly in anaphase 1 or 2. So, one of the sets will end up with more or less chromosomes than you should have.
62
Outline the stages of oogenesis and draw the diagram
2n primordial germ cell --> mitosis --> 2n oogonia (becomes primary oocyte) --> meiosis 1 (primary oocyte is suspended in prophase until puberty) --> n secondary ooyte and n small polar body (discarded) --> meiosis 2 (only on fertilisation) --> secondary oocyte differentiates into ovum and small polar body after meiosis 2 is left behind
63
outline stages of spermatogenesis
2n primordial germ cell --> 2n spermatogonium --> mitosis --> two 2n primary spermatocyte --> meiosis 1 --> two 1n secondary spermatocyte --> meiosis 2 --> 4 1n spermatids --> spermatogenesis (differentiation) --> 4 spermatozoa (sperm)
64
Stages of fertilisation
- sperm makes contact with egg - acrosome reacts with zona pellucida - acrosome reaction - hydrolytic enzymes released by exocytosis digest through zona pellucida to reach cell membrane - plasma membrane of sperm and egg fuse - sperm nucleus enters egg - cortical reaction - cortical granules fuse with egg plasma membrane causing zona pellucida to harden - prevents polyspermy
65
outline what happens in early development of embryo to blastocyst stage
zygote undergoes several rounds of mitosis to form ball of cells called morula around 5 days later, morula forms hollow ball called blastocyst blastocyst implants into wall of uterus
66
outline stages of microsporogenesis and where its made
microspore is made in anther 2n microsporocyte --> meiosis --> four 1n microspores --> after pollination: 1n generative nucleus and 1n pollen tube nucleus --> mitosis only generative nucleus --> 2x male gametes and 1n pollen tube nucleus
67
how does an embryo sac form in ovule (megasporogensis), learn diagram
2n megasporocyte --> meiosis --> produces four n but only 1 survives (megaspore) --> mitosis 1 --> two 1n --> mitsosis 2 --> four 1n --> mitosis 3 --> eight 1n --> DIFFERENTIATION --> mature embryo sac: 2x 1n polar nuclei, five 1n unused cells disintegrate, 1n female gamete
68
how does the male nuclei, formed by division of division of generative nucleus in pollen grain, reach embryo sac. INCLUDE ROLES OF TUBE NUCLEUS, POLLEN TUBE AND ENZYMES
pollen tube emerges from mature gametophyte (pollen grain) and grows down style towards ovary pollen tube secretes enzymes to digest tissue infront of it and use the digested products to grow pollen tube nucleus controls growth at tip of pollen tube when pollen tube reaches ovary it enters embryo sac through micropyle
69
what are the stages of double fertilisation in the embryo sac and what 2 things does it form
the 2 male gametes enter the embryo sac and 1 fuses with egg cell. The other fuses with 2 polar nuclei to form triploid endosperm. zygote develops into embryo triploid endosperm grows and develops into food store (endosperm). This noruishes developing embryo
70
draw and label the structure of a chromosome
has a centromere which is centre of chromosome has 2 sister chromatids section of chromosome is a gene
71
how is chromatin formed
DNA is wrapped around histones which coil up and stabilise DNA molecules
72
what is a homologous pair
2 copies of each chromosome: 1 from mother 1 from father
73
how are homologous pairs the same and different in
have same genes but different alleles
74
what is an allele
different versions of same gene
75
what is location of a gene called
loci

Biology (4 decks)

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