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Principals > Histology > Flashcards

Histology Flashcards

1
Q

How much water in a cell?

A 
average= 80%
range= 75-85%
comment= 90% free, 5% bound
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2
Q

How much protein in a cell?

A 
average= 15%
range= 10-20%
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3
Q

How much lipid in a cell?

A 
average= 2.5%
range= 2-3%
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4
Q

How much carbohydrate in a cell?

A 
average= 1.5%
range= 1%
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5
Q

How much inorganic in a cell?

A 
average= 1%
range= 1%
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6
Q

What cells contain the most water?

A

embryonic cells

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7
Q

What cells contain the least water?

A

old cells

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8
Q

What are common features to all eukaryotic cells?

A
  • outer membrane
  • an inner cytosol
  • a cytoskeleton
  • membrane bound organelles within the cytosol
  • inclusions
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9
Q

What is the cytosol?

A

a solution of proteins, electrolytes and carbohydrates. It has both fluid and gel-like properties

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10
Q

what is the cytoskeleton?

A

determines the shape and fluidity of the cell. Is made from thin and intermediate filaments and microtubules.

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11
Q

what are inclusions?

A

other structures within the cytoplasms which may or may not be bound by a membrane

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12
Q

What is the plasmalemma?

A

It is a bimolecular layer of amphipathic phospholipid molecules with their hydrophilic heads at the outer and inner surfaces and their hydrophobic fatty acid chains facing towards the middle of the 2 layers.

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13
Q

What does the plasmalemma do?

A

separates the cytoplasm from the outside environment

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14
Q

what does the plasmalemma contain?

A

integral proteins which the cells inserts into the membrane. These include receptors, channels, transporters, enzymes and cell attachment proteins.

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15
Q

What does the cell have the ability to do?

A

exocytose and endocytose material through the cell membrane

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16
Q

What can the cell membrane do?

A

it can change its shape easily as it is fluid.

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17
Q

What is the cell membrane permeable to?

A

It is selectively permeable

Highly permeable to: water, oxygen, small hydrophobic molecules

Virtually impermeable to charged ions

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18
Q

How can membrane proteins diffuse?

A

They can diffuse laterally, however many are anchored.

important to realise that many proteins are not distributed equally within the cell membrane

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19
Q

are all proteins distributed equally within the cell membrane?

A

no, as many are anchored

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20
Q

what are organelles?

A

small intracellular ‘organs’ with a specific function and structural organisation

they are essential to life

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21
Q

examples of organelles in the cytoplasm

A

Mitochondria - (energy production)
Rough endoplasmic reticulum - (protein synthesis)
Smooth endoplasmic reticulum - (cholesterol & lipid synthesis/detoxification)
Golgi apparatus - (modification & packaging of secretions)
Lysosomes – (hydrolytic enzymes for intracellular digestion)
Nucleus – (contains genetic code)

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22
Q

mitochondria function

A

energy production

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23
Q

RER function

A

protein synthesis

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24
Q

SER function

A

cholesterol and lipid synthesis/ detoxification

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25
Q

Golgi apparatus function

A

modification and packaging of secretions

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26
Q

lysosomes functions

A

hydrolytic enzymes for intracellular digestion

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27
Q

nucleus function

A

contains genetic code

28
Q

what are inclusions?

A

stored nutrients, secretory products and pigment granules

29
Q

what do inclusions represent?

A

components that have been synthesised by the cell itself (pigment , glycogen stores, lipid droplets, presecretion products etc)
OR
components that have been taken up from the extracellular environment (endocytotic vesicle)

30
Q

What are the cytoskeletal proteins?

A

a set of filamentous cytosolic proteins that maintain many cell functions

31
Q

What are the three main classes of filaments?

A

Microfilaments

  • 7nm in diameter
  • composed of the protein actin

Intermediate filaments

  • > 10nm in diameter
  • composed of 6 main proteins which vary in different cell types

Microtubules

  • 25nm in diameter
  • composed of 2 tubular proteins
32
Q

How do filamentous proteins become attached to the cell membrane and each other?

A

They anchor and join proteins to form a dynamic 3d internal scaffolding in the cell

33
Q

Microfilaments (MF)

A

One of the cytoskeleton proteins

composed of fine strands of actin

7nm diameter (or 0.007µm)

Actin molecules can assemble into filaments and later dissociate, making them very dynamic cytoskeletal elements.

34
Q

What polymerises to form filamentous (F) actin?

A

Globular (G) actin

35
Q

Intermediate Filaments

A

One of the cytoskeleton proteins

Bind intracellular elements together and to the
plasmalemma

10-15nm in diameter (0.01-0.015µm)

More than 50 types, but divided into classes.

they form a network throughout the cytoplasm

36
Q

Types of intermediate filaments

A

neurofilaments are found in nerve cells

glial fibrillary acidic protein are found in glial cells of nervous system

design found in muscle cells

cytokeratins found in epithelial cells

vimentin found in mesenchymal cells

filesin found in the lens of the eye

lamina found in the nuclei of all cells

37
Q

Microtubules

A

One of the cytoskeleton proteins

Microtubules: hollow tubule composed of two types of tubulin subunits, α & β in an alternating array.

Can be assembled and disassembled.

Originate from a special organising centre called the centrosome.

Include stabilizing proteins: microtubule-associated proteins (MAPS)

38
Q

what are microtubules made up of?

A

hollow tubule composed of two types of tubulin subunits, α & β in an alternating array.

39
Q

Are microtubules polar?

A

Yes as they polymerise in the central portion of the cell and radiate outwards

40
Q

What two proteins attach to microtubules and move along them?

A

Dynein and kinesin

41
Q

what is kinesin?

A

an ATPase that moves towards the cell periphery

42
Q

what is dynein?

A

an ATPase that moves towards the cell centre

43
Q

What is the centrosome also known as?

A

microtubule organising centre

44
Q

where do microtubules radiate from?

A

centrosome/ special microtubule organising centre

45
Q

what does the centrosome contain at its core?

A

centrioles which are composed of mainly specialised microtubule segments

46
Q

what is the nucleus enclosed by?

A

nuclear envelope

composed of an inner and an outer nuclear membrane which has nuclear pores which provides continuity with the cytoplasm

47
Q

what does the nucleus contain?

A

chromosomes and is the location of RNA synthesis

48
Q

where is mRNA and tRNA transcribed?

A

the nucleus

49
Q

where is rRNA transcribed?

A

the nucleolus

- a 1-3µm diameter dense area within the nucleus.

50
Q

what is the perinuclear cistern?

A

the space between the membranes of the nuclear envelope

51
Q

what is the perinuclear cistern continuous with?

A

the cistern of the endoplasmic reticulum

52
Q

What is studded with ribosomes?

A

the outer nuclear membrane as it is engaged in protein synthesis

it is also continuous with the cytoplasmic rough endoplasmic reticulum

53
Q

What does the nucleus contain?

A

Euchromatin (DNA that is more dispersed and is actively undergoing transcription)

Heterochromatin (DNA that is highly condensed and not undergoing transcription)

54
Q

what is the nucleus surrounded by?

A

a double nuclear membrane

55
Q

what is euchromatin?

A

DNA that is more dispersed and is actively undergoing transcription

found in the nucleus

56
Q

what is heterochromatin?

A

DNA that is not highly condensed and is not undergoing transcription

found in the nucleus

57
Q

Where are ribosomes formed?

A

nucleolus

essential in protein synthesis

58
Q

What is a ribosome made up of?

A

a small subunit which binds to RNA

AND

a large subunit that catalyses the formation of peptide bonds

59
Q

What does the export of ribosomes depend on?

A

the nuclear pore complex

60
Q

What are nuclear pore complexes (NPCs)?

A

they are the gateways connecting the nucleoplasm and cytoplasm

61
Q

What is the endoplasmic reticulum (ER)?

A

a network of interconnecting membrane-bound compartments in a cell

62
Q

what does reticulum mean?

A

net-like-structure

63
Q

what are the two types of ER?

A

rough (RER)

smooth (SER)

64
Q

what dopes the ER look like in micrographs?

A

flattened membrane sheets or elongated tubular profiles

65
Q

What does the RER do?

A

plays a vital role in protein synthesis (why it is studded in ribosomes)

It is destined for insert into membranes or for secretions

66
Q

Why does the amount of ER present in a cell vary?

A

It depends on how active the cell is.

Cells that are relatively metabolically inactive have relatively little ER

67
Q

What is synthesised on a polysome?

(floats free within the cytosol

A

proteins that are to remain unpackaged within the cytosol

Principals (2 decks)

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