BISC 162 Exam 1 (Leary) Gas Exchange, Osmoregulation, Muscle, Reproduction

What drives gas exhange?

Diffusion down a partial pressure gradient

What 4 factors affect diffusion (Fick’s Law)?

Surface area, concentration gradient, distance, diffusion coefficiant

Why is countercurrent exchange efficient?

Maintains a continuous diffusion gradient along the entire length of the exchange surface, allowing for maximal oxygen uptake

Why is gas exchange harder in water?

O2 diffuses slower + less dissolved O2

What does the Bohr effect do?

It says that low pH results in hemoglobin releasing O2

What is the difference between osmoconformers and osmoregulators?

Conformers match environment; regulators control internal balance

What happens in a hypotonic solution?

Water enters the cell resulting in swelling

What happens in a hypertonic solution?

Water leaves the cell, resulting in the cell shriveling.

Most toxic nitrogen waste

Ammonia

Why do bird use uric acid?

It helps them save water

What are the 4 steps of urine formation?

Filtration, reabsorption, secretion, excretion

What causes muscle contraction?

Actin + myosin sliding (requires ATP)

Why does rigor mortis happen?

No ATP → myosin stuck to actin

Slow vs fast twitch?

Slow = endurance; Fast = strength/power

Where is sperm produced?

Seminiferous tubules

What hormone triggers ovulation?

LH surge

What does hCG do?

Maintains corpus luteum (pregnancy signal)

How does birth control work?

Prevents LH surge → no ovulation

A fish gill system switches from countercurrent to concurrent flow. What happens to oxygen uptake?

It decreases because equilibrium is reached quickly, stopping diffusion

At high altitude, why does oxygen loading into hemoglobin decrease?

Lower atmospheric pressure → lower O₂ partial pressure gradient

Increasing which variable would MOST increase diffusion rate?

Increasing surface area

Why is hypoxia more likely in warm water?

Warm water holds less dissolved oxygen

If diffusion distance doubles, what happens to diffusion rate?

It decreases (inverse relationship)

Why is the tracheal system in insects so efficient?

Oxygen is delivered directly to cells without circulatory system

Why don’t birds experience “dead space” like mammals?

Unidirectional airflow keeps fresh air continuously moving

A cell placed in a hypertonic solution will:

Lose water and shrink

Why do freshwater fish produce large amounts of dilute urine?

Water constantly enters their bodies via osmosis

Which nitrogen waste requires the MOST water to excrete?

Ammonia

Why do birds use uric acid instead of urea?

Conserves water and is safer for egg development

Where does filtration occur in the nephron?

Glomerulus → Bowman’s capsule

What is the main function of the Loop of Henle?

Creates concentration gradient to concentrate urine

If ADH levels increase, urine will become:

More concentrated

What happens if ADH is NOT present?

Collecting duct is impermeable to water → dilute urine

Which process moves glucose back into the blood?

Reabsorption

Put in order: filtration, excretion, secretion, reabsorption

Filtration → Reabsorption → Secretion → Excretion

What directly causes the power stroke?

Release of ADP + Pi from myosin

What happens immediately after ATP binds to myosin?

Myosin detaches from actin

What exposes myosin-binding sites on actin?

Calcium binding → moves tropomyosin

If calcium cannot be released, what happens?

No contraction occurs

What happens to the H-zone during contraction?

It decreases or disappears

Why does rigor mortis occur?

No ATP → myosin cannot detach

Maximum force occurs when:

Optimal overlap between actin and myosin

Which fiber type has the most mitochondria?

Slow-twitch

A sprinter relies primarily on which ATP source?

Glycolysis (anaerobic)

Which fiber type appears red and why?

Slow-twitch due to high myoglobin

What stage is released during ovulation?

Secondary oocyte

What directly triggers ovulation?

LH surge

Why does estrogen switch to positive feedback before ovulation?

To trigger LH surge

What maintains the corpus luteum during pregnancy?

hCG

If hCG is NOT produced, what happens?

Corpus luteum degenerates → menstruation

What is the role of progesterone?

Maintain uterine lining

Most of the semen volume comes from

Accessory glands (not sperm)

Where are androgens produced?

Leydig cells

Birth control pills prevent ovulation by:

Preventing LH surge through negative feedback

A mutation reduces hemoglobin affinity for oxygen. What happens?

More oxygen is released to tissues

Why is urea less toxic than ammonia?

It requires less water and is chemically more stable

If the Loop of Henle is damaged, what happens?

Urine cannot be concentrated effectively

During intense exercise, why does oxygen unloading increase?

Lower pH (Bohr effect)

Why are slow-twitch fibers fatigue-resistant?

They rely on aerobic respiration and have more mitochondria

What happens in the proximal convoluted tubule?

Reabsorption of glucose, amino acids, water and ions

A patient has damage to their proximal convoluted tubule. Which of the following is MOST likely to occur?

Increased glucose in the urine