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biol 112 > 3 - Eukaryotic cells > Flashcards

3 - Eukaryotic cells Flashcards

1
Q

Endomembrane system

A

A network of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.

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2
Q

Why are eukaryotic cells larger than prokaryotic cells?

A

Because of their internal membrane system.

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3
Q

How is genetic material organised in eukaryotic cells?

A

Chromosomes enclosed in a nuclear envelope

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4
Q

How is genetic material organised in eukaryotic cells?

A

Chromosomes enclosed in a nuclear envelope

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5
Q

What do plant cells have that animal cells do not?

A

Chloroplasts, central vacuole/tonoplast, plasmodesmata and a cell wall.

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6
Q

What do chloroplasts do?

A

Capture light energy and convert it into chemical energy

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7
Q

Where does photosynthesis occur?

A

In the stacks of thylakoid sacs (grana)

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8
Q

What do vacuoles do?

A

Store various chemicals and play a role in cell growth

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9
Q

What does the plant cell wall do?

A

Maintains cell shape and prevents mechanical damage.

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10
Q

What is the plant cell wall composed of?

A

Cellulose fibres embedded in a protein/polysaccharide matrix consisting of hemicellulose and pectin

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11
Q

What do animal cells have that plant cells do not?

A

Lysosomes, centrioles and flagella (in some plant sperm)

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12
Q

What do animal cells have that plant cells do not?

A

Lysosomes, centrioles and flagella (in some plant sperm)

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13
Q

What is contained in the nucleus?

A

Chromatin, nucleolus and nuclear envelope

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14
Q

What is contained in the nucleus?

A

Chromatin, nucleolus and nuclear envelope

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15
Q

What is contained in the cytoskeleton?

A

Microfilaments, intermediate filaments and microtubules

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16
Q

Which is the largest organelle in the eukaryotic cell?

A

Nucleus

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17
Q

What does the nucleus do?

A

Contains most of the genes which control the cell, some are present in mitochondria and chloroplasts.

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18
Q

What does the nucleus do?

A

Contains most of the genes which control the cell, some are present in mitochondria and chloroplasts.

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19
Q

What does the nuclear membrane do?

A

Encloses nucleus and separates it from the cytoplasm

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20
Q

Nuclear membrane

A

A double membrane containing nuclear pores (100nm in diameter)

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21
Q

What happens to chromatin during cell division?

A

Condenses into chromosomes

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22
Q

Where is mRNA synthesised?

A

Inside the nucleus from a DNA template

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23
Q

What happens to mRNA after it is synthesised?

A

Released into the cytoplasm via nuclear pores.

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24
Q

What does the plasma membrane do?

A
  • Defines and contains the cell
  • Controls entry of nutrients and exit of waste products.
  • Maintains electrolyte balance
  • Acts as sensor to external signals
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25
Q

Plasma membranes

A

Assemblies of lipids and protein molecules held together by non covalent interactions. Fluid mosaic model.

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26
Q

What is the purpose of the lipid bilayer?

A

Provides the basic structure of the membrane and serves as an impermeable barrier to most water-soluble molecules

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27
Q

Where are the protein molecules in the plasma membrane?

A

Dissolved in the lipid bilayer.

28
Q

What will lipid molecules form in an aqueous environment?

A

Either micelles or bilayers

29
Q

Three major types of lipids in cell membranes

A

Phospholipids, cholesterol and glycolipids

30
Q

Three major types of lipids in cell membranes

A

Phospholipids, cholesterol and glycolipids

31
Q

How is the lipid membrane a 2D fluid?

A

Individual lipid molecules able to freely diffuse within lipid bilayers but rarely move from one side to the other.

32
Q

How do lipid molecules in the bilayer often move?

A
  • Exchange places adjacently

- Rotate rapidly about their axis

33
Q

What does the fluidity of a membrane depend on?

A

It’s lipid composition

34
Q

What does a high level of cholesterol do to membrane stability?

A

Increases it by interacting with phospholipid molecules

35
Q

How does the effects of cholesterol change at different temperatures?

A

Warm: Restrains movement of phospholipids
Cool: Maintains fluidity by preventing tight packing.

36
Q

Transmembrane proteins

A

Where the polypeptide chain of membrane proteins crosses the lipid bilayer several times. Amphipathic.

37
Q

How are peripheral membrane proteins associated with the membrane?

A

By non covalent linkages but are easily dislodged.

38
Q

How can the shape and distribution of membrane proteins be observed?

A

Freeze fracture electron microscopy

39
Q

How can the shape and distribution of membrane proteins be observed?

A

Freeze fracture electron microscopy

40
Q

Freeze fracture

A

Specialised preparation technique that splits a membrane along the middle of the bilayer.

41
Q

Freeze fracture

A

Specialised preparation technique that splits a membrane along the middle of the bilayer.

42
Q

Functions of membrane proteins

A
  1. ) Transport proteins
  2. ) Receptor sites
  3. ) Structural
  4. ) Cell junctions
43
Q

How do membrane proteins act as receptor sites?

A

The exterior region of a transmembrane protein may act as a receptor for a chemical messenger such as a hormone.

44
Q

How do membrane proteins play a structural role?

A

Integrins allow the cell to attach to the extracellular matrix

45
Q

How do membrane proteins play a role at cell junctions?

A

Separate apical and basal membranes which have different functions at tight junctions.

46
Q

Cystic Fibrosis

A

An autosomal recessive disease that’s caused by a defective chloride ion channel.

47
Q

What does the failure of the chloride channel result in?

A

A build up of viscous mucus within the lungs, making the individual prone to infections.

48
Q

Where is a glycocalyx (thin layer of carbohydrate) present?

A

On the outside of the plasma membrane of most cells.

49
Q

What are cell surface carbohydrates important for?

A

Cell-cell and cell-ECM recognition

50
Q

How are carbohydrates important in blood types?

A

The ABO types are determined by carbs on the surface of RBCs

51
Q

How are carbohydrates important in blood types?

A

The ABO types are determined by carbs on the surface of RBCs

52
Q

What are membrane glycoproteins involved in?

A

Infection mechanisms

53
Q

What must HIV do in order to infect a cell?

A

Must bind to the immune cell surface protein CD4 and a “co-receptor” CCR5

54
Q

What cells can HIV not enter?

A

Resistant individuals that lack normal CCR5.

55
Q

Endocytosis

A

The process where cells take in materials

56
Q

Endocytosis

A

The process where cells take in materials

57
Q

Pinocytosis

A

Cells infold parts of their plasma membrane to take up extracellular fluid in small vesicles. Non specific.

58
Q

Phagocytosis

A

Uptake of insoluble material and a form of feeding in protozoa

59
Q

What does receptor mediated endocytosis involve?

A

Binding of macromolecules to specific cell surface receptors which trigger endocytosis.

60
Q

What does receptor mediated endocytosis involve?

A

Binding of macromolecules to specific cell surface receptors which trigger endocytosis.

61
Q

What happens to macromolecules after endocytosis is triggered?

A

They become concentrated in endocytic pits.

62
Q

What are endocytic pits coated with?

A

Clathrin, a bristle like protein

63
Q

What does clathrin do?

A

Polymerises around the vesicle forming a cage like structure.

64
Q

Exocytosis

A

The process of material being exported from the cell.

65
Q

What does exocytosis involve?

A

Fusion of vesicles from the interior of the cell with the plasma membrane, the contexts then expelled into surrounding medium.

66
Q

Why is exocytosis important?

A

Secretion of numerous proteins e.g. hormones and extracellular structural proteins and fluids.

67
Q

How is receptor-mediated endocytosis used to deliver drugs into cells?

A

Drug is encapsulated in a liposome and the surface of the liposome has a peptide which binds to a cell surface receptor, triggering uptake of the liposome and drug into the cell.

biol 112 (12 decks)

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