Diffusion in Biology

Questions and Answers

What is the main factor that affects the rate of diffusion?

Distance

Surface area

Concentration gradient (correct)

Temperature

Facilitated diffusion requires energy to move substances across the cell membrane.

False

What is the term for the movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane?

osmosis

The cell membrane is partially _______________.

permeable Signup and view all the answers

What happens to an animal cell when it is placed in a dilute solution?

It swells and may burst Signup and view all the answers

Active transport requires energy to move substances against their concentration gradient.

True Signup and view all the answers

Match the following types of diffusion with their descriptions:

Simple Diffusion = Movement through a partially permeable membrane without assistance Facilitated Diffusion = Movement via protein channels or carriers in the membrane Signup and view all the answers

What is the term for the measure of the tendency of water to move from one place to another?

Water potential Signup and view all the answers

What happens to a cell placed in a solution with higher water potential than its cytoplasm?

Water enters the cell, causing it to swell Signup and view all the answers

When a plant cell is placed in a concentrated sugar solution, it becomes turgid.

False Signup and view all the answers

What is the term for the process of water entering a plant cell, causing it to swell?

turgid Signup and view all the answers

When a cell is placed in a solution with lower water potential than its cytoplasm, it undergoes ______________________.

crenation Signup and view all the answers

Match the following solutions with the effect on a cell:

Higher water potential = Water enters the cell, causing it to swell Lower water potential = Water leaves the cell, causing it to shrink Distilled water = The cell becomes turgid Concentrated sugar solution = The cell undergoes plasmolysis Signup and view all the answers

Study Notes

Diffusion

Movement of particles from a region of higher concentration to a region of lower concentration
Factors affecting diffusion:
- Concentration gradient
- Temperature
- Surface area
- Distance
Types of diffusion:
- Simple diffusion: movement through a partially permeable membrane without assistance
- Facilitated diffusion: movement via protein channels or carriers in the membrane
Examples in living organisms:
- Gas exchange in the lungs and tissues
- Nutrient absorption in the intestines

Osmosis

Movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane
Water potential: measure of the tendency of water to move from one place to another
Key concepts:
- Higher water potential (dilute solution) vs. lower water potential (concentrated solution)
Effects on cells:
- Animal cells:
  - In a dilute solution: cell swells and may burst (lysis)
  - In a concentrated solution: cell shrinks (crenation)
- Plant cells:
  - In a dilute solution: cell becomes turgid
  - In a concentrated solution: cell undergoes plasmolysis

Transport Across Cell Membrane

Methods:
- Passive transport: diffusion, facilitated diffusion, osmosis
- Active transport: requires energy (ATP) to move substances against their concentration gradient