PHYL 2066 Module 1 and 2

What are the three types of cell compartments?

The nucleus, cytoplasm and the plasma membrane.

What are the functions of the nucleus?

It is the control centre for the cell, it contains DNA (genetic material, and blueprint for function of the cell)

What are ribosomes?

Ribosomes are required for protein synthesis.

What are the two types of ribosomes?

There are bound, and free ribosomes. Bound ribosomes are bound to the endoplasmic reticulum, they function wiht an organelle, outside of the cell. Free ribosomes are suspended in the cytosol, and the proteins function in the cytosol.

What makes up the cytoplasm?

Organelles, which are cellular organs, cytosol, and the cytoskeleton

What is the endoplasmic reticulum?

They are the extensive network of membrane joining the nucleus, and there are two types, smooth and rough.

What is the purpose of the Rough endoplasmic reticulum?

It’s rough because its covered in ribosomes, and proteins are made in the rough ER and a ‘membrane factory’

What is the function of the smooth endoplasmic reticulum?

It packages and transports proteins to golgi complex, in transport vesicles,

What is the Golgi complex?

The Golgi complex is a series of curved sacs, which receives proteins from the endoplasmic reticulum, for further processing, it modify and ships out proteins. To outside the celll, to various other membranes or organelles.

What are lysosomes and peroxisomes?

They are membrane vesicles that contain enzymes that bud off of the Golgi complex. Lysosomes breakdown organic materials inside the cell (bacteria or old organelles), and peroxisomes degrade toxic molecules inside the cell.

What is the mitochondria?

the mitochondria is the powerplant of the cell, it converts food energy to cellular energy (ATP)

How is adenosine triphosphate utilised?

The chemical bond between, the last two phosphate groups is broken, and energy is released with the terminal phosphate is removed.

What are three ways of using ATP?

Synthesis of new compounds, transporting molecules across membranes and mechanical work.

What are the functions of the plasma membrane?

It forms a physical barrier (ECF from ICF), it has selective permeability (it determines what molecules pass in and out of the cell), it is important for creating an electrochemical gradient, and it receives and interprets signals from other cells.

What is the structure of the plasma membrane?

it is a lipid bilayer, which means two layers of phospholipids. with each phospholipid having a head and two tails. The head is hydrophilic, and the tails are hydrophobic

What are membrane proteins?

Membrane proteins are proteins that are imbedded in cell wall, and can change shape to allow different molecules in and out of the cell.

What are the types of plasma membrane receptors?

Chemically gated channels, receptor enzymes and G-protein coupled receptors.

What are the types of extracellular messengers?

Paracrine secretion, neurotransmitter secretion, Hormonal secretion, Neurohormone secretion.

What are Paracrine secretions?

They are short range chemical messengers, which only effect neighbouring cells in immediate environment.

What are neurotransmitters?

They are short range chemical messengers secreted by neuron’s in response to an action potential. They will act locally on neurons, muscles or glands.

What are hormones?

They are long-range chemical messengers, secreted into the blood by endocrine glands.

What are neurohormones?

Neurohormones are hormones released into the blood by neurons. Thye are distributed by blood to the far away target cells.

How do extracellular receptors work?

A target cell will detect a signal when the extracellular messenger binds to a receptor. Extracellular messengers have a specific shape that will only bind to a specific receptor. The receptor cell will change shape and will activate when the messenger binds to it.

Where can cellular receptors be found?

They can be found in the cell membrane, or inside of the cell itself.

What are the three mechanisms an extracellular messenger can have an affect on a cell, and what is the most common way for receptors to bind?

The most common way for an extracellular messenger to bind, is to receptors in the cell membrane. When these messengers bind, they cause an effect through three mechanisms, these are: opening/closing a chemically gated receptor channel, activating receptor enzymes or activating a second messenger pathway through a G-protein coupled receptor.

How do extracellular messengers affect chemically gated receptor channels?

The binding of the messenger to a chemically gated channel will cause the channel to open or close. This will change the movement of ions that cross the plasma membrane.

What is signal transduction?

Signal transduction is when a signal outside of a cell is converted to a signal inside of the cell. This process usually involves protein kinases, which are enzymes that transfer phosphates from ATP to other proteins, and those proteins may transfer the phosphate to other proteins again.

How do receptor enzymes work?

When the extracellular messenger binds to the receptor enzyme in the plasma membrane, it causes the receptor enzyme to be activated, which will they activate other proteins may transfer kinases. The last kinase in the cascade alters the designated protein which in turn will cause a cellular response.

How do G protein coupled receptors work?

The receptor is linked to a G protein. The binding of the messenger causes the G protein to activate. The G protein will travel along the plasma membrane until it stimulates an effector protein, which will produce a second messenger. Which in turn activates a cascade of protein kinases, which will alter the designated protein leading to a cellular response.

What is an intracellular receptor?

An intracellular receptor is found inside of the cytoplasm, or nucleus. They are messengers that bind to intracellular receptors produce an effector protein by activating genes.

How does an intracellular receptor work?

Once the messenger binds to a receptor (usually very small and will penetrate the plasma membrane, and a hormone(maybe)), is will then penetrate the nucleus and bind to a specific region of DNA. Once bound to the DNA, it will activate a specific gene, will then transcribe an mRNA, a new protein will then be produced, which carries out the desired response.

What are the 7 major ways in which the endocrine and nervous system.

1. The way they’re linked (wired vs wireless)

2. Type of chemical messenger (neuron transmitters vs hormones)

3. Distance of action

4. Specificity of action (some cells responding but not others)

5. Speed of response

6. Duration of action

7. Major function (fast, precise responses vs long duration activities)

What do transport proteins do?

Any molecule that can’t cross the plasma membrane can use transport proteins to cross the membrane.

What is passive transport?

Passive transport doesnt require cellular energy, and will go down the concentration gradient.

What is active transport?

It requires cellular energy, and goes against the concentration gradient.

What do channels do?

Hydrophilic tunnel through the plasma membrane, which will transport small molecules such as ions. These channels can be gated which will open or close in response to a stimulus.

What are carrier proteins?

Carrier proteins will change their shape to transport solutes across the membrane. And carriers are for larger, hydrophilic molecules, which are slower and always open to one side of the membrane.

What is the difference between primary and secondary active transport?

Primary active transport directly uses ATP, whereas secondary will indirectly use ATP.

What is primary active transport?

The terminal phosphate group in ATP is transferred to the carrier, called phosphorylation, and it will cause the carrier to change shape. (Sodium, potassium pump)

What is secondary transport?

Secondary transport is the movement of a solute down its concentration gradient, which provides a driving force for the movement of a second solute against its concentration gradient. Symport, is the same direction, and antiport is in opposite directions.

What is vesicular transport?

Vesicular transport is the transport of materials between ICF and ECF within vesicles. (Fluid filled sacs enclosed by a membrane) and it requires ATP

What are the two types of vesicular transport?

Endo and exocytosis. Transport into and out of the cell respectively.

What are the types of membrane transport?

Passive and active

What are the types of passive transport?

Diffusion, osmosis and facilitated diffusion

What are the types of Active transport

Primary, secondary, and vesicular transport

What is diffusion?

The movement of molecules from an area of high concentration to low concentration

What is a concentration gradient?

The difference if concentration across two areas, the greater the difference, the greater the concentration gradient.

What is the diffusion rate controlled by?

It is controlled by the size of the concentration gradient, and the membrane surface area, the size of the molecule and the diffusion distance.

What is osmosis?

Osmosis is the diffusion of water across a membrane. This can also be the movement of water from an area of low solute concentration to high solute concentration.

What is tonicity?

Tonicity is the ability of a solution to change the shape (tone) of a cell by changing the internal water volume via osmosis.

What is a synapse?

A synapse is a junction that allows the information to transfer from one cell to another. It occurs between a pre and post synaptic neuron. One being the neuron before, and the one after the junction. And synapses can also occur between a neuron and an effector cell.

What are the two types of Synapses?

Electrical and chemical junctions. Electrical are rare, between smooth and cardiac muscle. Chemical junctions utilise a chemical messenger, which diffuses across the junction.

How does a chemical synapse work?

An electrical signal (action potential) is converted to a chemical signal (neurotransmitter) and back to an electrical signal (Graded potential). The action potential depolarises the axon terminal. This causes voltage gate to open, which then makes synaptic vesicles to fuse with plasma membrane of the terminal bud. A neurotransmitter is then released into the synaptic cleft. The neurotransmitters will then activate receptors on the postsynaptic neuron to open certain channels.

What are the two types of neurotransmitter responses?

Excitatory and inhibitory

What do excitatory neurotransmitters do?

Excitatory neurotransmitters, such as acetylcholine or glutamine, cause an excitatory post synaptic potential, EPSP, which is depolarising, which is caused by chemically gated channels to release Na+.

What do inhibitory neurotransmitters do?

Neurotransmitters, such as glycine or GABA, cause an inhibitory post synaptic potential, IPSP, which causes hyper polarisation, opening chemically gated, cl- and k+ channels, to make the potential more negative.

What are temporal and spatial summations?

A summation is the addition of all EPSP and IPSP that a cell receives, and it determines whether or not an action potential will fire or not. Temporal summation, is when two of the same EPSP fire in close enough span of time to summate to an AP, whereas special summation is where two types of EPSP fire and summate to an AP.

What is convergence?

Convergence is where many inputs converge onto on post synaptic neuron, and divergence is when one presynaptic neuron diverge to multiple post synaptic neurons.

What is a resting membrane potential?

It is the voltage of a cell body, caused by the separation of charades across a plasma membrane. (The outside of the cell is positive compared to the inside.)

What causes membrane potential to change?

The concentration, and ion gradient. The concentration gradient will cause ions to move based on the concentration on either side of the plasma membrane, and the ion gradient will cause ions to move based on the charge on either sides of the plasma membrane.

What is the movement of Potassium ions in a cell?

The concentration of potassium ions is greater inside the cell, therefore, they move outside the cell. As a result of this, more anions are left inside the cell, causing the positive potassium ions to move inside the cell. The equilibrium potential is -90 mV for potassium.

What is the movement of the sodium ions?

Sodium ions have a higher concentration outside of the cell, so they move into the cell because of the concentration gradient, which leaves behind cl- ions, causing the Na ions to move back out of the cell. The equilibrium potential for sodium is +60 mV

How do potassium and sodium work together?

The movements of both ions, cause the membrane to have a potential, however if both ions are constantly moving down their respective ion gradients, they would run out of the potential to move, so there is a sodium pump in place to ensure there is always a concentration gradient to move to. It pumps out 3 sodium for every 2 potassium. using primary active transport.

What can change the membrane potentials?

Changing the number of open channels, and changing the membrane permeability for Na and K.

What is a graded potential?

A graded potential is an input potential, which varies in strength.

What is depolarisation?

Depolarisation is an increase in the cell voltage (decreasing in negativity, getting closer to 0) by increasing the number of positive ions (Na+)

What is hyper polarisation?

Hyper polarisation, is the increase in negative charges, either K+ exiting, or Cl- ions entering.

What is repolarisation?

repolarisation is when, the channels close, and the membrane potential returns to its resting value.

How does a grading potential work?

When a triggering event opens an ion channel, it causes positive ions to flow into the cell, which is depolarisation. The depolarisation will then spread throughout the cell, dissipating.

What is an Action Potential?

An action potential is a brief reversal of a cell’s membrane potential. It is used to send long distance signals. It only occurs in muscle cells. They do not decay overtime.

What triggers an action potential?

An action potential occurs when a voltage threshold is reached, and triggers a voltage gated Na+ channel to open. It will allow rapid opening of a voltage gate to let heaps of Na flow in. It will then snap shut with another threshold which will close the inactivation gate.

What is a refractory period?

A refractory period is where the cell is unresponsive to further stimulation.

What is the purpose of a refractory period?

It ensure the one way propagation of the action potential, and the maximum frequency of action potentials over a given period.

What is the point of mylentation?

Mylenation insultates the axon from the ECF.

What is the sarcolemma?

The Sarcolemma is the plasma membrane which warps around the muscle fibres.

What is the sarcoplasmic retinaculum?

It is the smooth endoplasmic retinaculum in muscle fibres.

What does the Sarcoplasmic reticulum do?

It surrounds each myofirbil like a mesh sleeve and it stores Calcium ions, which is released during a muscle contraction.

What are the T tubules?

Transverse tubules are part of the sarcolemma, which carry the action potentials between the sarcoplamis reticulum, and cause release of Calcium ions.

What is a Myofibril?

It is a specialised intracellular structure in a muscle fibre. They are the units that contract in muscles. They are organised into sarcomeres.

What are Myofilaments?

There are three types of myofilaments, thick, thin and elastic.

What are thick filaments?

Thick filaments are made of myosin, each myosin has two heads and a tail. The myosin heads have two attachment sites, an actin site, and an ATP attachment site.

What are thin filaments?

Thin filaments are Made of three parts: actin, troponin and tropomyosin.

What are actin molecules?

Actin are sphere-like molecules with sites for myosin attachments.

What are troponin molecules?

They bind to actin and tropomyosin to stabilise thin filaments. They also have binding sites for Ca2+ ions.

What is tropomyosin?

Tropomyosin are rope like proteins that block myosin binding sites in relaxed muscle.

How do thin and thick filaments work together?

When a muscle’s cell receives an action potential to move, Ca2+ ions are released into the sarcomere. Calcium (Ca2+) ions attach to the troponin, which is attached to the tropomyosin, rope like structures which cover the actin’s binding sites. When the Ca ions attach to troponin, they pull the tropomyosin away, exposing the actin’s binding sites and allowing myosin’s head to bind. When ATP attaches to myosin’s second head, it moves the thin filament and moves it in towards the middle of the myosin.

Explain the excitation-contraction coupling.

The action potential arrives at the motor neuron axon terminal. ACh is released into neuromuscular junction, which binds to receptors on sarcolemma. The ACh receptor gated receptor channel for cation flow opens, which depolarises the local membrane. And if the graded potential reaches the threshold, it will trigger an action potential in sarcolemma. The AP travels across the membrane, and along T Tubules. Which in turn causes the sarcolemma reticulum to release Ca2+ ions. Which then causes the power stroke cycle.

What is a twitch summation?

When two APs are received far enough apart, the contractile activity will be two separate contractions. When they are closer together, they will excite a greater contraction.

What is tetanus?

Tetanus is smooth, sustained contraction at maximal strength.

What is a motor unit?

A Motor unit is a motor neuron and the fibres it innervates. (They contract simultaneously)

Explain the term Motor unit recuirment

It means the more motor units that are stimulated, the stronger the response given.

What are the three types of muscle fibres?

slow-oxidative (type 1), Fast-oxidative (type 2), and Fast-glycolytic (type 2 x) fibres.

What is a membrane potential?

The cell’s voltage

What makes a membrane’s potential?

The movements of calcium and potassium ions through the membrane (K+ out, Na+ in). They move due to the concentration gradient, via leakage channels. (K+ has more leakage channels than Na+)

What is the sodium potassium pump?

The sodium potassium pump is primary active transport that pumps sodium and potassium against their concentration gradients to ensure that there will always be ion gradients available for resting membrane potential. The pump transports 3 Na+ for every 2 K+

What can change the membrane potential?

Changing the membrane permeability, and changing the number of open channels.

What is a graded potential?

A graded potential is short distance signalling, which creates small changes in the cells resting potential, in response to input signals for presynaptic neuron.

What is depolarisation?

When the membrane potential becomes less negative (closer to 0). Via opening ion channels, Na+ enters