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Cytology > L1 > Flashcards

L1 Flashcards

1
Q

Hierarchical organisation of the human body

A

Atoms and molecules < Macromolecules and organelles < Cells < Tissues < Organs < Organ systems

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2
Q

What’s cytology?

A

Branch of science studying cells which differ in size/shape/function etc. but are the structural and functional units of all living organisms

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3
Q

Main features of eukaryotic cells

A
  • nucleus with genetic information
  • membrane-bound organelles
  • cytoplasmic matrix
  • cell membrane
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4
Q

Cell or plasma membrane:

  • where?
  • why?
A

Around cells and organelles.

  1. to maintain structural integrity
  2. to enable movement and expansion
  3. to receive and transmit info
  4. selective barrier
  5. trafficking of molecules
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5
Q

What are the main components of the cell membrane?

A
  • phospholipids 30-40%
  • proteins 40-50%
  • cholesterol
  • sugars (glycoproteins, glycolipids)
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6
Q

Main features of the plasma membrane

A

Heterogenous
Dynamic
Asymmetry
Bilayered

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7
Q

Phospholipids

A
  • amphipathic
  • phosphoglycerides vs. sphingolipids
  • residues
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8
Q

What’s peculiar about phosphatidyl-serine?

A

Found only on the internal layer.

If on outer layer, signal of apoptosis

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9
Q

What are the 3 functions of cholesterol in the plasma membrane?

A
  1. less deformable
  2. less permeable
  3. prevents crystallization of FA tails
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10
Q

Thickness of cell membrane

A

7.5 nm

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11
Q

Glycocalyx : composition and functions

A

Mucus layer of glycoprotreins and glycolipids, on external layer ONLY!

Selective barrier and molecular filter, may contain enzymes (ie. GI tract).

Also involved in cell-to-cell adhesion and recognition (ie. diapedesis of WBCs)

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12
Q

Structural classification of proteins in the bilayer (2 groups)

A

Extrinsic vs. Integral

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13
Q

Functional classification of proteins in the bilayer (4 groups)

A
  1. Enzymes
  2. Linkers
  3. Receptors (ie. EGFR and lipid rafts)
  4. Transporters
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14
Q

Fluid-mosaic model

A

Mosaic - because of its heterogenous appearance

Fluid - phospholipids and proteins able to move (mostly laterally, flip-flop movement rare)

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15
Q

Evidence for fluid mosaic model?

A

Hybrid mouse-human cell - mixed molecules in plasma membrane

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16
Q

Factors affecting fluidity?

A

Temperature and unsaturated FA chains - direct proportionality

Proteins, cholesterol, longer FA chains - inverse proportionality

17
Q

3 forms of transport across the membrane (for small-medium molecules only)

A
  1. simple diffusion ie. O2, CO2
  2. facilitated diffusion ie. glucose, aquaporins
  3. active transport ie. sodium-potassium pump
18
Q

…how about transport across the plasma membrane of large molecules?

A

Vesicle-mediated

= endocytosis and exocytosis

19
Q

Clinical drop. Vincristine and ABC transporter

A

Chemotherapeutic drug able to enter cancer cells via simple diffusion. However, if ABC transporter present, drug expelled.

What can be done? Inhibit the transporter to reinstate drug sensitivity

20
Q

Endomembrane system

A

System of intracellular, membraneous organelles including:

  • nucleus
  • endoplasmic reticulum
  • golgi apparatus
  • mitochondria
  • lysosomes
21
Q

General features of endoplasmic reticulum

A

System of tubules/cisternae of variable shape, extension based on cell needs

22
Q

rER

A

Rough - many ribosomes

Continuation of nuclear envelope

Functions include:

  • PROTEIN SYNTHESIS
  • post-translational modifications (ie. proteolysis, phosphorylation, glycosylation only at asparagine)
  • protein steric conformation
  • hydroxylation of lysine and proline residues
23
Q

Import of proteins into rER

A

Signal hypothesis (SRPR - signal recognition particle receptor)

Soluble vs. membrane proteins

24
Q

Ribosomes, main features

A

Molecules of DNA, RNA and proteins

2 subunits, bound only for protein synthesis (60, 40, 80 in eukaryotes, 50, 30, 70 in prokaryotes)

Free (proteins remaining within the cell) vs. rER ribosomes (proteins for cell membrane or to be secreted)

25
Q

sER

A

Smooth - no ribosomes

Functions include:

  • synthesis of lipids and steroids
  • storage of ions
  • glucose-6-phophatase in hepatocytes (glycogen catabolism)
  • biogenesis of cell membranes (phospholipids and flippases)
  • detoxification processes (addition of OH group to facilitate elimination)

Cytology (2 decks)

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