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Biology > Pack 2 - Cell Structure > Flashcards

Pack 2 - Cell Structure Flashcards

1
Q

Define resolution.

A

The minimum distance apart two objects can be in order for them to be distinguishable as two separate objects.

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2
Q

What determines the resolution of a microscope?

A

The wavelength of radiation being used. (e.g the wavelength of light)

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3
Q

What is the approximate resolution of a light microscope?

A

0.2μm

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4
Q

Why is the resolving power of an electron microscope higher than a light microscope?

A

The wave length of electrons is shorter than the wavelength of light.

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5
Q

What is cell fractionation?

A

The process where cells are broken up and the organelles they contain are released and separated out.

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6
Q

What THREE conditions must a tissue be under before cell fractionation can take place and WHY?

A
  • Cold - To reduce enzyme activity that may break down ORGANELLES.
  • Isotonic (same Ψ as tissue) - to prevent bursting or shrinking of ORGANELLES due to osmosis.
  • Buffered (same pH as tissue) - to prevent enzymes denaturing or the changing in the structure ORGANELLES.
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7
Q

Describe cell fractionation in 4 steps.

A
  1. Homogenisation - cells are broken up by a blender into a homogenate releasing organelles.
  2. Filtration - whole cells/debris removed
  3. Ultracentrifugation - homogenate is spun in a CENTRIFUGE at a low therefore the densest organelles fall to the bottom.
  4. Repeat - the supernatant is poured of and the process is repeated on the supernatant at higher speeds to obtain less dense organelles.
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8
Q

What is the fluid at the top of a centrifuge tube called after centrifugation?

A

Supernatant

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9
Q

Order the following organelles by increasing speed of centrifugation.
• Mitochondria
• Nuclei
• Lysosomes

A
  1. Nuclei
  2. Mitochondria
  3. Lysosomes
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10
Q

How are electrons focused in an electron microscopes?

A

Using electromagnets (because electrons are negatively charged).

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11
Q

What is an important condition needed for all electron microscopes and why?

A

A near vacuum - because electrons are deflected and absorbed by air molecules.

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12
Q

What kind of image does a transmission electron microscope (TEM) produce?

A

2D, Black and White

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13
Q

What is the approximate resolution of a transmission electron microscope (TEM)?

A

0.1nm

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14
Q

Why can the maximum resolving power of a transmission electron microscope (TEM) no always be produced?

A
  • Difficulties preparing the specimen.

* high energy electron beams required would destroy the specimen.

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15
Q

What are 4 main limitations of a TEM?

A
  • The whole system must be in a near vacuum therefore living specimens cannot be observed.
  • A complex staining process is required.
  • The specimen must be extremely thin to allow electrons to pass through.
  • The image may contain artefacts due to the way the specimen is prepared.
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16
Q

What kind of image does a scanning electron microscope (SEM) produce and how?

A

3D - Black and white

Rather than penetrating the sample, a SEM passes a beam of electrons over the sample in a regular pattern. The electrons are scattered depending on the surface. A computer builds a 3D image based on the scattering of electrons.

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17
Q

What are the advantages of a SEM over a TEM?

A
  • Specimen does not have to be thin.

* 3D image

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18
Q

What is the approximate resolution of a scanning electron microscope (SEM)?

A

20nm

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19
Q

Name the 5 components of the nucleus and their roles.

A
  • Nuclear envelope - controls the entry and exit of materials; contains reactions taking place in the nucleus.
  • Nuclear pores - allows passage of large molecules in and out of the cell e.g. mRNA
  • Nucleoplasm
  • Chromosomes - consist of protein bound linear DNA
  • Nucleolus - manufactures ribosomal RNA and assembles ribosomes.
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20
Q

Describe the structure of the nuclear envelope.

A

Double membrane; outer membrane is continuous with the ER; often has ribosomes on its surface.

21
Q

What are 3 functions of the nucleus?

A
  • Controls protein synthesis through the production of mRNA and tRNA
  • Retains genetic material of the cell
  • Manufactures ribosomal RNA and ribosomes
22
Q

Name the 3 components of mitrochondria and their roles.

A
  • Double membrane - controls the entry and exit of materials
  • Cristae (extensions of the inner membrane) - large surface area for attachment of enzymes and other proteins used in respiration.
  • Matrix - remainder of the mitochondria; contains proteins, lipids, ribosomes and DNA; allows mitochondria to control the production of some of their own proteins.
23
Q

What is the function of mitochondria?

A

Site of aerobic stages of respiration.

Produces ATP

24
Q

Give an example of a cell that would have lots of mitochondria.

A

Any metabolically active cell - e.g. muscle cell, epithelial cell…

25
Q

Name the 5 main components of a chloroplasts.

A
  • Chloroplast envelope - highly selective double plasma membrane.
  • Thylakoids - contain chlorophyll where light absorption takes place.
  • Grana - stacks of thylakoids
  • Stroma - fluid containing DNA starch and ribosomes
  • DNA - for quick protein synthesis
26
Q

Give 3 ways chloroplasts are adapted to their function.

A
  • Grana have large surface area for attachment of chlorophyll, electro carriers and enzymes that carry out the first stage of photosynthesis.
  • Stroma contains all the enzymes needed in the section stage of photosynthesis.
  • Stroma contains DNA and ribosomes for quick manufacture of proteins needed for photosynthesis.
27
Q

What are the sacs called that the endoplasmic reticulum enclose.

A

Citernae

28
Q

What are the 2 functions of the rough endoplasmic reticulum?

A
  • Large surface area containing ribosomes forth synthesis of proteins and glycoproteins.
  • Pathway for the transport of materials especially proteins
29
Q

What are the 2 functions of the smooth endoplasmic reticulum?

A
  • Synthesis store and transport lipids.

* Synthesis store and transport carbohydrates.

30
Q

Give an example of a cell that would have a large endoplasmic reticulum.

A

Liver/secretory cells as they manufacture and store large quantities of proteins, carbohydrate and lipids.

31
Q

Give 5 functions of the Golgi Apparatus

A
  • adds carbohydrates to proteins to form glycoproteins
  • produces secretory enzymes
  • secretes carbohydrates (such as those to be used in cell walls)
  • transports, modifies and stores lipids
  • forms lysosomes
32
Q

What are vesicles.

A

Small rounded hollow structures that transport molecules from the Golgi apparatus (may be to the cell surface).

33
Q

What are lysosomes?

A

Vesicles that contain enzymes such as proteases and lipases as well as lysozyme (enzymes that break down bacteria cell walls).

34
Q

What are the functions of lysosomes?

A
  • to hydrolyse material ingested by phagocytic cells.
  • to release enzymes to outside the cell (exocytosis) to destroy material around the cell.
  • to digest worn out organelles.
  • break down dead cells.
35
Q

Describe the structure of ribosomes.

A

A small sub-unit and a large sub-unit both containing ribosomal RNA and protein.

36
Q

Name the two types of ribosomes and which type of cell they are found in.

A

70s - prokaryotic

80s - eukaryotic

37
Q

Describe the structure of a cell wall.

A
  • number of polysaccharides such as cellulose.

* middle lamella marks the boundary between adjacent cell walls and cements them together.

38
Q

Name 3 functions of the cell wall.

A
  • Prevent bursting through osmotic pressure.
  • Mechanical strength as a whole
  • to allow water to pass along the cell and move throughout the plant as a whole.
39
Q

What type of membrane does a vacuole have and what is it called?

A

Single membrane - tonoplast

40
Q

Give 3 functions of a vacuole.

A
  • Support herbaceous parts of plants by making cells turgid.
  • Contains sugars and amino acids that may act as a temporary food store.
  • Pigment colours petals to attract insects.
41
Q

Where do all cells come from?

A

Fertilised egg

42
Q

What are the main differences between prokaryotes and eukaryotes?

A
  • Lacks a nucleus or any membrane bound organelles.

* Genetic material forms one circular molecule of DNA

43
Q

What is a bacteria’s cell wall made of?

A

Murien

44
Q

What are the 2 main functions of bacterial cell wall?

A
  • Physical barrier

* protects against mechanical damage and osmotic lysis

45
Q

What are the cell walls of fungi made of?

A

chitin, glycan and glycoproteins

46
Q

What three features can prokaryotes have that eukaryotes don’t and what are their functions?

A
  • Plasmid - can reproduce themselves independently; give the cell resistance to harmful substances.
  • Capsule - protects from other cells; bacteria can stick together for protection
  • Flagellum - locomotion
47
Q

Give 4 differences between the structure of DNA in prokaryotes and eukaryotes.

A
  • Prokaryotes have no nucleus.
  • Prokaryotes have one circular molecules of DNA. eukaryotes have linear DNA
  • Prokaryotes can have plasmids
  • Eukaryotes’ DNA is associated with proteins called histones.
48
Q

Describe 4 features of viruses and their functions.

A
  • RNA/DNA as genetic material.
  • Capsid - a protein that enclose the genetic material.
  • Lipid envelope (some viruses)
  • Attachment proteins - used to identify and attach to host cell.
49
Q

Why is a virus not a living organism?

A

It cannot survey by itself. Therefore they are described as particles NOT CELLS.

Biology (18 decks)

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