Cell Biology Flashcards
0
Q
What are the levels of DNA packaging?
A
Nucleosomes, 30nm fibre, loops, chromosomes.
1
Q
Why is it important to have a nucleus?
A
To separate transcription and translation.
Regulates import/ export of proteins.
2
Q
What is heterochromatin?
What is euchromatin?
A
Highly packaged DNA. Genes on this DNA are silenced.
Genes less tightly packed. Genes on this DNA are active.
3
Q
What is the nuclear pore made of?
A
Proteins
4
Q
What are NLS’s?
A
A nuclear localisation signal is a positively charged amino acids sequence. It can be anywhere on the protein. They ‘tag’ proteins for import into the cell nucleus by nuclear transport.
5
Q
What are importins?
What are the two types of importins.
A
A protein that binds to the NLS to move proteins in and out of the nucleus.
Importin B binds directly.
Importin A uses an adaptor.
6
Q
What are nuclear lamina? What do they do?
A
Lamins are long proteins that interact to form a rope like structure. They lie next to the inner membrane. They provide support and organisation.
7
Q
How is mitosis different to cytokinesis?
A
Mitosis is when the nucleus divides and cytokinesis is when the cytoplasm divides forming two separate cells.
8
Q
What are the stages of cell division?
A
Interphase:
- G1
- S phase
- G2
M-phase
- Prophase
- Prometaphase
- Metaphase
- Anphase
- Telophase
- Cytokinesis
9
Q
What is a signal peptide?
A
A short, hydrophobic series of amino acids that tell the cell a protein needs to be made and inserted into the ER.
10
Q
In the Golgi apparatus where are the cis and trans faces?
A
The cis is closest to the ER and is where ER vesicles dock.
The trans face is the site where vesicles depart.
11
Q
What is Calnexin?
A
A chaperone that prevents incomplete from being dispatched to the Golgi.
12
Q
What do these coat proteins do?
- Copl
- Copll
- Clathrin
A
Cop l coats vesicles going from the Golgi back to the ER.
Cop ll coats vesicles going from the ER to the Golgi.
Clathrin coats vesicles going between Golgi, lysosomes, and plasma membrane. It’s made of 3 large and 3 small polypeptides that form a triskelion.
13
Q
What is dynamin?
A
A protein which helps release vesicles by winding around the vesicles neck.
14
Q
How much DNA is wound around the histone core and in the nucleosome?
A
146 nucleotides
15
Q
Which additional protein is used to twist the beads on a string form of chromatin into the 30nm fibre.
A
Histone H1
16
Q
What are chromatin loops attached to?
A
Nuclear scaffold
17
Q
Which rRNA is not synthesised in the nucleolus?
A
5S
18
Q
The nucleolus forms around how many chromosomes?
A
10
19
Q
What part of a ribosome does the incoming tRNA first interact with?
A
A site
20
Q
What direction is mRNA read in?
A
5’ to 3’
21
Q
What catalyses peptide bond formation in eukaryotic ribosomes?
A
28s rRNA
22
Q
What is catalytic RNA called?
Give an example.
A
Ribozyme
28s ribosomal RNA
23
Q
What is the start codon?
What amino acid does it encode?
A
AUG or ATG
Methionine
24
What is the name of eukaryotic protein degradation machinery?
What is its structure?
Proteasome
Hollow tube
25
What is the name of the molecule added to proteins to target them for degradation?
What amino acid is this signal added to?
What is the enzyme that catalyses the reaction?
Ubiquitin
Lysine
Ubiquitin lipase
26
Name two types of protein synthesised in the endoplasmic reticulum.
What is the name of the complex which recognises the ER signal peptide?
What is the name of the enzyme that removes a signal peptide from a soluble secretory protein?
Secretory and transmembrane
Signal recognition particle
Signal peptidase
27
Describe how a secretory protein is translocated into the endoplasmic reticulum.
The signal peptide binds to the signal recognition particle. This pauses translation. The SRP interacts with the SRP receptor in the ER membrane. The plug blocking the protein translocator is displaced allowing the protein to be translated directly into the ER lumen.
28
During N-linked glycoslylation sugars are added to what amino acid?
What is the enzyme that transfers pre assembled oligosaccarides to the elongating peptide?
Asparagine
Oligosacchairde transferase
29
What are the flattened compartments of the Golgi called?
Moving from the face nearest the ER to the face from which the vesicles leave the Golgi name each of the three compartments,
Cisternae
Cis, medial, trans
30
What happens to a protein containing the KDEL sequence when it reaches the Golgi?
Retrieval to the endoplasmic reticulum
31
What provides the energy required to bring the vesicle and recipient membranes close together?
Winding of v- and t- SNAREs
32
What is the default route taken by a protein once it has completed its journey through the Golgi?
Constitutive exocytosis
33
What type of enzyme is found in lysosomes?
Hydrolases
34
What is the pH inside a lysosome?
What maintains it?
5
H+ pump
35
How does a cell protect itself from its own hydrolytic enzymes?
They only function at low pH. They are kept within a membrane.
36
What are the 3 routes that substrates for infra cellular digestion take to the lysosome?
Phagocytosis, autophagy, endocytosis
37
What marker is recognised by the receptors which target hydrolases into vesicles which will transport them to the lysosome?
What causes mannose-6-phosphate to dissociate from its receptor once reaching the late endosome?
Mannose-6-phosphate
The environment is more acidic
38
What are the two electron donators in oxidative phosphorylation? Briefly Describe the process of oxidative phosphorylation, what is its purpose?
NADH and FADH are electron donators.
The first enzyme complex NADH dehydrogenase in the membrane dehydrates NADH and steals electrons. There are two other complexes that also take electrons.
There is increasing affinity for electrons down the ETC.
The final electron acceptor is oxygen which has the highest affinity.
The point of the ETC is to release energy slowly not all in nor go.
39
Why is there a electrochemical gradient in the mitochondria?
| What is the difference in pH and charge?
Movement from low to high affinity is energetically favourable. Energy released is used to pump H+ ions into the inter-membrane space. This generates an electrochemical gradient across the inner membrane.
The inside of the mitochondria has a negative charge and pH of 8. The inter-membrane space has a more positive charge and pH of 7.
40
What are the 3 types of filaments that make up the cytoskeleton? Describe them
Actin - smallest, individual globular proteins that form helical polymers, role in cell shape and motility.
Microtubules - largest, globular protein (tubulin), hollow tube, rigid.
Intermediate - middle size, long filamentous proteins which form rope like structure, mechanical support.
41
Why are interactions in the cytoskeleton not covalent?
How is cytoskeleton growth controlled? What are the two phases?
So monomers can be rapidly added or removed.
By adding or removing monomers. 2 phases cultural concentration - when addition and removal are at the same rate.
Equilibrium phase - when they stop, critical concentration reached
42
What are accessory proteins? What do they do?
Proteins that can initiate new filaments in the cytoskeleton. They can bind to monomers to change addition rates. Also involved in disassembly.
43
How to myosin proteins motor?
Myosin head bound to actin.
ATP binds to myosin, actin released.
ATP hydrolyses and head cocks and changes conformation.
Head reattaches to actin and phosphate is released.
44
Apart from myosin what are the other type of motor proteins? What are they like?
How do they motor?
Kinesins and dyneins. Microtuble motor proteins, globular head interacts with the cytoskeleton.
Leading head (1) bound to tubulin. Trailing head to bound to ADP.
Head 1 binds to ATP causing conformation change throwing H2 forward.
H2 binds to tubulin.
H2 releases ADP and H1 hydrolyses ATP.
H2 now leading H1 trailing.
45
What are the two types of microtuble that play a role in separating sister chromatids during anaphase of cell division?
Astral and kinetochore
46
What are the the 3 check points (in order) in the cell cycle?
Restriction point, G2-M transition and metaphase-anaphase transition.
47
What are the two types of cell death?
Why do we need programmed cell death?
Does apoptosis require energy?
Necrosis (accidental) and apoptosis (programmed).
For cells infected with viruses, cells with DNA damage, cancer cells.
Yes from ATP
48
What are caspases?
What is the order they are activated in?
What sets off the caspase cascade?
Cell death proteases
Initiator caspases, activate a cascade and generate lots of effector caspases.
Intrinsic pathway:
-Damage or stress
Extrinsic pathway:
-Proteins from other cells bind to death receptors on cell surface, death receptors aggregate and cause caspase 8 to be cleaved which the cascade.
49
What is histology?
What is histochemistry?
What is cytology?
The study of the structure of tissues.
Deals with the chemical composition of the cells and tissues of the body.
The medical and scientific study of cells.
50
What is the process of staining a sample?
Fixation
Dehydrate in increasing concentrations of alcohol (70%, 90%, 100%, 100%, 100%)
Clearing stage
Impregnate with molten wax
Embed in wax blocks
Section cutting using a microtome
Rehydrate
Stain with Haematoxylin and Eosin (blue and pink)
Dehydrate in alcohol and attach cover slip with DPX mountant.
51
What is tissue?
What are the four types of tissue?
A group of cells similar in structure and function.
Epitheial, connective, muscle and nervous.
52
What are the functions of epithelial tissue?
What are the characteristics of epithelial tissue?
Provide protection, control permeability, provide sensation and absorb nutrients.
Polarity, specialised contacts, attachments, avascularity and regeneration.
53
What are the two types of glands in epithelial tissue and describe them.
Endocrine - ductless glands secretion not released into duct.
Hormone is released directly into extracellular space.
Exocrine - product secreted into ducts, can be unicellular or multicellular.
54
Name in the order they occur, the subdivisions of prophase 1 of meiosis.
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Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis
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55
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What functions do the following cells play in bone?
Osteoid
Osteoclast
Osteoblast
Osteocyte
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Extracellular matrix of bone
Bone re absorption
Cells at growing surface secreting ECM
Cells within bone ECM; bone maintinance
56
Name three types of cell found in connective tissue.
Fibroblasts, osteoblasts, chondrocytes
57
What type of junction seals epithelial sheets?
Occluding junction
58
What are the proteins found in tight junctions?
Claudins and occludins
59
What junctions join cells to cells?
What junctions join cells to the ECM?
Desmosomes and adherens junctions
Hemidesmosomes and focal adhesions
60
What is the enzyme that breaks down hydrogen peroxide to water and oxygen?
Catalase
61
What histones make up core nucleosomes?
Two each of H2A, H2B, H3, H4
62
What is the name of the sequence of bases where transcription starts?
Promoter
63
What is the name of the enzyme that transcribes DNA into RNA?
RNA polymerase 2
64
What type of bond joins DNA to the histone octamer?
Hydrogen bonds
65
What are microtubles attached to?
Microtuble organising centre (also called a centrosome)
66
When Kinesins move along microtubles what causes the trailing head to be thrown forward?
ATP binding to leading head
67
Which cytoskelital element is connected to the following forms of motility:
- Microvilli in the gut
- Flagella and cilia
- Cell crawling
- Muscle contraction
Actin
Microtubles
Actin
Actin
68
What does haematoxylin do, what colour does it go?
What does eosin do, what colour does it go?
Binds acidic groups in Nucleic acids, turns blue
Binds protein amino groups (mainly in cytoplasm) turns red
69
What stain would you use to view:
- Glycogen
- Lipid
- Iron
- Calcium
PAS
Oil red O
Perl's Prussian blue
Alizarin red
70
What are the three different types of muscle? Describe them.
Skeletal - voluntary and striated
Cardiac - involuntary and striated
Smooth - involuntary
71
What rRNA goes into the small ribosomal subunit?
What rRNA goes into the large ribosomal subunit?
18s
28s, 5.8s and a 5s (made elsewhere)
72
What are the ribosomal binding sites from left to right?
E-site, P-site and A-site
73
In what direction is mRNA read?
5' to 3'
74
What is the stop codon?
Where does the release factor bind?
TAG, TAA or TGA
A-site
75
What type of proteins are made in the ER?
Secretory, transmembranous, ER and Golgi proteins and lysosomal proteins
76
What are the two processes by which cartilage grows?
Appositional growth - from the edges
Intersitial - from within the cartilage
77
On reaching the late endosome, what causes the mannose-6-phosphate to dissociate from its receptor?
The environment is more acidic
78
What happens during apoptosis?
```
Cell surface 'bleb' appears
Shrinkage of cell and nucleus
Cleavage of nuclear proteins
Cleavage of nuclear DNA
Condensation of chromatin
Nucleus fragmentation
Cleavage of cytoskeleton
Cellular fragmentation (apoptic bodies)
All events require ATP
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