cells Flashcards
(98 cards)
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
2
Q
Describe the PM
A
- hydrophobic lipid tail repels water
- bilayer satisfies molecular properties of the phospholipid; energetically-favourable
- self-healing
3
Q
Where is it possible to have more than one plasma membrane?
A
- gram -VE cell
- periplasmic space and peptidoglycan
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)
5
Q
Summarise what prokaryotes are.
A
- simplest cellular organisms
- oldest
- most abundant
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
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
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
9
Q
Are bacteria monomorphic or pleomorphic?
A
- most monomorphic
- some pleomorphic
10
Q
What does a prokaryotic cell wall provide?
hint - a landing site
A
- ligands for cell attachment (good therapeutic targets)
11
Q
What do outer membrane LPS in prokaryotes often cause?
A
a toxic/immunological response
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)
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
14
Q
By which process do bacterial cells exchange gene information between different species?
(Hint - people unite to form a congregation)
A
conjugation
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
16
Q
Why is horizontal gene transfer a problem?
A
- increased bacterial drug-resistance
- genesthen transferred
17
Q
Which four cell components do all bacteria have?
A
- PM
- cytoplasm
- 70s ribosomes
- nuclear region of DNA
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
19
Q
How do flagella and cilia help cells and how are eukaryotic flagella different from prokaryotic?
A
- help cells move
- eukaryotic more complex
20
Q
Which seven features do all eukaryotes have?
A
- nucleus
- ribosomes (protein production)
- cytoplasmic DNA separation
- membrane-bound organelles (i.e. centriole, vacuole)
- internal membranes (i.e. ER)
- cytoplasmic fibres (i.e. cytoskeleton) for structural support
- wide range of organisms
21
Q
What are large free-living cells?
A
- higher plants and animals
- multicellular
- specialised functions
- complex communication mechanisms
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)
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
24
Q
What are internalised in a cell apart from the cell membrane and why?
A
- most internal organelles
- ideal environment for chemical activities
25
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) 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
26
Describe what staining of a plasma membrane by osmium metal would look under an electron microscope.
- 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)
27
What is the best model to describe plasma membrane structure?
fluid mosaic model:
- two fluid layers of lipid
- proteins within/on lipid layers
28
Describe the phospholipids found in the plasma membrane.
| Hint - the 4 As
- asymmetrically-distributed
- amphiphilic
- a hydrophilic head
- a hydrophobic tail
29
What are each of the molecules mentioned below:
a) phospholipids
b) glycolipids
c) sterols
- phospholipids (phosphate group lipids)
- glycolipids (carbohydrate lipids)
- sterols (steroid alcohols)
30
Describe the chemical composition of phospholipids.
- two HC tails, usually FAs
- tail betw/ 14-24 C atoms length
- small kink from cis-double bonds in one of many tails
31
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.
lipid shape
1. cone-shaped lipid (single-chain) molecules – micelles
2. cylinder-shaped phospholipid (double-tailed) – bilayers
32
What is a phosphoglyceride?
glycerol-based phospholipid
33
Name some phosphoglycerides.
- phosphatidylcholine (phospholipid w/ choline head)
- phosphatidylethanolamine (phospholipid w/ ethanolamine head)
- phosphatidylserine (-) (phospholipid w/ serine head)
- phosphatidylinositol (phospholipid w/ linositol head)
34
What is a sphingolipid and what is the main one in a plasma membrane?
- lipids containing backbone of sphingoid bases
| - sphingomyelin
35
State the compound(s) shown in each picture.
(L to R)
| free fatty acids, glycerol, diglyceride
36
What are the 3 parts of a phospholipid?
polar head (such as choline, ethanolamine, serine, inositol)
lipid backbone
glycerol/sphinogosine-based
37
How is a glycolipid formed?
by addition of CHO group/s to lipids
38
What is a lipid called if it is:
a) glycerol-based
b) sphingosine-based
c) a combination of glycerol & sphingosine-based
- glycerol-based: glycolipid
- sphingosine-based: sphingolipid (sphingosine is an amino alcohol)
- combination of glycerol and sphingosine-based: glycosphingolipids
39
Where are glycosphingolipids prominent?
membranes of myelin sheaths of nerve tissue/s
40
What are the 3 parts of a glycolipid?
- carbohydrate head group
- lipid backbone
- glycosidic bond joining the two
41
Give a popular example of glycolipids.
| Hint - to do with how we classify RBC's
i.e. blood group antigens are glycolipids
42
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 ceramide
b) A sphingomyelin
c) A cerebroside
d) A ganglioside
43
In which cells can we find lots of cholesterol and what does it do?
- eukaryotic cells
- increases permeability barrier
- intercalated betw/ phospholipids (less packing) to maintain stability
- ‘buffers’ fluidity changes over a range of temps
44
On which 2 things is fluidity of a plasma membrane dependent on?
1) composition (of phospholipids); long or short chain
| 2) temperature: movements decrease when temp. drops
45
State the 3 kinds of movements a phospholipid molecule is capable of in its own membrane.
1. rotation
2. lateral diffusion (exchanging places w/ neighbours in same monolayer)
3. transverse diffusion/“flip-flop” (one monolayer to next) (rare)
46
How does composition of phospholipids affect PM fluidity?
- 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
Why are trans-fats and saturated fats considered to be poor for your health?
- raise blood cholesterol levels
| - increases risk of heart disease
48
Why are polyunsaturated fatty acids considered to be good for your health?
- help reduce bad cholesterol
- lower risk of heart disease
- provide essential body fats (omega-3 and 6 FAs)
49
Which factor is diffusion of lipids dependent on?
temperature
50
Which substances decrease plasma membrane fluidity and have clinical consequences?
- cis-unsaturated FAs
- saturated FAs
- excess cholesterol
51
Which substances promote plasma membrane fluidity and have clinical benefits?
trans-unsaturated fatty acids
52
Name four types of membrane proteins.
| Hint - CERT
transporters
receptors
cell-cell interaction proteins
enzymes
53
Name the three classes of membrane proteins named depending on how they are linked to the bilayer.
- 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
What is a lipid raft?
- transient clusters of lipids and proteins w/in membrane
- high concentrations of cholesterol and glycosphingolipids
- increase functional efficiency of membrane
55
State the 3 main functions of a plasma membrane.
1) barrier function
2) transport
3) signal detection
56
Define 'transport.'
- selective movement of ions/organic molecules
| - across membranes
57
What can pass through the PM?
- macromolecules (DNA, RNA, proteins)
| - and solutes (ions, metabolites, AAs)
58
What are the two types of active transport?
| Hint - also the two modes of bulk transport
endocytosis
| exocytosis
59
Define simple diffusion and give a biological example of this.
- 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
Define facilitated diffusion.
- transport aided via proteins
| - to allow large and polar substances to pass through PM
61
How do the molecules pass through the PM via facilitated diffusion?
- via transport proteins which form a path through hydrophobic lipid bilayer (tails) facilitating diffusion
62
State the gradients that used the following molecules use to get through a PM:
a) uncharged molecules
b) ions
a) concentration gradient
| b) electrochemical gradient (difference in charge)
63
Give a biological example of facilitated diffusion.
- 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
Define 'transport protein.'
- integral membrane proteins containing trans-membrane
| - i.e. carrier and channel proteins
65
In which direction do carrier proteins transport solutes?
in either direction (inward/outward)
66
Complete the following diagram of carrier proteins and state the mechanism by which transport through them occurs.
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
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) 1 solute; EITHER in/out
b) 2 solutes; SAME direction simultaneously
c) 2 solutes; OPPOSITE directions
68
What is GLUT 1?
an integral membrane protein glucose transporter (uniport)
69
How much faster does GLUT 1 transport glucose into the membrane than regular diffusion?
50,000x faster
70
In which cells are GLUT 1 transporters located?
liver and muscle cells
71
Describe the mechanism by which GLUT 1 transports a glucose molecule into a cell.
- 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
Define 'channel proteins.'
- form hydrophilic (head) transmembrane channels to allow specific solutes to pass through the PM
- i.e. ion channels, porins, aquaporins
73
What are 'ion channels?'
- small pores lined w/ hydrophilic AA side chains
| - allow rapid passage of specific ions
74
What does 'voltage gated' mean a channel opening/closing triggered by?
change in membrane potential
75
What does 'ligand gated' mean a channel opening/closing triggered by?
binding of specific molecules
76
What does 'mechano-sensetive' mean a channel opening/closing triggered by?
mechanical forces
77
What do ion channels have a vital role in and what do they maintain in cells?
(Hint - like a radio station)
- cellular communication and electrical signal transmission in nerve cells (Na+ and K+)
- maintain salt balance in cells
78
Explain the role of ion channels in cystic fibrosis.
- a specific Cl- ion channel (CFTR) maintains conc. in epithelial cells of lungs
- defects in this ion channel cause excessive mucus build-up
79
Define 'active transport.'
movement of solutes against a conc./electrochemical gradient, requiring ATP
80
State three instances where active transport may be required.
1) uptake of nutrients when conc. is higher inside the cell
2) remove waste materials
3) enables cell to maintain intracellular ion conc.
81
What does the mechanism of active transport involve and what does it produce?
(Hint - what any chemical reaction involves)
- pumps for solute movement
- exergonic reaction (energy released)
- a non-equilibrium steady state
82
Using the example of the Na+/K+ pump explain how it maintains the electrochemical ion gradient.
(Hint - cells are less salty inside than outside)
↑[ K+] ↓[ Na+] = inside
| ↓[K+] ↑[Na+] = outside
83
How are large materials transported across the PM (in only eukaryotes)?
- exocytosis
| - endocytosis
84
In which activities are exocytosis and endocytosis used for?
| Hint - like a cell refurbishment
- delivery
- recycling
- turnover of membrane proteins
85
Define 'exocytosis.'
- process by which the contents of secretory granules are released to exterior of cell
- by vesicle fusing w/ PM
86
State 3 substances that travel via exocytosis.
| Hint - three types of typical enzyme examples
- peptides and protein hormones
- enzymes
- neurotransmitters
87
State the 4 stages of exocytosis.
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
Give a biological example of exocytosis.
| Hint - immunology version of the terminator
- activated mast cells (discharge of vesicle contents to exterior)
89
Define 'endocytosis.'
process by which external material is internalised by cells
90
State 2 activities endocytosis is important in.
| Hint - one good stuff and other bad stuff to be deactivated
- ingestion of nutrients
| - defence against microorganisms (WBCs)
91
State the stages of endocytosis.
- a small segment of the PM invaginates inwards
| - pinching off to form an endocytic vesicle containing ingested substances/particles
92
What is phagocytosis?
- ‘cellular eating’
| - how large & solid particles are ingested
93
Name 2 phagocytes.
- macrophages and neutrophils
| - engulf/digest foreign material/microorganisms
94
What is pinocytosis?
- ‘cellular drinking’
| - (non-specific) liquids containing soluble molecules are taken up
95
Describe the stages of pinocytosis.
| Hint - to do w/ the protein which rhymes with catherine
PM invaginating to form clathrin-coated vesicles
96
How does an electron microscope differ to light microscope?
- uses electrons to visualize specimen so much more powerful
| - can see cell ultrastructure
97
How do electron micrographs give so much detail compared to light microscopes?
- EM allows us to cell organelles
- electron beam <<< Light beam
- shorter wavelength (higher resolution) <<< larger wavelength (x100,000)
98
Define empty magnification.
when magnification is increased but results in a larger, blurry image (rather than a more detailed one)
