Exocytosis, Osmosis, and Diffusion: Cell and Kidney Physiology

What is exocytosis?

The process by which a membrane-bound vesicle fuses with the plasma membrane to release its contents to the cell exterior.

What proteins are involved in the fusion of vesicles during exocytosis?

V-SNAREs on the vesicle and t-SNAREs on the plasma membrane.

What is osmosis?

The movement of water across a semi-permeable membrane from a region of high solvent concentration (low solute) to a region of low solvent concentration (high solute).

What is the difference between osmolarity and osmolality?

Osmolarity refers to the concentration of solute particles in a liter of solution, while osmolality refers to the concentration of solute particles in a kilogram of solvent.

Define isotonic solution.

A solution with the same solute concentration as another solution.

Define hypertonic solution.

A solution having a greater solute concentration compared to another solution.

Define hypotonic solution.

A solution having a lesser solute concentration compared to another solution.

What is the relationship between osmotic pressure and solute concentration?

The greater the solute concentration, the greater the osmotic pressure.

What is the molarity of a solution?

The number of moles of solute per liter of solution.

What is the difference between molarity and molality?

Molarity is moles of solute per liter of solution, while molality is moles of solute per kilogram of solvent.

What happens to water movement in a hypertonic solution?

Water moves out of the cell, causing it to shrink.

What happens to water movement in a hypotonic solution?

Water moves into the cell, causing it to swell or potentially burst.

What is osmotic pressure measured in?

Osmolarity or osmolality, typically expressed in osmoles (Osm) or milliosmoles (mOsm).

How do sugars behave in solution regarding osmotic pressure?

Sugars do not ionize or dissociate in solution, contributing one osmole per mole of sugar.

How do salts behave in solution regarding osmotic pressure?

Salts ionize or dissociate in solution, contributing multiple osmoles per mole of salt.

What is the osmolarity of red blood cells (RBC) in a hypertonic solution?

Higher than the surrounding plasma, causing water to move out of the RBC.

What is the osmolarity of plasma in a hypotonic solution?

Lower than that of red blood cells, causing water to move into the RBC.

What is the typical osmolarity of plasma?

Approximately 0.278 Osm.

What is the typical osmolarity of red blood cells?

Approximately 0.308 Osm.

What is the significance of osmotic pressure in kidney function?

Osmotic pressure helps regulate water reabsorption and filtration in the kidneys.

What is the effect of dehydration on plasma osmolarity?

It increases plasma osmolarity, making the plasma hypertonic relative to RBCs.

What is the effect of excessive water intake on urine color?

It dilutes plasma, making urine clear due to lower solute concentration.

What is the formula for calculating molarity?

Molarity (M) = moles of solute / liters of solution.

What is the formula for calculating molality?

Molality (m) = moles of solute / kilograms of solvent.

What is the primary function of the kidneys?

To filter blood, regulate volume and chemical makeup of blood, and maintain balance between water, salts, and acids/bases.

What are the three major processes involved in urine formation?

Glomerular filtration, tubular reabsorption, and tubular secretion.

What is glomerular filtration?

The process by which blood is filtered in the glomerulus to form filtrate.

What is tubular reabsorption?

The process of reclaiming water and solutes from the filtrate back into the blood.

What is tubular secretion?

The active process of moving substances from the blood into the filtrate.

What percentage of ATP is used by the kidneys?

About 20%.

What is the glomerular filtration rate (GFR) for men?

Approximately 125 ml/min.

What is the glomerular filtration rate (GFR) for women?

Approximately 120 ml/min.

What is the maximum urine concentration achievable?

1200 mOsm, or four times the osmolarity of blood.

What structures are involved in the blood supply to the kidneys?

Aorta, renal artery, segmental arteries, interlobar arteries, arcuate arteries, interlobular arteries, afferent arterioles, and efferent arterioles.

What is the role of the renal capsule?

To protect the kidney and maintain its shape.

What is the function of the urinary bladder?

To provide a temporary storage reservoir for urine.

What are the paired ureters responsible for?

Transporting urine from the kidneys to the bladder.

What is the role of the nephron?

The functional unit of the kidney that filters blood and forms urine.

What is the filtration membrane in the kidneys?

A barrier that allows certain substances to pass from the blood into the filtrate while retaining larger molecules.

What is the osmotic gradient in the renal medulla?

A gradient that helps concentrate urine and is crucial for water reabsorption.

What is the significance of fenestrated capillaries in the kidneys?

They are highly permeable and facilitate the filtration process.

What are the components of the filtration pressure in the glomerulus?

Hydrostatic pressure, blood colloid osmotic pressure, and capsular hydrostatic pressure.

What is the net filtration pressure in the glomerulus?

Approximately 10 mmHg, which must always be positive for filtration to occur.

What is the role of the countercurrent multiplier system?

To create an osmotic gradient in the renal medulla that aids in water reabsorption.

What is renal clearance?

The volume of plasma from which a substance is completely removed by the kidneys per unit time.

What is the function of ADH in the kidneys?

To increase water reabsorption in the collecting ducts.

What is the role of the major and minor calyx in the kidneys?

To collect urine from the renal pyramids and transport it to the renal pelvis.

What is the renal pelvis?

The funnel-shaped structure that collects urine from the calyces and directs it to the ureter.

What is the significance of the renal pyramids?

They contain the nephrons and are involved in urine formation.

What is the function of the peritubular capillaries?

To facilitate the exchange of substances between the blood and the renal tubules.

What is the importance of maintaining electrolyte balance in the kidneys?

To regulate bodily functions and maintain homeostasis.

What is the role of the urethra?

To transport urine from the bladder out of the body.