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A Level Biology > Studying Cells > Flashcards

Studying Cells Flashcards

1
Q

Contrast the structures of prokaryotic and eukaryotic cells (7)

A
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2
Q

Where is pili found?

A

In prokaryotic cells

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3
Q

What is the role of a pili?

A

-May connect between bacteria allowing horizontal DNA transfer between bacteria

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4
Q

Describe prokaryotic cells/bacterial cells (2)

A

-prokaryotes do not have a nucleus or other membrane bound organelles
-The DNA of a prokaryotic cell is circular and is not associated with histones

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5
Q

What is the cell wall in prokaryotic/bacterial cells made of?

A

PEPTIDOGLYCON (NOT CELLULOSE)

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6
Q

What type of ribosomes do a prokaryotic cells have?

A

70 S

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7
Q

What part of eukaryotic cells have 70s ribosomes?

A

Chloroplasts and mitochondria

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8
Q

Describe what a virus is

A

-acellular
-Not alive
-Very small
-Require a living cell to replicate inside

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9
Q

Describe the structure of a virus (4)

A

-contains DNA or RNA, (which can be single or double stranded)
-Surrounded by a protein coat called a capsid
-Also a virus has attachment proteins which enable it to bind to host cells
-Has enzymes that it uses to replicate genetic information and insert into the host cell DNA

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10
Q

What can viruses not do because they have no organelles?

A

-They’re unable to replicate independently so they can’t synthesise proteins or DNA to make copies of themselves
-They need to use host cell organelles to do this

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11
Q

Create a table for the features of prokaryotic cells, viruses and eukaryotic cells

A
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12
Q

Describe the features of a light microscope

A

-Specimen are illuminated with light (can be living or dead)
-Focus using glass lenses and viewed using the eye
-organelles need to be stained with a dye to make them more visible
-Can magnify by a larger amount (x1500)
-At higher magnification the microscope loses resolution

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13
Q

What is the resolution of light microscope limited by?

A

The wavelength of light (400-600 nm for visible light)

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14
Q

If the wavelength of the light/electrons is shorter what happens to the resolution?

A

Resolution is better

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15
Q

Name two structures found within a eukaryotic cell that cannot be identified using an optical microscope

A

Any two from
Mitochondria/ribosome/endoplasmic reticulum/lysosome/cell surface membrane

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16
Q

What are the two types of electron microscope?

A

-transmission electron microscope (TEM)
-Scanning electron microscope (SEM)

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17
Q

What is the difference between a transmission electron microscope and a scanning electron microscope?

A

TEM produce 2D images
SEM produce 3D images

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18
Q

What do both types of electron microscopes use?

A

-A beam of electrons to illuminate the specimen (rather than light)
-Electrons can be easily produced and focused using electromagnets and detected using a Phosphor screen or photographic film
-Electrons have a very small wavelength so they can produce images with higher resolution

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19
Q

Describe transmission electron microscopes

A

-electrons passed through the specimen (must be dead & kept in a vacuum )
-less dense areas absorb less electrons and appear lighter, dense areas absorb more electrons so appear darker
-Allow you to view organelles and internal structures

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20
Q

Describe scanning electron microscopes

A

-specimens are not sliced and electron bounce off the surface of the specimen
-images are always in black-and-white
-They always produce a 3D image

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21
Q

Give a summary table of the comparison of electron and light microscope

A
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22
Q

Describe the principles and the limitations of using a transmission electron microscope to investigate cell structure (5)
Principles (how it works)
Limitations (drawback/disadvantages)

A
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23
Q

Give one advantage of using a TEM rather than an SEM

A

Higher resolution/higher magnification/higher details
OR
Allows internal details or structures to be seen within cells

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24
Q

Give one advantage of using an SEM rather than a TEM

A

Thin sections do not need to be prepared/show surface of specimen/ can have 3-D images

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25
Q

Scientist use optical microscopes and transmission electron microscopes to investigate cell structure. Explained the advantages and limitations of using a TEM to investigate cell structure

A

advantages:
-Small objects can be seen
-TEM has higher resolution
-wavelength of electron shorter

Limitations :
-Cannot look at living cells
-Must be in a vacuum
-Must cut section/thin specimen
-Preparation may cause artefacts (false images)

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26
Q

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cell when using an optical (light) microscope

A
  • add a drop of water to the microscope slide
    -Get a thin section of plant tissue and float on the drop of water
    -stain with KI solution
    -Lower the cover slip using a mounted needle to avoid air bubbles
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27
Q

When using an optical microscope, which two pieces of equipment are required?

A

Eyepiece lens graticule and stage micrometer

28
Q
A
29
Q
A
30
Q

Describe how to convert units and give some examples

A
31
Q

What is the equation for magnification?

A
32
Q

Why must cell fractionation and differential centrifugation occur

A

To separate organelles from the cell for electron microscopes

33
Q

What is the name of the method of separating organelles and describe it?

A
  • homogenising
    -Tissue is homogenised and blender to break up the cells releasing and organelles into a solution
    -filter to the mixture to remove any large pieces of tissue/cellular debris producing a solution of suspended organelles
34
Q

When homogenising a solution, what must the solution be and why?

A
  • ice cold-reduces action of enzymes that would digest organelles
    -Isotonic (same water potential)- prevents osmosis of water in or out of organelles so organelle don’t burst or shrivel
    -Buffered-to stop pH changes which could denature proteins
35
Q

Describe how differential centrifuge of the supernatant can occur

A
  • centrifuge at a high speed ( dense organelles are forced to the bottom of the tube into a pellet which is removed) the supernatant can be spun again to obtain smaller organelles
  • Centrifuge at a higher speed-the next densest organelles are forced to the bottom of the tube into a pellet. This pellet is removed and can be suspended.
    -This process can be repeated many times at higher speed with each step (this separates organelles according to their densities)
36
Q

Describe how you could use cell fractionation to isolate chloroplasts from leaf tissue (3)

A
  • Break up the cells in a blender/homogeniser and filter to remove cellular debris
    -Place in an ice cold, isotonic, buffered solution
    -Use differential centrifugation
    -Chloroplasts are in the second pellet
37
Q
A
38
Q

What are eukaryotic cells?

A

-Cells with the true nucleus that have membrane bound organelles
-Linear DNA molecules called around histone proteins to form chromatin

39
Q

What are the four eukaryotic kingdoms?

A

-animalia
-Plantae
-protostica (algae)
-Fungi (unicellular yeast cells)

40
Q

Give some examples of eukaryotic cells

A

Plants
Animal
Fungi
Algae
Protozoan

41
Q

Draw a eukaryotic/animal cell

A
42
Q

Draw a eukaryotic/animal cell

A
43
Q

What organelles are found within eukaryotic cells?

A

-Nucleus
-Mitochondria
-Rough endoplasmic reticulum
-Smooth endoplasmic reticulum
-Cytoplasmic ribosome
-Golgi apparatus/body
-lysosome
-Cell surface membrane
-Centrioles

44
Q

Describe the structure of a nucleus within a eukaryotic cell

A

-nuclear envelope/double membrane and pores
-Chromosomes/chromatin (DNA associated with histones)
-Nucleolus

45
Q

Describe the function of a nucleus within a eukaryotic cell

A

-stores genetic information for polypeptide production
-Site of DNA replication
-Site of production of mRNA (transcription) and TRNA
-Site of production of rRNA/ribosomes (nucleolus)

46
Q

Describe the structure of mitochondria in eukaryotic cells

A

-double membrane (between inner and outer membrane /inter-membrane space- filled with fluids )
-Inner membrane highly folded to form (increase surface area)
-Matrix (liquid part) containing mitochondrial DNA, ribosomes, proteins, and lipids

47
Q

Describe the function of mitochondria in eukaryotic cells

A

-Site of ATP production by aerobic respiration
-Cells that need a lot of ATP have lots of mitochondria e.g muscle cells (for muscle contraction) and epilethial cells (for active transport of ions)

48
Q

Describe the structure of the rough endoplasmic reticulum in eukaryotic cells

A

-Highly folded membranes with 80S ribosomes embedded
-The membrane is folded into flattened sacks called cisternae
-Joined to the nucleus

49
Q

Describe the function of the rough endoplasmic reticulum in eukaryotic cells

A
  • synthesise and transports proteins throughout the cell
    -Cells which make lots of protein e.g antibodies have lots of rough endoplasmic reticulum (antibodies producing plasma cells)
50
Q

Describe the structure of the smooth endoplasmic reticulum in eukaryotic cells

A

Highly folded membranes flattened into sacks called cisternae

51
Q

Describe the function of the smooth endoplasmic reticulum in eukaryotic cell

A

-recombines glycerol and fatty acids to make triglycerides
-Packages triglycerides into vesicles and transports them to the golgi apparatus

52
Q

Describe the structure of the cytoplasm ribosome in eukaryotic cells

A

-made up of two sub units that are made of long strands of RNA and ribosome proteins
-Eukaryotic cells contain 80s cytoplasmic ribosomes

53
Q

Describe the function of cytoplasmic ribosome in eukaryotic cells

A

Site of protein synthesis from amino acids

54
Q

Describe the structure of the Goldie apparatus/body in eukaryotic cells

A

-flattened sacs made of membrane filled with fluids
-Golgi vesicles pinch off from the main membrane

55
Q

Describe the function of the Golgi apparatus in eukaryotic cells

A
  • Sorts, modifies and packages proteins and triglycerides into vesicles
    -Golgi vesicles may be used to form lysosomes
    -Cells with extensive Golgi, packages lots of molecules for export
56
Q

Describe the structure of lysosomes in eukaryotic cells

A
  • Membrane bound organelle that stores and releases many hydrolytic enzymes
57
Q

Describe the function of lysosomes in eukaryotic cells

A

-contains hydrolytic enzymes- phagocytes are a type of white blood cell that contain many lysosomes, as they hydrolyse invading pathogens

58
Q

Describe the structure of cell surface membranes in eukaryotic cells

A

-made up of phospholipids, specific transport proteins, and carbohydrates arranged into what is described as fluid mosaic model

59
Q

Describe the function of cell surface membrane in eukaryotic cells

A

Controls the passage of molecules in and out of the cell

60
Q

Describe the structure of centrioles in eukaryotic cells

A

-microtubules

61
Q

Describe the functions of centrioles in eukaryotic cells

A

-from a network of spindle fibres onto which chromosome attach
-Pull chromosomes/chromatids apart during mitosis
-THESE ARE ONLY FOUND IN ANIMAL CELLS (NOT PLANT CELLS)

62
Q

Draw a plant cell (eukaryotic)

A
63
Q

Describe the structure of chloroplasts and the function of each organanelle

A

-granum- stack of thylakoid membranes
-thylakoid membrane- contains chlorophyll for photosynthesis and ATP synthase enzyme to produce ATP
-Stroma- fluid filled part, some of the photosynthetic reactions occur heee
-starch grains- the energy storage molecule in plants
-DNA and ribosomes- contain their own DNA and 70s ribosomes for synthesis of enzymes needed for photosynthesis

64
Q

Describe the structure of cellulose cell walls (in plants and algae)

A

-very strong (many weak hydrogen bonds between cellulose fibrils), this limits the volume of water that can move into the cell and stop osmotic lysis (bursting)
-The wall is permeable to most molecules, unlike the membrane
-Has plasmodesmeta which has gaps in the cell wall that connects cytoplasms together to allow water soluble molecules to move easily

65
Q

Describe the key differences between plant and animal cells

A

A Level Biology (7 decks)

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