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Biology > Cell structure and microscopes > Flashcards

Cell structure and microscopes Flashcards

1
Q

What is the structure and function of Lysosomes?

A

They are vesicles that contain hydraulic enzymes( lysozymes) to break bonds and break down molecules.

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2
Q

What is the structure and function of Centrioles?

A

They are paired barrel shaped organelles located in the cytoplasm of animal cells near the nuclear envelope. They organise microtubules that serve as the cells skeletal system.

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3
Q

What is the structure and function of the cytoskeleton?

A

Its made up of microtubules, actin filaments and intermediate filaments/ a network of protein fibres. They form cell shape, allow cell to move and allows organelles to move within the cell.

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4
Q

What is the structure and function of cell surface membrane?

A

Plasma membrane - partially permeable. It separates the interior of the cell from the surrounding environment

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5
Q

What is the structure and function of ribosomes?

A

They are very small (20nm), spherical structures which are free in the cytoplasm. They make/assemble proteins for protein synthesis and make/assemble protiens which are going to be used inside the cell.

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6
Q

What is the structure and function of the rough endoplasmic reticulum?

A

It continues with the outer nuclear membrane. It is folds of membrane that have ribosomes on their outer surface. It produces proteins from ribosomes on its surface and sends them to another organelle to be packaged and sent out of the cell.

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7
Q

What is the structure and function of the Golgi apparatus?

A

It is fused cisternae, flattened membrane. It modifies (adds molecules to proteins), packages and labels substances like proteins before sending them in Golgi vesicles to different parts of the cell.

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8
Q

What is the structure and function of the smooth endoplasmic reticulum?

A

Its a long network of folded tube like structures. It makes, moves and packages lipids and carbohydrates.

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9
Q

What is the structure and function of the nucleus?

A

It contains DNA which is linear and is tightly wound around histone proteins to form thread like structures called chromosomes.

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10
Q

What is the structure and function of the nucleolus?

A

It is the largest structure in the nucleus. It makes ribosomal RNA to form functioning ribosomes.

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11
Q

What is the structure and function of the nuclear envelope?

A

The nucleus is surrounded by a double membrane called the nuclear envelope which contains nuclear pores. It allows some molecules to move out of the nucleus NOT DNA.

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12
Q

What is the structure and function of mitochondria?

A

Double membrane - cristae, matrix, outer and inner membrane, inter membrane space. Its the site of aerobic respiration - produces ATP

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13
Q

What is the structure and function of the cytoplasm?

A

Cytosol - gel like substance.
Where all the chemical reactions in the cell take place and where all the membrane bound organelles are held.
It separates the organelles from the external environment.

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14
Q

What is the difference between a prokaryotic and a eukaryotic cells?

A

Eukaryotic cell: contains a nucleus and membrane bound organelles.
Prokaryotic cell: No membrane bound organelles, no nucleus so genetic material free floating.

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15
Q

What is the cell wall in a prokaryotic cell made from?

A

Peptidoglycan

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16
Q

What is the structure and function of a capsule in a prokaryotic cell?

A

Around the outside of cell, helps prokaryotic cell cling to each other and various surfaces, its a defence against host cells and prevents cell from drying out.

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17
Q

What is the structure and function of pili in a prokaryotic cell?

A

They are short hair like structures on cell surface which increase surface area, they are involved in adherence to surfaces - facilitates infection, they have a role in movement.

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18
Q

What is the structure and function of a flagellum in a prokaryotic cell?

A

Some prokaryotic cells have them, they help an organism in movement, they are sensory organs so they detect temperature and pH and they get energy from chemiosmosis which is movement of H+ across a biological membrane - generates ATP

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19
Q

What is the structure and function of free chromosomal DNA in a prokaryotic cell?

A

Nucleoid region
allows direct connection to translation and transcription
contains genetic material

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20
Q

What is the structure and function of a ribosome in a prokaryotic cell?

A

Smaller than 70s
Different type of ribosome made of proteins - tRNA

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21
Q

Explain the cell surface membrane of a plant cell

A

made out of cellulose - beta glucose chains hold together by hydrogen bonds. fully permeable to and contents of the cell push against it allowing it to support the cell and those around it. If there is not enough water present the cell wall holds onto the water and supports - stops cell from collapsing, if there is too much water present the cell wall prevents lysis
(cell bursting)

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22
Q

Explain the structure and function of chloroplasts

A

They are found in the areas above ground in plants. They have a double membrane, fluid in the centre in the stomata. Internal membranes are made of flattened sacs called thylakoids and stacked to make grana. The grana contain photosynthetic pigments like chlorophyll

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23
Q

Explain the structure and function of the permanent vacuole

A

Membrane bound sac containing cell sap. The membrane is often called tonoplast. It stores cell sap and may also store nutrients and proteins. Keeps cell turgid (swollen and hard). Some play a similar role to lysosomes - digest

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24
Q

What organelles does a plant cell have that a animal cell doesn’t?

A

vacuole
chloroplasts
cellulose cell wall

25
Q

What organelles does an animal cell have that a plant cell doesn’t?

A

Centrioles
lysozymes

26
Q

What happens first in the process ‘organelles involved in protein synthesis’

A

Proteins are synthesised at the ribosomes.

27
Q

What happens second in the process ‘organelles involved in protein synthesis’

A

Proteins pass into the cisternae of RER and are packaged into vesicles.

28
Q

What happens third in the process ‘organelles involved in protein synthesis’

A

Vesicles move towards the Golgi via the cytoskeleton.

29
Q

What happens fourth in the process ‘organelles involved in protein synthesis’

A

Vesicles fuse with cis surface of Golgi. Proteins enter and are modified. They leave in vesicles via the trans face of the Golgi.

30
Q

What happens fifth in the process ‘organelles involved in protein synthesis’

A

Vesicles move to plasma membrane to release proteins that are needed are needed outside of the cell. Some are transported round the cell to where they are needed.

31
Q

What is the equation for magnification?

A

Magnification= size of image/actual size

32
Q

What is magnification?

A

It is the number of times greater than that an image is than the object.

33
Q

What is resolution?

A

It is the ability to distinguish between two objects very close together, the higher the resolution the better the detail that can be seen.

34
Q

What is a TEM?

A

Transmission electron microscope

35
Q

What is a SEM?

A

Scanning electron microscope

36
Q

Describe light microscopy

A

> coloured images
living specimens
requires a light source
not very detailed images
easy to use
affordable

37
Q

Describe TEM microscopy

A

> electrons pass through sample
electromagnets
max resolution = 0.5 nm

38
Q

Describe SEM microscopy

A

> electrons reflected off the surface
image of only the surface
max resolution = 3-10 nm

39
Q

What are the similarities between a light microscope and a TEM?

A

> 2D Images
Thin samples

40
Q

What are the similarities between a light microscope and a SEM?

A

> Objective lens
Use reflection

41
Q

What are the similarities between a SEM and a TEM?

A

> Difficult to use
Electron guns
Detailed
Black and white
Stream of electrons
Large
Expensive
Dead specimen
Viewed in a vacuum
Maximum magnification = 500,0000

42
Q

What are the similarities between a light microscope, a SEM and a TEM?

A

> Stream of energy to view stream
Make sample appear bigger

43
Q

What are the features of a laser scanning confocal microscope?

A

Maximum resolution = 200 nm
2D/3D Image
Coloured images
Used to observe an object at a certain depth within a cell
Can view living cells

44
Q

How does an image produced by laser scanning confocal microscope differ from that produced by an electron microscope?

A

It has a lower resolution
Can see movement

45
Q

What is the average magnification and resolution of a light microscope?

A

Magnification = 1500 x
Resolution = 200nm

46
Q

What is the average magnification and resolution of a TEM?

A

Magnification = 500000 x
Resolution = 0.2nm

47
Q

What is the average magnification and resolution of a SEM?

A

Magnification = 100 000 x
Resolution = 0.2nm

48
Q

Explain how to measure the diameter of the nucleus of a cell when observing cells through a light microscope

A

> calibrate eye piece graticule using stage micro meter - calculate the length of one epu.
measure the diameter of the nucleus in epu (graticule units)
take repeat measurements and calculate a mean diameter
use calibrated epu to calculate diameter of nucleus in um.

49
Q

What needs to be done on a drawing of image of something observed under a microscope?

A

> A scale
Labels
Sharp pencil
Title
No shading/cross hatching

50
Q

What is the formula for the volume of a sphere?

A

V = 3/4 x Pi x r^3

51
Q

Why do we stain samples?

A

To provide a contrast - different parts of the cell take up different amounts of stain.

52
Q

What is differential staining?

A

It can be used to differentiate between types of cells that otherwise cannot be distinguished.
E.g; gram staining - two different bacteria one pink, one purple, one +1, one -1

53
Q

What is a dry mount?

A

Is used to view thin slices which are cut with a sharp blade, no liquid - such as hair samples, pollen and insects.

54
Q

What is a wet mount?

A

Is when the specimen is covered with a drop of liquid such as water, oil or a stain. A cover slip is gently placed over the sample at an angle to stop any air bubbles.

55
Q

What is a squash slide?

A

When a sample is squashed between the slide and the cover slip. Its a type of wet mount and is used for soft tissues such as root tips.

56
Q

What is a smear slide?

A

Is when a slide is used to smear the sample across another slide such as a thin layer of blood.

57
Q

What are two examples of positively charged stains?

A

Crystal violet and methylene blue - they are attracted to the negatively charged components such as organelles.

58
Q

What are two examples of negatively charged stains?

A

Nigrosine and Congo red - are attracted to the outside of cells.

59
Q

How to use a light microscope?

A
  1. Prepare the slide - glass slide and cover slip
  2. Adjust the light - light source and adjust intensity
  3. Start with low power - lowest mag objective lens to locate specimen
  4. Focus - roughly focus with coarse focus knob then fine-tune with fine focus knob
  5. Increase magnification - switch mag higher for more detail - refocus when changing
  6. Analyse the specimen - noting its structure and details
  7. Record observations - for later reference

Biology (12 decks)

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