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Biology - Module 2 > 2.1.1 - Cell Structure > Flashcards

2.1.1 - Cell Structure Flashcards

1
Q

How does a light microscope work?

A

It uses light to form an image. Light that passes through or reflects from the surface of the specimen is seen.

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2
Q

What images are produced by light microscopes?

A
  • Poor resolution due to the long wavelength of light (200nm)
  • Low magnification (2000x)
  • Colour image
  • 2D
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3
Q

Which specimens can be examined by light microscopes?

A

Living and non-living specimens

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4
Q

How does a transmission electron microscope work?

A

It uses electrons to form an image. The electrons that pass through the specimen are detected.

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5
Q

What images are produced by transmission electron microscopes?

A
  • High magnification (1000000x)
  • High resolution due to short wavelength of electrons (0.2nm)
  • Black and white
  • 2D
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6
Q

Which specimens can be examined by transmission electron microscopes?

A

Only non-living specimens as the microscope must be in a vacuum so the air doesn’t absorb the electrons.

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7
Q

How does a scanning electron microscope work?

A

It uses electrons to form an image. Electrons that are reflected from the surface on the specimen are detected.

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8
Q

What images are produced by scanning electron microscopes?

A
  • High magnification (1000000x)
  • High resolution due to short wavelength of electrons (3-20nm)
  • Black and white
  • 3D
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9
Q

Which specimens can be examined by scanning electron microscopes?

A

Only non-living specimens as the microscope must be in a vacuum so the air doesn’t absorb the electrons.

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10
Q

How does a laser scanning microscope work?

A

It uses a laser beam to scan an object pixel by pixel creating an image of the reflected photon.

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11
Q

What images are produced by laser scanning confocal microscopes?

A
  • High resolution
  • 2D and 3D images
  • Black and white/computer generated colour
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12
Q

What are dry mounts?

A

When thin slices or whole specimens are viewed with just the coverslip placed on top

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13
Q

What are wet mounts?

A

When water is added to the specimen before lowering the coverslip with a mounted needle to prevent air bubbles from forming. This is used for aquatic organisms.

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14
Q

What are squash slides?

A

Wet mounts which you then push down on the coverslip to squash the sample to ensure you have a thin layer to enable light to pass through. This is used for a root tip to view the chromosomes in mitosis.

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15
Q

What are smear slides?

A

When you use the edge of another slide to smear the sample across the slide to create a smooth, thin and even coated specimen. A cover slip is placed on top after smearing. This is used when examining blood cells in a blood sample.

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16
Q

How do you calibrate an eye piece graticule?

A
  • Line up the stage micrometer and eyepiece graticule whilst looking through the eyepiece
  • Count how many divisions on the eyepiece graticule fit into one division on the micrometer scale
  • Each division on the micrometer is 10μm so this can be used to calculate what one division on the eyepiece graticule is
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17
Q

Why are stains used in microscopy?

A
  • To make cells more visible
  • Increase contrast
  • Identify different cell components
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18
Q

What is the formula for magnification?

A

Magnification = image size/object size

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19
Q

What is magnification?

A

The number of times greater the size of the image is than the size of the real object

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20
Q

What is resolution?

A

The ability to distinguish between two objects that are very close together. A higher resolution means more detail.

21
Q

What is the structure of the nucleus?

A
  • Nuclear envelope which is a double membrane that has nuclear pores to control exchange between the nucleus and cytoplasm
  • Nucleoplasm which is a granular jelly like material
  • Chromosomes which are protein bound linear DNA
  • Nucleolus which is a smaller sphere inside which is the site of rNA production and makes ribosomes
22
Q

What is the function of the nucleus?

A
  • Site of DNA replication and transcription
  • Contains the genetic code for each cell
  • Site of ribosomal synthesis
23
Q

What is the structure of flagella?

A

Long whip like structure

24
Q

What is the function of flagella?

A

Involved in mobility and sometimes as sensory organelle for chemical stimuli

25
Q

What is the structure of cilia?

A

Short hair like projections out of cells

26
Q

What is the function of cilia?

A
  • Can be mobile or stationary
  • Mobile cilia help move substances in a sweeping motion
  • Stationary cilia are important in sensory organs such as the nose
27
Q

What is the structure of centrioles?

A
  • Made of microtubules
  • Occur in pairs to form a centrosome
28
Q

What is the function of centrioles?

A

Involved in the production of spindle fibres and organisation of chromosomes in cell division

29
Q

What is the structure of the rough endoplasmic reticulum?

A
  • Has folded membranes called cisternae
  • Covered in ribosomes
30
Q

What is the function of the rough endoplasmic reticulum?

A

Site of protein modification and protein synthesis

31
Q

What is the structure of the smooth endoplasmic reticulum?

A

Has folded membranes called cisternae

32
Q

What is the function of the smooth endoplasmic reticulum?

A
  • Synthesises lipids, steroids and some hormones
  • Synthesises, stores and transports carbohydrates
33
Q

What is the structure of the Golgi apparatus?

A
  • Folded membranes making cisternae
  • Secretory vesicles pinch off from the cisternae
34
Q

What is the function of the Golgi apparatus?

A
  • Makes lysosomes
  • Adds carbohydrates to proteins to form glycoproteins
  • Transport, modify and store lipids
  • Finished products are transported to cell surface in Golgi vesicles where they fuse with the membrane and contents are released
35
Q

What is the structure of lysosomes?

A

Bags of digestive enzymes

36
Q

What is the function of lysosomes?

A
  • Hydrolyse phagocytic cells
  • Break down dead cells
  • Exocytosis - release enzymes to outside of cell to destroy material
  • Digest worn out organelles for reuse of materials
37
Q

What is the structure of mitrochondria?

A
  • Double membrane
  • Inner membrane highly folded into cristae
  • Fluid centre called the mitochondrial matrix
  • Loop of mitochondrial DNA
38
Q

What is the function of mitochondria?

A
  • Site of aerobic respiration
  • Site of ATP production
  • Contains DNA to code for enzymes needed in respiration
39
Q

What is the structure of ribosomes?

A
  • Small made up of two sub units of protein and rRNA
  • 80S is a large ribosome found in eukaryotic cells (25nm)
  • 70S is a smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts
40
Q

What is the function of ribosomes?

A

Site of protein synthesis

41
Q

What is the structure of chloroplasts?

A
  • Surrounded by a double membrane
  • Contains thylakoids which are folded membranes embedded with pigment arranged in stacks called grana
  • Fluid filled stroma contains enzymes for photosynthesis
  • Found in plants
42
Q

What is the function of chloroplasts?

A

Site of photosynthesis

43
Q

What is the structure of the cell wall?

A
  • Found in plant and fungi cells
  • In plants it is made of microfibrils of the cellulose polymer
  • In fungi it is made of chitin which is a nitrogen containing polysaccharide
44
Q

What is the function of the cell wall?

A

Provides structural strength to the cell

45
Q

What is the structure of the plasma membrane?

A
  • Found in all cells
  • Phospholipid bilayer with molecules embedded within and attached on the outside such as proteins, carbohydrates and cholesterol
46
Q

What is the function of the plasma membrane?

A

Controls the exchange between the cell and its environment

47
Q

How are proteins produced and secreted?

A
  • Polypeptide chains are synthesised on the RER
  • These polypeptide chains move to the cisternae in the RER and are packaged into vesicles to be sent to the Golgi apparatus via the cytoskeleton
  • In the Golgi apparatus the proteins are modified and packaged into vesicles
  • The secretory vesicles carry the proteins to the cell surface membrane where it fuses and releases the protein by exocytosis
48
Q

What are the 3 main functions of the cytoskeleton?

A
  • Provides mechanical strength to cells
  • Aids transport within cells
  • Enables cell movement
49
Q

What are the key differences between prokaryotic and eukaryotic cells?

A
  • Prokaryotic cells are much smaller
  • Prokaryotic cells have no membrane bound organelles
  • Prokaryotic cells have smaller ribosomes
  • DNA is not contained within the nucleus in prokaryotic cells
  • Prokaryotic cell wall contains peptidoglycan
  • Prokaryotic cells may also contain plasmids, flagella and a capsule around the cell

Biology - Module 2 (6 decks)

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