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BIOLOGY MODULE 2 > 1 - CELL STRUCTURE > Flashcards

1 - CELL STRUCTURE Flashcards

1
Q

What is magnification?

A

It describes how much bigger an image appears compared with the original object.

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2
Q

How is magnification calculated?

A

Total magnification = magnifying power of objective lens x magnifying power of eyepiece lens

Magnification = Image size/ Actual size of image

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3
Q

What is resolution?

A

It is the ability of an optical instrument to see or produce an image that shows detail clearly.

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4
Q

Describe optical microscopes.

A
  • use visible light
  • relatively cheap
  • easy to use
  • portable
  • able to be used in the field as well as in laboratories
  • able to be used to study whole living specimens
  • maximum magnification = x1500-x2000
  • limited resolution = 0.2um which means organelles cannot be differentiated
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5
Q

What is a photomicrograph?

A

It is the photograph of the image seen using an optical microscope.

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6
Q

Describe laser scanning/ confocal microscopes.

A
  • use laser light to scan an object point by point
  • pixels are assembled into one image by computer
  • have depth selectivity and so can focus on structures at different depths/ planes within a specimen
  • can be used to observe whole living specimens
  • used in the medical profession
  • maximum magnification resolution
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7
Q

Describe SE microscopes.

A
  • specimen must be fixed (dead) and coated in film of metal in a vacuum to be viewed
  • produces a 3-D B&W image
  • magnification ranges from x15000 to x20000
  • maximum resolution is 0.002um
  • electrons are knocked off of specimen and gathered in a cathode ray tube to form the image
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8
Q

Describe TE microscopes.

A
  • specimen must be chemically fixed by dehydration and staining with metal salts to be viewed
  • maximum magnification = x2 million (or x50 mil)
  • maximum resolution is 0.0002um
  • produces 2D B&W image - colour can be added to it by computer software
  • electrons pass through specimen after being focused in beams by electromagnet
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9
Q

What are the disadvantages of both types of electron microscopes?

A

They are very large, expensive, and require skill and training to be used.

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10
Q

How are specimens prepared to be viewed under microscopes?

A
  • Slides are dry mounted or wet mounted
  • Dehydration
  • Embedding in wax (prevents distortion when slicing)
  • Making into sections which are differentially stained
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11
Q

What is differential staining?

A

Using coloured chemicals to identify different structures/ organelles within different cells under different microscopes

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12
Q

List all types of stains.

A
  • Methylene blue (all-purpose)
  • Acetic orcein - binds to DNA and stains chromosomes dark-red
  • Eosin - stains cytoplasm
  • Susan red - stains lipids
  • Iodine in potassium iodide solution:
    • stains cellulose (in cell walls) yellow
    • stains starch granules blue/black
      (appear violet under microscopes)
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13
Q

How are unstained specimens observed?

A

Using light interference to illuminate a colourless specimen against a dark background

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14
Q

What organelles are membrane-bound?

A

Nucleus, nuclear envelope , RER, SER, Golgi apparatus, mitochondrian lysosomes, chloroplasts, cell surface mebrane, flagella, cilia, and vacuole.

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15
Q

NUCLEUS

A
  • Has a double membrane
  • Houses all of th cell’s genome
  • Contains chromatin which consists of DNA wound around histone proteins
  • Has instructions for making proteins
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16
Q

NUCLEAR ENVELOPE

A
  • Has 2 membranes with fluid in between them
  • Surronds the nucleus
  • Has pores which allow the passage of relatively large molecules
17
Q

ROUGH ENDOPLASMIC RETICULUM

A
  • Has cisternae - flattened membrane sacs
  • Continuous with outer nuclear membrane
  • Studded with ribosomes which enables transportation of proteins to plasma membrane or outside of cell
18
Q

SMOOTH ENDOPLASMIC RETICULUM

A
  • Has cisternae - flattened membrane sacs
  • Continuous with outer nuclear membrane
  • Not studded with ribosomes
  • Invovled in essential lipid production
19
Q

GOLGI APPARATUS

A
  • Has a double membrane
  • Stack of membrane-bound falttened sacs
  • Recieves proteins from RER and modifies them by adding sugar - glycoproteins
  • Packages modified proteins into vesicles for transportation or secretion from cell
20
Q

MITOCHONDRIA

A
  • Double membrane speprated by a fluid filled space
    in the centre called the matrix
  • Highly folded inner membrane forms cristae
  • Site of ATP production which drives almost all cell activites
21
Q

LYSOSOMES

A
  • Abundant in phagocytic cells
  • Conatin powerful digestuve enzymes which break down materials
  • Engulf old organelles and foreign matter
22
Q

CHLOROPLASTS

A
  • Double membrane seperated by fluid-filled space
  • Inner membrane is continuous with falttened sacs called thylakoids forming granum which are repented by chlorophyll
  • Site of photosynthesis in plant cells
  • Found in some protoctists
23
Q

FLAGELLA

A
  • Long extension or tail
  • Contains microtubules in 9+2 arrangement
  • Enables movement
24
Q

CILIA

A
  • Short hair-like extensions
  • Contains microtubules in 9+2 arrangement
  • Enables fro movement of substances
25
Q

VACUOLE

A
  • Filled with water and solutes

- Maintains cell stability and regulates turgidy

26
Q

What organelles are non-membrane bound?

A

Ribosomes and centrioles

27
Q

RIBOSOMES

A
  • Consists of 2 sub-units
  • Site of protein synthesis
  • Act as assembly line where mRNA assembles amino acids into proteins
28
Q

CENTRIOLES

A
  • Microtubules - small tubes of protein fibres

- Take part in cell division by forming spindles and moving chromosomes

29
Q

What cells are eukaryotic?

A

Animal, plant, fungal and protoctist (including yeast and amoebae) cells

30
Q

What cells are prokaryotic?

A

Bacterial cells (microogransims)

31
Q

How are eukaryotic cells and prokarytoic cells similar?

A

They both have have plasma membranes surrounding their cytoplasms as well as ribosomes, DNA and RNA

32
Q

How do prokaryotes differ?

A
  • Have a much less developed cytoskeleton
  • Do not have centrioles
  • Do not have a nucleus
  • Smaller ribosomes
  • DNA is naked as it is not wound around histone proteins but floats freely as a loop (plasmid) in an area within the cytoplasm called the nuceloid
  • Organelles are non-membrane bound
  • Cell wall is made of peptidoglycan not cellulose
  • Protective waxy capsule protects cell wall by surrounding it
  • Do not have linear chromosomes and so divide by a process of binary fission not mitosis
33
Q

What does the endosymbiont theory suggest?

A

That eukaryotic cells have evolved from prokaryotes after prokaryotic cells found to be engulfed by others but not digested which folded a double membrane, creating chloroplasts and mitochondria.

34
Q

What are the roles of the cytoskeleton?

A
  • supporting the cell by maintaining its stability
  • changing the shape of the cell for endo/exocytosis
  • moving flagella/cilia to move the cell as a whole
  • moving vesicles and mRNA within the cell

BIOLOGY MODULE 2 (5 decks)

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