LAB 3 - Behaviour of living cells

Cells are…

they are the building blocks of the human body

• the activity of the human organism depends on the individual and the collective actions of it's many cells

  • changes that disrupt the cell structure can lead to the injury or death of living cells

Cell membrane

this forms the boundary that separates the living cell from it's external environment

• molecules that enter or leave the cell must pass through the membrane or channels in the membrane

Cell membrane: Selectively permeable

also known as a semipermeable membrane

• means that it only allows certain molecules to pass through it, while excluding others

  • primarily lets small molecules in and excludes large molecules (needs help)

  • water can freely move back and forth b/w the cell membrane

Diffusion

defined as the movement of molecules from a region of high [ ] to a region of low [ ] until a state of equilibrium is reached

• can be across a membrane but not always

  • an increase of heat causes diffusion to occur faster and a decrease of heat reduces the rate of diffusion

    • inc temp → inc kinetic energy

Osmosis

the diffusion of water molecules from an area of high [ ] of water, to a low a low [ ] of water through a selectively permeable membrane until equilibrium is achieved.

• this helps regulate the water content in the cell

Dialysis tubing exercise

consists of a dialysis bag & a solution in a beaker

• starch solution - large particles, high [ ] of starch, low [ ] of water

• iodine solution - small particles, low [ ] of iodine, high [ ] of water

Dialysis tube exercise - Part A

• iodine solution in the dialysis bag

• starch solution in the beaker

RESULTS:

• colour around the bag and the starch solution turns blue

  • indicates that iodine molecules were moving out of the bag

    • this is bc they are small molecules

• Bag slightly became smaller

  • indicates that water molecules moved out

    • this bc the starch has a low [ ] of water

• Bag solution was still yellow

  • indicates that no starch moved inside the bag

    • this bc the molecules are too large

Dialysis bag exercise - Part B

• starch solution in the bag

• iodine solution in the beaker

RESULTS:

• solution in the bag turned blue

  • indicates that iodine molecules moved in bc they are small molecules

• bag volume increased

  • indicates water molecules moved in

    • this is bc starch solution has a low [ ] of water

• iodine solution in the beaker remained yellow

  • indicates starch did not move out the bag

    • this is bc the molecules are too bid

Tonicity

a measure of the solution's ability to change the shape of cells by affecting the cells’ internal water volume

• 3 types

  • isotonic

  • hypotonic

  • hypertonic

Isotonic

where two solutions or the cell & the solution have the same [ ] of solutes and water molecules

• iso means the same

  • the cell shape remains the same

    • water movement is occurring however the rate that it moves in/out is equal

Hypotonic

Where the solution has a greater [ ] of water than the cell

• (solution: low solute & high water. cell: high solute, low water)

  • hypo means below

    • water molecules move into the cell via osmosis bc they are moving to a place of low [H2O]

      • this causes the cell to swell up (inc in volume) and can burst

Hypertonic

where the solution has a lower [H2O] than the cell

• (solution: high solutes, low water. cell: low solute, high water)

  • water molecules move out of the cell to balance the [ ]

    • this causes the cell to shrink

Tonicity in a quail egg

Eggs were placed in 3 diff solutions

• 42% sucrose solution - caused the egg to shrink (hypertonic)

• distilled water - caused the egg to enlarge (hypotonic)

• 28% sucrose solution - caused no change in the egg (isotonic)

Red blood cells + Isotonic solution

Red blood cells and an isotonic solution, like blood plasma, causes no net flow of water to occur

• the red blood cell stays the same shape

Red blood cells + hypotonic solution

red blood cells in a hypotonic solution, like distilled water, causes the water to move into the cell

• this causes the RBC to increase in size, and swells until it bursts

  • the rupturing of a RBC is called hemolysis

Red blood cell + hypertonic solution

red blood cells in a hypertonic solution, like a highly concentrated salt solution, causes water to exit the RBC

• this makes the RBC shrink and change shape

  • known as crenation

Disruption of the cell membrane

The cell membrane is made of a double layer of phospholipids with proteins immersed or floating throughout the membrane

• this can be disrupted if the either the lipid or protein component is altered/disturbed

  • when it is disturbed it causes the cellular content to spill out

Disruption of the cell membrane - Beets and Heat

Beets were heated for 15 mins

• this caused the water to turn pink

  • this meant that the cellular membrane was disturbed bc the cellular components contained the pigment

    • specifically the proteins were disturbed because heat causes them to denature and release the cellular components

Disruption of cell membrane - Beets and ethanol

Beets were placed in ethanol

• this caused the solution to turn pink

  • this meant that the cell membrane was disrupted

    • specifically the phospholipids because they have polar components, and since acetone is polar it can cause the phospholipids to dissolve

      • this causes the cell membrane to breakdown and release the cellular components