Tx Across Cell Membranes Flashcards by Betsy McCoy

What is the most abundant EXTRACELLULAR Cation and its gradient values?

Sodium/Na+
Extracellular–> intracellular
140mEq/L –> 14 mEq/L

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What is the most abundant INTRACELLULAR cation and its gradient?

Potassium.

Intracellular –> Extracellular
140 mEq/L. –> 4 mEq/L

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This cation has very low intracellular levels bc it can be lethal if accumulates and inhibits mitochondrial activity.

Calcium

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What is Calcium’s gradient?

Extracellular –> Intracellular

2.4 mEq/L –> .0001 mEq/L

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What is Magnesium’s gradient?

Intracellular –> Extracellular

58 mEq/L –> 1.2mEq/L

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What is the most abundant EXTRACELLULAR ANION and its gradient?

Chloride
Extracellular –> Intracellular
103 mEq/L –> 4 mEq/L

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What is the most abundant INTRACELLULAR anion and its gradient?

Inorganic Phosphate

Intracellular –> Extracellular
75 mEq/L –> 4mEq/L

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What is the gradient for glucose? What is glucose used for inside of the cell?

Glucose gradient favors going from
Extracellular –>. Intracellular
90mEq/L –> 0-20 mEq/L

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What is oxygens gradient? What is O2 used for in side the cell?

Favors

Extracellular. –> Intracellular
35-40 mmHg –>. ~20mmHg

Used for oxidative metabolism

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What is the gradient for CO2?

Favors
Intracellular –> Extracellular
45-50mmHg –> 40-45mmHg

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What is the gradient for AA? What are AA used for inside the cell?

Favors
Intracellular –> Extracellular
200 mg/dL –> 30 mg/dL

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Type of Tx when you move particles with their gradient. E is not extracted from ATP.

Passive Tx or Diffusion

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Type of Tx when moving particles against their gradient; must extract E from ATP

Active Transport

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What are 4 lipid/fat soluble substances

Oxygen
Carbon dioxide
Nitrogen
Alcohol

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What two qualities must a substance have to diffuse directly through the phospholipid bilayer cell membrane?

Lipid soluble and electrically neutral

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Why do lipid soluble substances also have to be electrically neutral to transverse the cell membrane?

Bc of the polarized phosphate head, opposite charges on opposite poles will repel - and + charged substances

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These are selectively permeable, basing Tx of a substance on size, shape, and electrical charge within the channel.

Protein Channels

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This type of channel is always open

Protein Leak Channels

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What are two common examples of protein leak channels?

Sodium Leak channels

Potassium leak Channels

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What is the gradient of Na+ and K+ leak channels?

Which channel is the most leaky?

Sodium leak channels are constantly leaking Na+ into the cell

Potassium leak channels are constantly leaking K+ outside the cell

Potassium Leak Channels are much MORE leaky than sodium channels.

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These channels are typically closed until some stimulus/activity opens it up. Diffusion is only allowed when gate is open. What is an example?

Gating of Protein channels

Ex? Ligand gated channels

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What is a ligand?

Chemical substance

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Closed channel has a messenger of some type bind to its receptor, opens channel, ions move through open channel with their gradient, and there is a change in electrical properties of the cell.

What is this process?

Ligand (chemical) gated channels

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How long do ligand gated channels stay open?

As long as ligand is bound with receptor site

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These channels are activated by changes in the electrical charge across the cell membrane

Voltage-gated channels

The electrical charge inside the cell is different from the electrical charge outside the cell = ?

Each cell has an electrical gradient across the cell membrane

What is the electrical gradient of most cells in the body?

-90mV

Electrical gradient -90mV in a statement?

The inside of the cell is -90mV more negative than the outside of the cell

Voltage gated sodium channels are fast/slow?

FAST

In fast voltage gated sodium channels, some stimulus occurs and the electrical gradient is changed form -90mV to _____, and the channel is opened. ____mV change

-90mV --> -60mV ~30mV change

Why are voltage gated sodium channels "FAST"?

It doesn't take much voltage change to open them The channel is lined with - charges which aids faster tx of + charged sodium

Voltage gated sodium channels will close when electrical gradient reaches ~____mV.

~20mV

Voltage gated Potassium channels are fast/slow?

SLOW

Why are Voltage gated potassium channels "slow"?

There are no negative charges lining the channel and the RMP has to increase a lot more to open the channel

Slow voltage gated potassium channels stay closed all the way until the RMP reaches ____mV

+20mV

When do voltage gated potassium channels close?

When enough K+ leaves the cell and the RMP reaches -90mV again

Facilitated diffusion is Passive/Active Tx?

Passive Tx

What is a common example of facilitated diffusion?

Glucose transporters

What causes a confirmational change in a glucose transporter and allows the opening and facilitated diffusion of glucose into the cell?

When glucose inserts part way into the channel and binds with the receptor

What can cause accumulation of glucose or other solutes in the extracellular compartment, when dealing with tx proteins and facilitated diffusion? Happens quickly.

When the channels/receptors become saturated

What kind of pts do we worry about with saturation of GLUT?

DM pts bc their blood glucose will increase quickly without insulin to activate GLUT

Insulin is NOT the GLUT.. True or False?

TRUE

What does insulin do for GLUTs in some cells?

Insulin regulates and number and activity of GLUTs in some cells

Virtually ALL cells are insulin DEPENDENT/INDEPENDENT?

DEPENDENT

Which cells are insulin-independent??

``` Neurons Hepatocytes Proximal tubules of kidneys Small intestine Exercising skeletal muscle fibers ```

These cells are insulin-independent, but insulin does increase glucose tx into these cells

Hepatocytes

Exercising muscle fibers require MORE insulin for glucose tx than resting muscle fibers.. TRUE/FALSE?

FALSE Exercising skeletal muscle fibers require LESS insulin for glucose tx than resting skeletal muscle fibers

Concentration gradient, electrical gradient, pressure gradient, or a combination of two or more gradients all affect what?

Rate of diffusion across a cell membrane

This is the movement of water across a semipermeable membrane from area of lesser concentration of solutes to an area of higher concentration of solutes. (From area of more water to area of less water)

OSMOSIS

Osmosis has a FASTER/SLOWER rate of movement than just simple diffusion of water across a semipermeable membrane

Faster

Osmosis is a PASSIVE/ACTIVE transport process

Passive

Avogadro number is what?

6.02 x 10^23

1 ______ = 1 mole (avogadro's # of particles) in 1 liter or 1 kg of water

Osmole

Moles of solute per kg of water

Osmolality

Moles of solute per liter of water

Osmolarity

Atomic weight of Na = __ | So one mole of Na = __ gm (avogadro's # of atoms)

Atomic weight of Cl = ____ | 1 mole Cl = ____ gm (avo's # of atoms)

35.5

1 mole of NaCl = ____ gm (av's # of molecules) | Molecular wt of NaCl = ____

58.5

What type of chemical bond is for NaCl?

Ionic bond

NaCl dissociates in _____ into 1 mole Na+ and 1 mole of Cl-. (2 x avo's # of ions)

Water

1 mole of NaCl (58.5 gm) contributes what to 1 L or 1 kg of water?

2 osm (2 x avo's number of particles)

Glucose dissociates in water. (TRUE/FALSE?)

FALSE. Glucose does NOT dissociate in water.

Atomic weight of: Carbon = __ Hydrogen = __ Oxygen = __

``` C = 12 H = 1 O2 = 16 ```

Molecular wt of glucose? | c=12; h=1, o2=16

C6 H12 O6 C = 12 x 6 = 72 H = 1 x 12 = 12 O = 16 x 6 = 96 72 + 12 + 96 = 180

Which changes the osmolality of the water more? Glucose or NaCl added to the water? Why?

Larger substances added to the water, such as glucose, change the osmolality of the water LESS than adding NaCl bc it dissociates and contributes 2 osm instead of just 1

The pressure a fluid exerts on the walls of its container

Hydrostatic pressure

The point at which the water reaches a hydrostatic pressure that will stop movement of water across the cell membrane

Osmotic pressure

What determines the osmolality/osmolarity? | What does not?

The number of particles determines osmolality, NOT the size

EVERY PARTICLE, regardless of size, makes an equal contribution to osmolality/osmolarity. TRUE/FALSE

TRUE

If osm equilibrates on 2 sides of the membrane, movement of water will ____.

Stop

The volume of water that moves from A to B depends on what two factors?

Changes in hydrostatic pressure | Conc gradientZ?

The amount of hydrostatic pressure that stops osmosis of water is the ________ pressure

Osmotic pressure

The contribution of proteins to osmolality/osmolarity of body fluids

Colloid osmotic pressure (oncotic pressure)

What is the normal, primary protein that contributes to osmolality? Where is it primarily found?

Albumin, found in plasma primarily

What is normal body fluid osmolality?

~ 300 mOsm/L

What can we do to increase body fluid osmolality?

Give hypertonic saline | Let blood glucose rise

If body fluid osmolality stays increased for an extended period of time, such as in pts with ________, the intracellular compartment will have LESS/MORE osmolality from increased blood glucose. Water will move out of the cells which dehydrates or _______ them.

DM pts | Intracellular compartment will have less osmolality, so glucose will exit the cell and cell will CRENATE

When DM pts have increased extracellular osmolality in the extracellular compartment from increased blood glucose, water moves out of the cell and dehydrates cells. This is a contributing factor to what condition in DM pts?

Peripheral neuropathy

What can we do to decrease body osmolality?

Give water/free water Hypotonic .5/.25% saline Lots of D5W

If we decrease body fluid osmolality very quickly, then water will move outside to inside the cell and will increase _____________ inside the cell and cause cell __________.

Increase pressure and cause cell LYSIS

Need to extract E from ATP for this tx process of solutes against their gradient.

Active transport

E is used DIRECTLY in this type of transport

Primary active transport

E is used INDIRECTLY in this type of transport

Secondary active transport

What does the PRIMARY ACTIVE SODIUM POTASSIUM PUMP do?

Takes an ATP, breaks it down into ADP and an inorganic phosphate; holds on to the E from that breakdown and uses it to pump 3 SODIUMS OUT, 2 POTASSIUMS IN!!

Primary active sodium potassium pump pumps ___ sodiums ___, ____ potassiums _____.

3 SODIUMS OUT | 2 POTASSIUMS IN

Does the primary sodium potassium pump INCREASE/DECREASE intracellular charge?

DECREASES intracellular charge | (3 + charges go out, 2+ charges come into the cell.

What are 3 things the Na-K pump does for your cells/body?

Regulates intracellular Na/K concentrations Regulates intracellular osmolality Generates the majority of heat in your body

How does Na-K pump contribute to intracellular water levels?

Sodium dissociates and is a big contributor to osmolality bc water follows sodium

These are in skeletal, cardiac and smooth muscle fibers and they are another example of primary active transport

Calcium pumps

Calcium pumps pump Ca across cell membrane from _________ to _________ compartment

Pump Ca ions from intracellular to extracellular

Ca pumps pump Ca ions from cytoplasm to ___________ __________

Sarcoplasmic reticulum

Why do we have to have transient increase of Ca in muscle cell?

So we can have muscle contraction

What are 3 examples of secondary active co-transport?

Sodium - glucose Sodium - AA Sodium - potassium

What are 2 examples of secondary active counter-transport?

Sodium - hydrogen | Sodium - calcium

Secondary active co-transport is found only in what two places

Small intestine | Proximal tubule of the kidneys

What creates and maintains the electrical gradient for sodium to move with its gradient and other solute (glucose, potassium, AA) against its gradient?

Primary active sodium potassium pump

What would happen FIRST if ran out of ATP in secondary active co-tx?

Primary active na-k pump would stop first Once the gradient for sodium is lost, then the secondary active transporters would stop working

Why is the gradient different for glucose and AA in the small intestines and proximal tubule of the kidney?

They are reabsorbed so quickly that glucose and AA are more abundant inside of the cell than in the prox tubule or the small intestine

Where is secondary active counter-transport found in the body?

In the kidneys in the renal tubules

What does the secondary active counter transport in the renal tubules do for the body?

Regulates acid base balance via a transport protein

How does secondary active counter-tx regulate acid-base balance?

H is pumped into the renal tubule, buffered and excreted in the urine to rid of excess H's in the body

Two types of endocytosis

Pinocytosis | Phagocytosis

Endocytosis is and ________ transport mechanism

ACTIVE TX

Cell "Drinking" | Ingestion of smaller particles

Pinocytosis

In pinocytosis, the membrane of the cell will invaginate and take in _____ and whatever is dissolved in the ______ into the cell and form a _______.

Water; water; vesicle

Cell "Eating" | Ingestion of larger particles

Phagocytosis

In phagocytosis, membrane will invaginate, particle taken into the cell and incorporated into a phagocytic _________.

Vesicle

What comes into contact with phagocytic vesicle and breaks down the particle

Lysosomes

What two types of cells are very good at performing phagocytosis

Neutrophils and macrophages

Exocytosis is ACTIVE/PASSIVE transport

Active transport

What type of cells are good at exocytosis

Endocrine cells | Neurons

In exocytosis, _________ vesicle fuses with plasma membrane of cell and releases contents of the vesicle

Secretory vesicle

What activates/opens voltage gates Ca channels on an axon in exocytosis of neurotransmitter

Action potential or electrical charge

Once voltage gated Ca channels are open, | Ca flows...

From outside cell to inside

What stimulates fusion and exocytosis of NT into the synaptic cleft?

Influx of Ca

Why is endocytosis/exocytosis considered Active tx ?

Membrane has to change/invaginate, which requires contractile proteins which require ATP directly to change the structure of cell membrane to form and invaginate or open up for exocytosis.