Cell structure and organisation Flashcards
1
Q
Whats the basic unit of biological organisation ?
A
The cell
2
Q
What do the multiple types of cells refect?
A
specialisation in different tissues/ organs
3
Q
Tell me the 6 characteristics of the cell
A
- Capacity to generate any of the protein products of the genome
- Capacity for selective gene expression to reflect specialisation
- Capacity to replicate itself by cell division and mitosis
- Capacity to metabolise and stay alive
- Capacity to die where necessary (apoptosis)
- Capacity to communicate with external environment
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
5
Q
Whats the main function of the cell membrane?
A
Allow the cell to regulate its own composition and remain stable
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
7
Q
Tell me the components of the phospholipid structure?
A
8
Q
What can the phospholipid sometimes have instead of a glycerol backbone?
A
A sphingosine backbone
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)
10
Q
Whats Sphingomyelin?
A
glycerol replaced by amino alcohol, sphingosine
11
Q
Whats does cholesterol provide to the membrane?
A
Rigidity. cholesterol rich membranes are rigid
12
Q
What are Glycolipids?
A
Carbohydrate linked fatty acids via a glycosidic bond
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
14
Q
Proteins and glycoproteins are also present in the cell membrane. Where can they be found?
A
- Integral
- peripheral
15
Q
What do integral membrane proteins have to help anchor them?
A
hydrophobic amino acids
16
Q
What are proteins commonly tethered to?
A
Membrane cytoskeleton
17
Q
This image shows the basic structure/ organisation of the cell membrane
A
18
Q
Tell me some membrane proteins functions
A
- Cell to cell and cell to extracellular matrix adhesion for tissue formation
- Receptors for receiving external signals or bringing large molecules into cell (endocytosis)
- Transport proteins to control entry and exit of small molecules and ions
19
Q
Plasma membranes acts mainly as a barrier, but what sort of molecules can get through the cell membrane?
A
20
Q
What are the 3 types of protein conformation changes required for all transport proteins?
A
- ATP- powered pumps
- Channels
- Transporters
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
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
23
Q
Name 3 types of transporters
A
- Uniporters
- Symporters
- Antiporters
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
25
Tell me about **symporters**
coupled movement of substrate down its concentration gradient (coupled in the same direction)
its a type of **Cotransporter**
26
Tell me about **antiporters**
coupled movement of substrate against its concentration gradient
a cotransporter involved in secondary active transport
27
Cells in the small intestine and kidney need to transport glucose across their membrane ... a large concentration gradient
against
28
With a Na+/glucose symporter, what the ratio of glucose/ Na+ ions into the cell?
couples import 1 glucose to import 2 Na+ ions
29
in the Na+/glucose symporter, the Na+ moves down its concentration gradient, what is this used to power?
Its used to power the uphill movement of other molecules e.g. glucose
30
Whats the Na+/K+ pumps used to power?
the import of amino acids into the cells (e.g. lysine)
31
What two features does a polarised cell tend to contain?
An apical and basal domain
32
What type of tissue lines organs?
epithelial tissue e.g. lining of the gut or outer layer of skin
33
What does the epithelial cell provide ?
A selective permeability barrier
34
What is the basal lamina rich in?
Extracellular matrix
35
What does the basal lamina help to do?
organise tissues and create a structure
36
What does cell-cell anchoring junctions help to provide?
polarity to the cell
37
Can gap junctions communicate?
yes
38
what to **Hemidesmosomes** have and what does this do?
they have transmembrane proteins that link it to the extracellular matrix
39
label this epithelial cell...
40
Whats the function if the **Tight junctions?**
to seal the gap between epithelial cells
41
Whats the function of the **adherens junction?**
It connects the actin filament bundle in one cell with that in the next
42
Whats the function of the **desmosome?**
It connects the intermediate filaments in one cell to those in the next cell
43
Whats the function of the **Gap junction?**
It allows the passage of small water-soluble molecules from cell to cell
44
Whats the function of **Hemidesmosomes?**
It anchors the intermediate filaments in a cell to extracellular matrix
45
Whats the function of **actin-linked cell-matrix junction**
It anchors the actin filaments in a cell to extracellular matrix
46
Do tight junctions tend to be near the apical or basal domain?
the apical domain
47
Is the tight junction a selective barrier?
yes
48
What do the tight junctions contains and what does this help with?
They contain multiple types of cell-cell and cell-extracellular matrix attachments that regulate epithelial function and polarity
49
What are the tight junctions linked to and what does this help with?
These complexes are linked to the internal cytoskeleton (actin or intermediate filaments) to maintain epithelial cell structure
50
What are the tight junctions comprised of?
A branched network of sealing strands that encircle each cell within the epithelium
51
Tight junction formation requires what 2 main major transmembrane proteins?
**occludins** and **claudins**
52
What type of molecule is not able to cross the epithelium?
tracer molecules
53
What type of transport across epithelial tissue do tight junctions prevent ?
passive transport
54
Tell me the steps to glucose transport across the epithelial cell
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
What does the septum in prokaryotic organisms do?
facilitates cell division
56
Whats the **Nucleoid** in prokaryotic organisms?
A DNA rich region which is not membrane bound
57
Does the **Cytosol** in prokaryotic organisms have ribosomes?
yes
58
What are **Mesosomes?**
invaginations of plasma membrane that play a role in cell division, respiration, secretion and DNA sythesis
59
Label this prokaryotic organism...
60
Label this eukaroytic organism...
61
What do mitochondria and chloroplasts originate from and why is this thought to be the case?
Bacteria as they both contains inner and outer membrane and harvest energy
62
Tell me what processes in mitochondria and chloroplast produce ATP?
Mitochondria- oxidative phosphorylation to produce ATP
Chloroplast- Photosynthesis to produce ATP
63
Which parent does the mitochondrial DNA come from?
mother
64
the mitochondria express specific enzymes which are involved with what?
respiration
65
What have mitochondria evolved from?
Symbiotic bacteria
66
What is the mitochondria the main site of?
ATP production during aerobic metabolism
67
Label this mitochondria...
68
Which area does ATP production occur in the mitochondria?
the cistae (invaginations) which are rich in protein complexes
69
What occurs in the **Central matrix** and what does this help with
H+ ions pumped out of the matrix into the intermembrane space, creating a gradient, this helps to eventually drive ATP production
70
What are **Plasmodesmata?**
specialised cell junctions that connect cells and allow for communication between cells (similar to gap junctions in animal cells)- allow exchange of molecules
71
Label this plant cell...
72
There is only one vacuole per cell, what % of the plant cells space does the vacuole occupy?
about 80% of the plant cell
73
What is the vacuole a store for?
water
ions
nutrients
sucrose
amino acids
metabolic waste products
74
Is the vacuole a degradative organelle ?
yes
75
Tell me about the pH of a vacuole
It has an acidic pH (membrane H+ proton pumps and Cl- channels)
76
Tell me about the structural role of the vacuole?
1. Osmotic pressure leads to hydrostatic pressure and plant rigidity, **turgor pressure**
2. keeps plant from wilting
77
What are the **Stomata** good for?
They are pores important for gas exchange
78
How to guard cells minimise water loss?
by controlling the opening of stomata
79
When do stomata open/ close and why?
Stomata open in light to allow CO2 in and close at night to prevent water loss
80
What causes the guard cells to open and what is it mediated by?
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
Label this stomata...
82
How many membranes does the chloroplast contain?
it contains a double membrane
83
The cistae of mitochondria are connected to the inner membrane, but in the chloroplast is the thylakoid membrane connected to the inner membrane?
no its not continuous with the inner membrane
84
New offspring in chloroplasts is produced how?
For each new offspring they are produced by the growth of pre-existing organelles followed by fission
85
What is chloroplasts the site for?
Photosynthesis
86
What is a chloroplast comprised of?
comprised of a thylakoid membrane system with grana (disc-shaped membrane stacks with chlorophyll)- site of photosynthetic light capture and energy conversion
87
The energy from photosynthesis is used to produce what?
carbohydrates out of CO2 and water
88
Protein complexes that perform photosynthetic electron-transfer reactions are embedded in what?
The thylakoid membrane
89
What does the stroma matrix contain?
What is it the site for?
It contains; starch granules, metabolic enzymes
site of; ATP production
90
Label this chloroplast...
91
Label this chloroplast...
92
Tell me types of nucleus organisations
1. **Chromatin**
2. **Nucleolus**
3. **Nuclear inner and outer membrane**
4. **Lamins**
93
Whats organised within chromatin?
DNA bound to histones (makes up chromosomes)
94
Tell me about the nucleolus and some of its functions
Not surrounded by membrane, transcription and processing of ribosomal RNA (rRNA), produces ribosomal subunits
95
What is the inner nuclear membrane comprised of ?
Nuclear lamina- fibrous intermediate filament network
96
What do the nuclear lamina provide?
structural support
help to anchor chromosomes
regulate transcription
97
What are nuclear lamins linked to and by what?
They are linked to the nuclear membrane via membrane associated proteins
98
What is the outer nuclear membrane continuous with?
the endoplasmic reticulum membrane
99
What does the **nuclear pore complex** facilitate?
and between what?
The passage of biomolecules (mRNA, transcription factors, etc.) between the nucleus and cytoplasm
100
What is the nuclear pore complex made up of?
nucleoporins
101
is the nuclear pore complex selective?
yes and also large and highly structured
102
Name the 2 types of nucleoporins found in the nuclear pore complex
1. **channel nucleoporins**
2. **scaffold nucleoporins**
103
What does the nuclear pore complex block?
The transport of substances over 40-60 KDa
104
Label this nuclear pore complex...
105
Tell me the steps to transport across the nuclear pore complex...
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
