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BIOL1006 > Cell structure and organisation > Flashcards

Cell structure and organisation Flashcards

1
Q

Whats the basic unit of biological organisation ?

A

The cell

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2
Q

What do the multiple types of cells refect?

A

specialisation in different tissues/ organs

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3
Q

Tell me the 6 characteristics of the cell

A
  1. Capacity to generate any of the protein products of the genome
  2. Capacity for selective gene expression to reflect specialisation
  3. Capacity to replicate itself by cell division and mitosis
  4. Capacity to metabolise and stay alive
  5. Capacity to die where necessary (apoptosis)
  6. Capacity to communicate with external environment
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4
Q

What is the cell membrane impermeable to and what does this help to do?

A

The cell membrane is impermeable to water which helps to isolate from the external environment

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5
Q

Whats the main function of the cell membrane?

A

Allow the cell to regulate its own composition and remain stable

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6
Q

Whats the plasma membrane made from and its polarity?

A

Its a two-layer shell of phospholipids with outer hydrophilic globular heads and an inner hydrophobic fatty acid chains

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7
Q

Tell me the components of the phospholipid structure?

A
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8
Q

What can the phospholipid sometimes have instead of a glycerol backbone?

A

A sphingosine backbone

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9
Q

Tell me what the organic polar group can be in a phospholipid?

A

Organic/polar group can be choline (phosphatidylcholine), serine (phosphatidylserine), ethanolamine (phosphatidylethanolamine) or inositol (phosphatidylinositol)

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10
Q

Whats Sphingomyelin?

A

glycerol replaced by amino alcohol, sphingosine

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11
Q

Whats does cholesterol provide to the membrane?

A

Rigidity. cholesterol rich membranes are rigid

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12
Q

What are Glycolipids?

A

Carbohydrate linked fatty acids via a glycosidic bond

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13
Q

Membrane lipids are laterally mobile. How many times per second, and at what temperature, can phospholipid neighbours exchange places?

A

107 times/sec at 37˚c

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14
Q

Proteins and glycoproteins are also present in the cell membrane. Where can they be found?

A
  • Integral
  • peripheral
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15
Q

What do integral membrane proteins have to help anchor them?

A

hydrophobic amino acids

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16
Q

What are proteins commonly tethered to?

A

Membrane cytoskeleton

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17
Q

This image shows the basic structure/ organisation of the cell membrane

A
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18
Q

Tell me some membrane proteins functions

A
  1. Cell to cell and cell to extracellular matrix adhesion for tissue formation
  2. Receptors for receiving external signals or bringing large molecules into cell (endocytosis)
  3. Transport proteins to control entry and exit of small molecules and ions
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19
Q

Plasma membranes acts mainly as a barrier, but what sort of molecules can get through the cell membrane?

A
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20
Q

What are the 3 types of protein conformation changes required for all transport proteins?

A
  1. ATP- powered pumps
  2. Channels
  3. Transporters
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21
Q

Tell me about ATP- powered pumps

What type of transport is used to carry out this process?

A

Couple movement of substrate against its concentration gradient to ATP hydrolysis

active transport is used

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22
Q

Tell me about Channels

What type of transport is used for this process?

A

They form a hydrophilic passageway allowing ions or water to move down a concentration gradient

this is done by Facilitated diffusion

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23
Q

Name 3 types of transporters

A
  1. Uniporters
  2. Symporters
  3. Antiporters
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24
Q

Tell me about Uniporters

A

Move a substrate down its concentration gradient

Uses Facilitated diffusion

Rate of this is slower than in channels

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25
Q

Tell me about symporters

A

coupled movement of substrate down its concentration gradient (coupled in the same direction)

its a type of Cotransporter

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26
Q

Tell me about antiporters

A

coupled movement of substrate against its concentration gradient

a cotransporter involved in secondary active transport

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27
Q

Cells in the small intestine and kidney need to transport glucose across their membrane … a large concentration gradient

A

against

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28
Q

With a Na+/glucose symporter, what the ratio of glucose/ Na+ ions into the cell?

A

couples import 1 glucose to import 2 Na+ ions

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29
Q

in the Na+/glucose symporter, the Na+ moves down its concentration gradient, what is this used to power?

A

Its used to power the uphill movement of other molecules e.g. glucose

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30
Q

Whats the Na+/K+ pumps used to power?

A

the import of amino acids into the cells (e.g. lysine)

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31
Q

What two features does a polarised cell tend to contain?

A

An apical and basal domain

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32
Q

What type of tissue lines organs?

A

epithelial tissue e.g. lining of the gut or outer layer of skin

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33
Q

What does the epithelial cell provide ?

A

A selective permeability barrier

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34
Q

What is the basal lamina rich in?

A

Extracellular matrix

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35
Q

What does the basal lamina help to do?

A

organise tissues and create a structure

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36
Q

What does cell-cell anchoring junctions help to provide?

A

polarity to the cell

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37
Q

Can gap junctions communicate?

A

yes

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38
Q

what to Hemidesmosomes have and what does this do?

A

they have transmembrane proteins that link it to the extracellular matrix

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39
Q

label this epithelial cell…

A
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40
Q

Whats the function if the Tight junctions?

A

to seal the gap between epithelial cells

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41
Q

Whats the function of the adherens junction?

A

It connects the actin filament bundle in one cell with that in the next

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42
Q

Whats the function of the desmosome?

A

It connects the intermediate filaments in one cell to those in the next cell

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43
Q

Whats the function of the Gap junction?

A

It allows the passage of small water-soluble molecules from cell to cell

44
Q

Whats the function of Hemidesmosomes?

A

It anchors the intermediate filaments in a cell to extracellular matrix

45
Q

Whats the function of actin-linked cell-matrix junction

A

It anchors the actin filaments in a cell to extracellular matrix

46
Q

Do tight junctions tend to be near the apical or basal domain?

A

the apical domain

47
Q

Is the tight junction a selective barrier?

A

yes

48
Q

What do the tight junctions contains and what does this help with?

A

They contain multiple types of cell-cell and cell-extracellular matrix attachments that regulate epithelial function and polarity

49
Q

What are the tight junctions linked to and what does this help with?

A

These complexes are linked to the internal cytoskeleton (actin or intermediate filaments) to maintain epithelial cell structure

50
Q

What are the tight junctions comprised of?

A

A branched network of sealing strands that encircle each cell within the epithelium

51
Q

Tight junction formation requires what 2 main major transmembrane proteins?

A

occludins and claudins

52
Q

What type of molecule is not able to cross the epithelium?

A

tracer molecules

53
Q

What type of transport across epithelial tissue do tight junctions prevent ?

A

passive transport

54
Q

Tell me the steps to glucose transport across the epithelial cell

A
  1. Na+/K+ ATPase on the basal domain of epithelial cell generates Na+ and K+ concentration gradients
  2. Outward movement of K+ through non-gated channel generates inside negative membrane potential across plasma membrane.
  3. Na+ gradient and negative membrane potential drives uptake of glucose from intestinal lumen by symporter in apical domain.
  4. Glucose leaves the cell by facilitated diffusion through GLUT2 uniporter in basal domain of epithelial cell
55
Q

What does the septum in prokaryotic organisms do?

A

facilitates cell division

56
Q

Whats the Nucleoid in prokaryotic organisms?

A

A DNA rich region which is not membrane bound

57
Q

Does the Cytosol in prokaryotic organisms have ribosomes?

A

yes

58
Q

What are Mesosomes?

A

invaginations of plasma membrane that play a role in cell division, respiration, secretion and DNA sythesis

59
Q

Label this prokaryotic organism…

A
60
Q

Label this eukaroytic organism…

A
61
Q

What do mitochondria and chloroplasts originate from and why is this thought to be the case?

A

Bacteria as they both contains inner and outer membrane and harvest energy

62
Q

Tell me what processes in mitochondria and chloroplast produce ATP?

A

Mitochondria- oxidative phosphorylation to produce ATP

Chloroplast- Photosynthesis to produce ATP

63
Q

Which parent does the mitochondrial DNA come from?

A

mother

64
Q

the mitochondria express specific enzymes which are involved with what?

A

respiration

65
Q

What have mitochondria evolved from?

A

Symbiotic bacteria

66
Q

What is the mitochondria the main site of?

A

ATP production during aerobic metabolism

67
Q

Label this mitochondria…

A
68
Q

Which area does ATP production occur in the mitochondria?

A

the cistae (invaginations) which are rich in protein complexes

69
Q

What occurs in the Central matrix and what does this help with

A

H+ ions pumped out of the matrix into the intermembrane space, creating a gradient, this helps to eventually drive ATP production

70
Q

What are Plasmodesmata?

A

specialised cell junctions that connect cells and allow for communication between cells (similar to gap junctions in animal cells)- allow exchange of molecules

71
Q

Label this plant cell…

A
72
Q

There is only one vacuole per cell, what % of the plant cells space does the vacuole occupy?

A

about 80% of the plant cell

73
Q

What is the vacuole a store for?

A

water

ions

nutrients

sucrose

amino acids

metabolic waste products

74
Q

Is the vacuole a degradative organelle ?

A

yes

75
Q

Tell me about the pH of a vacuole

A

It has an acidic pH (membrane H+ proton pumps and Cl- channels)

76
Q

Tell me about the structural role of the vacuole?

A
  1. Osmotic pressure leads to hydrostatic pressure and plant rigidity, turgor pressure
  2. keeps plant from wilting
77
Q

What are the Stomata good for?

A

They are pores important for gas exchange

78
Q

How to guard cells minimise water loss?

A

by controlling the opening of stomata

79
Q

When do stomata open/ close and why?

A

Stomata open in light to allow CO2 in and close at night to prevent water loss

80
Q

What causes the guard cells to open and what is it mediated by?

A

Guard cells open by the swelling of the vacuole.

This is mediated by the opening of K+ and Cl- ion channels- increase osmotic pressure to increase water entry

81
Q

Label this stomata…

A
82
Q

How many membranes does the chloroplast contain?

A

it contains a double membrane

83
Q

The cistae of mitochondria are connected to the inner membrane, but in the chloroplast is the thylakoid membrane connected to the inner membrane?

A

no its not continuous with the inner membrane

84
Q

New offspring in chloroplasts is produced how?

A

For each new offspring they are produced by the growth of pre-existing organelles followed by fission

85
Q

What is chloroplasts the site for?

A

Photosynthesis

86
Q

What is a chloroplast comprised of?

A

comprised of a thylakoid membrane system with grana (disc-shaped membrane stacks with chlorophyll)- site of photosynthetic light capture and energy conversion

87
Q

The energy from photosynthesis is used to produce what?

A

carbohydrates out of CO2 and water

88
Q

Protein complexes that perform photosynthetic electron-transfer reactions are embedded in what?

A

The thylakoid membrane

89
Q

What does the stroma matrix contain?

What is it the site for?

A

It contains; starch granules, metabolic enzymes

site of; ATP production

90
Q

Label this chloroplast…

A
91
Q

Label this chloroplast…

A
92
Q

Tell me types of nucleus organisations

A
  1. Chromatin
  2. Nucleolus
  3. Nuclear inner and outer membrane
  4. Lamins
93
Q

Whats organised within chromatin?

A

DNA bound to histones (makes up chromosomes)

94
Q

Tell me about the nucleolus and some of its functions

A

Not surrounded by membrane, transcription and processing of ribosomal RNA (rRNA), produces ribosomal subunits

95
Q

What is the inner nuclear membrane comprised of ?

A

Nuclear lamina- fibrous intermediate filament network

96
Q

What do the nuclear lamina provide?

A

structural support

help to anchor chromosomes

regulate transcription

97
Q

What are nuclear lamins linked to and by what?

A

They are linked to the nuclear membrane via membrane associated proteins

98
Q

What is the outer nuclear membrane continuous with?

A

the endoplasmic reticulum membrane

99
Q

What does the nuclear pore complex facilitate?

and between what?

A

The passage of biomolecules (mRNA, transcription factors, etc.) between the nucleus and cytoplasm

100
Q

What is the nuclear pore complex made up of?

A

nucleoporins

101
Q

is the nuclear pore complex selective?

A

yes and also large and highly structured

102
Q

Name the 2 types of nucleoporins found in the nuclear pore complex

A
  1. channel nucleoporins
  2. scaffold nucleoporins
103
Q

What does the nuclear pore complex block?

A

The transport of substances over 40-60 KDa

104
Q

Label this nuclear pore complex…

A
105
Q

Tell me the steps to transport across the nuclear pore complex…

A
  1. larger molecules are actively and selectively transported
  2. mRNAs coupled to proteins (mRNPs) move through pore by uncoiling
  3. mRNAS can then immediately associate with cytoplasmic ribosome for translation
  4. RNPs have ‘nuclear export sequences’ (NES); transcription factors have ‘nuclear localisation signals’ (NLS)
  5. NES and NLS bind to shuttle proteins that control passage across nuclear pore

BIOL1006 (5 decks)

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