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Principles > Anatomy of the Cell > Flashcards

Anatomy of the Cell Flashcards

Revision

1
Q

What is an inner cytosol?

A

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

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2
Q

What is a cytoskeleton made of and what is its role?

A

A cytoskeleton determines the shape and fluidity of the cell. It is made from thin and intermediate filaments and microtubules.

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3
Q

What are 5 features common to all eukaryotic cells

A 
An outer membrane
An inner cytosol
A cytoskeleton
Membrane bound organelles within the cytosol
Inclusions
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4
Q

What are Inclusions?

A

Structures within the cytoplasm which may or my not be bound by a membrane. They reflect the function of a cell but are normally not essential for function.
They are dispensible and may be present only as transients. they represent components that have been synthesised by the cell itself (pigment, glycogen stores, liquid droplets, presecretion product) or taken up from the extracellular environment endocytotic vesicle).

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5
Q

What is the Plasmalemma composed of?

A

It is a bimolecular layer of amphipathic phosphilipid molecules with their polar hydrophilic heads at the outer and inner surfaces and their non-polar hydrophobic fatty acid chains facing towards the middle of the two layers.
It contains integral proteins which the cell inserts into the membrane. E.g. receptors, channels, transporters, enzymes and cell attachment proteins. It also contains peripheral proteins and cholesterol embedded in it.

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6
Q

What is the role of the Plasmalemma?

A

It separates the cytoplasm from the outside environment.
It provides a selective, structural barrier between the cell and the outside world.
The cell can exocytose (send material out of the cell) and endocytose (take material into the cell) material through the cell membrane.

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7
Q

The cell membrane is selectively permeable. what is it highly permeable to and what is it virtually impermeable to?

A

The cell membrane is highly permeable to water, oxygen, small hydrophobic molecules
It is virtually impermeable to charged ions (e.g. Na+. The cell uses this separation to create charges.)

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8
Q

What are 4 features of a cell membrane?

A

It is fluid
It can change it’s shape easily
Membrane proteins can diffuse laterally in the cell membrane.
The cell membrane is selectively permeable

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9
Q

Are proteins distributed equally within the cell membrane?

A

No they are not. Membrane proteins can diffuse laterally in the cell membrane but many are anchored.

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10
Q

Are the cell membrane and plasmalemma the same thing?

A

Yes

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11
Q

What environment do cells exist in?

A

A water based fluid environment both inside and outside the cell.

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12
Q

What does trilaminar mean?

A

it means 3 layer effect

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13
Q

What are organelles?

A

They are small intracellular organs with a specific function and structural organization. they are essential to life

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14
Q

What is the role of the mitochondria?

A

Energy production

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15
Q

What is the role of the Rough endoplasmic reticulum?

A

Protein synthesis

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16
Q

What is the role of the smooth endoplasmic reticulum?

A

Cholesterol and lipid synthesis/detoxification

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17
Q

What is the role of the golgi apparatus?

A

Modification and packaging of secretions

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18
Q

What is the role of lysosomes?

A

hyrolytic enzymes for intracellular digestion (act as the stomach of the cell)

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19
Q

What is the role of the nucleus?

A

Contains almost all of the genetic code in the form of chromosomes and is the location of RNA synthesis.

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20
Q

What are cytoskeletal proteins and what is their role in the cell?

A

Cytoskeletal proteins are a set of filamentous cytosolic proteins that maintain several functions of the cell. These filamentous proteins become attached to the cell membrane and to each other by anchoring and joining proteins to form a dynamic 3D internal scaffolding in the cell.

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21
Q

What are the main classes of filaments?

A

Microfilaments
Intermediate filaments
Microtubules

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22
Q

What protein are microfilaments composed of and how do they assemble to form a microfilament?

A

They are composed of the protein actin. The globular actin molecules can assemble into filaments and later disaccociate, making them very dynamic cytoskeletal elements.
(Actin filaments often are seen accumulated under the cell membrane).

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23
Q

What proteins are intermediate filaments composed of?

A

They are composed of six main roteins which very in different cell types.

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24
Q

What proteins are microtubules composed of?

A

They are compose of two tubulin proteins.

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25
Q

How big are microtubules?

A

7nm diameter

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26
Q

Role of Intermediate Filaments

A

They bind intracellular elements together and to the plasmalemma. The filaments form a network throughout the cytoplasm.

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27
Q

What size are intermediate filaments?

A

They have a diameter of 10-15nm.

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28
Q

What are the uses for intermediate filaments in medicine?

A

There are more than 50 types of intermediate filaments, but they are divided into classes. Theses classes are used in pathology to identify origins. e.g. Neurofilaments are found in nerve cells.

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29
Q

What are microtubules composed of?

A

They are hollow tubules composed of two types of tubulin subunits, alpha and beta in an alternating array. Microtubules can be assembled and disassembled. they include stabilizing proteins: microtubule-associated proteins (MAPS).

30
Q

what is the special microtubule organising centre that the microtubules originate from called?

A

It is called the centrosome. it contains at its core a pair of organelles called centrioles which themselves are composed mainly of specialized microtubule segments.
Microtubules polymerize in the central portion of the cell and radiate outwards. Thus they are polar.

31
Q

What is the role of microtubules?

A

They serve as the “motorway” network of the cell. Two proteins, dyneim and kinesin attach to the microtubules and move along them. They associate with the membrnes of organelles and vesicles and “drag” them along the microtubule.
These proteins are very important in the movement of componetns in cells with long processes e.g. the very long axonal process of many neurons.
Can appear as a railway track appearance unde the microscope.

32
Q

What is Kinesin?

A

It is an ATPase that moves toward the cell periphery.

33
Q

What is Dynein?

A

It is an ATPase that moves toward the cell centre.

34
Q

What is the nuclear envelope composed of?

A

The nuclear envelope encloses the nucleus. It is composed of an inner and outer nuclear membrane with nuclear pores providing continuity with the cytoplasm.
Between these two sheets is the perinuclear cistern. The perinuclear cistern is continuous with the cistern of the endoplasmic reticulum. The outer nuclear membrane is studded with ribosomes and is continuous with the cytoplasmic rough endoplasmic reticulum.

35
Q

Where is the site of mRNA, tRNA and rRNA transcription?

A

Both mRNA and tRNA are transcribed in the nucleus, and rRNA is transcribed in the nucleolus, a 1-3µm (micrometer) diameter dense area within the nucleus.

36
Q

What types of DNA 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).

37
Q

What is the nucleus surrounded by?

A

It is surrounded by a double nuclear membrane.

38
Q

Where are ribosomes formed?

A

They are formed in the nucleolus

39
Q

What is each ribosome made up of?

A

Each ribosome is made up of a small subunit which binds RNA an a large subunit which catalyses the formation of peptide bonds ( this is why ribosomes are instrumental in protein synthesis).

40
Q

What does the export of ribosomes depend on?

A

It depends on the nuclear pore complex.

41
Q

What does the endoplasmic reiculum (ER) form?

A

Reticulum means “net-like structure”. The ER forms a network of interconnecting membrane-bound compartments in the cell.
In micrographs, it appears as flattened membrane sheets or elongated tubular profiles.

42
Q

What are the 2 types of Endoplasmic reticulum?

A

Rough ER and Smooth ER.

43
Q

What is the role of RER?

A

RER is so called because its studded with ribosomes. It plays a vital role in the synthesis of proteins destined for insertion into membranes or for secretion. It is also associated in the initiation of glycoprotein formation.

44
Q

Why does the amount of ER present in cells vary?

A

It varies with how active the cell is. Cells that are relatively metabolically inactive have relatively little ER.

45
Q

How are proteins that remained unpackaged in the cytosol synthesised?

A

Thy are synthesised on polysomes floating free within the cytosol.

46
Q

Basic process of protein synthesis

A

Free ribosome attaches to mRNA.
If ER signal peptide sequence is present, growing peptide is inserted int oa pore i the ER
Growing peptide forms in the ER; signal sequence removed.
Ribosome detaches. most completed proteins then enter the SER.

47
Q

What is the role of the SER?

A

The SER continues the processing of proteins produced in the RER.
The SER plays a vital role as the site of the synthesis of lipids.
Most cells contain relatively little SER, but in some (e.g. cells synthesizing steroid hormones) it is extensive.

48
Q

What is the role of the Golgi apparatus?

A

Transport vesicles arrive at the Golgi from the SER/RER.
Golgi cisterns function in the modification and packaging of macromolecules that were synthesised in the ER.
Adds Sugars
Cleaves some proteins
Sorts macromolecules into vesicles.

49
Q

What is the Golgi apparatus compose of?

A

It is composed of a group of flattened, membrane bound cisternae. These are arranged in sub-compartments.

50
Q

What are mitochondria composed of?

A

They are composed of an outer and an inner membrane. The inner membrane is extensively folded to form cristae, which act to increase the available surface area.

51
Q

What are the shape and length of mitochondria?

A

They are oblong, cylindrical organelles, typically 0.5-2µm in length.

52
Q

What is the role of mitochondria?

A

They are the power generators of the cell. They function in the generation of ATP, via oxidative phosphorylation, and in the synthesis of certain lipids and proteins.

53
Q

What is unusual about mitochondria?

A

They contain their own DNA and system for protein production.

54
Q

What does cells with large numbers of mitochondria tell you about the metabolic activity of these cells?

A

I tells us that they have a high level of metabolic activity.

55
Q

What is the role of intercellular junctions?

A

These are specialized membrane structures which link individual cells together into a functional unit. They are particularly prominent in epithelia.

56
Q

What are the three types of intercellular junctions?

A

Occluding junctions link cells to form a diffusion barrier.
Anchoring junctions provide mechanical strength.
Communicating junctions allow movement of molecules between cells.

57
Q

What is the role of Occluding junctions/tight junctions/zonula occludents?

A

They prevent diffusion, and

appear as a focal region of close apposition between adjacent cell membranes.

58
Q

What is the role of Adherent junctions/zonula adherens?

A

They link submembrane actin bundles of adjacent cells.

59
Q

What does transmembrane cadherin bind to?

A

Transmembrane cadherin molecules bind to each other in the extracellular space.
Through link molecules they also bind to actin in the cytoskeleton.

60
Q

How strong are adherent junctions?

A

they are very strong but not as strong as desmosones.

61
Q

What is the role of desmosomes?

A

Desmosomes/macula adherens link submembrane intermediate filaments of adjacent cells.
They are very common in the skin where they provide mechanical stability.
They occur as little spots. The epidermis is held together by thousands of desmosones giving it good structural integrity.

62
Q

What is a junctional complex?

A

It is a close association of several types of junctions found in certain epitherial tissues.

63
Q

What is the role of Communicating/gap junctions?

A

They allow a selective diffusion of molecules between adjacent cells. It involves the direct connection of one cell to another.

64
Q

What do communicating junctions consist of?

A

Each junction is a circular patch studded with several hundred pores. These pores are produced by connexon proteins

65
Q

Where are communicating junctions found?

A

They are found in the epithelia, but also in some smooth muscle and in cardiac muscle, where it is critical for the spread of excitation.

66
Q

How can you tell it is a gap junction?

A

Notice how closely the membranes approach each other.
In a gap junction, physical pores are created by a protein between two cells and connexons allow materials to pass through.
Huge numbers of gap junctions allow waves of movement to occur. Skeletal muscle does not contain gap junctions.

67
Q

What are 3 methods that material can move across the cell membrane in a variety of ways?

A

Diffusion
Via transport proteins (pumps/channels)
By incorporation into vesicles (vesicular transport). There are several types of vesicular transport.

68
Q

What is the role of endocytosis?

A

Endocytosis allows material from the extracellular space to be incorporated into the cell.

69
Q

What is the process of endocytosis?

A

The cell membrane invaginates (turns inside out), fuses and the newly made endocytotic vesicle (endosome) buds into the cell. This process is often receptor mediated.
Exocytosis works in a revers fashion to discharge material.

70
Q

What is the role of phagocytosis?

A

Phagocytosis allows bacteria/larger particulate material from the extracellular space can be incorporated into the cell.

71
Q

What is the process of phagocytosis?

A

The bacterium binds to the cell surface receptors triggering extensions of the cell to engulf it forming a phagosome. The phagosome binds with a lysosome carrying digestive enzymes producing a phagolysosome.

Principles (57 decks)

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