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CELS191 > Cell Structure & Diversity 2 - Endomembrane System & Regulation of Animal Cell Shape > Flashcards

Cell Structure & Diversity 2 - Endomembrane System & Regulation of Animal Cell Shape Flashcards

1
Q

What is included in the endomembrane system?

A

Nuclear envelope, endoplasmic reticulum (smooth and rough), Golgi complex, vesicles, lysosomes, vacuoles, plasma membrane

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2
Q

What is the endomembrane system?

A

A membrane system interconnected by direct physical contact or by vesicles transferring

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3
Q

What is the endoplasmic reticulum continuous with?

A

The nuclear envelope

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4
Q

What is the endoplamic reticulum structure?

A

Made of tubules with the open space between them called lumen

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5
Q

What is the two types of endoplasmic reticulum?

A

Smooth and rough

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6
Q

What are the functions of the smooth endoplasmic reticulum?

A

Metabolism of carbohydrates, lipid synthesis for membranes, detoxification of drugs and poisons, storage of calcium ions which are used as a signal in the cell

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7
Q

What is special about the amount of endoplasmic reticulum in cells?

A

The amount varies depending on the function of the cell and whether it is needing its function or not

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8
Q

Is there more smooth or rough ER in cells?

A

Rough

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9
Q

Why is rough endoplasmic reticulum rough?

A

Because it has ribosomes on it

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10
Q

What process is the rough ER involved in?

A

Protein synthesis

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11
Q

What is the role of the rough ER in the endomembrane system?

A

Secreted membrane bound proteins enter the lumen of the rough ER and are processed (synthesised and folded) by the rough ER and the rest of the endomembrane system for release from the cell or to be used in the cell membrane

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12
Q

What happens once the proteins are processed in the rough ER?

A

They accumulate in different areas, form a vesicle and then move to the Golgi complex

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13
Q

What is the Golgi complex?

A

A series of membrane sacs and associated vesicles which receives, modifies, sorts and ships proteins arriving from the rough ER

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14
Q

What are the two faces of the Golgi complex called?

A

Cis and trans

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15
Q

What face of the Golgi complex do vesicles arrive at?

A

The cis face

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16
Q

What face of the Golgi complex do vesicles leave?

A

The trans face

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17
Q

What are the 3 functions of the Golgi complex?

A

Glycosylation, sorting proteins and directing vesicle traffic

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18
Q

What is glycosylation?

A

Carbohydrates are added to proteins/ the proteins are modified which is important for secreted or cell surface proteins in fulfilling their function.

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19
Q

What is sorting proteins?

A

Molecular markers are added to direct the same types of proteins to the same area of the Golgi to be in the correct vesicles before budding from the trans face

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20
Q

What is directing vesicle traffic?

A

The molecular tags which are added to the surface of the vesicle leaving the trans face direct them to the correct target. Molecular tags can then act as docking sites

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21
Q

What are molecular tags usually?

A

Proteins

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22
Q

Where are vesicles directed?

A

Lysosomes and to secretory pathways so they can perform their function outside of the cell

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23
Q

What happens during exocytosis?

A

Material is transported out of the cell or to the cell surface and the vesicle membrane remains part of the plasma membrane.

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24
Q

What is constitutive exocytosis?

A

Exocytosis which is continuous

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25
Q

What is regulated exocytosis?

A

Exocytosis that requires a signal before the vesicles can leave the cell.

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26
Q

What does constitutive exocytosis release?

A

Extracellular matrix proteins

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27
Q

What does regulated exocytosis release?

A

Hormones and neurotransmitters

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28
Q

What is endocytosis?

A

When the cell takes in molecules and particulate matter from the external environment at the plasma membrane

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29
Q

What is phagocytosis?

A

The uptake of extracellular food particles

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30
Q

How does phagocytosis occur?

A

A pseudopodium pulls it in to form a phagocytic vacuole which is digested by the lysosomes

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31
Q

Where does phagocytosis occur?

A

In macrophage cells

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32
Q

What is pinocytosis?

A

The uptake of extra cellular fluid containing various solutes

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33
Q

How does pinocytosis occur?

A

A vesicle for uptake(coated pit) is formed with the help of coat proteins. The extracellular fluid and dissolved solutes flow in.

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34
Q

In endocytosis selective or non-selective?

A

Non-selective

35
Q

What is receptor mediated endocytosis?

A

A specialised form of pinocytosis which allows the cell to uptake specific substances which may be present at only low concentrations in the extracellular fluid

36
Q

What is the function of receptor proteins?

A

To selectively capture the required solute. Other things will also float into the coated pit.

37
Q

What does it mean by receptors being recyclable?

A

They can be used again once they are outside the cell

38
Q

What are lysosomes?

A

Membrane bound organelles made by the rough ER And Golgi complex which contain hydrolytic digestive enzymes

39
Q

What is the pH in lysosomes and why?

A

Around 5 so that the enzymes can be cative

40
Q

What do lysosomes do?

A

Phagocytic vacuoles fuse with lysosomes and they then degrade the proteins, lipids, carbohydrates and nucleic acids within the phagocytic vacuoles so that breakdown products can be released

41
Q

What is autophagy?

A

The process when lysosomes digest and recycle unwanted and no longer useful cellular materials/parts. Whole cell death can also occur when lysosomal enzymes are released into the cytoplasm

42
Q

What vacuoles may be found in animal cells?

A

Large vesicles derived from rough ER and Golgi as well as food vacuoles in phagocytosis.

43
Q

What are animal cells surrounded by?

A

Extracellular fluid and may be connected to other cells

44
Q

What is a feature of the shape of animal cells?

A

It is dynamic and the organelles aren’t fixed in position

45
Q

What is the function of the cytoskeleton?

A

To maintain cell shape and the position of organelles within the cell

46
Q

How can the cytoskeleton cause the cell to change shape?

A

By rapidly being amen to disassemble and reassemble depending on what the cell is needed for

47
Q

What are the 3 components of the cytoskeleton?

A

Microtubules, microfilaments and intermediate filaments

48
Q

What are microtubules made of?

A

Tubulin units arranged in a spiral structure

49
Q

How are microtubules arranged?

A

They may be arranged beside each other or radiating out from the organising centre (centrosome) in a particular arrangement

50
Q

What is the function of microtubules?

A

To resist compression so that cell shape is maintained and can also provide motility

51
Q

What structures provide motility?

A

Flagella and cilia

52
Q

What is the motion of flagella?

A

Snake-like

53
Q

What is the motion of cilia?

A

rowing-like

54
Q

Why is cell motility useful?

A

It means cells can move through fluid

55
Q

Explain organelle motility

A

ATP powered motor proteins can walk organelles such as vesicles along microtubules allowing the vesicles or other organelles to be transported to specific targets in the cell

56
Q

What are microfilaments made of?

A

Double chain of actin subunits twisted into strands

57
Q

How are microfilament arranged?

A

Can form linear strands and 3D branched network structures

58
Q

What are the functions of microfilaments?

A

The dense cortical network under the plasma membrane which is anchored to proteins helps make the region more rigid and maintain the cell shape. Therefore, tension can be resisted.

59
Q

How do microfilaments support cell movement?

A

Interactions between motor proteins and actin allow for muscle contraction, amoeboid movement and cytoplasmic streaming

60
Q

What are intermediate filaments made of?

A

Proteins including keratins in hair, lamins in the nucleus and neurofilaments in neurons which are supercoiled into cables

61
Q

What is the function of intermediate filaments?

A

Because they are less dynamic, they form fairly permanent structures which means they can anchor organelles in place and maintain cell shape

62
Q

What happens to intermediate filaments once the cell dies?

A

They remain

63
Q

What are the 3 types of cell junctions?

A

Tight junctions, desmosomes and gap junctions

64
Q

What is the function of tight junctions?

A

To hold together neighbouring cells which are tightly pressed beside each other and prevent movement of fluid across cell layer

65
Q

What is the structure of tight junctions?

A

A continuous seal

66
Q

What do tight junctions attach to?

A

Microfilaments

67
Q

Are tight junctions all the same?

A

No, some have the ability to let some substances through (they are looser)

68
Q

What are desmosomes?

A

Anchoring junctions that act like rivets

69
Q

What is the function of desmosomes?

A

To provide attachments between sheets of muscle

70
Q

What connects desmosomes to the cell?

A

Intermediate filaments which makes them really strong

71
Q

How much space is between cells with desmosomes?

A

More space than in tight junctions

72
Q

What are gap junctions?

A

A point of cytoplasmic contact between two cells where the cytoplasm connects and becomes continuous

73
Q

What is the structure of gap junctions?

A

Proteins with a pore running through them

74
Q

What is the function of gap junctions?

A

To allow ions and small molecules to pass from cell to cell and allow rapid intercellular communication

75
Q

How do cells join together?

A

By the extracellular matrix

76
Q

Do all cells join directly to other cells?

A

No, some are connected by the ECM

77
Q

What is the composition of the ECM?

A

Material secreted by cells, proteins mainly glycoproteins especially collagen of which the fibres are embedded in a proteoglycan complex matrix

78
Q

What are proteoglycans?

A

Proteins with extensive sugar additions

79
Q

How does secretion into the extracellular matrix occur?

A

By constitutive exocytosis

80
Q

What is the function of proteoglycans?

A

To trap water within the ECM which is needed because it resists compression and tissue shape is therefore maintained

81
Q

What attaches cells to the ECM?

A

Glycoproteins called fibronectins

82
Q

What attaches the ECM to the Cytoskelton?

A

Membrane proteins called integrins

83
Q

Why are integrins important?

A

They provide a communication link from the ECM to the interior

CELS191 (23 decks)

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