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Biology Year 13 > Cells & Viruses > Flashcards

Cells & Viruses Flashcards

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1
Q

What are the two types of cells

A

Prokaryotic and eukaryotic

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2
Q

Give 3 examples of eukaryotic cells

A

Animal cells, plant cells, fungal cells

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3
Q

What are the three types of microscopes

A

Light microscope
Electron microscope
Transmission electron microscope

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4
Q

Define the term resolution

A

The ability to discriminate fine detail, two neighbouring points are seen as separate

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5
Q

Why does the electron microscope have better resolution?

A

Electrons have a shorter wavelength than light

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6
Q

What is the main advantage of using a light microscope?

A

Living processes such as mitosis can be observed
The interior of an electron microscope is a vacuum therefore the specimens have to be dead

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7
Q

Give 3 comparisons of light microscopes and transmission electron microscopes

A

Light:light reflected by glass lens
TEM:beams refracted by electromagnetic lenses

Light:Low magnification 1500X maximum
TEM: High magnification 1 000 000X maximum

Any others from:
TEM have higher resolution
Image formed on the retina from Light microscopes but imagine is formed on fluorescent screen in TEM
Light microscopes can view living specimens, TEM can’t

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8
Q

What is the difference in the scanning electron microscope (SEM) and transmission electron microscope (TEM)?

A

TEM specimens are coated in a film of gold so electrons reflect off the surface to create a 3D effect image

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9
Q

Describe the process of homogenisation

A

Place chopped up specimen into a cold isotonic buffer solution
Blend the tissue to break open cells releasing the organelle
Filter the mixture to remove debris

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10
Q

Describe the process of centrifugation

A

Mixture is spun so the denser parts are thrown to the bottom, forming a sediment
The supernatant is poured into a tube leaving the sediment ( contains the nucleus )
This is repeated at higher speeds multiple times to retrieve different organelles

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11
Q

Describe a safety precaution of using a centrifuge

A

Having an equal mass/ counter balance

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12
Q

Why is it a cold isotonic buffer solution?

A

Cold- to reduce enzyme activity which could break down organelles
Isotonic- to prevent the organelles bursting from osmosis
Buffer- to maintain a constant pH so enzymes/proteins aren’t denatured

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13
Q

Compare the cell walls in eukaryotic cells

A

Animal- none
Plant- cellulose
Fungal- chitin

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14
Q

Describe the types of granules found in eukaryotic cells

A

Animal- Glycogen
Plant- Starch
Fungal- Glycogen

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15
Q

Which eukaryotic cells have lysosomes

A

Animal and fungal

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16
Q

Which eukaryotic cells have vacuoles

A

Plant
Fungal

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17
Q

Describe the structure of the nucleus

A

Largest organelle enclosed within a double membrane , contains chromatin and nucleoli

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18
Q

Outline the function of the nucleus

A

Nuclear pores allow large molecules in and out of the nucleus.
Nucleolus synthesis ribosomal RNA and manufactures ribosomes

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19
Q

Describe the structure of ribosomes

A

Small bodies of protein and RNA
Either attached to RER or free in cytoplasm

20
Q

Outline the function of ribosomes

A

Site of polypeptide synthesis
Free ribosomes will produce proteins that will function within the cytoplasm

21
Q

Describe the structure of RER

A

It is a membrane system with flattened sacs, it continues with the outer nuclear membrane, covered with ribosomes

22
Q

Describe the role of RER

A

The polypeptides made on the ribosomes accumulate in the rough ER to be passed on,in vesicles, to the Golgi apparatus

23
Q

Describe the structure of SER

A

membrane system of interconnecting tubules

24
Q

Describe the role of SER

A

synthesis of lipids and their distribution throughout the cell

25
Q

Describe the structure of the Golgi apparatus

A

A stack of membrane bound sacs ( called cisternae)
Formining face has vesicles from the rough ER joining it
Mature face has vesicles pinching off

26
Q

Describe the role of the Golgi apparatus

A

Polypeptides are combined ( to form quaternary proteins ) or modified ( e.g glycoproteins )
Finished proteins are packaged into vesicles either for secretion by exocytosis or delivery within the cell

27
Q

Describe the structure of lysosomes

A

Vesicles produced by the Golgi apparatus that contain hydrolytic enzymes

28
Q

Describe the role of lysosomes

A

They combine with membrane-bound degenerate organelles ( or ingested particles )
This forms secondary lysosomes
Hydrolytic enzymes digest the contents

29
Q

Describe the structure of mitochondria

A

Sausage shaped surrounded by a double membrane, inner membrane is folded into cristae
It has a fluid-filled matrix

30
Q

Outline the role of mitochondria ( mitochondrion)

A

Synthesis of ATP by aerobic respiration

31
Q

Describe the structure of chloroplasts

A

Ovoid, surrounded by a double membrane, has a system of lamellae with thylakoids stacked into grana, also contain lipid droplets and starch grains

32
Q

Outline the role of chloroplasts

A

Site of photosynthesis
Chlorophyll molecules are attached to the lamellae

33
Q

Describe the structure of a vacuole

A

Large permanent structure, membrane of the sap vacuole in plant cells is called the tonoplast

34
Q

Outline the role of a vacuole

A

Storage of water and ions

35
Q

Describe the structure of microtubules

A

Tubular, formed from the protein Tubulin, Occur within centrioles and throughout the cytoplasm, animal and fungal cells both contain a pair of centrioles.

They occur as nine triplets of microtubules in a circular arrangement

36
Q

Outline the role of microtubules

A

Centrioles form the spindle fibres during cell division, microtubules also form part of the cytoskeleton and allow movement of cell organelles

37
Q

Describe the structure of microvilli

A

Finger-like folds of the cell surface membrane

38
Q

Outline the role of microvilli

A

Increases the surface area for absorption of molecules and ions

39
Q

Describe the structure of Plasmodesmata

A

Strands of cytoplasm between neighbouring plant cells that pass through pores in the walls

40
Q

Outline the role of plasmodesmata

A

Allow the transport of materials between adjacent plant cells

41
Q

What are viruses measured in and what is their typical range of size

A

They are so small they are measured in manometers (10nm-300nm)

42
Q

Describe the structure of a virus

A

Encased in a protein coat that surrounds nucleic acid (the nucleic acid can be DNA or RNA)

43
Q

What is the structure of a phage and what do they do?

A

 Bacteriophages or phages have a DNA core and parasitise bacteria.

 Inside their hosts (bacteria), the viral DNA codes for new proteins to make the capsid

 The DNA replicates to make lots of new copies that are packaged within these protein coats, forming new viruses.

 The bacterial cell ruptures releasing lots of new viruses to continue the cycle. The bacterial cell is destroyed in the process.

44
Q

Describe the structure and function of a retrovirus e.g HIV

A

 Retroviruses have an RNA core

 This RNA is encased in protein coat and surrounded by a lipid bilayer containing glycoprotein.

 The RNA is delivered into the host cell by the retrovirus, along with the enzyme reverse transcriptase.

 Reverse transcriptase catalyses the formation of DNA from
this RNA.

 This DNA is used to synthesise new viruses, by making
protein coats and viral RNA.

Normally, DNA is used to synthesise RNA, however in retroviruses the reverse happens and the RNA is used to make DNA.

45
Q

Why does HIV cause immunity problems

A

because it invades a particular lymphocyte called a helper T- cell.
Helper T cells are important in protecting against disease. The more cells that are invaded the less effective the immune system, until it becomes critically compromised, and AIDS may develop.

46
Q

Describe 3 features of a prokaryotic cell

A

 The earliest formed organisms

 They have no “true” nucleus.

 Cell or organism’s DNA is not organised into chromosomes and is not surrounded by a nuclear membrane

 They possess naked, circular DNA, small ribosomes, possibly plasmids and a cell wall made of peptidoglycan or murein.

 There are no membrane bound organelles.

 Examples include Bacteria and blue green algae

47
Q

Describe Fungal cells 7 features

A

 A cell wall made of chitin

 Often contain a vacuole

 Glycogen as a carbohydrate store

 Lysosomes

 Often multinucleate (many nuclei within each cell)

 They do NOT photosynthesise and do NOT have chloroplasts

 Many fungal cell appear long and have elongated threads of hyphae that spread through the substrate

Biology Year 13 (6 decks)

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