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MBChB Year 1 Principles Embryology, Histology & Radiology > Histology - Anatomy of the Cell > Flashcards

Histology - Anatomy of the Cell Flashcards

1
Q

What % of the cell is water?

A

80% average (75-85% range)

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2
Q

What % of the cell is protein?

A

15% average (10-20% range)

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3
Q

What % of the cell is lipid?

A

2.5% average (2-3% range)

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4
Q

What % of the cell is carbohydrate?

A

1.5% average

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5
Q

What % of the cell is inorganic?

A

1% average

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6
Q

Do embryonic or old cells have more water?

A

Embryonic

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7
Q

What features are common to all eukaryotes?

A

An outer membrane, an inner cytosol, a cytoskeleton, membrane bound organelles in the cytosol and inclusions

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8
Q

What is the inner cytosol?

A

A solution of proteins, electrolytes and carbohydrates. Has both fluid and gel-like properties

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9
Q

What is the function of the cytoskeleton?

A

Determines shape and fluidity of the cell

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10
Q

What is the cytoskeleton made of?

A

Thin and intermediate filaments and microtubules

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11
Q

What are inclusions?

A

Structures within the cytoplasm which may or may not be membrane bound - they are dispensable and may be present only as transients

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12
Q

What is the plasmalemma?

A

A bimolecular layer of amphipathic phosphoric molecules with the ability to exocytose and endocytose material through it

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13
Q

What is the role of the plasmalemma?

A

To separate the cytoplasm from the outside environment

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14
Q

What proteins are in the plasmalemma?

A

Integral - receptors, channels, transporters, enzymes and cell attachment proteins and peripheral.

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15
Q

Why are proteins not distributed equally in the cell membrane?

A

Some diffuse laterally into the membrane but some are anchored

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16
Q

What is the membrane highly permeable to?

A

Water, oxygen, small hydrophobic molecules

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17
Q

What is the membrane virtually impermeable to?

A

Charged ions

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18
Q

Other than proteins what else in embedded in the plasmalemma?

A

Cholesterol

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19
Q

What are organelles?

A

Small, intracellular ‘organs’ with a specific function and structural organisation. They are essential to life

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20
Q

What is the role of mitochondria?

A

Generation of ATP (via oxidative phosphorylation) and the synthesis of certain lipids and proteins

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21
Q

What is the role of the rough endoplasmic reticulum?

A

Protein synthesis

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22
Q

What is the role of the smooth endoplasmic reticulum?

A

Cholesterol and lipid synthesis/detoxification

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23
Q

What is the role of Golgi apparatus?

A

Modification and packaging of secretions

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24
Q

What is the role of lysosomes?

A

Hydrolytic enzymes for cellular digestion

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25
Q

What is the role of the nucleus?

A

Contains the genetic code

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26
Q

Where can inclusions come from?

A

Can be synthesised by the cell (pigment, glycogen stores, lipid droplets, presecretion product) or can be taken up from the environment (endocytotic vesicle)

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27
Q

What are the 3 main classes of filaments?

A

Microfilaments, intermediate filaments and microtubules

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28
Q

What is the structure of microfilaments?

A

7nm, and composed of fine strands of actin (which can later dissociate = very dynamic)

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29
Q

What is the structure of intermediate filaments?

A

> 10nm, composed of 6 main proteins which vary dependent on cell type

30
Q

What is the structure of microtubules?

A

25nm, hollow tubule composed of two types of tubular subunits - alpha and beta (in an alternating array)

31
Q

How do filaments attach?

A

Anchoring and joining proteins to form a dynamic 3D internal scaffolding in the cell = cytoskeleton

32
Q

What is the function of intermediate filaments?

A

To bind intracellular elements together and to the plasmalemma

33
Q

What are types of intermit filaments at their location?

A 
Neurofilaments - nerve cells
Glial fibrillary acidic protein - glial cells in nervous system
Desmin - muscle cells
Cytokeratins - epithelial cells
Vimentin - mesenchymal cells 
Filesin - lens of the ye
Laminators - nuclei of all cells
34
Q

Where do microtubules originate from?

A

Centrosome (special organising centre)

35
Q

What types of protein do microtubules contain?

A

Stablising proteins - microtubule-associated proteins (MAPS)

36
Q

Where do microtubules polymerise?

A

The central portion of the cell and radiate outwards = polar (this is important in cilia, flagella and the mitotic spindle)

37
Q

What two proteins attach to microtubules to move them along?

A

Dyenin and kinesin by associating with membranes of organelles and vesicles and ‘dragging’ them along the microtubule

38
Q

What is kinesin?

A

An ATPase that moves towards the cell periphery

39
Q

What is dynein?

A

An ATPase that moves towards the cell centre

40
Q

What organelle is at the core of centrosomes?

A

A pair of centrioles mainly composed of specialised microtubule segments

41
Q

What encloses the nucleus?

A

A nuclear envelope - composed of an inner and outer membrane with pores (gives continuity in the cytoplasm)

42
Q

What is found between the nucleus and the nuclear envelope?

A

The perinuclear cistern - continuous with the cistern of the endoplasmic reticulum

43
Q

What studs the outer nuclear membrane?

A

Ribosomes and is continuous with the cytoplasms RER

44
Q

Where are mRNA and tRNA transcribed?

A

Nucleus

45
Q

Where is rRNA transcribed?

A

Nucleolus - a small dense area within the nucleus

46
Q

What 2 types of DNA does the nucleus contain?

A

Euchromatin (more dispersed and actively undergoing transcription) and Heterochromatin (highly condensed and not undergoing transcription)

47
Q

Where are ribosomes formed?

A

Nucleolus

48
Q

What are ribosomes composed of?

A

A small subunit which binds RNA and a large subunit which catalyses formation of peptide bonds

49
Q

What is the export of ribosomes dependent on?

A

The nuclear pore complex

50
Q

What does the endoplasmic reticulum form?

A

A network of interconnecting membrane-bound compartments in the cell

51
Q

Why is RER ‘rough’?

A

Studded with ribosomes

52
Q

Where does RER play a vital role?

A

The synthesis of proteins defined for insertion into membranes or secretion

53
Q

How does amount go ER in the cell affect how active the cell is?

A

Little ER = low metabolic activity

54
Q

What is synthesised on polysomes?

A

Proteins that are to remain unpackaged in the cytosol

55
Q

What is protein synthesis in relation to RER?

A

Free ribosomes attach to mRNA. If ER signal peptide sequence is present the growing peptide is inserted into a pore in the ER. The growing peptide forms in the ER and then the signal sequence is removed. Ribosome detaches and most completed proteins then enter the SER

56
Q

What is the role of SER?

A

Continue processing the proteins produced in the RER

57
Q

What is the Golgi apparatus composed of?

A

A group of flattened, membrane bound cistern arranged in sub-compartments

58
Q

Where do transport vesicles from SER/RER go?

A

Golgi apparatus

59
Q

How does the Golgi apparatus modify/package macromolecules?

A

Adds sugars, cleaves some proteins and sorts macromolecules into vesicles

60
Q

What is the structure of mitochondria?

A

Outer and inner membrane, the inner is folded extensively to form cristae (inverses surface area).

61
Q

What are the 3 types of intercellular junctions?

A

Occluding, anchoring and communicating junctions

62
Q

What do occluding junctions do?

A

Prevent diffusion by linking cells - appear as a focal region of close apposition between adjacent cell membranes (also known as tight junctions to zonula occludens)

63
Q

What do anchoring junctions do?

A

Link submembrane actin bundles of adjacent cells to provide mechanical strength (also known as adherent junctions or zonula adherent)

64
Q

What do demosomes do?

A

Link submembrane intermediate filaments of adjacent cells (macula adherent) - common in skin

65
Q

What is a junctional complex?

A

The close association of several types of junctions found in certain epithelial tissues

66
Q

What do communicating junctions do?

A

Allow selective diffusion of molecules between adjacent cells (often termed gap junctions). Each junction is a circular patch with several hundred pores produced by connexon proteins - found in epithelia but also smooth and cardiac muscle for spread of excitation

67
Q

How can material move across the membrane?

A

Diffusion, transport proteins (pumps/channels) or incorporation into vesicles (vesicular transport)

68
Q

What are the 2 types of vesicular transport?

A

Endocytosis and phagocytosis

69
Q

What is endocytosis?

A

Material from the extracellular space is incorporated into the cell. The membrane invaginates, fuses and the new endocytotic vesicle (endoscope) buds into the cell - often receptor mediated. (reverse in exocytosis)

70
Q

What is phagocytosis?

A

Bacteria or larger particulate material is incorporated into the cell by phagocytosis. Bacterium binds to cell surface receptors triggering extensions of the cell to engulf it = phagosome. Phagosome binds with lysosome carrying digestive enzymes = phagolysosome

MBChB Year 1 Principles Embryology, Histology & Radiology (5 decks)

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