Unit One Flashcards
The permeability barrier ,which is created by the phosolipid bilayer ,prevents the passage of …
Ions and most uncharged polar molecules
What features of a molecule will allow it to move more quickly across the bilayer
Less strongly it associates with water and the smaller the molecule
What are multi pass proteins
Proteins which polypeptide chains extend over the bilayer many times
What is the benefit of multi pass proteins forming a “protein lined pathway “
Enables hydrophilic spouted to pass through the bilayer without directly contacting the hydrophobic interior
Transporter proteins ______ to solutes and move them across the membrane
Bind
What is the reason for transporter proteins conformation to change upon binding to a solute
It allows the protein to alternatively expose the solute binding sites on either side of the membrane
Transporters and channels allow small ______ molecules to pass through the membrane
Hydrophilic
How do channels transport solutes across the membrane ?
They create a continuous open pore which spreads the entire width of the membrane
What are the two differences between transporter proteins and channel proteins ?
Transporter proteins interact more strongly with the solute than channels but channels move the solute across the membrane quicker
Aquaporins are responsible for transporting water across the membrane and what else ?
Increasing the membranes permeability to water
State the definition of active transport
Where a force of energy is required to move solutes against their concentration gradient
_____ are responsible for moving solutes required for active transport
Pumps
What is the key feature of gated proteins
Open and close under certain circumstances
What are voltage gated channels controlled by ?
Changes in ion concentration
What type of gated channel is controlled by signal molecules
Ligand gated channels
Cytoskeleton is linked with controlling what type of gated channel
Mechanic
What do the sense organs and the central nervous system consist of ?
Sense organs are the eyes and ears
Central nervous system is the spinal cord and the brain
What is the main role of a neuron ?
To receive,combine and transmit signals
Every neuron has a cell body which contains a nucleus and an axon,what is the role of an axon
Transport electrical signals from the cell body towards the distant target cells
The shorter , branching extensions which come off axons are called _____ and their role it to ?
Dendrites
Supply an enlarged surface area to receive signals from axons and other neurons
Complete
Neurons carry signals from the sense organs to …
The central nervous system where neurons signal each other through massive complicated networks which allows the Brian and Spinal cord to analyse and respond to the signals from the sensory organs
Give the definition of signal transduction ..
Process where by one type of signal is converted to another eg: extra cellular signal to a intracellular response
What is the role of receptor proteins on the surface if target cells ?
To bind to extracellular signal molecules and convert it into a intracellular response which alters the behaviour of the target cell
Is a receptor protein a signal transducer ?
Yes
Give an example of when cells response to a signal will be slow and explain why
Cell division or cell growth
As the the response requires the gene expression to change and for new proteins to be created.
The huge diversity of membrane proteins is reflected in the ….
wide variety of functions they offer
What are the two names of the sodium potassium pump ?
Na+\K+ ATPase
Na+\K+ pump
What direction does the sodium potassium pump transport sodium and potassium ?
Sodium is transported out of the cell (from the cytoplasm to the extracellular space)
Potassium is transported in to the cell (from the extracellular space into the cytoplasm )
Where does the sodium potassium pump get its energy from transport the ions ?
Hydrolysis of ATP
Explain what happens to the phosphate group after ATP has been hydrolysed ?
The phosphate group attaches to the sodium potassium pump which induces a conformational change in the pump.This change lowers the pumps affinity for sodium,allowing the ions to be expelled out of the cell.
The sodium potassium pump has a high affinity for the _____ ion inside the cell
Sodium
What are the sequence of events that follow when the pumps affinity for potassium increases ?
Potassium ions bind the the pump outside the cell which then causes the phosphate group to be released form the pump,the release of phosphate results in the protein returning to its original confirmation.This allows the potassium ions to be released into the cell.
High affinity for sodium is restored.
Give four examples of important functions of the sodium potassium pump …
1) Maintaining an osmotic balance in animal cells
2) generation of the ion gradient required for glucose symport in the small intestine
3) generation of ion gradient
4) generation and maintenance of ion gradient for resting potential in neurons
How are cell surface receptor proteins classed ?
By their transduction mechanisms
Ion channel coupled receptors are involved in rapid signalling between nerve cells and other _____________ such as muscle cells .
Electrically excitable target cells
Ion channel coupled receptors signalling is mediated by ?
Neurotransmitters
What is the impact of a neurotransmitter opening or closing the ion channel in the receptor protein ?
Briefly changes the ions permeability of the target cells plasma membrane
G-protein coupled receptors act by …..
Regulating the activity of a separate target protein which is bound to the plasma membrane,usually an enzyme or ion channel
A) What type of protein is responsible for mediating the interaction between the activated receptor and the target protein ?
(Related to protein coupled receptors)
B) the activation of a target protein can have what affect on an ion channel ?
GTP - binding protein or G-protein for short
B) changing the ion permeability
Enzyme coupled receptors either function as enzymes or ?
Associate directly with enzymes that they activate
Enzyme coupled receptors are commonly kinases proteins which do what to proteins in the target cell when ____
Phosphorylate
Activated
Signal transduction may result in the rearrangement of the …
Cytoskeleton
A) Transporters that move many solutes across the plasma membrane are called what ?
B) what is the difference between a uniport and an antiport
Coupled transporters
A pump that moves both solutes in the same direction across the membrane is a symport whereas antiports move solutes in different directions
The active transport of glucose and transport of sodium in the small intestine is based on what statement ?
A gradient of any solute can be used to drive the active transport of second molecule.The movement of the first soluble down its gradient provides the energy to power the uphill transport of the second.
In relation to the glucose symport : soduim ions moves down their gradient from a high concentration outside the cell to a low concentration inside the cell,the movement of soduim ions down their concentration gradient drives the active transport of glucose from a low concentration outside the cell to a higher concentration inside the cell
What is the electrical potential difference across every plasma membrane known as ?
Membrane potential (voltage)
In neurons,the membrane potential difference is -70mV when the cell is …..
Not transmitting signals
What is the name given to proteins that are capable of sensing and responding to light ?
Photoreceptor proteins
Name the photoreceptor protein used by archaea
Bacteriorhodopsin
State three facts about Bacteriorhodopsin
Membrane protein
Contains three polypeptide chains
Retinal molecule is found inside each polypeptide chain of the protein
What is a retinal molecule?
A light absorbing molecule
What is the function of ATP synthase ?
To convert the energy of protons moving down their concentration gradient into the synthesis of ATP
Why do Bacteriorhodopsin molecules absorb light ?
To pump protons across the membrane which,through ATP synthase,generates ATP and allows archaea to convert light energy into chemical energy
Explain the events that occur when a Bacteriorhodopsin absorbs a photon of light.
When a photon of light is absorbed,the retinal molecule changes shape,from straight to a bent form.its this change in conformation which allows Bacteriorhodopsin to pump protons across the membrane,these proteins then return through ATP synthase which results in production of ATP.
What do plants use to convert light energy into chemical energy ?
Where are these found in a plant cell ?
The photosynthetic pigment chlorophyll.Found within the chloroplast and more specifically in the grand
What is the name of the membrane surrounding the grana?
Thylakoid
How are protein photosystems formed ?
When chlorophyll binds to a protein molecule
When a molecule of chlorophyll absorbs light,one of its electrons is boosted to a higher level,as the election moves across a series of protein carriers , what happens to the hydrogen ions ?
Hydrogen ion which are pumped across the Thylakoid membrane of chloroplasts diffuse through ATP synthase,resulting in production of ATP
What is the function of the retina in the human eye ?
To convert light into electrical signals
What is the function of the light sensitive pigment found in Rod cells ?
To be sensitive to changes in light intensity therefore useful for vision in areas of dim lighting
Give the name of the cells which are particularly sensitive to specifics colours(wavelengths) of light including green,red,blue and in some animas UV?
Cone cells ; allow animals to have colour vision.
Each rod or cone cell contains visuals pigments which consist of ?
Light absorbing molecules called retinal
How is the signal receptor protein Rhodopsin formed ?
When retinal becomes bounded to a membrane protein called opsin.
What impact can different forms of opsin have on cone cells ?
The cells can be sensitive to different wavelengths of light
In rod cells,the rhodopsin absorbs a ______ range of wavelengths and a greater degree of amplification form a single ______ of light.
Wider
Photon
Nerve transmission is a wave of….
Depolarisation
Describe what depolarisation is and how it affects the resting potential of a neuron.
Depolarisation is a dramatic electrical change.
The resting potential of the neuron increases,meaning it becomes less negative
Describe how nerve transmission is stimulated ?
Stimulated when the signal molecule ,neurotransmitter ,triggers the opening of a ligand gated ion channel.
Explain what happens at the synapse in relations to events occurring in nerve transmission.
Signalling molecules called neurotransmitters act as ligands that bind to ion channel coupled receptors.As these ligands bind,the channels open which allow the positive ions to enter the cell which depolarises the neuron.The next neurons membrane potential must rise to the threshold -50mV in order for a nerve impulse to be generated.
The change in voltage triggers the opening of voltage gated Na+ channels resulting in a rapid increase of Na+ ions down their electrochemical gradient,creating an action potential.Once one voltage gate has open,like a domino effect,many more open along the axon causing the inside of the membrane to become more positive than the outiside.
Once the wave ,or domino effect,of depolarisation has passed,the channel proteins close and voltage K+ channeled open to restore the resting potential.This works as as potassium is being moved into the cell two at a time,occurring at the same time is Na+ being transported out of the cell three at a time.
Describe what the term action potential means
When the voltage change across a membrane is big enough to trigger a signal that carries information along axons.
A)Why is hyperpolarisation very important ?
B) how does it do this ?
As it assures the signal moving along an axon proceeds in one direction, ie ; doesn’t start to move back along the axon.
B) by raising the threshold
What are the three essentials factors needed for multicellular organisms to achieve coordination of communication ?
Extracellular signalling molecule
Receptors
Intracellular responses
What theory helps to explain why in a multicellular organism,different cell types may show a tissue-specific response to the same signal?
Different cell types produce specific signals which can only be detected and responded to by cells with the specific receptors
What type of signals require receptor molecules to be at the surface of the cell?
Hydrophilic
Give two examples of hydrophilic signal molecules
Neurotransmitters and peptide hormones
How can hydrophobic signal molecules pass through the plasma membrane ?
As they are lipid soluble seen as the inside of the plasma membrane (tails) are also hydrophobic.
Two important classes of hydrophobic signal molecules are ….
Steroid hormones (cortisol and testosterone ) Thyroid hormone ( thyroxine)
Where are hydrophobic signal molecules located and what are they collectively called ?
Cytoplasm and or nucleus
Nuclear receptors
When nuclear receptors are activated by hormone binding,they act as transcription regulators, explain no this occurs …
When the hormone binds to a nuclear receptor,it undergoes a large confirmation change that activates the protein which allows it to either promote or inhibit the transcription of a specific target gene depending on the signal.
What is the result of a male lacking the testosterone receptor ?
Their bodies make testosterone but their cells cannot respond to it
A) What is thyroxine involved in regulating
B) why is change in metabolic rate expressed as a percentage ?
A) Rate of metabolism
B) as each individual person starts at a different metabolic rate
Explain what happens when thyroxine binds to its receptor protein in the nucleus
When thyroxine is present the receptor protein undergoes a conformational change and no longer binds to DNA which allows the transcription of the gene for Na / K ATPase to take place , resulting in more Na / K ATPase in membrane so more energy expenditure and higher metabolic rate
Specifically what type of hormones are responsible for maintaining a constant blood glucose level ?
Peptide
What organ is resposible for detecting a rise in blood glucose and what is its response ?
Detected by cells in the pancrease and will produce insulin
Insulin plays an important role in ….
Allowing fat and skeletal muscles cells to absorb glucose from the bloodstream
Binding of insulting to its receptors triggers what response
The recruitment of GLUT4 glucose transporters to the cell membrane,these transporters allow glucose to pass across the membrane and into the cell
Type 2 diabetes is caused by …
Loss of insulin receptors
What is the purpose of p53 ?
‘Genome guardian’ a protein activated by damage to DNA
Role of maintaining a functional genome
What three processes can be brought about by p53 after recognising damage ?
Activate DNA repair proteins to repair damage to DNA …
Hault the cell cycle at G1 checkpoint to give it time to repair the DNA
Asses if damage is too severe can signal programmed cell death
Describe the process activated by Apoptosis ?
Triggered by cell death signals,DNAases and proteinase are activated.togetehr these are known as capases.
DNAases is reponsible for hydrolysing the phosodiester bonds on the backbone of Dna
Proteinase is responsible for degradation of cell death.Aptodis bodies are engulfed by phagocytes
What is an isoeletric point ?
The characteristic pH of a protein where it has not net charge ,this make it less soluble in water as its a polar solvent
What gives a protein its overall charge and what other factor contributes to a proteins charge
Combined charges of amino acids and charge can also vary depending on the pH of the solution its in
Describe isoeletric focusing
This is where a pH gradient is set up alongside polyacrylamide gel using special buffers.Each protein will travel along the gel until it reaches its isoeletric point where at this pH the protein will move on further and form a band which can be visual after staining
True of false
A protein will have a positive charge when it’s pH is below its isoeletric charge ?
True
What properties dictate how far the components of a mixture will travel on chromatography paper ?
Since chromatography paper is made with cellulose fibres which are polar,any components of the mixture which are polar will bond with the cellulose fibres.therfore the further up components of the mixture travel,the less polar they are
What factor determines the location of a protein within a cell ?
The R groups at the surface of a protein
