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44 Cards in this Set
- Front
- Back
Membrane Characteristics (8) |
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 |
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Lipid |
Barrier to entry + exit of polar substances |
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Proteins |
Gatekeepers- regulate entry and exit |
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Patterns of fluidity of membrane |
More double bonds= mean increased fluidity Longer phospholipid tails= decreased fluidity More cholesterol= decreased fluidity |
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Integral membrane protein characteristics |
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
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Peripheral proteins |
Attached to either side of the membrane Easily removed |
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Functions of membrane proteins |
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. |
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Selective permeability: Permeable to: |
Non-polar, uncharged (O2, N2, benzene) Lipid soluble (steroids, fatty acids) Small polar uncharged (water, urea, glycerol) |
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Selective permeability: Impermeable to: |
Large, uncharged (glucose, amino acids) Ions (charged) eg Na+ K+ Cl- Ca2+ H+ |
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Diffusion |
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 |
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Approx how much blood circulates through our body |
5L |
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What is the daily throughput of the heart? |
14,000L |
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How much blood passes through capillary walls into tissue ad what does it become |
3L and interstitial fluid which re-circulates |
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What does blood transport and where does it go |
Oxygen from lungs to cells and carbon dioxide cellular waste back to lungs |
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What is one beat |
70mL |
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What is the circulation time |
1 minute |
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Rapid and slower? |
Rapid flow through large blood vessels and slower in smaller capillaries |
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Function of the blood |
Transportation of nutrients- oxygen, carbon dioxide, nutrients, heat, wastes, hormones Regulation- pH, temperature, salinity Protection- leakage control system- blood clotting Immune system |
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Blood components |
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%) |
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Security network= immune system |
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 |
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Erythrocytes (red blood cell) components |
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 |
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Haemoglobin |
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%) |
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Serum albumin |
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. |
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Immunoglobulin |
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. |
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IgG |
Consists mainly of beta-strands and contains no alpha-helices. |
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B lymphocytes/ B cells |
Antibody molecules made up of white blood cells |
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Leukocytes (White Blood cells) |
Cell types with or without visible cytoplasmic granules |
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What is the most common white blood cell |
Neutrophils- have visible cytoplasmic granules |
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Monocytes |
Produced in the red bone marrow and circulate in blood 5-8 days before migrating through capillary walls into tissue and developing into macrophages |
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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) |
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Neurons |
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 |
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Nervous system (3 components) |
Integrative, sensory and motor |
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Sensory |
Monitor internal and environmental events |
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Motor |
Generate responses |
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Integrative |
Process and store sensory and other info |
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Neuron Structure |
Inputs received on the dendritic tree and soma
Axon conducts action potentials usually away from the soma to the tips of the axons where their terminals/ boutons communicate with other neurons |
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Resting membrane potential |
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. |
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Action potential |
Nerve pulse or spike in the membrane potential so changes the voltage across the membrane |
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What are the two types of ion channels in the cell membrane that affect permeability and examples |
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. |
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Action potential |
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 |
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Stages of action potential (4) |
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 |
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Absolute refractory period |
Includes phases of fast depolarisation and repolarisation, during this period another AP cannot be regenerated |
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Relative refractory period |
Phase of after-hyperpolarisaiton during this period another AP can be generated but the stimuli must be strong enough to reach threshold. |
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Facts about AP |
AP generated in initial segment as this has the lowest threshold. Evoked by excitatory post-synaptic potentials (EPSPs) which spread mainly passively from dendrites. |