Unit 2👌

Question 1

Nucleus

Answer 1

Houses DNA of human cells and provides location of DNA transcription

The nucleus is the control center of the cell

Dna ( double stranded molecule contains genes) DNA are tightly bound around histones(proteins) and form chromatin. Which is then organized into chromosomes ( 2 sister chromatin)

Has 2 distinct lipid bilayers ( this disperses during mitosis) outer membrane is continuos with the ER

Lumen between ER and nuc are continuous except at the nuclear pores ( transport pathways between interior of nucleus and cytoplasm)

Outer membrane belongs to the endomembrane system ( nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, plasma membrane, and most vacuoles and vesicles)

mRNA sent out the nuclear pores to ribosomes to make specific proteins if this process is altered by mutations then making proteins not functional

• maintains integrity of genes and in turn regulates cell activity.

Question 2

Central dogma of bio

Answer 2

Inside the nucleus DNA is transcribed into mRNA (in the nucleus) then it is transported to the ribosomes that are docked to the Rough ER (cytoplasm) the mRNA is translated by the ribosome ( AUGC matched with corresponding amino acids) creating a polypeptide chain in the ER the not finished protein is then folded and then transported to the Golgi apparatus. Where it is further processed 4th structure and packaged into secretory vesicles which bud off the Golgi and make there way to the cell membrane where they bind with the membrane expelling protein out of cell (exocytosis)

Question 3

Er

Answer 3

Rough Er 
Has ribosomes (that bind when they come in contact with mRNA and unbind when done creating the protein with Er membrane) 
Proteins are read by ribosomes that then synthesise corresponding amino acid chains  in the lumen of the Er which are then folded (2nd and 3rd structure) and then be shipped to the Golgi 

Smooth ER

Synthesis’s lipids, phospholipids, and steroids
AIDS in the breakdown of carbs and steroids, help regulate and store calcium ions via calcium pumps

Question 4

Golgi body

Answer 4

Has a phospholipid membrane

Further processes of proteins designed for etxracelular secretion.

Proteins are sent from Er via vesicles to Golgi ( see cytoskeleton)

Transports lipids around the and creates lysosomes

It’s basically AMAZON

Question 5

The MITOCHONDRIA

Answer 5

The freaking power house of the the freaking cell

Has two membranes

Which is important for energy production

Has its set of DNA and genes

(Can synthesis it’s own proteins and even reproduce via division )

It’s a balloon withiinside a baloon

Outer mitochondrial membrane 
Itramembranous space 
Inner mitochondrial membrane 
Cristae (inner foldings of inner membrane) 
The matrix (interior space)

Number can be anywhere from 2000 per cell ( in the liver) and 0 in (red blood cells)

Question 6

Lysosomes

Proteasomes

Peroxisomes

Answer 6

Lysosomes
Part of endomembrane system
Specialized vesicles that bud off of Golgi
Uses pump to keep h+ concentrations high lowering the ph and making it more acidic which allows it to break down large molecules like proteins

Proteasomes : break down proteins when there is an abundance or the cell wants to quickly reduce the concentration. Protein bonds with ubiquitin

Peroxisome( not part of endo membrane system)
Detoxifies harmful substances within the cell) membrane bound protiens inside made by free floating ribosomes and can self reproduce and breakers down lipids coverts h2o2 into h20 and o2

Question 7

Cytoskeleton

Answer 7

Network of proteins that is constantly destroyed, renewed, rebuilt

Helps maintain shape, resists deformation, movement both inside ( transport of vesicles ) and migratory movement, cell signaling, endocytosis, exocytosis, and cell division

Microfilimants
Thinnest and composed of long chains of protein monomers called g-actin, they can generate force by growing into the cell membrane,
Myosin can move along the tract and pull against it generating contractile forces ( muscle cells)

Intermediate filaments 
Stronger then microfilimetents 
Help maintain shape
Serve as anchors for organelles and help serve as cell to cell junctions,
Maintains shape of nucleus 

Micro tubules
Largest of the three
Has a hollow structure made up of protein monomers called tubulin which wind like a staircase they are associated with the organizing center called the centrosomes
They serve as highways for transport vesselicles and act in movement in flagellum
Create spindle apparatus during cell division and pull the two chromosomes apart

Question 8

Plasma membrane

Answer 8

Without it the call dies

Semi permeable/ selectively permeable (small hydrophobic particles 👍)

Regulates what enters and leaves the cell

Responds to chemical messengers

Smaller non charged move easily through membrane (co2 and 02)

Question 9

Fluid mosaic model

Answer 9

Membrane constantly changes and moves.

Made up of many small parts

Phospholipids : hydrophobic inside hydrophilic outside (cell and out of cell) large hydrophilic molecules have are time crossing, small hydrophobic particles like o2 and co2 have easier time.

Cholesterol: hydrophobic region, helps regulate fluidity of membrane (escpecially in extremities where temp can very geatly) forms lipid
Forms lipid rafts that help with cell signaling

Cholesterol + phospholipids =50% of membrane

Proteins = 50%

Peripheral proteins/ extrinsic proteins: found only on surface and don’t extend through the membrane. Attaches membrane to cytoskeleton or to proteins of extracelular matrix

Integral or intrinsic proteins: pass all the way through the membrane and have hydrophobic sections that accsoiate with hydrophobic section of membrane.

Question 10

Channel proteins

Answer 10

Integral and transport protein

Allow hydrophilic materials such as ions across the membrane

Tubes between interior and exterior of cell

Usually gated : acts like a door and only allow things to cross when open

Question 11

Carrier proteins

Answer 11

Intrinsic and transport protein

Have cites that bind to specific solute

Once bonded carrier changes shape allowing solute to move across membrane

Open on inside or outside but not both at same time.

Ex : GLUt4

Question 12

Enzymes ( proteins)

Answer 12

Integral membrane

Catalyze important chemical reactions

Ex lactase is integral protein in small intestine

Question 13

Receptor protiens

Gprotien coupled receptor (GPCR)

Answer 13

Receptor protiens

Integral messenger protiens
Recieve cell messages
And then allow cell to respond
Ligand bonds which triggers a signal that regulates a function inside the cell.

GPCR:

Receptor protien and the gprotien complex (alpha beta and gamma sub units)
When ligand binds to receptor g protien binding site changes shape allowing the g protien to bind to receptor,
Which then causes the gprotien to change shape releasing GDP and replacing it with GTP
Which causes the alpha sub unit to seperate for the beta and gama subunits once actividaded alpha and beta gamma subunits can activate activity in the cell.

Mediated by adenylyl cyclase and phospholipase C

Responses include ( activation of metabolic enzymes, opening or closing ion chánals, turning on transporters, India ting gene transcription, regulate motility and contactility, stimulating secretion, and even controlling memory, after a short period GTP breaks down to gdp
Alpha combines with beta and gamma
Turning off the signal

There are over 800 genes for g protien couple receptors
Super common in physiology

Question 14

Attachment proteins

Answer 14

Integral protiens

Attaches cells together

As well as to extracellular matrix And intracellular protiens

(Perifrial protiens may act as a link between the structural protiens and the matrix)

Helps gives cells streangth and shape

If not formed can cause problems like muscular distrophy

Question 15

Marker protiens

Answer 15

Integral protiens
Allow cells to identify each other
( how sperm recognizes the oocyte )
(Ability of our immune cells to recognize bacteria, foreign cells)

Question 16

Carbohydrates in the membrane

Answer 16

Oligosacharides attach to proteins and lipids in extracellular region of memebrane

Glycoproteins = oligosacharide + protien ( help determine blood type)(glycocalyx on the apical surface of epithelial tissue, helps with cell recognition, adherence of cells to each other, and play a role in membrane permeability)

Glycolipid = okigosachride + lipid

Question 17

Passive vs active transport

Answer 17

Passive transport ( no energy required ie down gradient)

Active transport ( energy required ie up gradient)

Question 18

Simple diffusion

Answer 18

High concentration to low concentration

The difference in concentration = concentration gradient

Diffuse down or from high to low concentration)

Once they are equal distributed they reach the state of “diffusion equilibrium”
Molecules still move from one side to other but there is no longer net change

Simple diffusion means diffusion without the aid of a membrane protein

Ex o2 and co2 move across membrane

Question 19

Factors that affect rate of diffusion

Answer 19

Concentration gradient: greater difference faster rate of diffusion

Temperature: the higher the temp faster movement and faster rate of diffusion

Size of molecules: smalle molecules travel faster so rate is faster for smaller

Viscosity of the medium: measure of thickness, increase viscosity = decrease in diffusion rate

Membrane permeability: hydrophilic pass through slower (harder time) hydrophobic (pass through easily)

Surface area: the greater the surface area the faster the rate of diffusion.

Distance : the shorter the distance the faster the rate of diffusion. Travel long distance via diffusion would be very slow, that’s why blood stream is a lot faster

Question 20

Facilitated diffusion

Answer 20

Diffusion (passive transport)

Via channel or carrier protiens

Channel protiens
Fluid filled tubes (help ions across membranes like NA k ca and cl
Often only very specific ions allowed through
Can be gated:
Voltage gated (voltage/charge difference)
Ligand gated (requires ligand/chemical messenger)
Mechanical gated (pressure touch or temp)
Leak channel which opens and closes intrinsically and contributes to resting potential

Carrier proteins
Bind to specific solute (not open on both sides) once bound a confirmational shift occurs and it can be changed to open on other side
Saturation* occurs when solute concentration is to high GLUT1 to 12 are examples that carry gluecose across membrane.
Glut2 liver and pancreas
Glut4 skeletal muscle and fat tissue
Glut4 is the only one that requires insulin for maximal activity

Question 21

Active transport

Answer 21

Requires energy

Sub types

Primary active transport (uses ATP as energy to move substances against their gradients)
Ex sodium potassium pump NAKATPase ( 3 NA out and 2 K in)
SERCA pumps

Secondary (uses other gradients to help move solutes against gradients)
One with and one against 
Symptom (same direction)
Anti port (opposite directions)
Requires atp but not directly

Question 22

Bulk transport

Answer 22

Needed for much larger particles
Requires atp and are active transport

Endocytosis

Pinocytosis

Receptor mediated transport

Phagocytosis

Exocytosis

Question 23

Phagocytosis

Answer 23

Endocytosis

To eat
Only found in immune system
Sends extension of plasma membrane called a pseudo podia
Out and around a particle they eventually fuse together and create a vesicle contains the particle (phagasome)

Question 24

Pinocytosis

Answer 24

Cell drinking
Cell invaginates and then engulfs anything in the fluid that is taken into the cell

Occurs in most cells
Not interested in the water but rather the solutes in The water.

Nonspecific and not very efficient

Non selective mechanism to sample external cellular environment

Super common in cells in intestines and kidneys.

Question 25

Receptor mediated transport

Answer 25

Much like pinocytosis except

Is specific
Requires a ligand or specific material to bind which then triggers a clathrin coated pit to come to the surface and take in the specific ligand.

Taking iron into cell
Or cholesterol

Question 26

Exocytosis

Answer 26

Endocytosis in reverse

Secretory vesicles are filled with materials to be secreted

The vesicles then migrate and fuse with cell membrane releasing materials out side of the cell
The usual signal is when calcium ions in the cell

Question 27

Osmosis

Answer 27

Diffusion of water across a membrane. Through selectively permeable membrane from high to low concentration.

Permeable to water but impermeable to solute
And concentration of solute must differ in the two sides

Goes from lowcentraion of solute to high concentration of solute until concentrations are equal or some outside force limits

Passive process

Pressure sufficient to keep water from crossing membrane is osmotic pressure

Question 28

Osmolarity vs Tonicity

Answer 28

Concentration of solutes in water is about 285-295 “300” mOsmoles (1000 times less then osmol) per liter

Isosmotic - same amount of particles
Hyperosmotic - (more particles then the other)
Hypo osmotic- less particles the. Other side

Osmolarity takes into account all particles

Tonicity - how it affects fitness of cells / tissues
Only consider non permiable (polar substances)

Solution is hypotonic cell expands and explodes
Isotonic nothing happens

Solution is hypertonic cell shrinks

Some solutes can diffuse by then are eaten by the cell creating an imbalance

So isomotic solution of dextrose would be hypotonic

Any isometric solution of a permeable solute would become hypotonic

.9% NACL = isometric
5% dextrose = isometric

Question 29

Electrophysiology

Answer 29

Electrical properties of biological cells.

Cell membranes and ion interaction

Charged ions diffuse until charge is beginning to be pulled back from electrical gradient or when the force of chemical gradient is = to the force or pull of the electo gradient which creates equilibrium or resting state

Question 30

Resting membrane potential

Answer 30

When the electrochemical gradient is at equilibrium and one side is negative and the other positive

-70mv

Polarized state

NA K ATPase pump creates chemical gradient and electro gradient

High amounts of k+ inside wanting to leave ( they can leave through leak gates making the membrane 50 to 100 times more permeable to k+ at resting potential )

High amounts of NA outside wanting to come in (NA gates are closed at resting and very few can enter the cell)
La
As k+ leaves the cell it will leave a negative charge until it reaches equilibrium
Cause if inside the cell to be - and outside +
This state is the resting potential

Excitable (-50 to -85) mv neurons and skeletal muscle

Non excitable (-5 to -10) red blood cells

Question 31

NA K ATPAse pump

Answer 31

3 NA out
2 K in
Both against gradient
Requires atp

Makes inside the cell more negative and out side more positive
Found in very cell
Creates a concentration gradient for both NA and K

Question 32

Protien channels (action potentials)

Answer 32

Leaks channels (open all the time)
Gated channel those that are close all the time. 

Voltage gated - respond to electrical voltage

Mechanical gated - responds to mechanical stimulation

Chemical or ligand gated - respond to the presents of a ligand

Activation of voltage - lever or activation gate is positvly charged
And ball - inactivation gate

If inside becomes more positive the spring would go up and open the lever exposing the mouth or the side facing the cytoplasm

The ball being oppositely charged after few seconds is then attracted to the mouth and closes the channel

More channels creat more chemical pull causing more to leave until new equilibrium is found.

Question 33

Ion location and movement a trio. Potentials

Answer 33

NA ex 142 in 10 movement into cell makes inside more positive

K+ ex 4 in 140 movement out of cell makes in more negative

Ca++ ex 2.4 in .0001 movement into cell makes it more positive

Mg++ ex 1.2 in 58 as mg moves out cell becomes more -

Cl- ex 103 in 4 cl moves in in besotes more-

Hco3- ex 28 in 10 as hco3 moves into cell in becomes more -

Question 34

Depolarization

Answer 34

When inside becomes more positive or as the y axis increases (moves toward 0) it is depolarization

Opening channels Na and Ca

Question 35

Repolarization

Answer 35

When the voltage or charge goes back down or away from zero in a - way towards -70

Opening channels k or Cl

Question 36

Hyperolarization

Answer 36

When charge contues to drop past the rp (-70) and will still go down

Question 37

Graded potential v action potentials

Answer 37

Strong response = 10 mV
Weak response = 5mV

Graded potential
Weak
Opening of mechanical or ligand gated channels)
Does not excede threshold
Graded potentials can be added on top of each other to increase the response
Determined by number of channels opens or concentration of a chemical
Only short distances
Aka local potentials
Triggers
Depolarization occurs only a little
Can be both depolarization and hyperpolarization

The father away from site of activation the less strength it has.
Action potential is when graded potential surpasses the threshold (-55)
ALL or Nothing
Rapid change and rapid return
Muscle contraction and senses
Caused by the opening of voltage gated channels (most often NA+ volatage channels)

Only few (100000 NA are required to raise action potential to 100mv)

Question 38

Action potentials (over view)

Answer 38

(.5 msec) super speedy
Once graded potential reaches the activation threshold it has reached the point of no return and triggers Major depolarization

Activation gate on NA channel is activated. Allowing NA in and after a brief moment the inactivation gate closes and NA stops entering

Near the crest the activation gate of k+ channels open followed a short time later by inactivation gate closing during the brief interval k+ leaves the cell depolarizing it and even hyperpolarizes it do to the lag of the deactivation gate

It then returns to resting potential via k leak channels and the sodium potassium pump

Remember there is very little change in overall concentrations of ions on both sides

Question 39

Action potential graph step by step

Answer 39

Gradient potential is cause ligand or mechanical gated channels opening

It then reaches the the threshold which opens the NA+ v gates and NA+ rushes In

Near the peak
K v gates begin to open and sodium v channels begin to close

Other side of peak NA v channels closed and k v channels open k rushes out of cell

Now back at the threshold k v gated channels begin to close But potassium slowly leaves and the voltage drops below -70

At hyperpolarization all k leak channels are open and v channels still open

And back at resting all k vchannels are closed

Question 40

Refractory period

Answer 40

Time during which a cell is on able of repeating action potentials (reloading)

Absolute refractory period ( occurs during depolarization and repolarization and there canout be a new signal)because sodium inactivation gate is closed and ends when the inactivation gate opens

Relative refractory period ( is the interval of hyperpolarization, and although it takes more Energy and action potential can still happen again)

Question 41

Propagation and nodes of ranvier

Answer 41

Starts near cell soma and travels down the axon
The first area causes a polar change which then activates the next segments v gated channels and so on and so forth
Can’t go backwards because gates bead to be reset and process must complete (still in repolarization)

Nodes of ranvier (space in between Schwann cells of the myelin sheath ) act as relay station making a signal travel 10 times faster.
The original ap triggers the next node (skipping a decent chunk) to get close to threshold (saltatory conduction)
Each node the is triggered recreates the same action potential wave
Depolarization occurs only on bare axon and not this covered by the myelin sheath.

Question 42

Sodium v gate channel gates

Answer 42

The activation gate - sensitive to voltage and is the basis of the threshold and then shuts

The inactivation gate - the plunger is slightly delayed allows time for depolarization to occur and is accountable for making the absolute refractory period happen it is reset somewhere during the repolarization around the threshold mark

K+ gates are also triggered at threshold but are delayed until about the 30+ mv Marck (the crest)
And then don’t close until hypo polarization

Question 43

Ion concentrations and their effects

Answer 43

K+ is primary responsible for maintaining a resting potential

NA + cl- ca++high outside wants to come in
K+ mg++ high inside wants to go out

1. What changed?
2. Where and does it effect the gradient (is it permeable)
3. How does the gradient effect the charge

At resting potential NA and Ca don’t penetrate the membrane and don’t effect rmp

Hyperkalemia - causes the inside to be more positive ^ and depolarization

Hypokalemia - causes greater gradient causing inside to be more negative and cause hyperpolarization

Ca likes to keep the NA gates closed!!!!!

Hypo cálcemia depolarization
Hypercalcemia - causes hyperpolarization

NA leak would be depolarize
Ca leak depolarizer
Cl leak hypopolarized

Add k leak would cause inside more negative and create hyperpolarization

Less k leak would depolarization

Question 44

Ups

Answer 44

Uniquitin proteasome stystem

Helps recycle/ get rid of malfunctioning or surplus protiens to keep the protien concentrations balanced

Uses ubiquinome chain of 3 to tag protien which basically is tagged for destruction

Police station which tickets protiens and then sentencing them to death