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PMP101 > Week 5 eukaryotic and prokaryotic cells > Flashcards

Week 5 eukaryotic and prokaryotic cells Flashcards

1
Q

Cells intro

A

All living things = organisms
Made of cells -> smallest and fundamental units of life
New cells are made from pre-existing cells

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2
Q

Unicellular organisms

A

-Simpler organisms
-One cell exerting all life functions
-Bacteria
-Protozoa
-Unicellular Fungi

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3
Q

Multicellular organisms

A

-More evolute organisms
-Multiple cells with specialised functions
-Pluricellular Fungi
-Plants
-Animals/humans

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4
Q

Cell specialisation

A

-The human body is made up of ~1013 cells, with 200 types of specialised cells
-Distinct cell types vary in size,
shape, functions
-Cell shape and size determine a
particular specialisation
-Cooperation of different specialised cells allows complex organisms to perform a wide range of functions

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5
Q

Red blood cells

A

Main function:
O2 / CO2 transport
-Biconcave shape
-No nucleus
-Contain haemoglobin
-Small and flexible

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6
Q

Neurons

A

Propagation of nerve impulse
(action potential)
-Thin and long cells
-Branched at their ends
-Different subcellular parts
-Release of neurotransmitter signals

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7
Q

Organisation in the human body

A

The human body is organised into levels of increasing complexity;
Cell -> Tissue -> Organ -> Organ system -> Organism

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8
Q

Light microscope or optical microscope

A

The light microscope:
-Is used to observe living cells in a tissue
-Its resolution limit is ~ 0.2μm (not suitable for organelles)

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9
Q

Properties of microscopes

A

Magnification – the ratio of an object’s image to its real
size (up to 1000 times)
Resolution – it is the ability to distinguish between two very closely positioned objects

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10
Q

Fluorescence microscope

A

A technique to make specific parts of a cell or tissue that uses fluorophore proteins or dyes under a special light causing the fluorescent molecules to absorb this light and emit visible light, which makes them glow
-Used to monitor the localisation of target labelled molecules within a cell / tissue

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11
Q

Electron microscope (EM)

A

EM use:
-High resolution images of cell
structures (e.g. organelles)
-Living cells cannot be observed
-Resolution limit is ≈ 2 nm (nanometres)
Two main EM biomedical applications:
->Transmission EM (TEM) - to study organelles
->Scanning EM (SEM) - to study the cell surface

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12
Q

Two distinct type of cells:

A

-Prokaryotic cell
-Eukaryotic

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12
Q

Prokaryotic cell

A

-Without nucleus
-No internal compartments
-No organelles
-Simple internal organisation

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13
Q

Eukaryotic cell

A

-With nucleus
-Internal membranes that enclose the organelles
-Complex organisation

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14
Q

Basic components of a cell

A

-Plasma membrane
-Cytosol, a concentrated aqueous solution of chemicals
-Ribosomes
-GENOME -> genetic information of a cell represented by DNA
that carry hereditary information and define each species
-Biological macromolecules

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15
Q

Macromolecules in cells

A

Cells of all organisms contain 4 major organic (carbon atoms) macromolecules;
-Carbohydrates/Polysaccharides
-Proteins
-Lipids
-Nucleic acids
Macromolecules are polymers made by specific repeating molecular units, monomers

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16
Q

Monomers

A

mono- (one) and -mer (part)
-Building blocks or subunits
-Smallest units of molecules that can join with each other to form larger molecules, polymers

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17
Q

Anabolism

A

Cells link monomers together to form a polymer through polymerisation / condensation reactions (requiring energy)

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18
Q

Catabolism

A

Polymers are broken down into smaller molecules by hydrolysis (realising energy)

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19
Q

Metabolism

A

Catabolism + Anabolism

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20
Q
A
21
Q

Prokaryotic cell overview

A

Smaller (0.1-5 μm) and simpler cells
Intracellular compartment;
-Cytoplasm, nucleoid, ribosomes, plasmids, inclusion bodies
-Lack of nucleus and organelles
Internal boundary/ coating layers;
-Plasma membrane (internal boundary)
-Cell wall
-Glycocalyx/capsule
External appendages;
-Flagella, fimbriae, sex pili

22
Q

Prokaryotic cell – Intracellular composition

A

-Cytoplasm
-Ribosomes
-Bacterial DNA chromosome
-Inclusion bodies
-Plasmids

23
Q

Cytoplasm

A

Internal content of the cell - site of many reactions

24
Q

Ribosomes

A

Composed of a large (50S) and a small subunit (30S)
-Each subunit is made of rRNA and proteins
-Involved in protein synthesis, translating mRNA code

25
Q

Bacterial DNA chromosome

A

-Dispersed in a central cytoplasmic space - Nucleoid
-Single circular DNA - not linked to histone proteins

26
Q

Inclusion bodies

A

Aggregates of reserve material (Storing function)

27
Q

Plasmids

A

Additional/accessory circular DNA
-Confer new ability, such as degradative ability of antibiotics -> drug resistance

28
Q

Prokaryotic cell – surface layers

A

-Plasma membrane
-Cell wall
-Glycocalyx

29
Q

Plasma membrane

A

Internal boundary;
-Flexible lipid bilayer, as in eukaryotic cells (with no sterols)
-Controls the movement of molecules (nutrients/waste)
-Sometimes, site of reactions (respiration/photosynthesis)

30
Q

Cell wall

A

(Different composition in Gram+ve and –ve)
-Rigid structure to preserve cell shape & integrity

31
Q

Glycocalyx

A

Not always
->Polysaccharides layer: Capsule (organised and stable) or Slime layer (loosely attached)
->Protection against dehydration, immune system (phagocytosis) and antibiotics
->Adherence factor

32
Q

Prokaryotic cell – Appendages

A

-Flagellum
-Fimbriae / pili
-Sex pilus (pl. pili)

33
Q

Flagellum

A

-Long and whip-like appendages
-Used for cell motility (movement)
-It is also a sensory structure to detect nutrients

34
Q

Fimbriae / pili

A

-Short and thin projections
-Used for attachment to a surface or other cells

35
Q

Sex pilus (pl. pili)

A

-Rigid hair-like tubular structures (longer than fimbriae)
-Use to facilitate genetic material transfer between two bacteria (through the conjugation
process)

36
Q

Eukaryotic cell overview

A

-Cell wall is NOT present in human cells -> but present in plant and fungal eukaryotic cells
-Contain a nucleus (or more nuclei)
-Many membrane-enclosed organelles
->have specialised functions (like organs)

37
Q

Organelles system

A

-Nucleus
-Endoplasmic reticulum
-Mitochondria
-Golgi apparatus
-Lysosomes
-Peroxisomes

38
Q

General usefulness of organelles

A

-Membrane-bound intracellular components allowing
compartmentalisation
-Different enzymatic composition -> occurrence of
diverse metabolic reactions -> specialised functions
-Distinct eukaryotic organisms have different organelles
->Lysosomes are only in animals and chloroplasts are only found in plants

39
Q

Cytoplasm

A

Content inside the plasma membrane excluding the nucleus
-Highly organised and dynamic
-It includes:
-Cytosol
-Distinct cell organelles

40
Q

Cytosol

A

Gel-like fluid (pH 7.2) to support organelles
-It includes ribosomes, cytoskeleton, enzymes, etc
-It is the site of many cellular activities:
-Protein synthesis and degradation
-Metabolic reactions (e.g. glycolysis)
-Cell signalling pathways

41
Q

Distinct cell organelles

A

-Enclosed by membranes (separated by the cytosol)

42
Q

Ribosomes

A

Function: Cell machinery for protein synthesis
Structure:
Made by 2 subunits: large (60S) & small (40S)  forming 80S -> bigger than the prokaryotic ones (50s and 30S  70S)
Both subunits are combinations of : Ribosomal proteins + ribosomal RNA (rRNAs)
Types: Free floating in the cytosol or bound to the rough endoplasmic reticulum

43
Q

Cytoskeleton

A

A network of protein filaments and tubules that provides structural support

44
Q

Cytoskeleton functions

A

-Structural support: cell shape & resists mechanical stress
-Intracellular transport: facilitates movement of
organelles, vesicles, and molecules
-Regulates cellular processes (eg cell division & motality)

45
Q

Cytoskeleton structures - Composition

A

3 types of filamentous protein polymers (long repetitions of 1 or more proteins):
-Microfilaments (7 nm in diameter)
-Intermediate filaments (10 nm in diameter)
-Microtubules (25 nm in diameter)

46
Q

Cytoskeleton - microfilaments

A

-Actin filaments
-Long, thread-like filaments of 2 helical strands of actin protein repetitions - (7nm in ⌀)
-Depending on interaction with actin binding proteins (e.g. myosin).
Very dynamic- Rapid assembly and disassembly for quick rearrangements;
-Muscle contraction
-Assist with cell movement
-Support cell’s shape (e.g. microvilli in intestinal cells)
-Cell division: formation of contractile ring in cytokinesis

47
Q

Cytoskeleton - Intermediate filaments

A

Structure;
Rope-like fibres formed by many long strands of several types of proteins twisted together - (10nm in ⌀)
Function;
-Provide mechanical strength and stability to cells and tissues (abundant in muscle cells)
-Anchor cells in extracellular matrix
-No effect in cell motility (not bound to motor proteins). More stable

48
Q

Cytoskeleton - Microtubules

A

Structure;
-Long and rigid hollow cylinders made by repetitions of two
tubulin protein subunits (α & β) - (25nm in ⌀)
Major;
-Cell structural support
-Intracellular transport linked to motor proteins
-Generate force and cell movement (cilia and flagella)
-Cell divisions ->forming Centrioles -> DNA segregation

49
Q

Cytoskeleton defects

A

-Cytoskeleton defects can lead to cardiomyopathies, cancer
-Some anti-cancer drugs interfere with microtubule formation to block the uncontrolled cancer cell divisions

PMP101 (21 decks)

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