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MCB > MCB1 - Life Cells And Their Structural Organisation > Flashcards

MCB1 - Life Cells And Their Structural Organisation Flashcards

1
Q

What are the two types of cells.

A

Eukaryotic and prokaryotic.

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2
Q

What structures are present in the nucleus and give brief overview of their functions.

A

Nucleolus - distinct sub-nuclear structure producing ribosomes.
Nucleoplasm - contains unravelled chromosomes (chromatin).
Nuclear envelope - double lipid bilayer. Ribosomes on outer envelope.
Nuclear pore - controls import and export of proteins.

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3
Q

What constitutes most of the cell.

A

Cytoplasm - fluid that is rich in proteins, organelles, cytoskeletal filaments and macromolecules.

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4
Q

What is the name of the membrane around a cell.

A

Plasma membrane.

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5
Q

What does the nucleolus do and how does it do it.

A

Site of ribosome production. Contains synthesised rRNA and proteins which make the ribosome subunits.

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6
Q

Where in the chromosome are rRNA genes present.

A

Ends of pairs of chromosomes.

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7
Q

Define difference between heterochromatin and euchromatin.

A

Heterochromatin - condensed genetic information. Less active.
Euchromatin - less condensed genetic information. More accessible.

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8
Q

Define chromecentre.

A

Dark staining cluster of heterochromatin present in the nucleus of some cells.

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9
Q

What is the main function of a ribosome.

A

Organelle that reads mRNA and synthesised respective polypeptide chain.

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10
Q

What are the two types of proteins reduced by ribosomes and their location.

A

Cytoplasmic proteins - synthesised by free ribosomes in the cytoplasm.
Membrane/packaged proteins - synthesised by ribosomes attached to outer envelope of nuclear envelope or rough endoplasmic reticulum.

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11
Q

Define polyribosomes structure and purpose.

A

Multiple ribosomes binding to the same mRNA structure allowing multiple polypeptide chains to be produced from single mRNA.

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12
Q

Which direction does a ribosome read mRNA in

A

From 5’ start codon to 3’ stop codon.

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13
Q

What happens to the ribosome when it reaches the stop codon on a mRNA molecule.

A

Ribosome large and small subunit detach from mRNA, polypeptide chain becomes dissociated from ribosome.

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14
Q

What are ribosomes made from.

A

Ribosomal RNA and proteins.

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15
Q

Which terminal in a polypeptide chain is first formed during protein translation.

A

N terminal formed first and folds first. Followed by C terminal domain.

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16
Q

Discuss Svedburg units.

A

Used as scientific unit for sedimentation coefficient. Material spun in centrifuge at high speed and where/how it sediments is observed.

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17
Q

Can components with the same mass have different sedimentation coefficients.

A

Yes if they have different densities and shapes.

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18
Q

Size of ribosomes for prokaryotes, eukaryotes and mammalian mitochondria.

A

Eukaryotes - 80S
Prokaryotes - 70S
Mitochondria - 55S

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19
Q

What are the sizes of the large and small subunits for eukaryotic ribosomes.

A

Large subunit - 49 proteins, 60S rRNA

Small subunit - 33 proteins, 40S rRNA

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20
Q

What are the sizes of the large and small subunits for prokaryotic ribosomes.

A

Large subunit - 34 proteins, 50S rRNA

Small subunit - 21 proteins, 30S rRNA

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21
Q

What are the sizes of the large and small subunits for mitochondrial ribosomes.

A

Large subunit - 52 proteins, 39S rRNA

Small subunit - 30 proteins, 28S rRNA

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22
Q

Why does 50S large subunit and 30S small subunit not give 80S ribosome.

A

Density and shape of assembled units gives lower sedimentation coefficient.

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23
Q

Discuss relationship between nucleus and endoplasmic reticulum.

A

Outer envelope of nuclear envelope of nucleus is continuous with the endoplasmic reticulum.

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24
Q

What component of the cytoskeleton is present in the nucleus. Give its function.

A

Intermediate filaments nuclear lamina is present on internal surface of nuclear envelope. Controls assembly and disassembly of nuclear envelope during cell division.

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25
Q

What is the perinuclear space.

A

Space between two membranes in nuclear envelope middle.

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26
Q

Why is there physical continuity between nucleus and ER.

A

Allows exchange of molecules

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27
Q

Discuss structure of rough ER.

A

Stacks of flattened membrane leaflets known as cisternae. Ribosomes on outer layer.

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28
Q

Function of rough ER.

A

Membrane protein and proteins to be packed into vesicles synthesis

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29
Q

Structure of smooth ER and which cells are they commonly abundant in.

A

Tubular in structure with no ribosomes. Cells producing steroid hormones as they synthesise/package lipids which constitute steroid hormones.

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30
Q

Define role of smooth ER in cell signalling.

A

Store Ca2+ ions which are involved in cell signalling.

31
Q

Discuss other role of smooth ER.

A

Detoxification and lipid metabolism.

32
Q

Main purpose of Golgi apparatus and define its structure.

A

Modifies/sorts/packages macromolecules for secretion or delivery to other compartments. Stacks of membrane bound flattened sacs with small membrane bound vesicle surrounding it.

33
Q

Purpose of small membrane bound vesicles in Golgi apparatus.

A

Carries material between Golgi and different cell compartments.

34
Q

Which face of the Golgi faces what compartment in a cell.

A

Cis face - ER.

Trans face - cell periphery.

35
Q

Discuss intracellular membrane.

A

Constitutes the nuclear envelope, ER, Golgi and exchange membranes.

36
Q

Structure and function of mitochondria.

A

Aerobic energy metabolism producing ATP. Contain double membrane with inner membrane folded to give cristae. Inside space is mitochondrial matrix.

37
Q

What cells have high mitochondrial numbers

A

Cells with high metabolic activity.

38
Q

Which organelles are usually located close to mitochondria and why.

A

Peroxisome as it plays a role in metabolism.

ER as lipids are transferred by carrier protein. Also require proteins from nuclear DNA

39
Q

Define structure and role of peroxisomes.

A

Membrane bound organelle containing high concentration of enzymes. Appears to have paracrystalline structure due to high enzyme concentration.

40
Q

Which chemical reaction occurs frequently in peroxisomes.

A

Oxidation reactions producing peroxide as byproduct. Peroxide used in peroxidation reaction.

41
Q

What is a peroxidation reaction.

A

Lipid peroxidation is oxidative degradation of lipids.

42
Q

Define the cytoskeleton.

A

System of polymerised protein filaments that is highly dynamic and gives strength and structure to a cell. Rapidly remodelled by biochemical and biomechanical stimuli.

43
Q

What are the three components of the cytoskeleton.

A

Microtubules, intermediate filaments and microfilaments.

44
Q

Function of microtubules.

A

Involved in cell shape and movement - major structural and moto component. Act as tracks for movement of organelles.

45
Q

Discuss structure of microtubules.

A

Polymer of alpha and beta tubulin heterodimers. Radiate from microtubules organising centre (MTOC).

46
Q

How does movement occur in cilia and flagella.

A

ATP dependent motor proteins distort the structure of cilia/flagella, resulting in movement.

47
Q

Discuss structure of axoneme. Where is it present.

A

9 microtubules doublets arrange in circle. 2 central microtubules in the core. Makes 9+2 axoneme. Present in cilia and flagella core.

48
Q

Link between anticancer drugs and microtubules.

A

Microtubules form the mitotic spindle. Anticancer drugs can target the mitotic spindle to prevent cell division.

49
Q

Why are intermediate filaments, intermediate?

A

Intermediate in diameter between microtubules and microfilaments.

50
Q

Discuss structure of intermediate filaments and main function.

A

Linear polymers of filamentous protein. Staggered linear arrangement. Gives mechanical strength to cells.

51
Q 
Give types of intermediate filaments in the following structures: 
Epithelial cell.
Nucleus. 
Mesenchymal cells. 
Neurones.
Muscle cells.
A 
Epithelial cell - cytokeratins. 
Nucleus - nuclear lamins.
Mesenchymal cells - vimentin. 
Neurones - neurofilament protein. 
Muscle cells - desmin.
52
Q

Sizes of different components of cytoskeleton.

A

Microtubules - 25nm
Intermediate filaments - 8-12nm.
Microfilaments - 7nm.

53
Q

Discuss structure and function of microfilaments.

A

Globular actin monomers (G-actin) polymerising to form filamentous actin polymer (F-actin). Involved in cell shape and movement.

54
Q

What proteins do microfilaments work with to carry out their function.

A

Work with accessory proteins such as myosin to control cell movement. Associate with adhesion belts and plasma membrane proteins.

55
Q

Where in the cell are microfilaments present commonly.

A

In cell periphery.

56
Q

Which type of cell is actin most commonly found in. Discuss structure of what this cell makes up.

A

Muscle cells. Muscle cell composed of actin and myosin. Makes up myofibrils which makes muscle fibres which make muscle fascicles.

57
Q

What are muscle fascicles.

A

Bundles of muscle fibres surrounded by perimysium - a connective tissue.

58
Q

Is actin exclusively found in muscle cells.

A

No - also found in non-muscle cells.

59
Q

What are the three domains.

A

Bacteria.
Archaea.
Eukaryotes.

60
Q

Which two domains constitute prokaryotes.

A

Bacteria and archaea.

61
Q

How did bacteria and archaea get classified as two separate domains.

A

As a result of sequencing of proteins and nucleic acids.

62
Q

Define differences in previous and current taxonomy.

A

Previously based on structural similarities. Now done by nucleic acids and protein sequencing.

63
Q

What is cell theory.

A
  1. All living organisms are composed of one or more cell.
  2. Cell is basic unit of life.
  3. All cells arise only from pre-existing cells.
64
Q

Discuss differences between prokaryotes and eukaryotes.

A 
Cell size - P O.5-10uM, E 10-100uM
Nucleus - P no, E yes
DNA - P circular, E linear 
Membrane bound organelles - P no, E yes
Ribosome - P 70S, E 80S
Cilia/flagella - P rigid (made from flagellin), E flexible tubulin core
65
Q

What are the two types of bacteria and how are they classified.

A

Gram positive and gram negative. Gram positive has thick peptidoglycan layer (retains Gram dye) and single lipid bilayer. Gram negative has thin peptidoglycan later (does not retain Gram dye) and double lipid bilayer membrane.

66
Q

Discuss lipid bilayer of archaea.

A

Rarely have double lipid bilayer.

67
Q

Give type of environment archaea are mainly found in.

A

Extreme environments so considered extremophiles. E.g halophiles - high salt concentration species.

68
Q

Discuss environmental conditions leading to evolution of cells.

A

Originally, very little oxygen was present. Inorganic material was consumed as food as organic material ran out. Evolution of photosynthesis led to great oxygenation event which eventually killed majority of cells. Species developed both aerobic and anaerobic conditions. Cells formed endosymbiotic relationships to survive.

69
Q

Discuss similarities between mitochondria/chloroplasts and prokaryotes.

A

Small with double membrane.
Circular DNA.
Divide by binary fission.
Translation and transcription methods similar.

70
Q

What are the key events in the evolution of eukaryotes.

A

Archaeon cells package DNA into primate nucleus forming early eukaryotes.
Aerobic bacteria engulf anaerobic archaeon/early eukaryote forming endosymbiotic relationship eventually forming eukaryote with mitochondria.
Photosynthetic Cyanobacteria engulfed by eukaryotic cell forming endosymbiotic relationship eventually forming chloroplasts.

71
Q

Why are fewer genes present in mtDNA.

A

Due to the endosymbiotic relationship, many genes were transferred to the cell nucleus so were lost from circular mtDNA.

72
Q

Give three pieces of evidence for the evolutionary relationship between eukaryotes and archaea/bacteria.

A
  1. Translation and transcription similar in eukaryotes and archaea.
  2. Energy metabolism of eukaryotes similar to bacteria - bacterial origin of mitochondria.
  3. RNA and ribosomes similar in eukaryotes and archaea.
73
Q

Give in piece of evidence against the evolutionary relationship of bacteria/archaea and eukaryotes.

A

Phospholipids used in bilayer are different and are produced by different pathways.

MCB (13 decks)

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