Lab midterm 1

π osm (atm)

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CRT

R in CRT

gas constant = 0.082 (liter)(atm) / (˚K)(mol)

T in CRT

Kelvin temperature = 273 + ˚C

C in CRT

gas constant = 0.082 (liter)(atm) / (˚K)(mol)

Isotonic solutions

No net gain or loss of water because the osmolarity of the cell and its environment are equal. No osmotic gradient exists.

Hypotonic solution

The external medium is more dilute, so water enters the cell down its concentration gradient. In extreme conditions, the cell will swell and lyse.

Hypertonic solution

The external medium is more concentrated, so water leaves the cell, resulting in shrinkage, called "crenation" or "plasmolysis."

std dev formula

s = √[ Σ (X - X̄)² / (n - 1) ]

std error formula

s / √n

Osmolarity (isotonic movement)

between where it does and doesnt occur

Why use blank tubes?

Blanks dont measure ONP production (clear) and we measured the ONP (yellow)

Why is measuring DNA replication a good indicator of cell division?

Because DNA synthesis is required before a cell can divide.

What trend would you expect for DNA replication in untreated vs. drug-treated cells?

Untreated cells show increasing replication; drug-treated cells show reduced replication.

What is "fold change" in data analysis?

A ratio comparing treated vs. control values to show increase or decrease.

What would a strong inverse correlation between protein and doubling time suggest?

That the protein may promote faster cell division.

How are Parts I and II of the osmosis lab related?

-Both study osmosis—the movement of water across a semipermeable membrane.

-Part I uses dialysis bags to quantify water movement due to sucrose gradients.

-Part II uses red onion cells to visualize osmosis and determine when plasmolysis occurs.

-Both help estimate osmolarity—the concentration where no net water movement happens.

What would you expect the 30% bag to weigh at t = 2 hours? What forces cause the curve to level off?

It weighs that same t=2. The curve levels off as osmotic pressure reaches an equilibrium

What if a 20% NaCl solution was used instead of sucrose?

NaCl dissociates into 2 ions (Na⁺ and Cl⁻), doubling the effective osmolarity.

Osmotic pressure would be higher than with 20% sucrose.

Water would move out of the bag more rapidly, assuming the bag is impermeable to NaCl.

Greater mass change expected compared to sucrose

How would results change if the beaker contained 20% sucrose instead of water?

External solution would be hypertonic or isotonic, depending on bag concentration.

Water movement would decrease or reverse, especially for lower-concentration bags.

The cumulative change vs. time curves would flatten or dip below zero.