1

EVERYTHING

YOU NEED

TO GET A 7

IN BIOL1040 Lewis

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CONTENTS

Module 1 – Cell Function 4

Lecture 1 – Membrane Structure & Function 4

Lecture 2 - Transport 7

Lecture 3 – Cell Communication & Receptor Families 10

Module 2 - Nervous Systems 13

Lecture 1 - Neural Communication – Cells & Ions 13

Neurons 14

Nerves 15

Supporting Tissues 15

Ion Gradients 16

Lecture 2 - Action Potential Generation & Conduction 17

Overview 17

Stages of Action potential 18

Refractory Period & Local Anaesthetics 19

Conduction of Action Potentials 20

Memorisation points 20

Lecture 3 - Synaptic Transmission 21

Lecture 4 – Neuronal Organisation 24

Module 3 - Support & Movement 31

Lecture 1 - Skeletal muscle 31

Lecture 2 - Skeleton 39

Lecture 3 - Locomotion 45

Lecture 4 - Lectorial 49

Module 4 - Circulation & Gas Exchange 54

Lecture 1 – Circulation & Gas Exchange – Cardiovascular SysteM 54

Lecture 2 - Circulation & Gas Exchange – Blood Vessels 59

Lecture 3 - Blood 63

Lecture 4 – Gas Exchange 66

Lecture 5 – Gas Exchange 70

Module 5 – Endocrinology 74

Lecture 1 – Principles of Endocrine Function 74

Lecture 2 – Examples of Endocrine Function 77

Lecture 3 – Hypothalamus & Pituitary Hormones 81

Lecture 4 – Stress & the Adrenal Gland 84

MODULE 6 - Plant Form & Function 86

Lecture 1 – Photosynthesis 86

Lecture 2 - Plant Structure and Development 92

Lecture 3 – Transport in Vascular Plants 96

Lecture 4 – Plant Responses to Internal and External Signals 100

Lecture 5 – Plant Responses to Internal and External Signals (II) 104

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Lecture 6 – Plant Biotechnology 107

Module 7 – Developmental Biology 108

Lecture 1 108

Lecture 2 111

Lecture 3 114

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MODULE 1 – CELL FUNCTION

LECTURE 1 – MEMBRANE STRUCTURE & FUNCTION

Cell surrounded by “selectively permeable” membrane

Cell membrane made up of phospholipid bilayer

o Phospholipids are amphipathic (one end hydrophobic, the other hydrophilic)

Hydrophilic heads – phosphate group

Hydrophobic tails - hydrocarbon tails

Fluid mosaic model: membrane is a fluid with mosaic of proteins embedded in it

Two means of phospholipid movement in cell membrane:

o Lateral movement

Rapid side to side movement

Causes fluidity

~107 times per second

o Flip-flop movement

Phospholipid flip from one side of the bilayer to the other

Rare as hydrophilic head needs to move through hydrophobic region to which it is adverse

~ once per month

Membrane fluidity

o Fluidity depends on saturation of hydrocarbon tails

Unsaturated hydrocarbons: Kink in tail -> don’t pack as easily -> more fluid

Saturated hydrocarbons: no Kink -> pack easily -> less fluid (more viscous)

o Cholesterol has a buffering effect on fluidity – ONLY IN ANIMAL CELLS

Cold environment: prevents membrane from becoming too viscous

Warm environment: prevents membrane from becoming too fluid

Experiment Demonstrating Membrane Fluidity

o Mouse and human cell fused

o Observe that mouse and human membrane proteins mix on cell surface

o Hence, at least some membrane proteins are mobile

o Hence, membrane fluid

Not all proteins in membrane moving randomly

o Some move in specific directions – potentially driven along cytoskeletal fibres by motor proteins

o Many immobile due to attachment to cytoskeleton or extracellular matrix

Cytoskeleton – support structure inside cell

Extracellular matrix – support structure outside cell

o Localised groups of proteins carrying out similar functions exist on cell membrane

Determination of position of amino acid in transmembrane protein

o Different amino acids have different R groups

o Some R groups are hydrophilic (charged) and others are hydrophobic (uncharged)

o Hydrophobic (non-polar) region inside membrane

o Hydrophilic (polar) region outside membrane

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Transmembrane Protein Structure – Example: Bacteriorhodopsin

o N-terminus outside cell

o C-terminus inside cell

o 7 hydrophobic trans-membrane 𝛼-helicies within hydrophobic area of membrane

o Hydrophilic non-helical regions of amino acid contact water on extra-cellular and intra-cellular sides

Six major functions of membrane proteins

1. Transport

2. Enzymatic activity

3. Signal transduction

4. Cell-cell recognition

5. Intercellular joining

6. Attachment to the cytoskeleton and extracellular matrix (ECM)

Lipid bilayer is impermeable to most essential molecules and ions

o Selective permeability = able to control environment within cell

o Lipid bilayers not permeable to:

Ions

Small hydrophilic molecules (e.g. glucose)

Macromolecules (e.g. proteins & RNA)

o Macromolecules (e.g. proteins & RNA – too big)

o Lipid soluble molecules (uncharged, non-polar) can pass through easily (e.g. ethanol)

o Some permeability to small, uncharged molecules like:

Water

Oxygen

Carbon dioxide

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Passive Transport: diffusion of a substance across a membrane with no energy investment

o Down concentration gradient

o No work

o Diffusion: with time, due to random motion, molecules become equally distributed (i.e. molecules cross

membrane to eliminate concentration gradient)

Osmosis: diffusion of water through a selectively permeable membrane into another aqueous compartment containing

solute at a higher concentration

o On net water moves from area of low solute concentration to area of high solute concentration

Water actually moves in both directions, just more so in one direction

o Solutes cannot cross membrane, so to reach equilibrium water crosses instead

o Osmotica: osmotically active particles – solutes that cannot cross membrane

Tonicity: ability of solution to cause a cell to gain or lose water

Isotonic solution solute concentration of solution is the same as solute concentration inside the cell

-> no net water movement across plasma membrane

Hypertonic solution Solute concentration of solution is greater than solute concentration inside cell

-> cell loses water

Hypotonic solution Solute concentration of solution is less than solute concentration inside cell -> cell gains water

Molarity vs osmolarity

Osmolarity (osmol/l): Number of separate particles (in osmoles) per L of water

Molarity (M=mol/l): Number of moles of solute per L of water

1M NaCl = 2 osm/L (because NaCl will split up in water)

Determining Tonicity

Disregard solutes which can pass through the membrane

Relative osmolarity across the membrane is what matters (e.g. count NaCl x2)

o PPT slide confirms

o Not just relative concentration

Cells and Tonicity

Hypotonic Solution Isotonic Solution Hypertonic Solution

Animal Cell Lyse (pop)

Normal Shrivelled

Plant Cell Turgid (normal)

Flaccid Plasmolysed

Most animal cells fair best under isotonic conditions (unless has special adaptions to offset water loss / excessive

uptake)

Plant cells healthiest in hypotonic environment (osmotic pressure balanced by cell wall)

Red Blood Cell Characteristics

<300 mosmol/l hypotonic with RBC

300 mosmol/l isotonic with RBC

>300 mosmol/l hypertonic with RBC

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LECTURE 2 - TRANSPORT

Transport Protein: spans membrane, allowing SPECIFIC hydrophilic molecules to enter cell avoiding contact with lipid

bilayer.

o Transport proteins are highly specific, allowing only a specific substance (or small group of related substances) to cross

it

o Channel Protein: Type of transport protein which has a hydrophilic channel which certain molecules can pass through

– form “pores” for passage of molecules

Passive Transport // Facilitated Diffusion only

Examples of channel proteins:

Aquaporins – facilitate diffusion of water

Ion Channels – channel proteins which transport ions

Gated Ion Channels – ion channels which open/close in response to a stimulus

o Carrier Protein: Type of transport protein which functions by binding to molecule and changing shape to shuttle it

across membrane

Can do both active transport and passive transport // facilitated diffusion

Lecture slides also refer to as transporters

Passive Transport: diffusion of a substance across a membrane with no energy investment

o Down concentration gradient

o No work

Facilitated Diffusion: passive movement of molecules across plasma membrane via transport protein (

o Form of passive transport – no energy investment & molecules move down concentration gradiant

o Assist in diffusion process

Active Transport: pumping a solute across a membrane against is concentration gradient

o Requires energy input (i.e. ATP input)

o Exclusive to Carrier Proteins

channel proteins cannot do active transport (as channel proteins are basically just holes)

o Enables cells to maintain internal concentration of solutes that is different from concentrations in its surroundings

o Electrogenic Pump: transport protein that generates voltage across a membrane

Na+/K+-ATPase // sodium-potassium pump – main Electrogenic pump in animals

Pumps 3x Na+ out of cell for every 2x K+ moved into cell

Proton Pump – main Electrogenic pump in plants, fungi & bacteria

Pumps H+ out of the cell

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Cotransport: active transport of a solute indirectly drives transport of another solute

o A cotransporter can utilize the “downhill” diffusion of a solute to drive the “uphill” transport of a second

substance against is concentration gradient

o Example: Sucrose-H+ cotransporter

plants use gradient of hydrogen ions to drive active cotransport of nutrients into cell

H+ diffuses down concentration gradient via cotransporter protein

For every H+ that moves through the cotransporter protein, a sucrose molecule is driven up its

concentration gradient into the cell

Uses the potential energy of the concentration difference to drive transport

While not strictly a part of active transport: the H+ concentration gradient is maintained via a Proton

pump pushing H+ out of the cell (using ATP)

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Endocytosis and Exocytosis

o Results in bulk transport across plasma membrane

o Endocytosis: bulk transport into cell - cell membrane forms vesicle

around packet of particles allowing them to enter cell

o Exocytosis: bulk transport out of cell – vesicle formed around packet

of particles contacts cellular membrane and opens to the outside of

the cell, allowing particles to exit

Three types of Endocytosis:

o Phagocytosis - “cellular eating”

Cell engulfs food particle by extending pseudopodia around it and packing it within a

membranous sac called a food vacuole. This food vacuole then fuses with a lysosome for

digestion

Pseudopodia = temporary membrane protrusions

o Pinocytosis – “cellular drinking”

Cell continually “gulps” droplets of extracellular fluid into tiny vesicles formed by infolding of

plasma membrane

Cell obtains solutes dissolved in droplets

Nonspecific – takes in any solutes that happen to be outside the cell

Parts of plasma membrane that form vesicles often coated in “coat protein” on intracellular side

– hence called coated pits

o Receptor Mediated Endocytosis (considered a form of pinocytosis)

Receptors on extracellular side bind to specific molecule that is wanted

Receptor proteins cluster in coated pits

Pinocytosis proceeds, bringing specific molecules bound to receptors inside cell

Also brings some other molecules present in ECF, but high concentration of target molecule

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LECTURE 3 – CELL COMMUNICATION & RECEPTOR FAMILIES

Basic types of chemical signalling (more types in Module 5):

Long Distance Signalling

Endocrine Signalling Endocrine cell secretes hormones which diffuse into blood. Hormones circulate and trigger responses in target cells anywhere in body.

Local Signalling

Synaptic Signalling

Nerve cell releases neurotransmitter into synaptic cleft, stimulating target cell (e.g. muscle / nerve cell)

Can also be considered long-distance on a macroscale

Paracrine Signalling Cells secrete local regulator molecules which diffuse through ECF triggering response in neighbouring cells

Three stages of cell signalling:

1. Reception Signalling molecule binds to a target cells receptor

Receptor located on cell surface or within cell

2. Transduction Binding of signalling molecule changes receptor in some way, initiating transduction (occurs within cytoplasm)

Transduction converts incoming signal to a form that can bring about a specific cellular response

signal transduction pathway = steps of transduction

relay molecules = molecular intermediaries of transduction pathway

3. Response Transduction pathway brings about specific cellular response

Broadly two classes of receptors:

Cell-surface Receptors Intracellular Receptors

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Ligand hydrophilic so cannot enter cell Signalling molecule hydrophobic so enters cell

Ligand secreted by exocytosis from secretory cells Ligand diffuses out across membrane of secretory cells

Ligand travel freely in bloodstream Ligand binds to transport proteins that keep them soluble in blood

Ligand cannot pass through cellular membrane (as lipid-insoluble), so act on receptors on cell surface

Ligand unbinds from transport proteins and diffuses directly into target cells, binding to intracellular receptors in cytoplasm or nucleus

Induce signal transduction pathway which ultimately results in:

cytoplasmic response

sometimes alteration of gene transcription

Intracellular receptors perform the entire task of transducing a signal within target cell, directly resulting in:

changes in gene transcription

i.e. no signal transduction pathway with relay molecules, etc

Receptors usually initially located in cytosol. Binding of hormone to receptor creates a hormone-receptor complex which then moves to the nucleus.

Receptor types:

Cell-surface Receptors

Ion Channel Receptors Na+ channel opened by ligand – causing FAST neurotransmission Further in module 2

G Protein-coupled Receptors

7 transmembrane-spanning regions Further below

Tyrosine kinase linked receptors

metabolism, cell growth, cell reproduction e.g. insulin receptors Further below

Intracellular Receptors

Intracellular Receptors e.g. steroid receptors

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G Protein-Coupled Receptors (GPCRs)

o 7 Transmembrane regions

o G protein bound to the energy-rich molecule GTP

o Biologically critical

~1000 such receptors in human genome

~50% of drugs target such receptors

o Can accept activation from a wide range of stimuli (light,

ions, odorants, neurotransmitters, hormones, proteins)

o Control activity of enzymes, ion channels, intracellular signal

transduction pathways, etc

o G Protein-Coupled Receptors interact with G Proteins

All G proteins that are associated with GPCRs are

heterotrimeric (made up of three different proteins)

G Protein-Coupled Receptor Function – EX Adrenaline

o Adrenaline is the first messenger (signalling molecule). It

binds to G-protein-linked receptor, changing conformation of the receptor

o Change of receptor conformation causes G protein to bind to G-protein-linked receptor

o GDP originally bound to G protein. When receptor binds to G protein the GDP is exchanged for a GTP

o G protein + GTP + GPCR system facilitates the activation of enzyme adenylyl cyclase which causes the conversion

of ATP into cAMP (the second messenger)

o Second messenger cAMP triggers cellular response by acting on another protein (e.g. Protein kinase A)

o In this case, this leads to cellular response such as relaxation of muscles in airways

o N.B. changes in enzyme and G protein are only temporary

G Protein also functions as GTPase enzyme

hydrolyses GTP back to GDP + inorganic phosphate group

hence resets system

Signalling Amplification – G Coupled Protein Receptors

o Activation of receptor can cause production of very large amounts of second messenger

o Hence, small signal can illicit big response

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Tyrosine kinase linked receptors

o one transmembrane domain

o e.g. insulin receptors, growth factor receptors

o when signalling molecule binds to receptor it triggers a phosphorylation cascade ultimately leading to the

phosphorylation of a final protein. The phosphorylation of this final protein my activate it or inactivate it.

Phosphorylation = adding a phosphate group to the OH group in the amino acid

Amino acids Tyrosine, Threonine and Serine can be phosphorylated due to action of Tyrosine kinase

linked receptors

o The phosphorylation of final protein may activate it or inactivate it by:

changing its conformation

Changing its cellular location

Changing its protein-protein interactions

o EXAMPLE: Insulin Receptors

Insulin binds across two Tyrosine kinase linked receptors insulin receptors forming a dimer

Causes phosphorylation of tyrosine on receptor tails by transferring a phosphate group from ATP to

each tail

Leads to phosphorylation cascade (long chain of molecules phosphorylated)

No need to know any of the details of this phosphorylation cascade

Phosphorylation cascade causes glucose transporters to be taken to the membrane

Glucose can then move into the cell

Also activates glycogen synthase, converting glucose to glycogen

In this was insulin causes glucose uptake

Steroid Hormone Receptors (Intracellular)

o Steroid enters cell through cell membrane (as hydrophobic)

o Binds to receptor in ICF forming hormone-receptor complex

o hormone-receptor travels to nucleus where it activates or inactivates genes

o Hence causes production or inhibition of production of new proteins

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MODULE 2 - NERVOUS SYSTEMS

LECTURE 1 - NEURAL COMMUNICATION – CELLS & IONS

Three stages of information processing

o Sensory Input

peripheral nervous system

sampling raw sensory information

o Integration

central nervous system

determining what action should be taken in light of sensory information

o Motor output

Peripheral nervous system

taking action (e.g. flex muscle)

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NEURONS

Presynaptic Neuron transmits signal to Postsynaptic Neuron

Dendrites - Receive signals

o Many per neuron, receives input from many other neurons

Cell body (Soma) contains normal cell components (e.g. Nucleus containing DNA)

o Signals collected from dendrites aggregated here

Axon hillock – where action potentials are generated

o Base of axon (connection between axon and cell body)

Axon – sends signals

o One per neuron

o Wrapped in myelin sheath – acts as an insulator, critical for efficient neural communication

Prevents leakage of depolarisation wave

Boosts conduction speed 100x

o Divides into many branches at end, allowing it to transmit signals to many neurons

Axon Terminal // Terminal Boutons

o Forms synapses with the dendrites of another neuron

o Secretes neurotransmitter when action potential reaches them

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Three broad types of neurons:

o Sensory Neuron

Regular level of axon branching & dendrite

count

cell body located along axon

Transmit information from sensory organs to

brain

o Interneuron

dense & extensive dendrite structure – collect lots

of information

highly branched axon – sends information to lots

of other neurons

Integrate sensory input

Majority of neurons in the brain are

interneurons

o Motor neuron

Transmit information to muscle cells

Lots of dendrites – receive information from many locations

Regular level of axon branching

NERVES

Nerves = bundle of axons + supporting structures

o axons – transmit signals

o Connective tissue provides support

o Blood vessels supply nutrients to nerve & remove waste

SUPPORTING TISSUES

Galial Cells = supporting tissue in nerves & brain

o Vital for structural integrity & normal function

o 10-50x more glia than neurons in brain

Two types of Galial Cells: Astrocytes & Oligodendrocytes // Schwann cells

o Astrocytes

In CNS Provide structural support Regulate ECF ion & neurotransmitter concentrations Form blood-brain barrier

o Protective layer between blood vessels &

neurons preventing toxins from entering

neurons

o Two components of blood-brain barrier – restrict CNS access to only very lipophilic, small

molecules

1. Endothelium cells of brain blood vessels have very tight junctions, significantly

limiting the molecules that can exit the vessel between endothelium cells

2. Astrocytes surround blood vessel, so molecules have to pass through astrocytes to

enter CNS

o Molecules that need to access CNS have specific transporters which facilitate

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o Oligodendrocytes // Schwann cells

Oligodendrocytes = CNS

Schwann cells = PNS

Their lipid membranes act as insulators

Form myelin sheaths around axons

Myelination = speeds up action potential travel in axons

When insulator defective:

Action potentials may not be reliably transmitted down axon (i.e. may dissipate)

Impulses travel more slowly

Cross talk may occur between axons/neurons (e.g. AP may erroneously enter axon in

proximity)

myelinated sheaths are in white matter

ION GRADIENTS

o There are ion gradients across all cell membranes (not just neural cells)

o Resting membrane potential of neural cells = −70mV to −90mV

o Due to gradients of Na+ and K+ ions across membrane

o Nothing to do with voltage-gated ion channels

o Negative resting membrane potential chiefly maintained by Na+/K+-ATPase

Pumps 3x Na+ out of cell for every 2x K+ in

Hence more positive charge exiting cell than coming in

ATP energy investment -> Ions pushed against concentration gradients

o K+ channels: many open - allow K+ to exit cell down concentration gradient, increasing negativity

o Na+ channels: vast majority closed – Na+ cannot enter, maintain internal negativity

o Cl- channels: vast majority closed – Cl- cannot enter

o Build-up of negative charge in neuron limited because the negative charges exert an attractive force on K+ ions

preventing them from exiting the cell at some point (electrical gradient)

So the resting membrane potential is reached when the K+ electric gradient and the K+ chemical

gradient reach equilibrium

At resting potential:

K+ Na+ Cl- Large anions (A-)

Outside Concentration (mM) 5 150 120 -

Inside Concentration (mM) 140 15 10 100

o All cells have a membrane potential

o Rapid changes of membrane potential occur in excitable cells like:

Neurons

Myocytes

Pancreatic beta cells

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