Cells Alive Flashcards
(78 cards)
1
Q
Main organelles to be aware of in a cell
A
- Nuclear envelope
- Nuclear pore
-Nucleolus - Lysosome
- Mitochondria
- Endoplasmic Reticulum (smooth & rough)
-Intermediate filaments - Golgi apparatus
- Ribosomes
- Peroxisome
- Actin filaments
- Cytoplasm
- Microtubule
- Centriole
2
Q
Types of proteins in membranes
A
- Integral proteins; permanently attached either transmembrane or monotopic
- Peripheral proteins- temporarily attached to membrane
3
Q
Types of Integral proteins
A
- Transmembrane; span entire membrane
- Monotopic; each molecule only on one side of membrane
4
Q
Structure of a mitochondrion
A
- Organelles bound by double membrane
- Outer membrane
- Inner membrane forms invaginations called cristae
- Space between is intermembrane space
- Inside is matrix
5
Q
Functions of mitochondria
A
- Generate most energy a cell requires
- Produce CO2 and H2O and release energy in form of ATP
6
Q
ATP
A
- Adenosine + 3x phosphate groups
- Energy released by hydrolysis of phosphanhydride bonds
- ATP ——> ADP + Pi
7
Q
Acetyl-CoA production; respiration stage 1
A
- Glucose converted to pyruvate in glycolysis
- Pyruvate converted to acetyl-COA in link reaction; CO2 produced
- Fatty acids metabolised via beta-oxidation removes 2 Cs at a time to form acetyl-CoA
8
Q
Acetyl-CoA Oxidation; respiration stage 2
A
- Part of the Kreb’s cycle
- `Produces NADH and FADH2
- CO2 is waste product; 2x molecules per pyruvate in Krebs cycle
9
Q
Oxidative Phosphorylation; respiration stage 3
A
- NADH & FADH2 carry electrons for ETC in oxidative phosphorylation
- ADP + Pi ——> ATP
- O2 reduced to H2O
10
Q
Electron transport chain
A
- NADH ——–> NAD+ + H+ + 2e-
- FADH2 ——–> FAD + 2H+ + 2e-
Final electron acceptor is oxygen - 2H+ + 1/2 O2 + 2e- ——> h20
11
Q
What is complex 1?
A
NADH dehydrogenase (NADH)
12
Q
What is complex 2?
A
Succinate dehydrogenase (FADH2)
13
Q
What is Q transport molecule?
A
From Complex 2 ——> Complex 3
coenzyme Q or ubiquinone
14
Q
What is complex 3?
A
Cytochrome B-C 1 complex
15
Q
What is C?
A
From complex 3 ——> complex 4
Cytochrome c
16
Q
What is complex 4?
A
Cytochrome oxidase
17
Q
Electrochemical gradient in respiration
A
- Transfer of electrons from lower to higher affinity is energetically favourable
- The energy released is used to pump H+ into intermembrane space
- Pumping creates electrochemical gradient
18
Q
Proton motive force
A
- ATP synthase; utilises the energy from the electrochemical gradient to regenerate ATP from ADP and Pi
- Hydrophilic pathway for chemiosmosis
- H+ flow causes rotation of transmembranous rotor domain stalk
19
Q
Transport; outer mitochondrial membrane
A
- Outer membrane has large pores made of proteins called porins
- Gases ( O2 and CO2) diffuse freely across membranes
20
Q
Transport; inner mitochondrial membrane
A
- The electrochemical gradient used
- Pyruvate and inorganic phosphate transport is driven by the proton gradient; they are cotransported
- ATP and ADP are cotransported in opposite directions
21
Q
Mitochondrial DNA
A
- Have their own genetic systems
- Genomes are circular; vary in size
- Transcription and translation occur in the matrix
- Mitochondrial DNA is maternally inherited
- Mitochondria grow and divide by fission
22
Q
How did the mitochondria originate?
A
- They have their own DNA and ribosomes
- Grow and divide by fission
- Evidence that they originated by endosymbiosis
- Ancestral eukaryote consumed bacteria that became a mitochondrion.
23
Q
Other functions of mitochondria
A
- Apoptosis; release of cytochrome c triggers programmed cell death
- Calcium store
- Haeme synthesis; many enzymes etc. have haeme group at active site
- Steroid synthesis;
- In hepatocyte; detoxify ammonia
24
Q
Protein transport in mitochondria
A
- TOM; translocases of outer membrane
- TIM; translocases of inner membrane
- post-translational
-requires energy
25
3 types of filaments in the cytoskeleton
- microfilaments
- intermediate filaments
- microtubules
26
Microfilaments
- Made of globular actin
- 5-9nm
- 2x stranded helical polymers
- Dispersed through cell; concentrated beneath cortex
- FUNCTION; cell shape and motility
27
Intermediate filaments
- ~10nm
- Various filament proteins
- Extended alpha helix regions wind together to form dimers then associate into tetramers
- Rope-like fibres
- FUNCTIONS; mechanical support of cell structures
28
Examples of intermediate fibres
- Iamins; nuclear envelope
- Keratins; epithelial cells
- Vimentin; mesenchymal cells
- Desmin; muscle cells
29
Microtubules
- ~25nm
- Made of globular protein tubulin (alpha & beta)
- These dimerise to form hollow tubules
- More rigid than actin tubules
- FUNCTION; positioning organelles and intracellular transport
30
Structural Polarity of the Cytoskeleton
- Rate of growth and loss are greater at one end than the other
- Plus end polymerises and depolymerises fastest
31
Support & Communication functions of cytoskeleton
- SEAL (tight junctions); seal epithelial membranes limit the passage of molecules- aids cell polarity
- TRANSMIT (gap junctions); connect cytoplasms of adjacent cells, chemical & electrical connection
- HOLD (anchoring junctions); adheres junctions and desmosomes
32
Intracellular motility functions of the cytoskeleton
- Motor proteins move along the cytoskeleton
- Myosin binds to actin ; muscle contraction
- ATP hydrolysis required
- Kinesin and dynein bind to microtubules; kinesin moves from - to + end dynein opposite
- transport organelles and vesicles
33
Extracellular motility functions of the cytoskeleton
- CELL CRAWLING eg. in macrophages
- PHAGOCYTOSIS
- MICROVILLI eg. in gut epithelium
34
Process of cell crawling
Rearrangement of actin cytoskeleton
1) Protrusion; actin fibres form at leading edge
2) Attachment; to the surface across focal adhesion points
3) Traction; myosins pull trailing cytoplasm forward
35
Process of moving microvilli
- Bundles of actin extend to the tip
- Myosin attached to cell membrane "walk" along actin causing microvillus to wave
36
Endoplasmic Reticulum
FUNCTIONS: protein biosynthesis, lipid biosynthesis & intracellular Ca2+ store
STRUCTURE:
- Tubules and sacs surrounded by membranes
- These are developed from the nuclear outer membrane and interconnected
- Space enclosed by membranes is the lumen or cysternal space
37
Post-translational modifications made in the ER
- Disulphide bonds; stabilises the protein
- N-Glycosylation; attatchment of branched sugars to the amide nitrogen- this stabilises, protects from degradation, holds in the ER and serves as a signal for interacting with other proteins
38
The Golgi Apparatus; structure
STRUCTURE; located near nucleus, divided into cisternae that communicate through vesicles
39
The Golgi Apparatus; functions
- Carbohydrate synthesis
- Post-translational modification of proteins & lipids:
- Glycosylation (O-linked) sugar added to oxygen
- Phosphorylation
- Sulphation
-Sorting and dispatching station for products of ER
40
Early endosomes
- Reside under the plasma membrane
- Matures into late endosome
- Matures by fusing with each other or fusing with a late endosome
41
Late endosomes
- Located near the nucleus
- Sorting compartment
42
Lysosomes
- membrane keeps enzymes out of cytosol
- acid hydrolases dont work at cellular pH ~7.2 but at 5 like in the lysosome
- Digested products either diffuse or are pumped out of the lysosome
43
Vesicular transport; targeting
- Vesicles have surface markers, identify origin & cargo
- Complementary receptors on target membranes
- Each vesicular v-SNARE has a complimentary t-SNARE
- Form a trans-SNARE-complex; docking occurs which mediates membrane fusion
44
Transport between ER and Golgi
- Cargo at exit sites in SER
- COPII causes budding
- Vesicles shed their coat; (COPII shed from surface)
- Vesicles undergo homotypic fusion caused by SNAREs
- New vesicular tubular clusters (VTC) moved along microtubules by dyneins to the golgi where they fuse
-Cargo release mediated by drop in pH
45
Types of exocytosis
Constitutive secretory pathway; straight to plasma membrane don't require a signal to be secreted
Regulated secretory pathway; specialised cells, can be hormones, neurotransmitters or digestive enzymes.
- signal transduced by ligand
46
Endocytosis
- Intake of molecules from extracellular space
Pinocytosis or phagocytosis
47
Process of phagocytosis
Specialised WBCs
- Interaction receptor-phagocytosis trigger
- Rearrangement of cytoskeleton; pseudopods formed
- Formation of phagosomes
- Fusion of phagosome and the lysosome
48
What happens to endocytosed vesicles and their contents?
1) Recycling; sent to recycling endosome, vesicle returns to the plasma membrane
2) Transcytosis; vesicles return to a different part of the plasma membrane and transports material across the cell
3) Degradation; sent to late endosomes which mature to lysosomes, degraded to make new molecules
49
The Cell Cycle
INTERPHASE; G1, S , G2
- growth 1, synthesis of DNA, growth 2
M PHASE; mitosis and cytokinesis
50
Stages of mitosis
- Prophase
-Prometaphase
- Metaphase
- Anaphase
- Telophase
51
Interphase
- Cell growth, double protein content
- Organelles double in size or number
- DNA synthesis
- The centrosome replicates
52
Prophase
1) Chromosomes condense
2) Mitotic spindle forms
3) Centrosomes move apart
4) Protein complex forms at centromere of chromosome
53
Prometaphase
1) Nuclear envelope breaks down
2) Chromosomes attach to microtubules via kinetochore complex
54
Metaphase
1) Chromosomes align at the equator
2) Sister chromatids attach to opposite poles by kinetochore microtubules
55
Anaphase
1) Link between sister chromatids is released
2) Kinetochore microtubules shorten
3) Centrosomes move apart
Sister chromatids pulled to poles
56
Telophase
1) Daughter chromosomes reach the poles
2) New nuclear envelope develops
3) contractile ring forms around the equator
57
Cytokinesis
1) The ring contracts partitioning the cytoplasm to form two separate cells
58
3 checkpoints during cell cycle
1) Restriction Point (end of G1): Checks for growth factors, nutrients & cell size as well as damaged DNA
2) G2-M transition: cell size check, DNA damage check and replication complete
3) Meta-anaphase transition; chromosomes attached?
59
Prophase I meiosis
Zygotene: homologous chromosomes align and link by synaptonemal complexes (synapsis)
Pachytene: pairs of chromosomes coil; crossing over (recombination)
Diplotene: synaptonemal complexes break down Pairs linked at crossover points (chiasmata)
60
What is necrosis?
- Non-programmed cell death
- A non-physiological process
- Accidental death due to acute insult; may be trauma or a lack of blood supply
- Cells swell and burst
- Release of cell content; inflammation
61
What is apoptosis?
- Programmed cell death
- Cells are engulfed and digested in an organised manner
- Requires ATP
- No inflammation
62
Examples of apoptosis
- Development; eg. removal of interdigital webs
- Formation of synapses
- Defence; destroys virus-infected cells, cells with DNA damage and cancer cells
63
Apoptosis in the immune system
Cytotoxic T lymphocytes can induce apoptosis in other cells
64
The Caspase cascade
- Caspases are cell death proteases; break cell down from inside
- Synthesised as inactive pro-caspases
- They are activated by each other
- Small number are initiator caspases that cause a cascade forming many effector caspases
- ACTIVATION IS COMPLETE AND IRREVERSIBLE
65
The extrinsic pathway of apoptosis
- Initial signal is from outside the cell
- Death ligand binds to death receptors
- Adaptors interact with receptors and initiate DISC
- DISC; death-inducing signalling complex
- Procaspase 8 activated to capase 8 leads to caspase cascade
66
The intrinsic pathway of apoptosis
- Changes in mitochondrial membrane
- Opens the MPT pore
- Releases cytochrome c
- Cytochrome c binds to pro-caspase 9; causing it to be activated
- These events are caused by BAK and BAX proteins
67
Intracellular signals that cause apoptosis
- NEGATIVE SIGNALS; absence of growth factors and hormones that usually suppress apoptosis
- POSITIVE SIGNALS; radiation, toxins, hypoxia, viral infections
68
What is autophagy?
- Cell self-eating process
- Catabolic process that degrades cytoplasmic constituents and organelles in lysosome
- self-defence mechanism activated during starvation
- can lead to cell death
69
Define a stem cell
- A cell that has the ability to continuously divide and differentiate into various other cells/tissues
70
3x types of stem cell
- Totipotent
- Pluripotent
- Multipotent
71
Totipotent stem cells
Each cell can develop into any new individual cell
cells from early embryos; 1-3 days
72
Pluripotent stem cells
Cells can form any cell type (over 200)
Some cells of blastocysts; 5-14 days
73
Multipotent stem cells
Cells can differentiate but can only form a number of tissues
Adult stem cells
74
Locations of adult stem cells
- Bone marrow
- Skin
- CNS
- Gut
- Muscle
75
Embryonic stem cells
- derived from donated IVF embryos
- can be grown indefinitely in an unspecialised state
- pluripotent
- can restore function in animal models following tansplantation
76
Induced pluripotent stem cells
- Derived from adult stem cells
- Can be grown indefinitely in culture in an undifferentiated state
- Similar properties to ESCs- pluripotent
77
Cloning for agricultural purposes
Reproducing the best breed
- Diseases resistance
- body type
- fertility
- market preference
78
Therapeutic uses for stem cells; vet med
- Treating musculoskeletal injuries; inject SCs
- Preserving species, male germline
- Biomedical models; understanding gene function
