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ESA 1 - MCBG > Basic Cell Structure > Flashcards

Basic Cell Structure Flashcards

1
Q

What are the main differences between prokaryotes and eukaryotes?

A

Prokaryotes

  • No nucleus; plasmids + free DNA
  • No membrane-bound organelles
  • Peptidoglycan cell wall
  • 1-10 um

Eukaryotes

  • Nucleus; several chromosomes
  • Membrane-bound organelles
  • No cell wall
  • 10-100 um
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2
Q

Why are chemical reactions more efficient in eukaryotic cells than prokaryotic cells?

A
  • Eukaryotic cells are compartmentalised by internal membranes (membrane-bound organelles) - more efficient reactions.
  • In prokaryotes, all biochemical processes occur in the same compartment.
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3
Q

What is the largest organelle and describe its structure.

A
  • Nucleus
  • Surrounded by nuclear envelope containing nuclear pores.
  • Contains nucleolus (forms ribosomes).
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4
Q

How is DNA packaged inside the nucleus?

A
  • Folded into nucleosomes using histones - chromatin.
    1. Heterochromatin (10%): remains packed after mitosis (solenoid), transcriptionally inactive.
    2. Euchromatin: beads-on-a-string, transcriptionally active.
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5
Q

Which structures envelope the cell?

A
  • Plasma membrane (plasmalemma)

- Glycocalyx

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6
Q

What is the PM made up of?

A
  • Specific proteins, lipids and carbs.
  • Amphipatic phospholipids (hydrophilic heads and hydrophobic tails) assemble into a lipid bilayer - forms a relatively impermeable barrier to most water-soluble molecules.
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7
Q

What is the fluid mosaic model?

A
  • Proteins ‘swim’ in the fluid lipid layer and mediate most membrane functions.
  • Lipid rafts = membrane regions that assemble specialised proteins and lipids to perform a certain task.
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8
Q

What is the glycocalyx?

A
  • Cell coat made up of oligosaccharide and polysaccharide side chains of glycoproteins on the outside of the plasmalemma.
  • This glycosylation often changes the function of the associated protein.
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9
Q

Give examples of how membrane proteins can be associated with the lipid bilayer in different ways.

A
  • Integral membrane proteins: contain hydrophobic membrane-spanning domains (e.g. Alpha-helix) that interact with the phospholipid fatty acyl groups.
  • Peripheral membrane proteins: bound indirectly to membrane via interactions with integral membrane proteins or with lipid polar head groups.
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10
Q

Name the functions of the PM.

A
  1. Selective permeability
  2. Transport of materials along cell surface
  3. Endo- and exo-cytosol
  4. Intercellular recognition and adhesion
  5. Signal transduction
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11
Q

Which organelles are involved in protein synthesis? What is the structure of these?

A
  • Ribosomes
  • 2 large subunits made up of ribosomal RNA and proteins
  • Located free in cytoplasm or associated with rER
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12
Q

What is the ER?

A
  • Membranous extension of nuclear envelope.
  • Involved in: synthesis and transport.
  • 2 types that are continuous.
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13
Q

What are the different functions of the 2 types of ER?

A
  1. Smooth ER (no ribosomes).
    - Involved in:
    A) lipid synthesis
    B) metabolism of carbohydrates
    C) detoxification of drugs/poisons
    D) calcium storage (for cell signalling)
    - Less common type
  2. Rough ER (ribosomes)
    - Involved in: secretory enzyme processing
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14
Q

In which cell types is sER more commonly found in?

A
  • Liver cells and mammary glands (lipid biosynthesis)

- Ovary, testis and adrenal gland (steroidogenesis)

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15
Q

What is the function of the Golgi apparatus?

A

Modifies (e.g. O-glycosylation), sorts, concentrates and packages proteins synthesised on the rER.

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16
Q

What are the 2 faces of the Golgi called and where does vesicle budding take place?

A
  • Cis

- Trans (vesicle budding)

17
Q

Name the components of the Golgi.

A
  1. Cis Golgi network
  2. Golgi stack: cis cisterna, medial cisterna and trans cisterna
  3. Trans Golgi network
18
Q

What are the 3 fates of proteins exiting the Golgi?

A
  1. Constitutive secretion - targeted to PM
  2. Regulated secretion - signal-mediated diversion to secretory vesicles
  3. Signal-mediated diversion to lysosomes
19
Q

What are lysosomes?

A
  • Single-membrane organelles generated by the Golgi

- Degrade unwanted material, inc. pathogens

20
Q

How do lysosomes degrade material?

A
  1. Contain many hydrolytic enzymes
    E.g. Nucleases, proteases, glycosidases, phosphatases and phospholipases.
  2. Very acidic environment maintained by vacuolar H+ ATPase (proton pump)
21
Q

How is the membrane of lysosomes protected from enzyme damage?

A

Coated by a specialised glycocalyx.

22
Q

What are peroxisomes and what is their function?

A
  • Multi-purpose single membrane-bound organelles that contain many enzymes (crystalline core).
  • Functions include:
    • hydrogen peroxide (H2O2)/ROS metabolism
    • lipid metabolism (e.g. Fatty acid beta-oxidation, phytanic acid alpha-oxidation)
    • detoxification (oxidise) of a number of molecules inc. alcohol, phenols, formic acid and formaldehyde (in liver and kidney cells)
23
Q

What is the function of mitochondria?

A

Energy production: use sugars, fats and oxygen to produce ATP via oxidative phosphorylation using ATP synthase.

24
Q

Describe the structure of mitochondria.

A
  • Double membrane (separated by intermembrane space):
    • inner membrane folds to form cristae. Contains enzymes for oxidation reactions of respiratory chain.
    • outer membrane
  • Matrix: contains 100s of enzymes, ribosomes and mitochondrial DNA genome
25
Q

Name examples of MT-rich tissues.

A
  • cardiac cells
  • muscle
  • liver
  • brown adipose
26
Q

Give evidence for the endosymbiosis theory.

A
  1. Double-membrane
  2. Own genetic info
  3. Own ribosomes
  4. Divide by fission
27
Q

Name the 3 components of the cytoskeleton.

A
  1. Actin filaments
  2. Intermediate filaments
  3. Microtubules
28
Q

Where is each cytoskeleton filament found and what is their role?

A
  1. Actin microfilaments (5-9nm diameter)
    - Underlies plasma membrane (cortex): provides strength and shape
    - Forms cell surface projections, e.g. Microvilli and stereocilia
  2. Intermediate filaments (10nm diameter)
    - Forms star-like cytoplasmic array: tough supporting mesh work
    - Underlies inner nuclear membrane forming nuclear lamina
  3. Microtubules (25nm diameter)
    - Found in sites where structures are moved, e.g. Nerve fibre axon, mitotic spindle, cilia/flagella.
29
Q

Describe the structure and arrangement in cilia of MTs.

A
  • Long hollow cylinders made up of tubulin protein.

- 9+2 arrangement in cilia/flagella

ESA 1 - MCBG (23 decks)

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