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A Level Bio > Chapter 3 Microscope + Cells (3.1 - 3.6) > Flashcards

Chapter 3 Microscope + Cells (3.1 - 3.6) Flashcards

1
Q

Structure of the nucleus

A
  • Nuclear pores - allows the passage of large molecules out the nucleus
  • nucleoplasm
  • chromosomes
  • nucleolus -where rRNA production takes place and makes ribosomes
  • nuclear envelope (double membrane) - controls the entry and exit of materials and reactions taking place within the nucleus
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2
Q

Function of nucleus

A
  • Site of DNA replication and transcription (making mRNA) and the production of tRNA
  • manufacture of ribosomes
  • contains genetic code for each cell in the form of DNA and chromosomes
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3
Q

Structure of Golgi apparatus and vesicle

A
  • Folded membranes called cisternae
  • Secretary vesicles pinch off from the cisternae
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4
Q

Function of Golgi apparatus

A
  • Modifies proteins produced by the ER by adding carbs to form glycoproteins
  • modifies, transports and stores lipids
  • secretes carbs
  • secretes enzymes
  • labels molecules to allow them to he accurately sorted and sent to their connect destinations
  • produces lysosomes
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5
Q

Function of the vesicle in Golgi apparatus

A

Transports modified proteins and lipids to the cell surface where they fuse with the membrane and release their contents

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6
Q

Structure of mitochondria

A
  • Double membrane that controls the entry and exit of a material
  • inner membrane is folded to make cristae
  • cristae provides a large surface area for the attachment of enzymes and other proteins in respiration
  • matrix which contains proteins lipids ribosomes and DNA which allows the mitochondria to control the production of their own proteins
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7
Q

Function of mitochondria

A
  • Site of aerobic respiration
  • site of ATP production due to mitochondria and their cristae being found in a lot cells that have a high metabolic rate and therefore require a supply of ATP
  • contains DNA to code for the enzymes required for respiration
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8
Q

Structure for chloroplast

A
  • chloroplast envelope (double membrane ) which controls what can enter and leave the organelle
  • contains grana which are stacks thylakoids which contain chlorophyll, therefore photosynthesis takes place in the grana
  • fluid filled matrix called the stroma contains enzymes for photosynthesis
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9
Q

Function of chloroplast

A
  • Site of photosynthesis
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10
Q

How the chloroplast is adapted for photosynthesis

A
  • Grana provides a large surface area for the attachment of chlorophyll and enzymes that carry out the 1st stage of photosynthesis
  • stroma contains the enzymes needed to make sugars in the 2nd stage of photosynthesis
  • chloroplast contains DNA and ribosomes so that they can quickly make proteins for photosynthesis
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11
Q

Structure of cell wall

A

Plants: made up of microfibrils of the cellulose polymer
Fungi: made up of chitin a nitrogen polysaccharide instead of cellulose
Both: middle lamella which marks the boundary between adjacent cell walls and cements

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12
Q

Function of cell wall

A
  • Provides structural strength to prevent the cell busting from the pressure created by water
  • provides mechanical strength
  • contributes to the movement of water by allowing water to pass along it
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13
Q

Structure of plasma membrane

A
  • Found in all cells
  • phospholipid bilayer (moleules embedded or attached in the outside e.g proteins carbs and chloesteral)
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14
Q

Function of plasma membrane

A
  • Controls what enters end exit the molecules
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15
Q

Structure of vacuole

A
  • Contains toroplast which is a filled fluid that is surrounded by a single membrane
  • contains a solution of mineral salts, sugar, amino acids, wastes and pigments
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16
Q

Function of vacuole

A
  • Provides structural support the making cells turgid
  • temporary store of sugars and amino acids
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17
Q

Structure of ribosomes

A
  • Small, made up of 2 subunits of protein and RNA
    80s ribosome: found in eukaryotic cell (25 mm diameter)
    70s ribosome: found in prokaryotic cells, mitochondria and chloroplast and is smaller
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18
Q

Function of ribosome

A

Site of protiensynthesis

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19
Q

Lysosome structure

A

Bags of digestive enzymes e.g lysozome that hydrolyse the cell wall of bacteria

20
Q

Function of lysosome

A
  • Hydrolyse cells ingested by phagocytic cell -
  • exocytosis - release enzymes to the outside of the cell to destroy materials around the cell
  • digest worn out organelles so that the useful chemicals can be reused
  • autolysis - breaks down cells after they die
21
Q

Structure of endoplasmic reticulum

A

Rough endoplosmic reticulum
- have ribosomes on the cisternae
- have folded membranes called cisternae
Smooth endoplasmic reticulum
- have folded membranes called cisternae

22
Q

Function of endoplasmic reticulum

A

RER
-Provides a large surface area for the synthesis of proteins and glycoproteins
- provides a pathway for the transport of materials

SER
- synthesise, store and transports lipids and carbs

23
Q

What is cell fractionating

A

A process used to isolate different organelles so that they can be studied to learn more about their structure and function

24
Q

In cell fractioning What solutions should cells be prepared in

A

Cold
Isotonic
pH buffer

25
Q

Why should the solution be cold in cell fractionating

A

To reduce enzyme activity as once the cell is broken up enzymes are released which could damage the organelles

26
Q

Why should the solution be ph buffer in cell fractionating

A

As the enzyme could denature and damage the organelle

27
Q

Why does the solution have to be isotonic in cell fractionating

A

The water potential has to be the same to prevent osmosis as this could cause the organelle to shrivel or burst

28
Q

steps of cell fractionating

A

1) homogenisation
2) ultracentrifugation

29
Q

What is the process o homogenisation

A

1) the cell is homoginsised using a scientific blender or homogeniser
2) the cell is blended in a cold, isotonic, ph buffer solution then filtered to remove large cell debris

30
Q

What is the process of ultracentrifugation,

A

The filtered solution is spun at different speeds in a centrifuge and separated according to their densities by differential centrifugation
When the centrifuge spins the denser organelles experience a larger force causing them to move down to the bottom
The centrifuge is first spun at a low speed and the process is repeated at increasingly faster speeds and each time the supernatant is removed leaving behind a pellet of organelles

31
Q

Most dense organelles to least dense organelles (nuclei, ribosomes Er chloroplast lysosome mitochondria )

A

Nuclei
Chloroplast
Mitochondria
Lysosome
Er
Ribosome

32
Q

Problem with cell fractionating

A

Its difficult to separate the organelles fully as the fraction may contain a very small number of other organelles

33
Q

What is the resolution of an optical (light) microscope and an electron microscope determined on

A

Optical: the wavelength of light
Electron: the wavelength of the beams of electron

34
Q

Properties of light microscopes

A
  • poor resolution due to the long wavelength of light so small organelles in a cell are not visible
  • low magnification
  • colour images
  • can view living samples
  • a beam of light is condensed to form an image
35
Q

Properties of electron microscope

A
  • beams of electrons are condensed by electromagnets to create an image
  • high resolving power as the have a short wavelength
  • high magnification
  • black and white images
  • samples are non living as they have to be in a vacuum as the electrons can be absorbed by air
36
Q

What happens in a transmission electron microscope

A
  • extremely thin specimens are stained and placed in a vacuum
  • an electron gun produces a beam of electrons that pass through the specimen which it then absorbs the electrons and appear dark
  • this produces a highly detailed 2d image of the internal structure of cells
37
Q

What happens in a scanning electron microscope

A
  • specimens don’t need to be thin since the electrons are not transmitting so the electrons are beamed onto the surface and scattered and reflected in different ways depending on the contours (depth) producing a 3d image
38
Q

Order of units nm m mm cm um

A

M cm mm um nm

39
Q

What does an eyepiece graticule do

A

Measures the size of the object you are viewing under the microscope

40
Q

Advantages of electron microscopes

A
  • short wavelength so it has a high resolving power
  • electrons are negatively charged so the beam can be focused using electromagnets
41
Q

Disadvantages of transmission electron microscope and scanning

A
  • the whole system has to be vacuumed so living organisms cannot be observed
  • the specimens has to be extremely thin (only TEM)
  • the final image may contain artefacts due to the complicated way it’s prepared so it may reduce the reliability of the photomicrograph as we are not sure if the cell exists in that form
  • high energy electron beam is required and may destroy the specimen
42
Q

Describe how the scientist could have used the temporary mounts of leaves to
determine the mean number of chloroplasts in mesophyll cells of a leaf.

A
  1. Select large number of cells / select
    cells at random;
  2. Count number of chloroplasts;
  3. Divide number of chloroplasts by
    number of
43
Q

Describe how temporary mounts are made.

A

Thin slice/section;
2. Put on slide in water / solution / stain;
3. Add cover slip;

44
Q

In large cells of U. marinum, most mitochondria are found close to the cell-surface membrane. In smaller cells, the mitochondria are distributed evenly throughout the cytoplasm. Mitochondria use oxygen during aerobic respiration.

Use this information and your knowledge of surface area to volume ratios to suggest an explanation for the position of mitochondria in large U. marinum cells.

A

-larger cells have a smaller SA:vol
-so it takes longer for oxygen to diffuse as diffusion distance is longer

45
Q

Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of
proteins from eukaryotic cells (5 marks)

A
  • DNA in nucleus codes for protein
  • rough endoplasmic reticulum produce protein through protein synthesis on the ribosomes
  • mitochondria produce ATP for protein synthesis
  • Golgi modifies proteins by adding carbohydrates to form glycoproteins
  • vesicle transports and fuse with the membrane

A Level Bio (15 decks)

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