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Cell Biology Flashcards

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1
Q

When was the cell discovered and by who?

A

Hooke (1665)
» Used a microscope to look at cork (ie tree bark)
» Saw little rooms, which he called “cellulae”

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2
Q

What is the cell theory and who invented it?

A

1830s - Schwann and Schleiden propose cell theory:

  1. The cell is the most basic unit of life
  2. All living organisms are composed of one or more cells
  3. All cells arise from pre-existing, living cells
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3
Q

Why are larger cells less common?

A
  • Cells are very small (< 100 microns across)

- Large cells have less surface area per unit volume → less capable of transporting materials across the cell membrane

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4
Q

How do you work out the surface area of a cell?

A 
Surface area (μm^2)
(A = 4 π r^2)
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5
Q

How do you work out the volume of a cell?

A

Volume (μm^3)

V = 4/3 π r^3

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6
Q

What is the value of 1 micron?

A

1 micron = 1 μm

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7
Q

Some cells have evolved strategies to overcome issue of surface area:volume ratio, what are they?

A

» Low metabolic activity (eg, egg cells)
» Thin elongated cells (eg, giant squid neuron)
» Folds in membrane → increase surface area

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8
Q

What are the advantages of being a bigger organism? Why don’t we have more of them?

A

» Receive more sunlight
» Better defence against predators
- large cells are not efficient that’s why we have multicellular organisms

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9
Q

What does a light microscope do? What is its resolution

A

visible light is passed through the specimen and then through glass lenses. The lenses refract (bend) the light in such a way that the image of the specimen is magnified as it is projected into the eye or into a camera. Resolution = 0.2 μm

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10
Q

What is resolution?

A

a measure of the clarity of the image; it is the minimum distance two points can be separated and still be distinguished as two points.

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11
Q

What does an Electron Microscope do? What is its resolution?

A

focuses a beam of electrons through the specimen or onto its surface. Resolution = » Resolution ≈ 0.000 05 μm

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12
Q

All cells share four basic needs, what are they?

A

» Separate internal and external environments: plasma membrane (inside is jelly-like cytosol)
» Store information and pass it on to next generation (reproduce): DNA
» Read genetic code to build proteins: RNA and proteins (eg, ribosome)
» Conduct chemical processes of life: ingest food and energy, use it for metabolic activity and growth, and expel waste
- All cells do this, hinting at common ancestor

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13
Q

What are the three types of cells?

A

» Archae = “Prokaryotes”
» Bacteria = “Prokaryotes”
» Eukarya = “Eukaryotes”

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14
Q

What are Prokaryotes?

A

» Have DNA, ribosomes, and proteins enclosed in plasma membrane, but no internal separation
» Early life forms ≈ 4 BYA

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15
Q

What are Eukaryotes?

A

Eukaryotes have internal separation = “organelles”
» In particular, a nucleus which holds DNA
- Usually larger size (≈10× avg prokaryote)
- Appear later than prokaryotes (≈2.1 BYA)

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16
Q

How is DNA organised in a Eukaryote?

A

Eukaryotes have a double membrane (“nuclear envelope”) that
surrounds nucleus and protects DNA
» DNA is organised on many linear chromosomes

17
Q

How is DNA organised in a Prokaryote?

A

Prokaryotes don’t have nucleus
» DNA is on one main circular chromosome
» Also numerous plasmids = small additional DNA
• Makes swapping DNA b/w prokaryotes much easier
(eg, antibiotic resistance)

18
Q

Eukaryotes also evolved multicellularity, what does this mean?

A

» Collection of cells provide the benefits of larger size without exceeding size constraints of single cell
» Different cells needed to coordinate their activities
» Evolution refined coordination to the point where cells began to specialise in function

19
Q

The lack of organelles in prokaryotes implies they have a different organisation, what does this mean?

A

» Prokaryotes have more metabolic options than eukaryotes
» Prokaryotes can survive in environments where eukaryotes cannot (reflection of their origin)
» There are more E. coli in the gut of a single human than there have ever been human beings on the planet
• Of 100 trillion cells in human body, 90% are bacteria

20
Q

What is Emergence

A

Complex systems arise out of
multiple simple interactions
» Cells < organs (eg, brain)
» Organism < population (eg, termite mounds)

21
Q

What is an organelle?

A

specialised membrane-bounded structure within a
living cell
» Remember: only eukaryotes have organelles (prokaryotes do not)

22
Q

What is the nucleus?

A

Control centre of the cell
» Bound by double membrane (nuclear envelope)
» Encloses genetic material (DNA)
» Processes input from cytoplasm and carries out instructions on DNA (genes)
» Nuclear pores allow large
molecules (mRNA) to pass

23
Q

What is the Nucleolus?

A

Dense centre of the nucleus where ribosomal RNA (rRNA) is synthesised

24
Q

What is the Endoplasmic Reticulum?

A

Biosynthetic factory that is split into the rough ER and Smooth ER

25
Q

What is the Rough ER

A

Rough ER
• Connect directly to nuclear envelope
• Appears “rough” because studded with ribosomes
• Site of secretory protein synthesis

26
Q

What is the Smooth ER

A

Smooth ER
• No ribosomes
• Involved in lipid synthesis
• Detoxification of drugs and poisons

27
Q

What are ribosomes

A
  • They are not an organelle
  • Protein-producing factories
    » Made up of rRNA and proteins
    » Translates mRNA into protein
    » Visible by electron microscope so often listed alongside organelles, but not membrane bounded, so technically not an organelle
28
Q

What is the Golgi Apparatus?

A
  • Shipping and receiving centre
    » Consists of flattened membrane sacs
    » Receives transport vesicles from rough ER, packed with proteins
    » Finishes proteins and sends them to final destination
29
Q

What are vesicles?

A

Small “sacs” within the cytosol with a

variety of functions

30
Q

What is a vacuole?

A

A type of Vesicle used for storage (eg food, transport)

31
Q

What is a Lysosome?

A 
digestive compartments
» Contain digestive enzymes that break down
food items (macromolecules) and old
organelles into nutrients (AA, sugars etc)
32
Q

What is a Peroxisome?

A

hazardous waste handlers
» Contain enzymes that break down molecules
» Detoxify metabolic waste or ingested toxicants
(eg, alcohol or drugs)

33
Q

What is the cenral vacuole?

A
  • in plants only
    “General store” (including food and toxic substances)
  • Also stores water → rigidity and support to plant cell
34
Q

What is the mitochondria?

A 
Energy powerhouse
» Synthesise ATP (cell’s main energy source) through cellular respiration
» Endosymbiotic origin
• Enclosed in two membranes
• Has its own circular DNA
• Has ribosomes
35
Q

What are chloroplasts?

A 
- in plants only
Capture of light energy
» Site of photosynthesis
» Builds carbohydrates (complex sugars) using
CO2, water and energy from sunlight
» Endosymbiotic origin
• Enclosed in two membranes
• Has its own circular DNA
• Has ribosomes
36
Q

What are cytoskeletons?

A

Source of microtubules (→ cytoskeleton)
» “Microtubules” = long hollow rods, provide support to cell and tracks along which organelles equipped with motor proteins can move
» Note: plant cells also have cytoskeleton, but no centrosomes (organised differently)

37
Q

What is the plasma membrane?

A
  • Outer barrier of the cell
  • Composed of phospholipid bilayer
    » Contains proteins, cholesterol and carbohydrates
  • Regulates what can enter and exit the cell
    » Passive/active transport
    » Endo/exocytosis
38
Q

What is the cell wall?

A
  • In plants only
  • Rigid structure outside of plasma membrane
  • Provides support, protection and structure
  • Made of cellulose
  • “Plasmodesmata” = perforation in cell wall allowing cell to cell communication

Biology (27 decks)

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