unit 2

Question 1

Cell theory

Answer 1

• animals and plant made of eukaryotic
• cells can change into other cells later on
• cell represents the smallest unit which performs physiological processes
• every cell has its own homeostasis

Question 2

how is physiological processes performed and homeostasis maintained

Answer 2

• body uses biomolecules such as proteins, lipids and sugars to produce energy to perform..

Question 3

cell metabolism

Answer 3

• chemical process converts carbs, fats, proteins into energy for cellular functions.

Question 4

what is energy needed for from cell metabolism

Answer 4

• muscle contraction
• membrane transport
• synthesis of enzymes, hormomes.

Question 5

ATP

Answer 5

• unit of currency transfers enegry in living cells.
• ATP hydrolysed to form ADP

Question 6

plasma membrane -physical barrier outside n inside of cell

Answer 6

• barrier prevents general ingress, preserves cells status
• controls movement of desirable material into a cell
• excretes waste material out of the cell
• communicates with whats outside of the cell, has various receptors that bind with sepcific chemical messengers changing activity of cell
• makes physical connections

Question 7

Transporters

Answer 7

• carrier proteins specialized membrane - soanning proteins that assist in movement of ions, peptides, small molcules, lipids and macromolecul;es acrosss biological membrane.
• passive transport, no energy as transprort follows concentration gradient.

Question 8

diffusion

Answer 8

random movement of membrane permeable substance across membrane down the conc gradient from an area of high concentration to an area of low concentration.

Question 9

facilliated transport

Answer 9

the movement of a membrane impermeable substance across the membrane via transporters down the concentration gradient

Question 10

Active transport

Answer 10

requires ATP to transport substaces into a cell

Question 11

primary active transport

Answer 11

• transport protein containd an ATPase which hydrolyses ATP to generate energy for transport. e.g ion pump

Question 12

Secondary active transport

Answer 12

no direct coupling of ATP with transporter, useses electrochemical potential between cell and fluid. pups ions out of the cell by primary active transport
- creates electro chemical potential and ATP is still consumed by mode of transport

Question 13

Concentration gradient affects diffusion across a membrane

Answer 13

if molecule can pass through a membrane there is a natural flow from areas of high con to an area of low conc

Question 14

surface area

Answer 14

SA of membrane increases the rate of diffusion increases, more space for molecules to diffuse across the membrane.

Question 15

molecular size

Answer 15

smaller the molecule the easier it can move through a membrane by passive diffusion

Question 16

state of ionisation

Answer 16

most drugs are weak acid bases which exist in ionised and unioinised form depending on the pH
- it is the lipid - soluble, non - ioinised from of the drug that readily diffuses across the membrane.

Question 17

cytoskeleton

Answer 17

• cells structural suppourt
• influences shape, strength and flexibility of the cell and movement of the cell
• made up of proteins such as actin and tubulin
• cells such as flagella and cilia have extracellular structures built around core of cytoskeletal proteins

Question 18

ribosomes

Answer 18

• 25nm
• small and large ribosomal sub - unit which comes together for protein synthesis where mRNA is translated to protein.
• manufacturers proteins destined for the cytosol.

Question 19

endoplasmic reticulum

Answer 19

• network of membranes with responsibilities for the synthesis and storage of proteins, carbohydrate and lipids,
• transportation of molecules within its enclosure and the detoxification of dangerous materia.

Question 20

rough endoplasmic reticulum

Answer 20

• Receives newly manufactured protein chains from ribosomes, and secondary / tertiary structures are achieved
• Modification of proteins into glycoproteins
  -Packaging of proteins / glycoproteins into transport vesicles, to be sent to Golgi apparatus

Question 21

Smooth endoplasmic reticulum

Answer 21

-Synthesis of phospholipids and cholesterol for endoplasmic reticulum, nuclear membrane, Golgi apparatus
-Synthesis of steroid hormones,
- Synthesis & storage of (tri)glycerides and glycogen
- Detoxification of drugs and alcohol

Question 22

lysomes

Answer 22

• roving vesicles that engulf and digest their targets, acting as the “stomach” of the cell.
• clear damaged organelles, invading bacteria / viruses or other organic waste

Question 23

peroximes

Answer 23

• group of digestive vesicles. - responsible for the digestion of large fatty acids and are the site of β-oxidation: larger numbers of peroxisomes are present in cells involved in lipid metabolism (e.g. liver cells). The reactive oxygen species hydrogen peroxide is generated during fatty acid breakdown.
• damaging material is kept safe inside the peroxisome and further degraded to water and oxygen before release.

Question 24

Mitochondria

Answer 24

• organelles responsible for energy generation, and as such their numbers are higher in cells with a large energy requirement.

Question 25

nucleus

Answer 25

• vast majority of a cells DNA
  -nucleus is surrounded by a double membrane called the nuclear envelope,
  -dotted with pores that allow ions and small molecules (such as RNA) to pass, but keeps larger molecules outside and the DNA inside. - -Almost all cells have a nucleus, but one notable exception is red bloods cells, which do not have a nucleus

Question 26

prokaryotic cells

Answer 26

-differ from eukaryotes as they have no membrane bound organelles.
- all DNA, proteins, nutrients, ions and non-membrane bound organelles are held within a single cytoplasm inside the prokaryotic cell membrane

Question 27

mitosis

Answer 27

• produces identical duaghter cells

Question 28

process

Answer 28

interphase
prophase
metaphase
anaphase
telophase
cytokinesis

Question 29

Sickle cell anaemia

Answer 29

• affects 1 in 2000 live births in the UK.
• a genetic disorder which causes red blood cells to be more rigid and mis-shaped.
• makes it harder for them to move through smaller blood vessels. This causes painful ischemia (restricted blood flow) and can also result in organ damage. Sickle cell anaemia is caused by a single substitution mutation in the HBB haemoglobin gene

Question 30

meiosis

Answer 30

daughter cells are not identical
diploid –> haploid to form gametes which contain half the DNA of the parent cells and then in sexual reproduction a sperm and an ovum combine to form a new diploid cell, which grows to become a new organism.

Question 31

recessive inherited disorder

Answer 31

• disorder is recessive, means that a healthy version of the gene will make up for the faulty copy
• if you have one good and one faulty copy of the gene you will be a carrier of the faulty gene but you won’t have the disorder yourself.

Question 32

endocrine factors

Answer 32

Released from cells and enter circulation to “act at a distance” e.g. Hormones, cytokines

Question 33

Paracrine factors

Answer 33

Released from cells and have local (nearby) site of action e.g. Neurotransmitters,

Question 34

Autocrine factors:

Answer 34

Released from cells and act on the same cells e.g. hormones

Question 35

membrane potential

Answer 35

A potential difference exists across the cell membrane because ions are distributed unevenly outside and inside cells.
-a high concentration of sodium (Na+) and chloride (Cl-) ions outside the cell (extracellular),
- and a high concentration of potassium (K+) and various anions inside the cell (intracellular), creating an electrochemical gradient across the cellular plasma membrane.
- the membrane acts as a barrier as the ions want to be equally spread across both sides

Question 36

resting membrane potential

Answer 36

Cells vary in their resting membrane potential.
around -70mV.

Question 37

change

Answer 37

• change in membrane potential happens because the cell becomes more permeable to particular ions, and so those ions are able to move across the membrane.

Question 38

Equilibrium potential

Answer 38

-potassium (EK) is approximately80mV, -equilibrium potential for sodium (ENa) is approximately +60mV. Remember the resting membrane potential of a neuron is -70mV, which is quite close to the equilibrium potential of potassium. This is because the membrane is more “leaky” to potassium than it is for sodium, and so the resting membrane potential is quite close to EK. If the membrane suddenly became more permeable to sodium, the membrane potential would rise closer to ENa.

Question 39

facilitated diffusion.

Answer 39

ion channel opens, it allows ions to flow down their concentration gradient. e.g with sodium ion concentrations being high outside the cell, these ions want to move into the cell, but they can’t as they aren’t able to freely pass through the membrane. If a sodium ion channel opens, this provides a path for the sodium ions to cross the membrane.

Question 40

Ligand-gated ion channels

Answer 40

binding site on them where particular specific substances (ligands) can attach to the ion channel and cause it to open. These could be endogenous ligands, such as neurotransmitters, or they could be drugs.

Question 41

Voltage-gated ion channels

Answer 41

sensitive to the membrane potential of the cell. VG sodium channels will be closed at the resting membrane potential, but if the membrane potential rises this will cause the protein which make up the channel to shift, opening the channel.

Question 42

neurons

Answer 42

are critical to your thoughts, feelings, sensations, and movement.

Question 43

Dendrites:

Answer 43

receive input from other neurons

Question 44

Cell body:

Answer 44

nucleus endoplasmic reticulum and mitochondria as well as all the organelles found in cells

Question 45

Axon

Answer 45

carries information in the form of electrical signal known as the action potential. The axon meets the cell body at the axon hillock. Axons can be myelinated or unmyelinated. Myelinated axons have a faster conduction speed.

Question 46

Axon Terminals

Answer 46

output region, release of neurotransmitter

Question 47

action potential

Answer 47

triggered by a rise in membrane potential.

Question 48

overview of action potential

Answer 48

• Cell starts at a resting state (resting membrane potential, RMP). A stimulus large enough to reach the threshold membrane potential (typically -55mV) will initiate an action potential.
• This is because sufficient voltage-gated Na+ channels open to cause a large depolarisation.
• During the rising phase and overshoot, there is depolarisation to a peak of ~ +30mV known as the equilibrium / reversal potential for Na+.
• a repolarisation to~ -90mV: the overshoot at the end of the repolarisation phase is known as hyperpolarisation.
• RMP is restored by sodium-potassium ATPase which pumps 3 Na+ ions out of the cell for every 2K+ ions back across the plasma membrane to restore the cell’s resting membrane potential.

Question 49

conduction of action potenial

Answer 49

• alteration in membrane potential spreads along the membrane to open other sodium channels, propagating a wave of depolarisation along the membrane.
• fast process
• action potential will move in a single direction along the membrane; this is because the refractory period of the membrane prevents the action potential turning back in the direction it has already travelled
• AP will travel from the cell body, along the axon, and down to the axon terminals.

Question 50

AP

Answer 50

Local potential
Threshold state Depolarisation phase (rising phase)
Peak
Repolarisation phase (falling phase)
Hyperpolarisation phase (undershoot)
Resting state.

Question 51

initiating

Answer 51

• If lots of these ligand-gated ion channels are activated together, then the local potential will rise more due to the increased amount of sodium ions entering the cell. If this local potential is strong enough, it will reach the threshold for generating an action potential.
• VGSC open when the membrane reaches -55mV. if the local potential reaches -55mV (threshold), then the voltage-gated channels open and cause further depolarisation of the membrane and initiating an action potential.

Question 52

Depolarisation

Answer 52

Na+ flows into the cell down its chemical gradient and its electrical gradient until it reaches its reversal potential (at +30 mV) when the Na+ channels close

Question 53

repolarisation

Answer 53

Voltage-gated K+ channels open, allowing K+ to flow out of the cell down its chemical gradient and its electrical gradient. This repolarises the membrane, bringing the membrane potential back towards the equilibrium potential Ek (approximately -80mV).

Question 54

hyperpolarisation

Answer 54

end of AP the membrane potential lowers than usual resting phase as some K= ions remian open so ions can pass through the membrane.
- refactory period occurs during this when when the neuron typically cannot fire another action potential, even if it is stimulated.

Question 55

absolute refractory period

Answer 55

immediately after the action potential. In this phase the voltage-gated sodium channels are still deactivated, so even if there is a local potential depolarising the membrane, the voltage-gated sodium channels are not ready to initiate another action potential.

Question 56

relative refractory period;

Answer 56

the voltage-gated sodium channels ready to generate another action potential, but the membrane is still hyperpolarised.
the membrane potential is still lower than the normal resting membrane potential, a bigger stimulus is required to reach the threshold of -55mV.

Question 57

salatory conduction

Answer 57

• neurons have a myelin sheath
• myelin sheath acts as an insulator to prevent the change in membrane potential diminishing along the axon, and it allows the signal to travel faster.

Question 58

nodes of ranvier

Answer 58

VGSC at NOR where no myelin
AP generated at Node thus the impulse “skips” the length of the axon rather than depolarising the entire membrane surface.

Question 59

drugs affect synaptic transmission

Answer 59

-Stop the chemical reactions that create neurotransmitters, inhibit enzymes.

Increase / decrease availability of precursor.
Storage (stored in synaptic vesicles in the axon terminal)
* Block neurotransmitters from entering or leaving vesicles.
* Empty neurotransmitters from the vesicles where they’re normally stored and protected from breakdown by enzymes.
Release (released in response to the arrival of an action potential and the influx of Ca2+ into the presynaptic terminal).
* Blockade of Ca2+ channels on the presynaptic terminals.
Activation of receptors (activate autoreceptors on the presynaptic terminal and/or diffuse across the synapse to activate postsynaptic receptors).
* Bind to receptors in place of neurotransmitters, e.g. agonists / antagonists.
* Interaction with presynaptic receptors that control neurotransmitter release
Inactivation/Reuptake (neurotransmitters are broken down enzymes and/or taken back up into the presynaptic terminal by specific transporters).
* Inhibit enzymes that breakdown neurotransmitters.
* Prevent neurotransmitters from returning to the presynaptic neuron (i.e. block the reuptake system).

Answer 60

• An action potential reaches the presynaptic terminal, opening voltage-gated calcium channels and allowing calcium ions (Ca2+) to enter the cell.
  2) NM in the presynaptic terminal are stored in vesicles; these are like bubbles of phospholipid bilayer within the cell. The increase in Ca2+ inside the cell cause the vesicles to merge with the presynaptic membrane, releasing the neurotransmitter into the synaptic cleft.
  3) NM crosses the synaptic cleft to bind with receptors on the postsynaptic membrane.
  4) The receptors initiate a response in the postsynaptic cell. The response will depend on the type of receptor present; in the example shown here the receptor is a ligand-gated ion channel

Question 61

ionotrophic receptors

Answer 61

very rapid responses
msecs> secs
used in NTransmission processes
agonist efficacy relates to mean channel open time

Question 62

metaphobric receptors

Answer 62

slower responses
secs>MINS>hrs
used in slower NTransmission processes
agnoist efficaicy relates to ability to activate g protein

Question 63

kinase - linked receptors

Answer 63

slower responses
mins > hours
Endogenous agonists include hormones and growth factors
involved in regualtion pf growth, differentiation and response to metabolic signals

Question 64

intracellular receptors

Answer 64

very slow responses
hours > days
response long lasting and remain long lasting after agonist binding

Question 65

Increases the synthesis of a neurotransmitter?