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Anil - Cells

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Cells

Cells

MCD YEAR 1

Anil Chopra

Contents

1MCD Cells 1 Cells and Organelles

3MCD Cells 2 Pathogenic Microbes

4MCD - Cells 3 Cell Membranes

7MCD- Cells 4 Blood

MCD Cells 1 Cells and Organelles

Anil Chopra

1. Understand what constitutes a cell, and the scale of cells and molecules

What Constitutes a Cell? make up tissues and organs

separated my membranes

if they live independently: protozoa

they can come together to form colonies ( specialise.

Many cells have polarity.

Scale if CellsSize of cell: 50m

Weight of a cell: (density = 1.06ng)

Size of virus: 0.1 m/100nm2. Demonstrate the following on a suitable transmission electron micrograph: nucleus; nucleolus; nuclear envelope; mitochondrion; rough endoplasmic reticulum; smooth endoplasmic reticulum; ribosomes; Golgi apparatus; secretory granule; plasma membrane; cytoskeletal components.

1 Nucleus 1a Euchromatin 1b Heterochromatin 2 Nucleolus 3 Nuclear membrane 4 Nucleopore 5 Ribosomes 6 Rough endoplasmic reticulum (with ribosomes) 7 Smooth endoplasmic reticulum8a Longitudinal- and cross-sections of a mitochondrion showing aristae8bLongitudinal- and cross-sections of a mitochondrion showing tubules 8c Longitudinal- and cross-sections of a mitochondrion of the prismatic type 8d Longitudinal- and cross-sections of a mitochondrion showing saccules 9 Longitudinal- and cross-sections of a centriole10 Golgi Apparatusus 11 Golgi vesicles 12 Endopinosomes, endopinocytotic vesicles13 primary lysosomes 14 secondary lysosomes, phagocytosomes 15 tertiary lysosomes

16, 17 Multivesicular bodies

18 peroxisomes, microbodies19 Secretory granules 20 Microtubules 21 Actin filaments 22 Intermediate filaments linking to desmosomes

24 Glycogen granules 25 Fat droplets 26 Synapse 27 Synaptic body28 Cell membrane with glycocalyx(polysaccharides and glycoproteins)29 Intercellular space 3031 Tight junction32 Adherens junction 33 Fascia Adherens with actin filaments (cardiac) 34 Punctum Adherens 35 Macula Adherens (desmosome) 36 Hemidesmosome (joins cell to basal lamina) 37 Gap junction38 Microvilli with glycocalyx 39 Cilia 40 Basal bodies of microcilia

41 Stereocilia

42 Basal lamina 3. Identify the essential characteristics of prokaryotic and eukaryotic cells.

ProkaryotesEukaryotes

Kingdoms of Monera and Archea Do not contain organelles

May have flagella for locomotion

Have 0.001 times DNA as eukaryote.

High degrees of mutation

DNA is circular

Smaller Ribosomes

Contins a single copy of chromosomes.

Contains peptidoglycan.

Less defined cytoskeleton. Kingdoms of Animals, plants and protocists.

Contain organelles inc. nucleus

Have a high degree of organisation

Have 1000 times DNA as prokaryote.

Relatively rare mutations

DNA chromosomal in nucleus

Larger Ribosomes

Diploid containing 2 different chromosomes

Contains NO peptidoglycan.

Well-defined cytoskeleton.

4. Explain the relationship of individual cells to the organisation of the whole body.

5. Understand that cancer is a disorder of cell divisionRelationships between cells and the whole body:

Cells ---make up( tissues ---which make up(organs---which make up( systems

Many diseases/conditions are caused by problems at a cellular level.

Cancer is caused by irregular cell division. Mutations include:

Cells signalled to divide but then not to stop

DNA copying correction mechanism is halted

Telomeres are lengthened

Calls not limited to tissue boundaries

Tumours spread to tother tissues

Cells die due to lack of O2.

6. Describe the predominant types of molecules in a cell

solutes include:

soluble proteins

ions (K+, Na+, Mg2+, Ca2+, PO42-, Cl-)

sugars

Nucleotides: e.g. ATP, cAMP, GTP

amino acids

mRNA

tRNA

Lipids, cholesterol

PeptidesMCD Cells 2 Pathogenic Microbes

Anil Chopra1. Name the main types of infectious agent causing disease in humans

2. List the key differences between prokaryotes and eukaryotes

3. Give examples of each type of infectious agent and the disease it causes

4. Name the distinguishing features of the different types of infectious agent and explain how they replicate

TypeExampleFeatures

BacteriaMycobacterium tuberculosis, E. coli, Neisseria meningitidesProkaryotes that replicated by binary fission, they contain chromosomes, but no nucleus. Their DNA is circular. They inhabit the gut, skin, they stimulate the immune system and aid with metabolism and provision of nutrients. Some are pathogenic and can in the immuno-compromised, cause infections (opportunistic infections).

VirusesHIV, common cold, influenzaNot cells in their own right (obligate parasites), inhibit host cell from replicating. Contain DNA or RNA and use reverse transcriptase to divide. Make use of a host cell nuclear synthetic machinery to replicate and divide by budding out of the host cell. Show host specificity but infect almost all other life forms including bacteria.

FungiCandida albicans (thrush), aspergillus fumigatusSingle celled eukaryotes that exist as yeasts or filaments. Yeasts bud or divide; filaments (hyphae) which have cross walls or septa.Usually affect immuno-compromised people. Causes mycoses (infection).

ProtozoaMalaria, leishmaniasisSingle celled eukaryotes, include intestinal, blood and tissue parasites. Replicate in host by binary fission or by forming trophozoites in a cell. Many have complicated life cycle involving 2 hosts. Infection acquired by ingestion or via a vector.

HelminthsTapeworm, fluke, roundwormsMulticellular organisms. Have life cycles outside human host, visible to the naked eye. Complex life cycle including embronation to generations in different hosts.

MCD - Cells 3 Cell Membranes

Anil Chopra1) Explain the function of phospholipids bilayers in aqueous environment.

Constitutes phospholipid bilayer

C=C unsaturated bond causes kink in chain. Causes them not to pack as tightly as the kinks take up room.

Lipids have a hydrophilic head (polar) and hydrophobic tail. To avoid water, the tails pack together.

They suspended in water and form micelles or droplets. They can also arrange themselves into bilayers (a layer two molecules thick). Droplets in cells are called liposomes.

Cholesterol is also found in membranes acts to increase membrane stiffness.

Glycolipids are found on the extracellular side of the membrane with negative charges inside the cell

The bilayers need to:

Have selective permeability

Be impermeable to macromolecules, biochemical intermediates

Be permeable to nutrients, waste products

Allow transfer of information (= signal transduction)

The Bilayer is Dynamic

Flip-flop: lipids switch sides in the bilayer - occurs less than once a month for any individual molecule.

Diffusion: lipid molecules readily exchange places with their neighbours within a monolayer (~107 times a second). This gives rise to a rapid lateral diffusion, with a diffusion coefficient (D) of about 10-8cm2/sec, which means that an average lipid molecule diffuses the length of a large bacterial cell (~2 m) in about 1 second.

2) Draw the structure of phosphotidylcholine and identify the component parts.

3) Describe the permeability properties of the phospholipid bilayer.

Bilayer Permeable to: Not permeable to: Some can

H2O

Cations (K+, Na+, Ca+) & Anions (Cl-, HCO3-) move by

O2 By osmosis/diffusion

Small hydrophilic molecules facilitated diff.

CO2 down diffusion gradient

Macromolecules or active trans.

4) Distinguish between simple diffusion, facilitated diffusion and active transport.

Lipids can exchange places with neighbours Lateral diffusion, but can rarely flip flop i.e. switch sides of the bilayer.

This can occur by:

Facilitated diffusion: charged pores, vary in size, shape and other characteristics.

Co-transport: coupled transporters, symporters, e.g. sugars and amino acids with Na+ or antiporters e.g. Na+/K+ exchange.

5) Functions of membrane proteins

Proteins in the membrane increase the cell fluidity. They are also used for transport, receptors, recognition and adhesion of cells, electron carriers.

Membrane Potential and Potassium GradientsThe Na+-K+ pump exchanges 3 Na+ ions from inside the cell for two K+ ions on the outside. There are two consequences:

Ionic gradients are created: less Na+ and more K+ inside the cell than outside.

A charge gradient is created, as more positive charges are pushed out than are coming in. This results in the inside of the cell being at a more negative potential than the outside. [K+]i is high inside the cell

There is a therefore a tendency for K+ to move out of the cell

This is counterbalanced by the electric potential which opposes the movement of positive charges out of the cell, as this would accentuate the voltage difference across the cell.

An equilibrium will be reached when the rate of inward movement of K+ ions down the electrochemical gradient equals the rate of outward movement down the concentration gradient Thus the electrical imbalance caused by the sodium pump will not quite be compensated by K+ move