Biosci 107

8nm across- thin, flexible, sturdy- surrounds cytoplasm of cell

Fluid mosaic model describes structure

50% lipid + 50% protein held together by H bonds

Hydrophobic core provides impermeable barrier to passage of charged ions

Phospholipid molecules are amphipathic and make up 75% of lipids

Control of passage mean concentration gradients are maintained

Controlled uptake of nutrients, discharge of waste, secretion

Membrane potential developed

Barrier to entry + exit of polar substances

Gatekeepers- regulate entry and exit

More double bonds= mean increased fluidity

Longer phospholipid tails= decreased fluidity

More cholesterol= decreased fluidity

Extend into or across membrane

Amphipathic (polar + non-polar)

Hydrophobic regions spanning hydrophobic core usually 5 amino acids across, non-polar amino acid coiled into helices

Hydrophilic ends of the proteins interact with aqueous solution

Attached to either side of the membrane

Easily removed

Receptors

Cell identity markers

Linkers of other cells or ECM

Enzymes

Ion channels- allow specific substance to move through water filled pore. Most plasma membranes include specific channels for several common ions

Transporters- transports specific substances across membrane by changing shape eg amino acids needed to synthesise new proteins enter body via transporters

Membrane proteins mediate transport of substances across membrane that cannot permeate hydrophobic core of lipid bilayer.

Non-polar, uncharged (O2, N2, benzene)

Lipid soluble (steroids, fatty acids)

Small polar uncharged (water, urea, glycerol)

Large, uncharged (glucose, amino acids)

Ions (charged) eg Na+ K+ Cl- Ca2+ H+

Random mixing of particles (result of kinetic energy) with net movement of particles from a high to low conc

Greater the gradient, greater diffusion rate

Higher temp, greater diffusion rate

Larger size of diffusing substance, slower diffusion rate (largest size- 29

5L

14,000L

3L and interstitial fluid which re-circulates

Oxygen from lungs to cells and carbon dioxide cellular waste back to lungs

70mL

1 minute

Rapid flow through large blood vessels and slower in smaller capillaries

Transportation of nutrients- oxygen, carbon dioxide, nutrients, heat, wastes, hormones

Regulation- pH, temperature, salinity

Protection- leakage control system- blood clotting

Immune system

Whole blood- 8%=

55% blood plasma= 91.5% water, 7% proteins (albumins 54%, globulins 38%, fibrinogen 7%, all other 1%) 1.5% solutes (electrolytes, nutrients, gases, regulatory substances, waste products)

Formed elements 45% = Platelets (150,000-400,000), red blood cells (4.8- 5.4 million, white blood cells (5000-10,000)- neutrophils (60-70%) lymphocytes (20-25%), monocytes (3-8%), eosinophils (2-4%), basophils (0.5-1%)

Prior knowledge- know what to identify- foreign objects- binding sites of surface molecules of bacteria etc, molecular recognition- knowledge stored in lymph nodes

Surveillance- agents which go out to look for trouble

Response- Clean up- get rid of the harmful bacteria

Memory- for future reference

Flattened spheres with a 8um diameter with no nuclei or internal organs

Contains approx. 280 million haemoglobin- each can bind to 4 O2 molecules so each erythrocyte can transport about a billion oxygen molecules

120 day lifetime

Carry blood group antigens on surface

Originate from myeloid stem cells in bone marrow- reticulocytes

Alpha-helical protein containing 4 iron- containing heme groups which bind oxygen. Iron causes the red colour of blood. Major protein in blood. Concentration 150mg/mL (15%)

Main component of blood plasma present at final conc of 35mg/mL. Serves as carrier for insoluble smaller molecules such as lipids and some hormones. It also binds and transports man-made drugs and is consequently important in pharmacology. Protein chain consists mostly of alpha-helices.

Contains up to 20mg/mL immunoglobulin which recognise foreign molecules like surfaces of bacteria or virus particles. 12 immunoglobulin domains. Main called IgG- produces millions and binds to different foreign molecule.

Consists mainly of beta-strands and contains no alpha-helices.

Antibody molecules made up of white blood cells

Cell types with or without visible cytoplasmic granules

Neutrophils- have visible cytoplasmic granules

Produced in the red bone marrow and circulate in blood 5-8 days before migrating through capillary walls into tissue and developing into macrophages

Thought of as the frontline police of immune system. Recognise more obvious features of commonly occurring infections and can ingest and destroy infecting material. Can also report infection to the centralised immune memory system for future reference. System can also produce molecular tags which can tag harder- to recognise infections so macrophages can destroy them (tags are anti-body molecules)

Principal building blocks and instruments of communication of the central and peripheral nervous system. Communication is electrical signals (dendrites, axon, cell body) or chemical signals (synapses).

Synaptic potential goes towards cell body from dendrites and action potential is towards synapses from cell body

Integrative, sensory and motor

Monitor internal and environmental events

Generate responses

Process and store sensory and other info

Axon conducts action potentials usually away from the soma to the tips of the axons where their terminals/ boutons communicate with other neurons

Voltage across the cell membrane which in neurons can change during various states of cell activity within a relatively large range (-100 and +50mV

In the absence of synaptic potentials and action potentials the membrane potential is referred to as the resting membrane potential (RMP)

Usually between -50 and -70mV (typically -65mV)

Potential outside cell is 0 so inside cell is more negative

Can be measured with intracellular micro-electrodes (measures voltage) and with patch-clamp pipettes (patch-clamp techniques, forming gigaohm seal with membrane and pipette; measures both voltage and current)

Created by the differences in conc for Na+ and K+ ions inside and outside the cell resulting in electrical and chemical gradients driving the movement of these ions. Na+ and K+ play a critical role in maintaining the RMP in neurons

Difference in permeability of the cell membrane to these ions.

Nerve pulse or spike in the membrane potential so changes the voltage across the membrane

Non-gated channels (egleak) opened at rest. Many K+ leak channels and very few Na+. Because of this at rest ration of Pk:PNa is about 40:1.

Gated channels (eg voltage or ligand-gated) usually closed at rest.

A very brief fluctuation (longer in soma/ cell bodies) in membrane potential caused by transient opening of voltage-gated ion channels which spreads along an axon (parts of the neuron).

The frequency of information transfers information.

Occurs after membrane reaches certain voltage called threshold.

Amplitude of depolarisation generally reaches 100mV and does not depend on stimulus intensity and considered an all-or-none event

Depolarisation to threshold: to about -55mV by stimulus (physical: current, stretch) chemical (synaptic excitation)

Fast depolarisation: about 30mV after the membrane potential reaches threshold

Repolarisation potential returns to RMP as Na+ channels inactivate (only short lasting) and voltage-gated K+ channels open

After-hyperpolarisation- potential drops below RMP then returns. Voltage gated K+ channels remain open then closE

Includes phases of fast depolarisation and repolarisation, during this period another AP cannot be regenerated

Phase of after-hyperpolarisaiton during this period another AP can be generated but the stimuli must be strong enough to reach threshold.

AP generated in initial segment as this has the lowest threshold. Evoked by excitatory post-synaptic potentials (EPSPs) which spread mainly passively from dendrites.