Physiology Exam Revision

Front 1

Homeostasis

Back 1

The bodies ability to maintain regulated variables at a narrow range which supports life.

Front 2

Law of mass balance

Back 2

If the amount of a substance in the body is to remain constant, any gain must be offset by a loss and visa versa. E.g. Water lost to external environment via sweat or urine must be balanced by water intake from the external environment.

Front 3

Local control systems

Back 3

Restricted to the tissue or cell involved. In local control an isolated change occurs in a cell or tissue. A nearby cell senses the change and responds.

Front 4

Long distance control/reflex control

Back 4

Changes that are widespread throughout the body (systemic). The nervous and endocrine systems rely on reflex control. Physiological reflexes can be:

Response loops

Feedback loops

Front 5

Response loop

Back 5

1. Stimulus

2. Sensor

3. Input signal

4. Integrating center

5. Output signal

6. Target

7. Response

Front 6

Positive feedback

Back 6

Not-homeostatic

Response reinforces a stimulus

An outside factor is required to shut off the cycle. E.g. childbirth

Front 7

Negative feedback

Back 7

Homeostatic

Keep the system at or near set point

Set point = normal range of a regulated variable

Front 8

Biomolecules

Back 8

Carbohydrates

Lipids

Nucleotides

Proteins

Front 9

Lipids

Back 9

Mostly carbon and hydrogen with a glycerol backbone. 1-3 fatty acid tails.

Non-polar & non-soluble

Saturated fats = more hydrogens. The more hydrogens the more saturated.

Front 10

Carbohydrates

Back 10

Carbon and water. For every carbon there is 2 hydrogen and 1 oxygen.

Monosacharides = 5 or 6 carbon sugars (ribose, glucose, lactose)

Disacharides = glucose + a monosacharide

Polysacharide = glucose polymer

Front 11

Lipid related molecules

Back 11

Eicosanoids - modified 20 carbon fatty acids with a complete carbon ring at one end and 2 carbon tails at the other. E.g. prostoglandins - regulate physiological functions

Steroids - cholesterol

Phospholipids - cell membrane

Front 12

Functional groups

Back 12

Combinations of elements that occur repeatedly and move from molecule to molecule as a single unit.

Amino group

Carboxyl group

Hydroxyl group

Phosphate group

Front 13

Proteins

Back 13

Amino acid polymers.

Amino acids consist of a carboxyl group, an amino group and a hydrogen attached to a carbon. There is also a variable R group.

Front 14

Peptide bonds

Back 14

Occur when amino acids join to form a chain. The amino group of one amino acid joins the carboxyl group of another

Front 15

Essential amino acids

Back 15

Must be obtained through diet.

Glutamine, tyrosine, arginine etc...

Front 16

Primary protein structure

Back 16

The sequence of any 20 amino acids in a peptide chain

Front 17

Peptides

Back 17

Oligiopeptide 2-9 amino acids

Polypeptide 10-100 amino acids

Protein 100+ amino acids

Front 18

Secondary protein structure

Back 18

Covalent bonds form between amino acid peptide chains to form a double helix

Front 19

Tertiary protein structure

Back 19

A proteins 3D shape

Globular proteins and fibrous proteins such as collagen fibers

Front 20

Quaternary protein structure

Back 20

Many sub-units combine with non-covalent bonds (many 3D protein structures come together)

E.g. hemoglobin is made of 4 globular protein sub-units

Front 21

Covalent bonds

Back 21

Sharing of electrons between atoms.

Will always involve a non-metal.

Covalent bonds form molecules.

Covalent bonds are strong and require energy to break them apart.

Front 22

Ions

Back 22

When an atom or molecule gains or loses an electron it becomes an ION. The ion then has an electrical charge.

Front 23

Cations

Back 23

Metals

Lose electrons = overall positive charge

Front 24

Anions

Back 24

Non-metals

Gain electrons = overall negative charge

Front 25

High energy electrons

Back 25

Only occur in certain atoms. They capture energy from their environment and transfer it to other atoms. This energy is used for synthesis, movement and other life processes.

Front 26

Free radicals

Back 26

Unstable molecules with an unpaired electron.

Contribute to ageing and disease development

Front 27

Ionic bonds

Back 27

Metals.

Taking or losing electrons via electrostatic attraction.

Front 28

Nucleotides

Back 28

Essential for energy and information transfer.

Nucleic acids (DNA & RNA) store and transmit genetic information.

ATP, AMP and cAMP are single nucleotides.

Front 29

Nucleotide structure

Back 29

Nitrogenous bases

5 carbon sugar

One or more phosphate groups

Front 30

RNA

Back 30

Ribonucleic acid. Single strand nucleic acid. Ribose is the sugar.

Front 31

DNA

Back 31

Deoxyribonucleic acid.

Double helix - 3D structure. Formed by 2 DNA strands linked by hydrogen bonds between complimentary base pairs. Deoxyribose is the sugar.

Front 32

Nitrogenous bases

Back 32

ADENINE -THYMINE = 2 hydrogen bonds

ADENINE - URACIL (mRNA) = 2 hydrogen bonds

GUANINE - CYTOSINE = 3 hydrogen bonds

Front 33

Proton

Back 33

Positive charge

Atomic number is calculated by number of protons

Front 34

Neutron

Back 34

Neutral

Front 35

Electron

Back 35

Negative charge

Front 36

Atomic mass

Back 36

Number of protons and electrons

Front 37

Isotope

Back 37

An atom that loses or gains a neutron becomes an isotope of the same element

Front 38

Polar molecules

Back 38

Overall neutral molecule BUT has regions of partial positive and negative charge.

Polar molecules are water soluble.

Nitrogen and oxygen have a strong attraction to electrons and are often associated with polar molecules.

Front 39

Hydrogen bonds

Back 39

Weak attractive force between a hydrogen and nearby oxygen, nitrogen or fluorine. No electrons are gained or lost, instead oppositely charged regions in polar molecules are attracted to each other.

Front 40

Van der waals forces

Back 40

Weak, non-specific attractions between the nucleus of ANY atom and the electrons of nearby atoms. Van der waals allow atoms to pack in closely together to occupy minimum amounts of space. E.g. globular proteins.

Front 41

Solubility

Back 41

The degree to which a molecule is able to dissolve in a solvent. Water is the biological solvent.

Front 42

Hydrophillic

Back 42

Water loving.

Soluble.

Front 43

Hydrophobic

Back 43

Water hating

Non-soluble

lipids and fats.

Front 44

pH

Back 44

Power of hydrogen.

Free hydrogen ions lower pH which results in an acidic solution.

Hydroxyl ions increase pH resulting in a basic solution.

Acids = free hydrogen

Bases = hydrogen acceptors

Front 45

Buffer

Back 45

Any substance that moderates changes in pH.

E.g. carbonic acid/bicarbonate buffer.

Usually consists of 2 parts. A weak acid and its conjugate base. The role of the buffer is to replace a strong acid or base with a weak acid or base resulting in minimal change to pH.

Front 46

Moles

Back 46

An expression of the number of solute molecules without regard to their weight.

Front 47

Electrolyte

Back 47

A solution that contains ions and can generate an electrical current. Electrolytes when combined with water dissociate (ionize) into their ions. Strong electrolytes = 100% dissociation (NaCl)

Weak electrolytes (HF) = partial dissociation

Front 48

Enzymes

Back 48

Biological catalysts

Speed up chemical reactions by lowering activation energy.

Crucial in metabolism

Front 49

Membrane transporters

Back 49

Proteins found imbedded in the cell membrane. Integral and carriers.

Move substances between the ICF & ECF

Front 50

Signal molecules

Back 50

Proteins and smaller peptides acting as hormones or other signal molecules for cell-to-cell communication.

Front 51

Receptors

Back 51

Proteins that bind to signal molecules which then initiate cellular responses.

Front 52

Binding proteins

Back 52

Found mostly in ECF. Bind and transport molecules around the body. E.g. hemoglobin transports oxygen.

Front 53

Immunoglobins

Back 53

Extracellular immune proteins (antibodies).

Protect the body from foreign invaders.

Front 54

Regulatory proteins

Back 54

Turn cell process on, off, up & down.

Front 55

Ligand

Back 55

Any molecule or ion that binds to another molecule.

Ligands that bind to an enzyme or membrane transporter are called SUBSTRATES.

Front 56

Specificity

Back 56

The ability of a protein to bind to a specific ligand or a group of ligands. The ligand and binding site must be compatible. When a ligand and binding site combine they interact via hydrogen bonds, ionic bonds and van der waals forces.

Front 57

Induced fit

Back 57

When a proteins binding site changes shape to compliment its specific ligand

Front 58

Affinity

Back 58

The degree to which a protein is attracted to a ligand. If a protein has a high affinity for a ligand it is more likely to bind.

Front 59

Competition

Back 59

Related ligands compete for binding sites.

Agonist - mimics a ligand

Antagonist - inhibit the effect, block the binding site and overall decrease activity.

Front 60

Saturation

Back 60

Proteins reach saturation when all binding sites are occupied. Addition of extra ligand has no effect.

Front 61

Central nervous system

Back 61

Brain and spinal cord.

The central nervous system acts as the intergrating center for the body

Front 62

Peripheral nervous system

Back 62

Located out of the CNS. Consists of afferent (in) neurons and efferent (out) neurons.

Front 63

Afferent division

Back 63

Also known as SENSORY division.

Afferent neurons send information to the Central nervous system.

Front 64

Efferent division

Back 64

Efferent neurons take information from the central nervous system to target cells. There are 2 branches of the efferent division: SOMATIC & AUTONOMIC

Front 65

Somatic divison of PNS

Back 65

Controls the skeletal muscles. Voluntary movement.

Front 66

Autonomic division of the PNS

Back 66

Controls smooth and cardiac muscle, exocrine glands, some endocrine glands and adipose tissue. Referred to as the visceral nervous system as it controls contraction and secretion in various organs. Autonomic neurons are further divided into the SYMPATHETIC AND PARASYMPATHETIC division.

Front 67

SYMPATHETIC division of the autonomic branch of PNS

Back 67

Involuntary. Fight or flight. Increases heart rate etc.

Front 68

PARASYMPATHETIC division of autonomic branch of PNS

Back 68

Rest and digest. Slows heart rate.

Front 69

Neuron

Back 69

Nerve cell. Functional unit of the nervous system.

Front 70

Interneurons

Back 70

Found in the central nervous system. Come in variety of forms and commonly have complex branching.

Front 71

Sensory neurons

Back 71

Carry sensory information from the periphery to the central nervous system (afferent neurons).

Front 72

Efferent neurons

Back 72

Carry information from the central nervous system to the periphery.

Front 73

Nerve

Back 73

The long axons of both afferent and efferent neurons that are bundled together with connective tissue in to cord like fibers. They extend from the central nervous system to targets.

Front 74

Schwann cell

Back 74

Glial cell peripheral nervous system.

Makes up myelin sheath of the peripheral nervous system

Front 75

Oligodendrocytes

Back 75

Glial cell central nervous system.

Myelin sheath of central nervous system.

Front 76

Node of ranvier

Back 76

Spaces between schwann cells/oligodendrocytes on the axon. The area of the axon where voltage gated sodium ion channels are located.

Front 77

Enteric nervous system

Back 77

Located in the digestive system. Can be controlled by the autonomic division of the peripheral nervous system OR autonomously.

Front 78

Axonal transport

Back 78

Proteins that are synthesised in the neuron cell body are moved down the axon by axonal transport. This process can be FAST or SLOW.

Front 79

Slow axonal transport

Back 79

Moves material cytoplasmically. Used for components that are not consumed rapidly. E.g. enzymes. Move at a rate of 0.2mm per day.

Front 80

Fast axonal transport

Back 80

Move at a rate of 400mm per day. The neuron uses microtubules to transport vesicles and mitochondria down the axon with the help of motor proteins. Motor proteins bind and unbind to microtubules with the help of ATP. Transport moves in both directions.

Anterograde - moving forward from cell body to axon terminal.

Retrograde - moving from axon terminal to cell body - empty vesicles and debris for recycling.

Front 81

Presynaptic cells

Back 81

Delivers the signal to a target.

Front 82

Post-synaptic cells

Back 82

Recieve the signal from pre-synaptic cells.

Front 83

Synaptic cleft

Back 83

Space between two cells where neurotransmitters are secreted. The synaptic cleft is filled with extracellular matrix which holds the pre and post synaptic cells in place.

Front 84

Glial cells

Back 84

Supporting cells.

Peripheral nervous system has 2 types: Schwann cells and satelite cells.

Central nervous system has 4 types: oligodendrocytes, astrocytes, microglia and ependymal cells.

Front 85

Satellite cells

Back 85

Glial cells peripheral nervous system.

Non-myelinating schwann cell. Forms supportive capsules around cell bodies located in ganglia.

Front 86

Ganglion

Back 86

Collection of nerve cell bodies found outside of the central nervous system. They appear as swellings or knots along the nerve.

Front 87

Astrocytes

Back 87

Glial cells central nervous system.

Make up 50% of all brain cells. Provide neurons with substrates for ATP production.

Maintain homestatis by monitoring potassium ion concentration and water.

Surround blood vessels to form the blood-brain barrier to ensure regulated movement of materials between the blood and ECF in the brain.

Front 88

Microglia

Back 88

Glial cells central nervous system.

Not made of neural tissue.

Specialised immune cells which when activated protect the brain and spinal cord from damaged cells and foreign invaders.

Front 89

Ependymal cells

Back 89

Glial cells central nervous system.

Create the selectively permeable epithelial cells that separate the fluid compartments in the central nervous system.

Front 90

Excitable tissue

Back 90

Nerve and muscle cells are known as excitable tissues due to their ability to propegate electrical signals rapidly in response to stimulus.

Front 91

Sodium ion concentration

Back 91

145mM extracellular fluid

15 mM intracellular fluid

Front 92

Potassium ion concentration

Back 92

5mM extracellular fluid

150mM intracellular fluid

Front 93

Chloride ion concentration

Back 93

108mM extracellular fluid

10mM intracellular fluid

Front 94

Calcium ion concentration

Back 94

1mM extracellular fluid

0.0001 mM intracellular fluid

Front 95

Membrane potential

Back 95

Membrane potential is influenced by an electrochemical gradient of ions across a membrane and the membranes permeability to those ions.

A resting membrane has a high permeability to potassium ions and a low permeability to sodium ions.

Neurons have a resting membrane potential of -70mV

Front 96

Depolarisation and membrane potential

Back 96

If a membrane becomes more permeable to sodium ions, the sodium moves IN to the cell causing the cell membrane to have a more positive charge - therefore the cell is depolarized.

Front 97

Hyperpolarisation membrane potential

Back 97

If the membrane becomes more permeable to potassium ions, the potassium moves down its concentration gradient OUT of the cell causing the cell to become more negative. This is referred to as hyperpolarisation.

Front 98

Repolarisation membrane potential

Back 98

When the cell is returning to its resting membrane potential

Front 99

Channel activation

Back 99

The speed at which a voltage gated ion channel opens/closes to allow the flow of ions.

Sodium ion voltage gated channels are RAPID

potassium ion voltage gated channels are SLOWER.

Front 100

Graded potential

Back 100

Occur in the dendrites and cell body.

Travel a short distance.

Lose strength as they travel through the cell. If a graded potential is strong enough it will produce an action potential.

Front 101

Sub-threshold graded potentials

Back 101

Start above threshold (-55mV) at initiation point but decreases in strength as it moves through the cell. By the time it reaches the trigger zone the graded potential is below threshold and therefore no action potential is generated.

Front 102

Supra-threshold graded potential

Back 102

A stronger stimulus maintains strength above threshold as it moves down the cell body and once it reaches the trigger zone is able to trigger an action potential.

Front 103

Trigger zone

Back 103

Axon hillock.

Integrating center of the neuron.

Has a high concentration of sodium ion gated channels.

Front 104

Depolarizing action potentials

Back 104

Excitory

Front 105

Hyperpolarising action potentials

Back 105

Inhibitory

Front 106

Events of an action potential

Back 106

1. Depolarising stimulus reaches trigger zone.

2. Voltage gated sodium ion channels open causing sodium to rush in to the cell, causing more sodium ion gated channels to open etc (positive feedback loop).

3. Membrane depolarises - rising phase.

4. At peak voltage gated sodium ion channels begin to inactivate and the slower opening potassium ion channels begin to open. This stimulus terminates the positive feedback loop.

5. Opening of potassium ion channels allows potassium ions to leave the cell causing the cell to begin repolarising.

6. Potassium ion channels keep opening which creates an overshot and then hyperpolarisation.

7. When the potassium channels close the cell returns to its resting membrane potential.

Front 107

Depolarising at peak

Back 107

+30mV

Front 108

Hyperpolarising at peak

Back 108

-80mV

Front 109

Action potential summary

Back 109

The action potential is a change in membrane potential. It occurs when voltage gated ion channels in the membrane open, increasing the cells permeability, first to sodium ions (in) and then potassium ions (out). The influx of sodium ions depolarises the cell. This is followed by an efflux of potassium ions which first hyperpolarise the cell and then repolarises the cell to its resting membrane potential.

Front 110

Absolute refectory period

Back 110

The time when an action potential will NOT fire regardless of stimulus strength. Action potentials will not travel backwards and can not overlap.

Voltage gated sodium ion channels take time to become active again after inactivation. During this time the membrane is hyperolarised and potassium is still leaving the cell. No action potential can occur.

Front 111

Relative refractory period

Back 111

Occurs after absolute refractory period.

Some sodium ion gated channels are active again shower the cell is still hyperpolarised. As a result an extra strong stimulus (above threshold) is required to generate an action potential.

Front 112

Larger neurons

Back 112

Conduct faster action potentials.

The larger diameter of the axon the more leak resistant the membrane is. E.g. the larger and wider the pipe the faster the water can flow.

Front 113

Myelination

Back 113

Increases conduction rate.

Myelinated axons limit the amount of axon in contact with the ECF which reduces leak.

Action potentials jump between nodes of ranvier = saltatory conduction

Front 114

Chemical synapse

Back 114

The electrical signal of a presynaptic cell is converted in to a neurocrine signal that crosses the synaptic cleft and binds to receptors on the target cell (post-synaptic cell).

Front 115

Synapse

Back 115

Each synapse has 2 parts.

1. The axon terminal of the pre-synaptic cell.

2. The membrane of the post synaptic cell.

Most synapses are CHEMICAL.

Front 116

Electrical synapses

Back 116

Pass an electrical signal directly from the cytoplasm of one cell to another via gap junctions. Information flows in both directions.

Front 117

Neurotransmitters

Back 117

Create rapid responses.

Released in vesicles (synaptic vesicles).

Act as paracrine signals - target cells are close to the neuron secreting them.

Front 118

Neurohormone

Back 118

Neuron releases neurotransmitter into the bloodstream, acting as a hormone.

Front 119

Axon terminal membrane

Back 119

Calcium ion gated channels

Front 120

Neurotransmitter release

Back 120

Neurotransmitters in the axon terminal are stored in vesicles. They are released in to the synaptic cleft by exocytosis. This process occurs faster in neurons.

Front 121

Events at chemical synapse

Back 121

1. Action potential arrives at the axon terminal resulting in depolarisation of the membrane.

2. Depolarisation triggers calcium ion gated channels to open, allowing calcium ions to enter the cell.

3. Calcium ions entering the cell triggers the release of neurotransmitter vesicles. Vesicles move to the cell membrane where they exocytose in to the synaptic cleft.

4. Neurotransmitters diffuse across the synaptic cleft and bind with receptors on the post-synaptic cell.

5. Neurotransmitter binding results in a response in the post-synaptic cell.

Front 122

Neurotransmitter termination

Back 122

Neural signalling is a short process. Neurotransmitter action terminates when the chemicals are:

1. Broken down

2. Taken in to the post-synaptic cell or back in to the pre-synaptic cell.

3. Diffuse away in the ECF.

If unbound transmitter is removed the synapse receptors release bound neurotransmitter which maintains equilibrium and terminates activity.

Front 123

Fast synaptic responses

Back 123

Fast synaptic responses are associated with the opening of ion gated channels. Ions move between the post-synaptic cell and ECF resulting in a change of membrane potential. Fast synaptic responses begin rapidly & last milliseconds.

If the synaptic potential is depolarising it is EXCITORY.

If the synaptic potential is hyperpolarised it is INHIBITORY.

Front 124

Excitory post-synaptic potential

Back 124

An excitory post-synaptic potential is more likely to result in an action potential in the post-synaptic cell.

Front 125

Inhibitory synaptic potential

Back 125

As a result of a hyperpolarisation potential of the post-synaptic cell.

Considering INHIBITORY as it moves the membrane away from potential.

Front 126

Neurotransmitter receptors

Back 126

Ligand-gated ion channels = IONOTROPIC.

G protein-coupled receptor = METABOTROPIC

Front 127

Ionotropic neurotransmitter receptors

Back 127

Ligand-gated ion channels.

Rapid response. Ions move in/out of the cell creating graded potentials. Potentials can be excitory (depolarising) or inhibitory (hyperpolarising).

Front 128

Metabotropic neurotransmitter receptors

Back 128

G protein-coupled receptors.

Slower responses.

Use second messenger pathways to create response in the post-synaptic cell.

Some receptors will result in the opening and closing of ion channels.

Associated with metabolic processes.

Front 129

Divergence

Back 129

In a divergent pathway ONE pre-synaptic neuron branches to affect a large number of post-synaptic neurons. This pattern is similar to second messenger pathways.

Front 130

Convergence

Back 130

In a convergent pathway many pre-synaptic neurons provide input to influence a small number of post-synaptic neurons.

Front 131

Neurocrines

Back 131

Neurocrines function as neurotransmitters, neurohormones & neuromodulators.

7 classes.

CNS releases MANY.

PNS only releases 3:

1. Acetylcholine

2. Norepinephrine

3. Epinephrine.

Front 132

Acetylcholine (ACh)

Back 132

Neurons that secrete or bind to ACh are Cholinergic receptors.

ACh is synthesised from choline and acetyl CoA at the synaptic terminal.

Cholinergic receptors are either:

Nicotinic - skeletal muscle, Autonomic division PNS and CNS. Opens ion channels>cell depolarises.

Muscarinic - CNS & Parasympathetic PNS. 5 subtypes with various second messenger pathways. Metabotropic.

.

Front 133

Epinephrine & norepinephrine

Back 133

Neurons that secrete or have receptors for epinephrine & norepinephrine are Adrenergic receptors.

2 classes alpha and beta with multiple sub-types of each.

G protein-coupled receptors working with different second messenger pathways. Some result in excitory responses and others inhibitory responses.

Derived from amino acid tyrosine.

Norepinephrine acts as a NEUROTRANSMITTER

Epinephrine acts as a NEUROHORMONE.

Front 134

Temporal summation

Back 134

Occurs when 2 graded potentials from 1 pre-synaptic neuro noccur close together in time.

If 2 sub-threshold graded potentials are too far apart in time they will not generate an action potential.

If 2 sub-threshold graded potentials arrive at the trigger zone within a short period of time they may initiate an action potential.

Front 135

Spatial summation

Back 135

Spatial summation occurs when currents from nearly simultaneous graded potentials from a pre-synaptic neuron combine on a post-synaptic neuron. The summation of several sub-threshold graded potentials simultaneously results in an action potential.

Front 136

Pre-Synaptic Inhibition

Back 136

One inhibitory post-synaptic potential sums with two excitory post-synaptic potentials to prevent an action potential from occuring in the post synaptic cell.

Front 137

Global pre-synaptic inhibition

Back 137

Excitory and inhibitory pre-synaptic neurons fire but due to the inhibitory neuron, summed signal is below threshold and no action potential is generated. All targets are inhibited.

Front 138

Selective pre-synaptic inhibition

Back 138

An excitory neuron fires generating an action potential. An inhibitory neuron fires at the pre-synaptic axon terminal of one collateral which blocks the release of neurotransmitter release at one synapse.

Front 139

Pre-synaptic modulation

Back 139

A pre-synaptic neuron synapses on to an axon terminal of a neuron and alters the action potential teaching the pre-synaptic terminal. This alters the release of neurotransmitters from the axon terminal.

Front 140

Presynaptic inhibition

Back 140

Decreases the release of neurotransmitter at the synapse

Front 141

Pre-synaptic facilitation

Back 141

Increases neurotransmitter release from synapse.

Front 142

Neuromodulator

Back 142

Alters the responsiveness of a target cell to neurotransmitters. Neuromodulators can change the type & number of receptors as well as affinity of receptors for a neurotransmitter.

Front 143

Isoform

Back 143

Closely related proteins which function in a similar manner as ligands, however affinity differs. E.g. hemoglobin has multiple isoforms (adult & foetal)

Front 144

Protein activation

Back 144

Some proteins are inactive when they are synthesised in the cell, in order for the protein to be activated enzymes must remove a part of the molecule. Protein hormones & enzymes commonly undergo activation.

Front 145

Proteolytic activation

Back 145

A protein is inactive and requires an enzyme to activate it

Front 146

Co-factor activation

Back 146

When an ion or small functional group must bind to an active site before the ligand will bind and become active. Many enzymes do not function without co-factors.

Front 147

Protein modulation

Back 147

The ability of a protein to bind to a ligand & initiate a response can be altered by various factors, including: temp, pH and other molecular interactions.

Front 148

Protein modulator

Back 148

Can either change a proteins ability to bind to a ligand or changes the proteins ability to create a response.

Front 149

Chemical modulators

Back 149

Molecules that bind covalently or non-covalently to proteins and as a result alters their binding ability or activity. Chemical modulators can activate or enhance ligand binding, decrease binding or completely inactivate a protein.

Front 150

Protein inactivation

Back 150

Can be irreversible or reversible

Front 151

Antagonists

Back 151

Inhibitors.

Chemical modulators that decrease activity. Often molecules that bind and block active sites.

Front 152

Competitive ligand inhibitors

Back 152

Reversible antagonists that compete with ligands for binding sites

Front 153

Irreversible ligand inhibitors

Back 153

Bind tightly to the active site and can not be displaced.

Front 154

Allosteric modulators

Back 154

Bind reversibly to a protein at a regulatory site which alters the protein binding site. Allosteric modulators can inhibit or activate.

Front 155

Covalent modulators

Back 155

Are atoms or functional groups that bind covalently to proteins = altered protein properties resulting in increased or decreased activity and binding ability.

E.g. phosphorylation is the covalent bonding of a protein and a phosphate group.

Front 156

Physical factors & effect on ligand binding

Back 156

Temp & pH can have dramatic effects on protein structure and function. When these variables exceed a critical level they disrupt the bonds holding the protein in its tertiary structure. When this occurs the proteins shape is altered, altering the binding site which ultimately results in a loss of function

Front 157

Up-regulation

Back 157

The programmed production of new protein receptors, transporters and enzymes is called up-regulation.

Front 158

Down-regulation

Back 158

The programmed removal of proteins from the cell membrane is called down-regulation. Membrane receptors, transporters and enzymes are exocytosed.

Front 159

Conjugated proteins

Back 159

Protein molecules combined with another biomolecule

Front 160

Lipoprotein

Back 160

Lipid + protein

Front 161

Glycosated molecules

Back 161

Molecules where a carbohydrate has been attached

Front 162

Glycoprotein

Back 162

Carbohydrate + protein

Front 163

Glycolipid

Back 163

Carbohydrate + lipid

Front 164

Solution

Back 164

A homogenous mixture of 2 or more substances.

Substances must be electrically attracted to water (polar) to dissolve.

Like disolves like.

Front 165

pH of ECF

Back 165

Homeostatic range of 7.35-7.45

Front 166

pH of ICF

Back 166

Homeostatic range of 7.0-7.2

Front 167

Fluid mosaic model of biological membranes

Back 167

Describes the plasma membrane as a fluid combination of phospholipids, cholesterol & proteins.

Front 168

Cytoplasm

Back 168

Includes all material inside the cell membrane EXCEPT the nucleus.

Front 169

Cytosol

Back 169

Intracellular fluid. Semi gelatinous. Contains dissolved nutrients, proteins, ions and waste products.

Front 170

Cytoskeleton

Back 170

The internal support system of a cell. Consists of:

Microvilli - increase S.A

Microfillaments - form a network inside the cell membrane to support and maintain shape.

Microtubules - largest cytoskeleton fiber. Hold organelles in place and used in mitosis.

Intermediate filaments: myosin & keratin fibers.

Front 171

Mitochondria

Back 171

Double membrane - cristae

Inner region - mitochondrial matrix

matrix intermembrane space site of ATP production in the ETS.

Front 172

Golgi apparatus

Back 172

Series of hollow curved sacs (cisternae) stacked on top of each other. Surrounded by vesicles. Receives proteins from E.R on the cis face. Participates in post-translational modification of proteins. Packages modified proteins and transports out in vesicles via the trans face.

Front 173

Endoplasmic reticulum

Back 173

Rough - studded with ribosomes. Site of protein synthesis.

Smooth - site of lipid synthesis and calcium stores.

Front 174

Nucleus

Back 174

Double membrane called the nuclear envelope. Pores within the membrane allow for communication with the cytoplasm. Outer membrane is continuous with the E.R. Nucleolus region contains the genes and proteins for synthesis of RNA & ribosomes. Nucleus houses chromatin (DNA & associated proteins).

Front 175

Lysosomes

Back 175

Digestive enzymes. Membrane bound vesicles.

Digest bacteria, cellular waste and old organelles.

Front 176

Peroxisomes

Back 176

Smaller than lysosomes. Membrane bound vesicles. Generate hydrogen peroxide. Degrade fatty acids & toxins. Reactions inside the peroxisome convert hydrogen peroxide in to oxygen and water.

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Ribosomes

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Proteins.

RNA structures.

Float freely in cytosol or embedded in the rough E.R.

Not membrane bound.

Used in protein synthesis > translation

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Protein synthesis

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Conversion of DNA in to functional proteins.

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Codon

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Triplet of bases that code for a specific amino acid

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Gene

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Specific region of DNA that contains the information needed to make a functional piece of RNA.

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Protein synthesis: Gene activation

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Occurring in the nucleus of the cell. A regulatory protein known as a 'transcription factor' binds to the DNA and activates a promoter. The promoter then attracts the transcription enzyme RNA POLYMERASE where to bind to the DNA. The RNA polymerase moves along the DNA unwinding the double helix by breaking the hydrogen bonds.

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Protein synthesis: Transcription

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Occurs in the nucleus of the cell. One strand of unzipped DNA acts as a template strand. The promoter region is not transcribed. Each nitrogenous base in the DNA template is paired with its complimentary RNA base pair (G + C, T + A, A + U). This process is similar to the formation of the DNA double helix. As RNA bases bind to the DNA template they form a functional piece of mRNA. The RNA polymerase reaches a stop codon (UAG, UAA or UGA). No more bases are added and the mRNA strand is released. mRNA consists of nitrogenous bases, a sugar and a phosphate backbone.

Processing is the following step.

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Protein synthesis: Processing

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Occurs in the nuclus of the cell.

mRNA is now inactivated/destroyed or it is processed by alternative splicing. Alternative splicing is the clipping of mRNA strands by enzymes. The mRNA is clipped into segments:

Introns: non functional units which are discarded,

Exons: functional segments which are put back together to form a shorter functional piece of mRNA. The mRNA can now leave the nucleus and head to the ribosomes for translation.

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Basic signal transduction

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Second messenger pathways

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Protein synthesis: Translation

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mRNA binds to ribosomes in the cytosol. Each ribosome has 2 sub-units. The small ribosomal sub-unit binds to the mRNA, the larger sub-unit then binds on top. The mRNA is sandwiched in the middle. This mRNA and ribosome complex is now ready for translation. During translation the mRNA codons are matched with an amino acid. This process occurs with the assistance of tRNA. tRNA contains anticodons which complement the codons on the mRNA. The mRNA codons attach to their complimentary tRNA anticodons, the correct pairing mRNA and tRNA codons puts amino acids in to their correct orientation which results in the formation of a peptide chain. Once the last amino acid has been added to the chain, it is released. The now empty tRNA is released where it can now attach to another amino acid molecule. The ribosomal sub-units separate ready for a new round of protein synthesis. The mRNA is broken down by enzymes.

The peptide chain of amino acids are now sorted. The protein may have a sorting signal which means it will automatically move where it is needed> organelles or to the membrane to be exocytosed. Proteins without a signal remain in the cytosol.

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Protein synthesis: post translational modification

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The amino acid sequence that is produced during translation is the primary structure of a protein. The protein can now form different types of bonds - fold, spilt, bind to functional groups, form globular proteins. This process mainly occurs in the golgi.

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Respiration

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The process which animals extract energy from biomolecules. Animals consume oxygen and produce carbon dioxide and water as a bi-product. When more energy is ingested than required it is stored in chemical bonds.

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Main energy source for humans

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Glucose and lipids

Triglycerides

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Energy

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The capacity to do work.

Chemical

Transport

Mechanical

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Mechanical work

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Movement at a cellular level - Cells changing shape.

Movement at macroscopic level - muscle contraction

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Chemical work

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Making and breaking of chemical bonds

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Transport work

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Movement of ions, molecules and large particles through the cell membrane and through the membranes of organelles.

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Kinetic energy

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The energy of motion.

Molecules moving down a concentration gradient produce kinetic energy.

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Potential energy

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Stored energy. Potential energy is stored chemical bonds - high energy electrons.

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Activation energy

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The energy required to initiate a chemical reaction

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Enzymes

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Biological catalysts

Lower activation energy

Enzymes are NOT used in the chemical reaction.

Most enzymes are proteins.

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exergonic reactions

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ENERGY IS RELEASED. The products of the reaction have LESS stored energy than the reactants.

Give off heat

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Endergonic reactions

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Energy is stored.

Products have MORE energy than the reactants. Synthesis reactions - complex molecules made from smaller molecules.

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Coupling endergonic and exergonic reactions

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Energy released exergonically can be trapped and stored endergonically.

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ATP

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Adenosine triphosphate

Energy transfer molecule.

Energy trapped in phosphate groups.

When the bond is broken, energy is released and ATP forms ADP & phosphate.

ATP is composed of Nucleotide AMP and 3 phosphate groups.

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FAD & NADH

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Molecules that trap high energy electrons

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Metabolism

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The sum of all chemical and physical processes that take place in the body

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Catabolism and anabolism

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Catabolism - reactions release energy via the breakdown of LARGE BIOMOLECULES > energy OUT

Anabolism - reactions build large molecules using energy (ATP) > energy IN.

Catabolic reactions drive anabolic reactions.

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Glycolosis

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Aerobic pathway to ATP production.

Occurs in the cytosol.

1 x 6 carbon glucose is phosphorylated to form glucose-6-phosphate.

A series of enzymatic reactions occur

Resulting in = 2 x 3 carbon pyruvate molecules and 2 x ATP.

Glycolsis does NOT require oxygen.

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Citric acid cycle.

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Step 1. If a cell has adequate oxygen the 2 x 3 carbon pyruvate molecules formed during glycolosis move in to the mitochondrial matrix where they react with coenzyme A (CoA) to form ACETYL CoA, 1 x NADH and 1 carbon dioxide.

Step 2. The 2 carbon acyl unit now enters the citric acid cycle.

It combines with a 4 carbon oxaloacerate, this process results in a series of enzymatic reactions forming a continuous cycle. With each turn of the cycle produces 2 ATP, 3 x NADH, 1 x FADH and carbon dioxide.

These steps occur twice in every cycle producing a net yield of 8 x NADH, 2 x FADH, 2 ATP and 6 carbon dioxide

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Electron transport system

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Final step of aerobic ATP production.

The energy transfer from high energy electrons to ATP.

Requires the electron transport system which is located in the space between the 2 mitochondrial membranes. The process of ATP synthesis is called oxiative phosphorylation.

NADH & FADH release their high energy electrons and hydrogen ions to the electron transport system.

The ETS is a series of proteins which span the inner mitochondrial membrane. The high energy electrons move along the proteins and their energy is released kinetically. This energy is used to move hydrogen ions against their concentration gradient OUT of the mitochondrial matrix into the intermembrane space. The hydrogen ion concentration gradient is a source of potential energy.

Each pair of electrons released by the ETS binds to 2 hydrogen ions and an oxygen to form water. The potential energy formed in the hydrogen ion concentration gradient is released when the hydrogen ions flow back down their gradient back in to the mitochondrial matrix through a protein channel called ATP SYNTHASE. As the hydrogen move in ATP SYNTHASE harvests the released kinetic energy and synthesises the ATP molecule. Energy is transfered to the phosphate bond. A small portion of this energy is lost as heat.

For every 3 hydrogen ions that pass through ATP SYNTHASE one ATP is created.

Net yield =

30-32 ATP

6 water molecules

6 carbon dioxide.

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Aerobic metabolism net equation

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Beta oxidation

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The process of fatty acids being catabolised in the mitochondria to be converted to acetyl CoA which can then enter the citric acid cycle.

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Fatty acids can only be used for energy aerobically

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When energy is required large molecules such as glycogen can be broken down in to components for glycolosis etc..

Proteins can be broken down in to amino acids

Lipids can be broken down into glycerol and fatty acids.

Glycerol feeds into glycolosis and fatty acids are used by acetyl CoA in the citric acid cycle.

MORE ENERGY IS STORED IN FATS THAN CARBOHYDRATES AND PROTEINS.

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Membrane dynamics

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Water is the only molecule that can move freely between cells and the ECF.

Potassium ions can LEAK out and Sodium ions can LEAK in but in order for them to return to their original compartments energy is required in the form of ATP.

Homeostatic mechanisms maintain a relatively stable condition in the ECF - continual input of energy is required to maintain solute concentrations.

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Osmotic equilibrim

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Free movement of water between ICF and ECF compartments.

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Intracellular fluid

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2/3 of the bodies water volume.

Slight negative charge due to large negatively charged anions.

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Extracellular fluid

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1/3 of bodies water volume

Slight positive charge.

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Osmosis

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The movement of water across a semi permeable membrane in response to solute concentrations. In osmosis water moves from it's area of high concentration to an area of low concentration. This relates to solute concentrations as an area with HIGH amounts of non-penetrating particles has a low free water concentration. An area with LOW amounts of non-penetrating particles has a high concentration of free water. When these solutions are separated by a semi permeable membrane the free water in the solution with low solute concentration will pass across the membrane DOWN it's concentration gradient in to the solution with high non-penetrating particles (low free water). The water will dilute the solution until osmotic equilibrium has been reached.

been reached.

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Diffusion

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Net movement of molecules from an area of high concentration to an area of low concentration.

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Simple diffusion

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Passive diffusion. Molecules diffuse across the cell membrane directly. In order to do this they must be SMALL, NON-POLAR AND LIPID SOLUBLE.

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Facilitated diffusion

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Molecules diffuse across the cell membrane via transporters and channels.

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Active transport

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Requires energy input. It is the movement of substances AGAINST their concentration gradients.

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Primary active transport

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Uses ATP. e.g. sodium potassium pump.

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Secondary active transport

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Uses the kinetic energy of one molecule moving down its concentration gradient to transport another molecule against its concentration gradient.

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Omolarity

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The number of particles in a solution.

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Osmotic pressure

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The force required to prevent movement of water across a membrane. The higher the osmotic pressure the more forcefully the water is pulled across. Larger concentration gradients produce higher osmotic pressure.

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Tonicity

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Solute concentration and it's effect on water movement in and out of the cell.

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Isotonic

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Solution has the same amount of non-penetrating particles in and out of the cell. Water moves freely back and forth with no net gain or loss

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Hypotonic

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Solution has a lower concentration of particles OUTSIDE Which results in a high free water concentration outside of the cell. Water rushes down its concentration gradient IN to the cell where the free water is low. This causes the cell to swell.

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Hypertonic

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The solution has a high concentration of non-penetrating particles outside of the cell and low free water. The water rushes down its concentration gradient out of the cell causing the cell to shrink.

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Channel proteins

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Create water filled passageways that link the ICF and ECF compartments. Movement through these channels is restricted to water and ions. They are named according to the substance that can pass through. E.g. sodium ion channels.

Channels are selective. This is determined by its size and electrical charge of the ions.

Channels can be:

Open - leak channels

Gated - open in response to signals.

Chemical - ligand binding

Voltage - change in membrane potential

Mechanical - physical forces

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Carrier proteins TRANSPORTERS

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Transporters bind with particular substrates and carry them across the membrane by changing formation.

Carries small organic molecules such as glucose and amino acids.

Uniport carriers - 1 type of molecule

Symport carriers - 2 molecules in the same direction

Antiport carriers - 2 molecules in opposite directions.

Carrier proteins exhibit:

Specificity - bind to specific molecules

Competition - substrates compete for binding sites. Competitive inhibitors can slow transport.

Saturation - when all active sites are full and working at capacity.

Cell may UP-REGULATE.

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Vesicular transport

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Transport molecules that are too large for channels and carriers.

Use ATP.

Phagocytosis - membrane bound vesicle engulfs bacteria and other particles. The vesicle fuses with lysosomes where digestive enzymes destroy the contents.

Pinocytosis - membrane bound vesicle full of fluid.

Exocytosis - movement of ICF and substances out of the cell in vesicles.

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Epithelial transport

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Transport of substances entering or leaving the body and between compartments must cross a layer of epithelial cells.

Cells are joined by tight junctions.

The surface of the cell facing the lumen = apical surface.

Surface facing ECF is the basolateral membrane.

Transport from the lumen of an organ to the ECF is ABSORBTION.

Transport of material from the ECF in to the lumen (or release of substances from a cell) SECRETION.

Paracellular transport - transport between adjacent epithelial cells through leaky tight junctions.

Transcellular transport - substances cross both apical and basolateral membranes using a combination of active and passive transport.