Biology Chapter on Diffusion

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Questions and Answers

What happens to plant cells in an isotonic solution?

They lose water and plasmolyze.

They actively transport ions out.

They neither gain nor lose water. (correct)

They gain water from the surroundings.

What is the main role of carrier proteins in active transport?

To facilitate passive diffusion of molecules.

To produce glucose from respiration.

To store excess ions in the cell membrane.

To undergo a shape change and move ions into the cell. (correct)

What energy source is used to power active transport in root hair cells?

Light energy from the sun.

ATP produced from fermentation.

Glucose from soil.

ATP produced from respiration. (correct)

Which of the following correctly describes a consequence of a respiratory poison on active transport?

Active transport will cease due to lack of energy. Signup and view all the answers

Why are mitochondria abundant in root hair cells?

They produce energy for active transport. Signup and view all the answers

What is a requirement for glucose and amino acids to be actively transported in the human small intestine?

Low concentration outside the epithelial cells. Signup and view all the answers

Which factor distinguishes the specific types of membrane proteins involved in transport?

Their specificity for certain ions or molecules. Signup and view all the answers

How do kidneys relate to active transport?

They actively reabsorb glucose and amino acids into the bloodstream. Signup and view all the answers

What happens to an animal cell in a hypertonic solution?

The cell shrinks and becomes crenated. Signup and view all the answers

What is the effect of a hypotonic solution on a plant cell?

Turgor pressure increases and the cell becomes turgid. Signup and view all the answers

What is the term for water moving out of a plant cell in a hypertonic solution?

Exosmosis Signup and view all the answers

What occurs when an animal cell is in an isotonic solution?

Net osmosis is zero. Signup and view all the answers

What provides support to plant cells and keeps them turgid?

Turgor pressure Signup and view all the answers

What happens when an animal cell continues to take in water in a hypotonic solution?

The cell bursts and dies. Signup and view all the answers

If the surrounding solution has a lower water potential than the cell, what is the expected consequence for the cell?

Water moves out of the cell. Signup and view all the answers

What change occurs to the plant cell's shape when it is placed in a hypertonic solution?

It becomes flaccid and loses pressure on the cell wall. Signup and view all the answers

What is diffusion primarily driven by?

Kinetic energy from random motion of molecules Signup and view all the answers

Which statement best describes osmosis?

The movement of water molecules from a region of low solute concentration to high solute concentration Signup and view all the answers

What role does a partially permeable membrane play in diffusion?

It permits the solvent to pass but restricts the solute Signup and view all the answers

What process is used for the movement of molecules against a concentration gradient?

Active transport Signup and view all the answers

What is the primary driving force for oxygen diffusion from the alveolus into the blood capillary?

Concentration gradient Signup and view all the answers

Which of the following examples best illustrates diffusion?

Perfume spreading in a room after opening the bottle Signup and view all the answers

In the context of nutrient absorption, what substance primarily diffuses through the epithelial cells into the blood capillaries?

Soluble food molecules Signup and view all the answers

How does diffusion contribute to cellular function?

By aiding in the exchange of gases and nutrients Signup and view all the answers

How do waste products produced by the fetus mainly move into the mother's blood through the placenta?

By simple diffusion Signup and view all the answers

When does diffusion cease to occur?

When equilibrium is reached Signup and view all the answers

What happens to the rate of diffusion as temperature increases?

It increases. Signup and view all the answers

How does the distance of diffusion affect the diffusion rate?

Longer distances decrease the diffusion rate. Signup and view all the answers

What happens to carbon dioxide molecules in mesophyll cells during photosynthesis?

They decrease in concentration. Signup and view all the answers

What is the main energy source for the process of diffusion?

Kinetic energy from random molecular motion Signup and view all the answers

Which factor increases the rate of diffusion the most?

Higher concentration gradient. Signup and view all the answers

What structure on a leaf allows for the diffusion of CO₂ from the air into the air spaces?

Stomata Signup and view all the answers

What defines an isotonic solution?

A solution with equal solute concentration. Signup and view all the answers

What is the correct sequence of the path taken by carbon dioxide molecules into the leaf?

Air--stomata--air spaces Signup and view all the answers

During gas exchange in the lungs, what happens to carbon dioxide in the blood?

It diffuses out of the blood into the alveolus. Signup and view all the answers

What is osmosis?

The diffusion of water molecules through a selectively permeable membrane. Signup and view all the answers

What structural adaptation of the placenta enhances the diffusion of food molecules to the fetus?

Highly folded surface Signup and view all the answers

In what type of solution do water molecules move into the cell due to a lower internal solute concentration?

Hypotonic solution. Signup and view all the answers

What is the role of the extensions of root hair cells in the process of diffusion?

To increase the surface area for absorption. Signup and view all the answers

Which of the following best describes a hypertonic solution?

A solution with greater solute concentration. Signup and view all the answers

Study Notes

Diffusion

Diffusion is the net movement of molecules from a region of higher concentration to a region of lower concentration, driven by random motion.
It occurs down a concentration gradient.
Example: Ink in water – ink molecules spread evenly throughout the water.
Example: Perfume in air – perfume molecules spread throughout the air.
The energy for diffusion comes from the kinetic energy of the molecules.
Diffusion continues until equilibrium is reached, meaning molecules are evenly spread.
Diffusion through membranes:
- A partially permeable membrane, such as a cell membrane, allows some molecules to pass through, but not others.
- Diffusion across membranes is crucial for nutrient intake and waste removal.
- Diffusion can occur either across a membrane or into/out of a cell.
Factors affecting the rate of diffusion:
- Temperature: Higher temperature, faster diffusion.
- Distance: Shorter distances, faster diffusion.
- Concentration gradient: Larger gradient, faster diffusion.
- Surface area: Larger surface area, faster diffusion.

Osmosis

Osmosis is the diffusion of water molecules across a partially permeable membrane from a region of higher water potential to a region of lower water potential.
Water potential is a measure of the tendency of water to move.
Types of solutions:
- Isotonic: Equal solute concentration inside and outside the cell.
- Hypertonic: Higher solute concentration outside the cell.
- Hypotonic: Lower solute concentration outside the cell.

Osmosis in Animal Tissues

Hypertonic solution: Water moves out of the cell, causing the cell to shrink.
Hypotonic solution: Water moves into the cell, causing the cell to swell and possibly burst.
Isotonic Solution: Water potential inside and outside the cell is equal. No net movement of water.

Osmosis in Plant Tissues

Hypotonic solution (fresh water): The cell swells up due to water entering. This pressure is called turgor pressure. Supports the plant.
Hypertonic solution (concentrated solution): Water moves out of the cell, causing the cell to become flaccid, and the plant to wilt.
Isotonic solution: No significant change in the plant cell size.

Active Transport

Active transport is the movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration, requiring energy.
It utilizes carrier proteins embedded in the cell membrane.
The energy for active transport is usually provided by ATP (adenosine triphosphate), produced during respiration.
Active transport is crucial for absorbing mineral ions, ions in kidneys, and various other physiological processes.
Active transport process is specific: A particular carrier protein transports one specific type of molecule like glucose or an ion.
Factors stopping active transport include: A respiratory poison can stop active transport since the energy for the carrier proteins is provided by respiration.

Examples of Diffusion in Biological Systems

Gas exchange in lungs: Oxygen diffuses from the air in the lungs into the blood, while carbon dioxide diffuses from the blood into the air.
Absorption of digested food: nutrients produced by digestion diffuse from the intestines into the bloodstream.
Exchange of food and wastes through placenta: Nutrients diffuse from the mother's blood to the developing fetus, and waste products diffuse from the fetus to the mother's blood.
Diffusion in plants: Carbon dioxide diffuses into the leaves from the atmosphere for photosynthesis.

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Description

This quiz covers the principles of diffusion, including the movement of molecules from high to low concentration, and its significance in biological systems. You'll learn about diffusion through membranes, factors influencing its rate, and real-life examples like ink in water. Test your understanding of how diffusion plays a critical role in cellular processes.