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Structure & Function 1 > Cells Alive > Flashcards

Cells Alive Flashcards

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
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2
Q

Types of proteins in membranes

A
  • Integral proteins; permanently attached either transmembrane or monotopic
  • Peripheral proteins- temporarily attached to membrane
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3
Q

Types of Integral proteins

A
  • Transmembrane; span entire membrane
  • Monotopic; each molecule only on one side of membrane
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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
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5
Q

Functions of mitochondria

A
  • Generate most energy a cell requires
  • Produce CO2 and H2O and release energy in form of ATP
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6
Q

ATP

A
  • Adenosine + 3x phosphate groups
  • Energy released by hydrolysis of phosphanhydride bonds
  • ATP ——> ADP + Pi
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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
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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
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9
Q

Oxidative Phosphorylation; respiration stage 3

A
  • NADH & FADH2 carry electrons for ETC in oxidative phosphorylation
  • ADP + Pi ——> ATP
  • O2 reduced to H2O
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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
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11
Q

What is complex 1?

A

NADH dehydrogenase (NADH)

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12
Q

What is complex 2?

A

Succinate dehydrogenase (FADH2)

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13
Q

What is Q transport molecule?

A

From Complex 2 ——> Complex 3
coenzyme Q or ubiquinone

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14
Q

What is complex 3?

A

Cytochrome B-C 1 complex

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15
Q

What is C?

A

From complex 3 ——> complex 4
Cytochrome c

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16
Q

What is complex 4?

A

Cytochrome oxidase

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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
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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
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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
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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
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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
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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.
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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
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24
Q

Protein transport in mitochondria

A
  • TOM; translocases of outer membrane
  • TIM; translocases of inner membrane
  • post-translational
    -requires energy
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25
Q

3 types of filaments in the cytoskeleton

A
  • microfilaments
  • intermediate filaments
  • microtubules
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26
Q

Microfilaments

A
  • Made of globular actin
  • 5-9nm
  • 2x stranded helical polymers
  • Dispersed through cell; concentrated beneath cortex
  • FUNCTION; cell shape and motility
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27
Q

Intermediate filaments

A
  • ~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
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28
Q

Examples of intermediate fibres

A
  • Iamins; nuclear envelope
  • Keratins; epithelial cells
  • Vimentin; mesenchymal cells
  • Desmin; muscle cells
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29
Q

Microtubules

A
  • ~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
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30
Q

Structural Polarity of the Cytoskeleton

A
  • Rate of growth and loss are greater at one end than the other
  • Plus end polymerises and depolymerises fastest
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31
Q

Support & Communication functions of cytoskeleton

A
  • 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
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32
Q

Intracellular motility functions of the cytoskeleton

A
  • 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
Q

Extracellular motility functions of the cytoskeleton

A
  • CELL CRAWLING eg. in macrophages
  • PHAGOCYTOSIS
  • MICROVILLI eg. in gut epithelium
34
Q

Process of cell crawling

A

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
Q

Process of moving microvilli

A
  • Bundles of actin extend to the tip
  • Myosin attached to cell membrane “walk” along actin causing microvillus to wave
36
Q

Endoplasmic Reticulum

A

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
Q

Post-translational modifications made in the ER

A
  • 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
Q

The Golgi Apparatus; structure

A

STRUCTURE; located near nucleus, divided into cisternae that communicate through vesicles

39
Q

The Golgi Apparatus; functions

A
  • 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
Q

Early endosomes

A
  • Reside under the plasma membrane
  • Matures into late endosome
  • Matures by fusing with each other or fusing with a late endosome
41
Q

Late endosomes

A
  • Located near the nucleus
  • Sorting compartment
42
Q

Lysosomes

A
  • 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
Q

Vesicular transport; targeting

A
  • 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
Q

Transport between ER and Golgi

A
  • 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
Q

Types of exocytosis

A

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
Q

Endocytosis

A
  • Intake of molecules from extracellular space
    Pinocytosis or phagocytosis
47
Q

Process of phagocytosis

A

Specialised WBCs
- Interaction receptor-phagocytosis trigger
- Rearrangement of cytoskeleton; pseudopods formed
- Formation of phagosomes
- Fusion of phagosome and the lysosome

48
Q

What happens to endocytosed vesicles and their contents?

A

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
Q

The Cell Cycle

A

INTERPHASE; G1, S , G2
- growth 1, synthesis of DNA, growth 2
M PHASE; mitosis and cytokinesis

50
Q

Stages of mitosis

A
  • Prophase
    -Prometaphase
  • Metaphase
  • Anaphase
  • Telophase
51
Q

Interphase

A
  • Cell growth, double protein content
  • Organelles double in size or number
  • DNA synthesis
  • The centrosome replicates
52
Q

Prophase

A

1) Chromosomes condense
2) Mitotic spindle forms
3) Centrosomes move apart
4) Protein complex forms at centromere of chromosome

53
Q

Prometaphase

A

1) Nuclear envelope breaks down
2) Chromosomes attach to microtubules via kinetochore complex

54
Q

Metaphase

A

1) Chromosomes align at the equator
2) Sister chromatids attach to opposite poles by kinetochore microtubules

55
Q

Anaphase

A

1) Link between sister chromatids is released
2) Kinetochore microtubules shorten
3) Centrosomes move apart
Sister chromatids pulled to poles

56
Q

Telophase

A

1) Daughter chromosomes reach the poles
2) New nuclear envelope develops
3) contractile ring forms around the equator

57
Q

Cytokinesis

A

1) The ring contracts partitioning the cytoplasm to form two separate cells

58
Q

3 checkpoints during cell cycle

A

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
Q

Prophase I meiosis

A

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
Q

What is necrosis?

A
  • 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
Q

What is apoptosis?

A
  • Programmed cell death
  • Cells are engulfed and digested in an organised manner
  • Requires ATP
  • No inflammation
62
Q

Examples of apoptosis

A
  • Development; eg. removal of interdigital webs
  • Formation of synapses
  • Defence; destroys virus-infected cells, cells with DNA damage and cancer cells
63
Q

Apoptosis in the immune system

A

Cytotoxic T lymphocytes can induce apoptosis in other cells

64
Q

The Caspase cascade

A
  • 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
Q

The extrinsic pathway of apoptosis

A
  • 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
Q

The intrinsic pathway of apoptosis

A
  • 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
Q

Intracellular signals that cause apoptosis

A
  • NEGATIVE SIGNALS; absence of growth factors and hormones that usually suppress apoptosis
  • POSITIVE SIGNALS; radiation, toxins, hypoxia, viral infections
68
Q

What is autophagy?

A
  • 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
Q

Define a stem cell

A
  • A cell that has the ability to continuously divide and differentiate into various other cells/tissues
70
Q

3x types of stem cell

A
  • Totipotent
  • Pluripotent
  • Multipotent
71
Q

Totipotent stem cells

A

Each cell can develop into any new individual cell
cells from early embryos; 1-3 days

72
Q

Pluripotent stem cells

A

Cells can form any cell type (over 200)
Some cells of blastocysts; 5-14 days

73
Q

Multipotent stem cells

A

Cells can differentiate but can only form a number of tissues
Adult stem cells

74
Q

Locations of adult stem cells

A
  • Bone marrow
  • Skin
  • CNS
  • Gut
  • Muscle
75
Q

Embryonic stem cells

A
  • derived from donated IVF embryos
  • can be grown indefinitely in an unspecialised state
  • pluripotent
  • can restore function in animal models following tansplantation
76
Q

Induced pluripotent stem cells

A
  • Derived from adult stem cells
  • Can be grown indefinitely in culture in an undifferentiated state
  • Similar properties to ESCs- pluripotent
77
Q

Cloning for agricultural purposes

A

Reproducing the best breed
- Diseases resistance
- body type
- fertility
- market preference

78
Q

Therapeutic uses for stem cells; vet med

A
  • Treating musculoskeletal injuries; inject SCs
  • Preserving species, male germline
  • Biomedical models; understanding gene function

Structure & Function 1 (11 decks)

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