Dr Bevington Flashcards
1
Q
Animals cells :
A
- flagella
- lysosomes
- 2 centrioles within a Centrosome
2
Q
Plant cells :
A
- cellulose cell wall
- chloroplasts
- central vacuole
- plasmodesmata
- Centrosome
3
Q
Cellular components common to all cells -
A
- plasma membrane
- cytosol
- ribosome
- chromosome
4
Q
Only Eukaryotic cells have -
A
- nucleus
- mitochondria
- endoplasmic reticulum
- Golgi apparatus
- Flagella
- chloroplasts
5
Q
In archaea membrane lipids usually contain…
A
Long hydrophobic prenyl chains comprising 20-25 carbon atoms instead of hydrophobic long chain fatty acids
6
Q
Fluid mosaic model - current model =
A
- Variable thickness
- patchy
- high level of proteins
- may not be very fluid
7
Q
Plasma membrane function :
A
- impermeable to water and water soluble molecules
- self healing
- signalling and transport ( embedded proteins)
- cell recognition
8
Q
Trans membrane proteins are comprised of …
A
Polypeptide chains winding back and forth across the lipid bilateral
9
Q
The capsule :
A
An additional thick polysaccharide layer secreted by some bacteria as an additional defensive layer
Encapsulated bacteria are resistant to phagocytosis
10
Q
Extracellular =
A
Outside cell
11
Q
Intracellular =
A
Inside cell
12
Q
Intercellular =
A
Spanning between two cells
13
Q
Polysaccharides -
A
Polymer of sugar units
E.g. cellulose & pectins in plant cell walls
14
Q
Glycosaminoglycans -
A
Polymers of chemically modified sugars
E.g. in extracellular matrix in animals tissues
15
Q
Glycoproteins -
A
Proteins with sugars covalently attached
E.g. cell surface proteins or secreted extracellular proteins in animals
16
Q
Proteoglycans -
A
Glycoproteins in which a sugar polymer is a large part of the molecule
E.g. cell surface molecules or secreted extracellular matrix molecules in animals
17
Q
Plant cell wall: structure
A
Primary cell wall - parallel aligned fibres ( flexible = deposited during growth )
Secondary cell wall - non aligned fibres ( rigid = deposited once growth has stopped )
Middle lamellar - sticky layer of polysaccharides hold adjacent cells together
18
Q
Plant cell wall: function
A
- inert - barrier, regulates entry/exit of substances
- rigid ( nonaligned fibres) - maintains shape despite movement of water
- flexible ( parallel aligned fibres of the primary cell wall) - allow growth
19
Q
Animal cells don’t have cell walls they have…
A
They have extracellular matrix
made up of glycoproteins :
- fibronectin ( binds to integrity proteins in membranes)
- collagen ( binds to fibronectin)
20
Q
Extracellular matrix :function:
A
Forms a gel - provides mechanical protection in tissues
Flexible - allows changes in shape + size
Communication - integrins can transmit signals between extracellular matrix and the inside of the cell
21
Q
Ribosomes -
A
Structure found in the cytosol or on the rough endoplasmic reticulum
protein synthesis
Translates a messenger RNA nucleotides sequence into a protein amino acid sequence
22
Q
Tetracycline antibiotic-
A
Act in bacteria :
Blocks binding of amino acyl-tRNA to A-site of ribosome
23
Q
eukaryotes:
A
Has a nucleus Multiple chromosomes Normally multicellular Has membrane bound organelles Larger ribosomes Only have cell walls in plants made of cellulose Approximately 10-100um in size in multi cellular organisms, most cells are specialised for particular function yeast, animals, plants and Protista
24
Q
prokaryotes:
A
Doesn’t have a nucleus One chromosome Normally unicellular No membrane bound organelles Smaller ribosomes Cell wall found in bacteria made of peptidoglycan Approximately 1-10um in size bacteria and archaea
25
Streptomycin antibiotic-
Prevents the transition from translation initiation to chain elongation and also causes miscoding
26
Chloramphenicol antibiotic -
Blocks the peptidyl transferase reaction on ribosome
27
Erythromycin antibiotic-
Binds in the exit channel of the ribosome and inhibits elongation of the peptide chain
28
last common known ancestor
Lokiarchaeota
29
eukaryotes and prokaryotes both have...
ribosomes
DNA
cytoplasm
plasma membrane
30
nucleus:
double nuclear envelope - separates cell content with nucleus content
nuclear pore - allows entry/exit of substances
nucleolus - production of ribosomes
31
chromatin:
the material in a chromosome
comprised of 8 core histones and DNA
Each histone octamer is composed of 2x histone proteins H2A, H2B, H3, and H4.
The function of chromatin is to efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence.
32
chromatin can be stained...
blue by toluidine blue
33
nuclear lamina -
maintains shape of nucleus
34
chloroplast function:
photosynthesis:
stroma - light independent reaction
thylakoid - light dependent reaction
35
plasmodesmata structure -
small holes in plant cell walls
lined by plasma membrane
cytosol of adjacent cells is continuous
36
plasmodesmata function -
specific transport of water, small solutes, specific proteins, RNA
37
cytosol -
semi fluid substance between plasma membrane and nucleus ( not including organelles)
environment for metabolic reactions
38
mitochondrial matrix -
citric acid cycle
39
mitochondrial cristae -
provide large surface area for membrane bound enzymes involved in electron transport and oxidative phosphorylation
40
rough endoplasmic reticulum -
same as smooth endoplasmic reticulum but has ribosomes which synthesise secretory proteins
41
smooth endoplasmic reticulum -
synthesises lipids
detoxifies proteins
stores calcium
42
golgi apparatus -
modify/package proteins into vesicles
consist of flattened membrane sacs called cisternae
their structure and enzyme content changes from cis to trans faces
43
protein synthesis and secretion-
1) transcribed mRNA leaves nucleus and attaches t a ribosome
2) ribosome synthesises a protein
3) a vesicle with the protein in pinches off of the rough endoplasmic reticulum
4) Golgi apparatus packages the protein
5) vesicle fuses to the plasma membrane where the protein is released via exocytosis
44
why do cells perform different reactions in different sub-cellular compartments?
some enzymes may be incompatible in the conditions in different sub-cellular compartments
45
glycolysis -
happens in cytosol
produces pyruvate that is converted to Acetyl CoA which drives ATP production in mitochondria
46
how are organelles turned over?
membrane vesicles fuse and accumulate to form an autophagosome which engulfs the organelle
47
lysosomes =
contain digestive enzymes
48
protein degradation -
1) lysosomal and autophagosomal proteases which are optimal at low ph
2) calcium activate cytosolic proteases which are active at neutral ph
3) ubiquitin proteasome pathway
49
the ubiquitin proteasome pathway-
ubiquitin = small protein which is covalently attached to proteins which have been targeted for degradation
proteasome = huge macromolecular cylindrical complex in the cytosol which contain proteases that degrade polyunbiquitinated proteins
50
why is it necessary for macromolecules in cells to be turned over?
1) to control the time course of gene expression - proteins or mRNA may need turning off/on
2) proteins may misfold
3) cumulative damage to the molecule - nee to be removed and replaced
51
reactive oxidation species =
produced as a by-product of electron transport and oxidative phosphorylation in mitochondria
produced by high energy radiation
= highly reactive oxidising molecules
= cause damage to biological molecules
52
sometimes oxidising molecules are not degraded and replaced...
e.g. oxidised lipids in atherosclerosis = accumulation of partly oxidised low density lipoprotein in the walls of blood vessels = cardiovascular disease
53
actin microfilaments =
made up of F-actin polymers
- resist tension on cell
- endocytosis/exocytosis
- localised contractions of cell
54
cytoskeleton structure -
microfilaments (actin)
microtubules (tubulin)
intermediate filaments (keratin)
55
the cortex =
a branched network of actin microfilaments around the perimeter of a cell
56
myosins (muscle contraction) -
motor proteins that pull actin filaments together and hydrolyse ATP to move away from the actin filament
57
microtubules =
hollow tubes of tubulin dimers
moved by kinesin
- compression resisting
- supports cell structure
- movement of vesicles
- cell division
58
cilia =
fluid circulation powered by dynein motor proteins e.g. move mucus
59
flagella =
driving movement of animal sperm
one per cell
powered by dynein motor proteins
60
intermediate filaments =
made up of keratin proteins assembled into fibrous subunits and supercoiled together
- resist tension
- maintain cell shape
- fix position of organelles
61
cell cycle : interphase -
G1: growth of organelles
S: DNA synthesis
G2: more growth
62
cell division in multi celled organisms =
```
mitosis = growth, tissue repair, development of fertilise egg
meiosis = generation of gametes
```
63
centriole =
a pair of structures in each centreosome, made up of specialised microtubules.
synthesis of spindles for moving chromosomes
64
centromere =
region of a chromosome where two sister chromatids join together
65
kinetochore =
a protein structure that forms at the centromere during mitosis
66
prophase
1st step of mitosis
chromatin condenses into chromosomes
centrioles move to opposite poles of the cell and form spindles
67
prometaphase
between 1st and 2nd step of mitosis
nuclear envelope breaks down
68
metaphase
2nd step of mitosis
chromosomes line up in middle of cell
spindles attach to the centromere
69
anaphase
3rd step in mitosis
kinetochores are cleave by separase enzyme
the centromere splits
spindle fibres pull sister chromatids towards the poles
cell elongation caused by the kinesin motor proteins
70
telophase
4th step in mitosis
nuclear envelope reforms
chromosomes become less condensed
spindle fibres disassemble
cell membrane starts to invaginate
71
phenotype =
the visible characteristic
72
an example of rapid cell differentiation =
somatic hyper mutation driven by DNA mutation in lymphocytes
73
cannot just rely on necrosis to eliminate cells -
necrosis = uncontrolled release of prtoease enzymes
releases degradative enzymes which may cause necrosis in other cells
74
apoptosis =
=programme cell death
- controlled activation of caspase (protease enzymes)
- cell dismantled from within without leaking toxic contents
- expose molecules on their surface so they can be engulfed by phagocytosis
75
virus =
protein complexes which replicate inside host cells
76
prions =
infectious proteins which replicate in a host by copying an misfolded protein structure = created amyloids
( contain no DNA)
77
smallest bacteria =
mycoplasma
