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Principles > Anatomy of a Cell > Flashcards

Anatomy of a Cell Flashcards

1
Q

What are the features of Eukaryotic cells?

A
  • outer membrane
  • inner cystol (fluid, gel like)
  • cytoskeleton (thin & intermediate filaments and microtubules)
  • organelles (membrane bound)
  • inclusions
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2
Q

Plasmalemma/Membrane

A
  • bimolecular layer of amphipathic phospholipid molecules
  • contains integral proteins (cell inserts into membrane)
    e. g. receptors, transporters, channels, enzymes, cell attachment proteins
  • also contains peripheral proteins and cholesterol
  • endocytose and exocytose through membrane
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3
Q

Plasmalemma fluidity

A
  • membrane proteins diffuse laterally in membrane
  • but, many are anchored: not distributed equally
  • selectively permeable (to H2O, O2… not charged ions)
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4
Q

Organelles

A
  • small, intracellular organs
  • essential to life
  • e.g. mitochondria, nucleus, RER, SER, Golgi apparatus, lysosomes
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5
Q

Inclusions

A
  • don’t necessarily have membrane

- are dispensable, may only be present as transients

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6
Q

Cytoskeleton

A
  • filamentous cytoskeletal proteins
    1. Microfilaments (actin protein)
    2. Intermediate filament
    3. Microtubules (tubulin protein)
  • attach to cell membrane/each other, by anchoring/joining proteins = scaffolding
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7
Q

Microfilaments

A
  • actin molecules assemble into filaments
  • can later dissociate
  • very dynamic
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8
Q

Intermediate Filaments

A
  • bind intracellular elements together
  • bind to plasmalemma
  • network throughout cytoplasm
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9
Q

Microtubules

A
  • hollow tubule
  • composed of tubulin subunits: α, β
  • can be assembled and disassembled
  • originate in centrosome
  • include microtubule-associated proteins
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10
Q

Microtubules (motorway network)

A
  • polar
  • the proteins dynein and kinesin attach to microtubules, move along them
  • dynein and kinesin associate with membrane of organelles, drag them
  • kinesin: moves towards cell periphery
    dynein: (direct) towards cell centre
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11
Q

Centrosome

A
  • microtubules originate
  • at core, contains centrioles
  • centrioles are mainly composed of specialized microtubule segments
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12
Q

Nucleus

A

-enclosed by nuclear envelope (inner/outer nuclear membrane, contain pores)
-inner membrane, perinuclear cistern, outer membrane
-outer membrane: ribosomes (is continuous with RER)
-contains chromosomes, RNA synthesis location
(mRNA, tRNA transcribed here. rRNA transcribed in nucleolus)
-contains euchromatin: more dispersed DNA, actively undergoing transcription
-contains heterochromatin: more condensed, not undergoing transcription

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13
Q

Ribosomes

A
  • formed in nucleolus
  • instrumental in protein synthesis
  • made up of small subunit (binds RNA) & large subunit (catalyses peptide bond formation)
  • export of ribosomes:depends on nuclear core complex
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14
Q

Endoplasmic Reticulum

A
  • network of interconnecting network bound compartments
  • Rough Endoplasmic Reticulum (studded with ribosomes, vital in protein synthesis)
  • Smooth Endoplasmic Reticulum
  • more ER, more metabolically active
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15
Q

Polysomes

A
  • where proteins that are to remain in the cytosol (unpackaged) are synthesised
  • polysomes float free within cytosol
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16
Q

Protein Synthesis

A
  • free ribosome attaches to mRNA
  • growing peptide chain is inserted into pore in ER, if ER signal peptide sequence is present
  • growing peptide forms in ER, so signal sequence is removed
  • Ribosome detaches, most proteins then enter SER
17
Q

Rough Endoplasmic Reticulum (RER)

A
  • associated with protein synthesis
  • associated with initiation of glycoprotein formation

(glycoproteins have carbs attached to their polypeptide chains)

18
Q

Smooth Endoplasmic Reticulum (SER)

A
  • continues processing of proteins from RER
  • vital role at site of lipid synthesis
  • most cells contain little SER
19
Q

Golgi Apparatus

A
  • transport vesicles arrive at Golgi from SER/RER

- Golgi cisterns modify and package macromolecules (which were synthesised in ER)

20
Q

Mitochondria

A
  • oblong, cylindrical organelles (contained in all cells)
  • contain own DNA
  • outer & inner membrane
  • inner membrane is extensively folded = cristae (increases surface area)
  • generate ATP, synthesise certain lipids and proteins
21
Q

Intercellular Junctions

A
  • specialized membrane structure
  • link individual cells together (form functional unit)
    1. Occluding Junctions: form a diffusion barrier
    2. Anchoring Junctions: provide mechanical strength
    3. Communicating Junctions: allow movement of molecules between cells
22
Q

Intercellular Junctions: Occluding

A
  • prevent diffusion
  • appear as focal region of close apposition between adjacent membranes
  • also known as: tight junctions / zonula occludens
23
Q

Intercellular Junctions: Anchoring

A
  • adherent junctions (link submembrane actin bundles of adjacent cells)
  • transmembrane cadherin molecules bind to each other, and to the actin of cytoskeleton
  • also known as: zonula adherens
  • Desmosomes/macula adherens: link submembrane intermediate filaments of adjacent cells
24
Q

Intercellular Junctions: Junctional Complex

A

-close association of several types of junction found in epithelial tissues

25
Q

Intercellular Junctions: Communicating

A
  • allow selective diffusion of molecules between adjacent cells
  • also known as: gap junctions
  • is a circular patch studded with hundreds of pores
  • pores produced by “connexon” proteins
  • found in epithelia, some smooth and cardiac muscle: is critical for spread of excitation
26
Q

Transport Into/Out of Cell

A

-material moves across cell membrane in variety of ways:
Diffusion

Via transport proteins (pumps or channels)

Vesicular transport (incorporation into vesicles)
e.g. endocytosis, phagocytosis
27
Q

Transport: Endocytosis

A
  • material from extracellular space can be incorporated into cell by endocytosis
  • cell membrane invaginates, fuses: newly made endocytotic vesicle (endosome) buds into the cell
  • this process is often receptor mediated

-exocytosis works in reverse fashion to discharge material

28
Q

Transport: Phagocytosis

A
  • bacteria (or larger particulate material) from the extracellular space can be incorporated into cell by phagocytosis:
  • bacterium binds to cell surface receptors
  • triggers extensions of cell to engulf it
  • forms phagosome
  • phagosome binds with lysosome carrying digestive enzymes
  • produces phagolysosome

Principles (6 decks)

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