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cells Flashcards

1
Q

State the 8 characteristics of all cells.

A
  • plasma membrane
  • DNA
  • genetic code (same in all cells)
  • RNA
  • proteins
  • ribosomes
  • energy (ATP)
  • derived from other cells
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2
Q

Describe the PM

A
  • hydrophobic lipid tail repels water
  • bilayer satisfies molecular properties of the phospholipid; energetically-favourable
  • self-healing
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3
Q

Where is it possible to have more than one plasma membrane?

A
  • gram -VE cell

- periplasmic space and peptidoglycan

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4
Q

What are the purpose(s) of tears and exposed edges in the plasma membrane?

(Hint - waterproof sealing of bubbles)

A
  • small tears (exclude water)
  • large tears (vesicles formed via folding)
  • exposed edges (flat sheet which bend and seal forming sealed compartment)
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5
Q

Summarise what prokaryotes are.

A
  • simplest cellular organisms
  • oldest
  • most abundant
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6
Q

What is the evidence to say all living organisms are derived from a single primordial cell?

A
  • resemblance among living cells
  • common cell components can be made IV from simple organic molecules (C, N, O)
  • fossil evidence
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7
Q

State the type of cells we had:

a) 3.5 bill. years ago
b) 1.5 bill. years ago

A
  • oldest cells - small, simple prokaryotes

- eukaryotic cells termed LECA (last eukaryotic common ancestor) symbiotic combo of ancestor and bacterial lineage

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8
Q

What are the ten main characteristics of prokaryotes?

A
  • simple, basic shapes
  • small (< 10μm)
  • simple compartment of cytoplasm
  • peptidoglycan cell wall
  • replicate quickly
  • horizontal gene transfer
  • binary fission division
  • wide range of food sources
  • aerobic and anaerobic metabolism
  • occupy wide range of ecological niches
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9
Q

Are bacteria monomorphic or pleomorphic?

A
  • most monomorphic

- some pleomorphic

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10
Q

What does a prokaryotic cell wall provide?

hint - a landing site

A
  • ligands for cell attachment (good therapeutic targets)
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11
Q

What do outer membrane LPS in prokaryotes often cause?

A

a toxic/immunological response

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12
Q

State the colours stained for Gram +VE and Gram -VE cells and their cells wall components.

A
  • gram +VE = purple (lipotechoic acid)

- gram -VE = pink (porin, endotoxin/LPS, periplasmic space)

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13
Q

State the niche(s) each type of bacteria occupies:

a) eubacteria
b) archaebacteria

(Hint - ‘eu-‘ means normal and ‘archae’ means radically different)

A

a) soil, water, large organisms

b) bogs, oceans, salt brines, hot acid springs

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14
Q

By which process do bacterial cells exchange gene information between different species?

(Hint - people unite to form a congregation)

A

conjugation

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15
Q

How does conjugation work and what does this process enhance?

A
  • donor cell attaches to recipient via pilus and transfers DNA
    (i. e. how E. coli acquired 1/5th of genome)
  • enhances natural selection advantage
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16
Q

Why is horizontal gene transfer a problem?

A
  • increased bacterial drug-resistance

- genesthen transferred

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17
Q

Which four cell components do all bacteria have?

A
  • PM
  • cytoplasm
  • 70s ribosomes
  • nuclear region of DNA
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18
Q

Which six cell components do some bacteria have?

Hint - hair extensions and circles

A
  • flagella (whip-like structure to move)
  • fimbriae
  • pilus (hair-like appendage)
  • cell wall
  • inclusions (stored nutrients/granules)
  • plasmid
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19
Q

How do flagella and cilia help cells and how are eukaryotic flagella different from prokaryotic?

A
  • help cells move

- eukaryotic more complex

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20
Q

Which seven features do all eukaryotes have?

A
  1. nucleus
  2. ribosomes (protein production)
  3. cytoplasmic DNA separation
  4. membrane-bound organelles (i.e. centriole, vacuole)
  5. internal membranes (i.e. ER)
  6. cytoplasmic fibres (i.e. cytoskeleton) for structural support
  7. wide range of organisms
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21
Q

What are large free-living cells?

A
  • higher plants and animals
  • multicellular
  • specialised functions
  • complex communication mechanisms
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22
Q

What are the six roles of the PM?

A
  • barrier betw/ internal/external environment
  • sites of metabolic activities
  • ion transport (facilitated diffusion etc…)
  • cell signalling (i.e. on glycoproteins)
  • cell shape (maintain a particular structure)
  • cell-cell interactions (i.e. junctions)
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23
Q

Why did we only discover the PM in the 1950s and how were we slightly aware of its existence?

A
  • no electron microscopy so too thin to be seen

- indirect evidence

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24
Q

What are internalised in a cell apart from the cell membrane and why?

A
  • most internal organelles

- ideal environment for chemical activities

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25
Q

For each year state the concept discovered about the plasma membrane.

a) 1890s
b) 1900s
c) 1920s
d) 1940s
e) 1960s
f) 1970-80s
g) 1980s-2000s

A

a) understanding lipid nature of membrane
b) lipid monolayer
c) lipid bilayer
d) lipid bilayer + protein sheets
e) unit membrane (electron microscope)
f) Fluid Mosaic Model
g) membrane protein structure; alpha helix

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26
Q

Describe what staining of a plasma membrane by osmium metal would look under an electron microscope.

A
  • trilaminar staining pattern by TEM: “railroad track”
  • 2 dark lines: outer & inner layer (polar head groups)
  • light central space (hydrophobic region of lipids doesn’t stain)
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27
Q

What is the best model to describe plasma membrane structure?

A

fluid mosaic model:

  • two fluid layers of lipid
  • proteins within/on lipid layers
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28
Q

Describe the phospholipids found in the plasma membrane.

Hint - the 4 As

A
  • asymmetrically-distributed
  • amphiphilic
  • a hydrophilic head
  • a hydrophobic tail
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29
Q

What are each of the molecules mentioned below:

a) phospholipids
b) glycolipids
c) sterols

A
  • phospholipids (phosphate group lipids)
  • glycolipids (carbohydrate lipids)
  • sterols (steroid alcohols)
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30
Q

Describe the chemical composition of phospholipids.

A
  • two HC tails, usually FAs
  • tail betw/ 14-24 C atoms length
  • small kink from cis-double bonds in one of many tails
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31
Q

Phospholipids spontaneously aggregate to keep hydrophobic tails in interior & expose hydrophilic heads to water. What does aggregation style depends? State each one and the structure it forms.

A

lipid shape

  1. cone-shaped lipid (single-chain) molecules – micelles
  2. cylinder-shaped phospholipid (double-tailed) – bilayers
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32
Q

What is a phosphoglyceride?

A

glycerol-based phospholipid

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33
Q

Name some phosphoglycerides.

A
  • phosphatidylcholine (phospholipid w/ choline head)
  • phosphatidylethanolamine (phospholipid w/ ethanolamine head)
  • phosphatidylserine (-) (phospholipid w/ serine head)
  • phosphatidylinositol (phospholipid w/ linositol head)
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34
Q

What is a sphingolipid and what is the main one in a plasma membrane?

A
  • lipids containing backbone of sphingoid bases

- sphingomyelin

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35
Q

State the compound(s) shown in each picture.

A

(L to R)

free fatty acids, glycerol, diglyceride

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36
Q

What are the 3 parts of a phospholipid?

A

polar head (such as choline, ethanolamine, serine, inositol)
lipid backbone
glycerol/sphinogosine-based

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37
Q

How is a glycolipid formed?

A

by addition of CHO group/s to lipids

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38
Q

What is a lipid called if it is:

a) glycerol-based
b) sphingosine-based
c) a combination of glycerol & sphingosine-based

A
  • glycerol-based: glycolipid
  • sphingosine-based: sphingolipid (sphingosine is an amino alcohol)
  • combination of glycerol and sphingosine-based: glycosphingolipids
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39
Q

Where are glycosphingolipids prominent?

A

membranes of myelin sheaths of nerve tissue/s

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40
Q

What are the 3 parts of a glycolipid?

A
  • carbohydrate head group
  • lipid backbone
  • glycosidic bond joining the two
41
Q

Give a popular example of glycolipids.

Hint - to do with how we classify RBC’s

A

i.e. blood group antigens are glycolipids

42
Q

State the name of a sphingosine when:

a) + fatty acid residue (fatty waxy one)
b) + phosphocholine/phosphoethanolamine group (to do with CNS)
c) + single sugar residue (sugar needed for cerebral cortex)
d) + oligosaccharude residue + sialic acid (dangling one)

A

a) A ceramide
b) A sphingomyelin
c) A cerebroside
d) A ganglioside

43
Q

In which cells can we find lots of cholesterol and what does it do?

A
  • eukaryotic cells
  • increases permeability barrier
  • intercalated betw/ phospholipids (less packing) to maintain stability
  • ‘buffers’ fluidity changes over a range of temps
44
Q

On which 2 things is fluidity of a plasma membrane dependent on?

A

1) composition (of phospholipids); long or short chain

2) temperature: movements decrease when temp. drops

45
Q

State the 3 kinds of movements a phospholipid molecule is capable of in its own membrane.

A
  1. rotation
  2. lateral diffusion (exchanging places w/ neighbours in same monolayer)
  3. transverse diffusion/“flip-flop” (one monolayer to next) (rare)
46
Q

How does composition of phospholipids affect PM fluidity?

A
  • shorter chain: reduces the tendency of tails to interact (less fluid)
  • cis-double bonds: produce kinks in chains so more difficult to pack (more fluid)
47
Q

Why are trans-fats and saturated fats considered to be poor for your health?

A
  • raise blood cholesterol levels

- increases risk of heart disease

48
Q

Why are polyunsaturated fatty acids considered to be good for your health?

A
  • help reducebadcholesterol
  • lower risk of heart disease
  • provide essential body fats (omega-3 and 6 FAs)
49
Q

Which factor is diffusion of lipids dependent on?

A

temperature

50
Q

Which substances decrease plasma membrane fluidity and have clinical consequences?

A
  • cis-unsaturated FAs
  • saturated FAs
  • excess cholesterol
51
Q

Which substances promote plasma membrane fluidity and have clinical benefits?

A

trans-unsaturated fatty acids

52
Q

Name four types of membrane proteins.

Hint - CERT

A

transporters
receptors
cell-cell interaction proteins
enzymes

53
Q

Name the three classes of membrane proteins named depending on how they are linked to the bilayer.

A
  • integral (embedded w/in the bilayer and secures a position in PM)
  • peripheral (more hydrophilic and made of AAs which interact w/ bilayer surface)
  • lipid-anchored (hydrophilic, covalently attached to lipids)
54
Q

What is a lipid raft?

A
  • transient clusters of lipids and proteins w/in membrane
  • high concentrations of cholesterol and glycosphingolipids
  • increase functional efficiency of membrane
55
Q

State the 3 main functions of a plasma membrane.

A

1) barrier function
2) transport
3) signal detection

56
Q

Define ‘transport.’

A
  • selective movement of ions/organic molecules

- across membranes

57
Q

What can pass through the PM?

A
  • macromolecules (DNA, RNA, proteins)

- and solutes (ions, metabolites, AAs)

58
Q

What are the two types of active transport?

Hint - also the two modes of bulk transport

A

endocytosis

exocytosis

59
Q

Define simple diffusion and give a biological example of this.

A
  • the unaided net movement of solute through lipid bilayer from high to low conc.
  • i.e. high conc. of O₂ in lungs and low in RBCs
  • O₂taken up by RBC and released to body tissues
60
Q

Define facilitated diffusion.

A
  • transport aided via proteins

- to allow large and polar substances to pass through PM

61
Q

How do the molecules pass through the PM via facilitated diffusion?

A
  • via transport proteins which form a path through hydrophobic lipid bilayer (tails) facilitating diffusion
62
Q

State the gradients that used the following molecules use to get through a PM:

a) uncharged molecules
b) ions

A

a) concentration gradient

b) electrochemical gradient (difference in charge)

63
Q

Give a biological example of facilitated diffusion.

A
  • i.e. glucose movement across the PM
  • [glucose] is higher in blood than RBC
  • transport protein allows the glucose to move as it is too large to pass by simple diffusion
64
Q

Define ‘transport protein.’

A
  • integral membrane proteins containing trans-membrane

- i.e. carrier and channel proteins

65
Q

In which direction do carrier proteins transport solutes?

A

in either direction (inward/outward)

66
Q

Complete the following diagram of carrier proteins and state the mechanism by which transport through them occurs.

A

A - conformational change
B - carrier-mediated solute transport
Mechanism:
- carrier proteins bind to 1+ solutes of PM
- causes protein to undergo conformational change
- allows solute to pass in/out

67
Q

For each type of carrier protein state the number of solutes transported and the direction the solutes take:

a) uniport
b) symport
c) antiport

A

a) 1 solute; EITHER in/out
b) 2 solutes; SAME direction simultaneously
c) 2 solutes; OPPOSITE directions

68
Q

What is GLUT 1?

A

an integral membrane protein glucose transporter (uniport)

69
Q

How much faster does GLUT 1 transport glucose into the membrane than regular diffusion?

A

50,000x faster

70
Q

In which cells are GLUT 1 transporters located?

A

liver and muscle cells

71
Q

Describe the mechanism by which GLUT 1 transports a glucose molecule into a cell.

A
  • glucose binds to GLUT 1 transporter on binding site outside the cell (T1 conformation)
  • binding causes GLUT1 to shift to T2 confirmation with the binding site open to inside cell
  • glucose released to interior of cell initiating second conformational change in GLUT 1
  • loss of bound glucose causes GLUT 1 to return to T1 conformation for the next transport cycle
72
Q

Define ‘channel proteins.’

A
  • form hydrophilic (head) transmembrane channels to allow specific solutes to pass through the PM
  • i.e. ion channels, porins, aquaporins
73
Q

What are ‘ion channels?’

A
  • small pores lined w/ hydrophilic AA side chains

- allow rapid passage of specific ions

74
Q

What does ‘voltage gated’ mean a channel opening/closing triggered by?

A

change in membrane potential

75
Q

What does ‘ligand gated’ mean a channel opening/closing triggered by?

A

binding of specific molecules

76
Q

What does ‘mechano-sensetive’ mean a channel opening/closing triggered by?

A

mechanical forces

77
Q

What do ion channels have a vital role in and what do they maintain in cells?

(Hint - like a radio station)

A
  • cellular communication and electrical signal transmission in nerve cells (Na+ and K+)
  • maintain salt balance in cells
78
Q

Explain the role of ion channels in cystic fibrosis.

A
  • a specific Cl- ion channel (CFTR) maintains conc. in epithelial cells of lungs
  • defects in this ion channel cause excessive mucus build-up
79
Q

Define ‘active transport.’

A

movement of solutes against a conc./electrochemical gradient, requiring ATP

80
Q

State three instances where active transport may be required.

A

1) uptake of nutrients when conc. is higher inside the cell
2) remove waste materials
3) enables cell to maintain intracellular ion conc.

81
Q

What does the mechanism of active transport involve and what does it produce?

(Hint - what any chemical reaction involves)

A
  • pumps for solute movement
  • exergonic reaction (energy released)
  • a non-equilibrium steady state
82
Q

Using the example of the Na+/K+ pump explain how it maintains the electrochemical ion gradient.

(Hint - cells are less salty inside than outside)

A

↑[ K+] ↓[ Na+] = inside

↓[K+] ↑[Na+] = outside

83
Q

How are large materials transported across the PM (in only eukaryotes)?

A
  • exocytosis

- endocytosis

84
Q

In which activities are exocytosis and endocytosis used for?

Hint - like a cell refurbishment

A
  • delivery
  • recycling
  • turnover of membrane proteins
85
Q

Define ‘exocytosis.’

A
  • process by which the contents of secretory granules are released to exterior of cell
  • by vesicle fusing w/ PM
86
Q

State 3 substances that travel via exocytosis.

Hint - three types of typical enzyme examples

A
  • peptides and protein hormones
  • enzymes
  • neurotransmitters
87
Q

State the 4 stages of exocytosis.

A

1) approach of vesicle to PM
2) fusion of membranes
3) rupture of PM
4) discharge of vesicle contents outside the cell; vesicle membrane becomes integrated into PM

88
Q

Give a biological example of exocytosis.

Hint - immunology version of the terminator

A
  • activated mast cells (discharge of vesicle contents to exterior)
89
Q

Define ‘endocytosis.’

A

process by which external material is internalised by cells

90
Q

State 2 activities endocytosis is important in.

Hint - one good stuff and other bad stuff to be deactivated

A
  • ingestion of nutrients

- defence against microorganisms (WBCs)

91
Q

State the stages of endocytosis.

A
  • a small segment of the PM invaginates inwards

- pinching off to form an endocytic vesicle containing ingested substances/particles

92
Q

What is phagocytosis?

A
  • ‘cellular eating’

- how large & solid particles are ingested

93
Q

Name 2 phagocytes.

A
  • macrophages and neutrophils

- engulf/digest foreign material/microorganisms

94
Q

What is pinocytosis?

A
  • ‘cellular drinking’

- (non-specific) liquids containing soluble molecules are taken up

95
Q

Describe the stages of pinocytosis.

Hint - to do w/ the protein which rhymes with catherine

A

PM invaginating to form clathrin-coated vesicles

96
Q

How does an electron microscope differ to light microscope?

A
  • uses electrons to visualize specimen so much more powerful

- can see cell ultrastructure

97
Q

How do electron micrographs give so much detail compared to light microscopes?

A
  • EM allows us to cell organelles
  • electron beam «< Light beam
  • shorter wavelength (higher resolution) «< larger wavelength (x100,000)
98
Q

Define empty magnification.

A

when magnification is increased but results in a larger, blurry image (rather than a more detailed one)

IMS (11 decks)

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