Biology Chapter: Enzyme Activity and Diffusion

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Questions and Answers

What is the optimum temperature for enzyme activity in the human body?

25°C

100°C

50°C

37°C (correct)

Higher temperatures always enhance enzyme activity.

False

What happens to enzymes when they become denatured?

They lose their shape and active site, resulting in a loss of activity.

Diffusion is the net movement of particles from a region of concentration to a region of concentration.

higher; lower Signup and view all the answers

Match the following concepts with their definitions:

Diffusion = Movement from higher to lower concentration Active Transport = Movement against a concentration gradient Denaturation = Loss of enzyme structure Optimum Temperature = Temperature at which enzyme activity is highest Signup and view all the answers

Which factor increases the rate of diffusion of gases in living organisms?

Increased surface area Signup and view all the answers

Active transport requires energy to move substances across membranes.

True Signup and view all the answers

Why is diffusion important for gas exchange in the lungs?

It allows oxygen to move from the alveoli into red blood cells and carbon dioxide to exit into the alveoli. Signup and view all the answers

What is the primary function of root hair cells in plants?

Active transport of ions and water Signup and view all the answers

Proteins are made up of only carbon, hydrogen, and oxygen.

False Signup and view all the answers

Which chemical elements make up fats?

Carbon, Hydrogen, Oxygen Signup and view all the answers

Starch is made from __________.

glucose Signup and view all the answers

Match the biochemical test with its corresponding positive result:

Iodine = Brick Red Benedict's = Blue Biuret = Purple Ethanol = Cloudy Signup and view all the answers

What happens to a plant cell in pure water?

It becomes turgid Signup and view all the answers

Diffusion moves particles from an area of lower concentration to an area of higher concentration.

False Signup and view all the answers

What term describes a cell that has shrunk due to loss of water?

Plasmolysed Signup and view all the answers

Oxygen diffuses from the alveoli of the lungs into __________.

red blood cells Signup and view all the answers

Which factor does NOT influence the rate of diffusion?

Color of the particles Signup and view all the answers

Study Notes

Enzyme Activity and Temperature

Enzymes function optimally at a specific temperature.
For the human body, this optimum is 37°C.
High temperatures disrupt the bonds holding the enzyme together, causing it to lose its shape (denaturation).
Lower temperatures decrease the kinetic energy of enzymes and substrates, leading to fewer collisions, reduced activity, and fewer products.
Enzyme activity increases with rising temperature until the optimum is reached, then decreases beyond it due to denaturation.

Diffusion

Diffusion is the movement of particles from high to low concentration due to random motion.
Substances move into and out of cells via diffusion through the cell membrane.
Gaseous Exchange in Lungs: Oxygen diffuses from the alveoli (lungs) into red blood cells.
Gaseous Exchange in Plants: Carbon dioxide diffuses into leaves for photosynthesis, and oxygen diffuses out.
Factors Affecting Diffusion:
- Larger surface area increases diffusion rate. (e.g., alveoli, root hair cells)
- Higher temperatures speed up particle movement and diffusion.
- A steeper concentration gradient leads to faster diffusion.

Active Transport

Active transport moves particles against their concentration gradient (low to high).
This process requires energy from respiration.
Crucial for transporting molecules and ions across membranes.
Example: Ion uptake by root hair cells (plant roots absorb ions from low-concentration soil).

Biological Molecules

Carbohydrates: Carbon, Hydrogen, Oxygen (CHO)
Proteins: Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur (CHONS)
Fats: Carbon, Hydrogen, Oxygen (CHO)
Large molecules (polymers) are built from smaller molecules (monomers).
- Starch and glycogen are made of glucose.
- Proteins are made of amino acids.
- Fats are made of fatty acids and glycerol.
Examples of Polymers and Monomers:
- Starch (glucose — plants, storage)
- Glycogen (glucose — animals, storage in liver & muscles)
- Cellulose (glucose — plant cell walls, structural)
- Proteins (amino acids — muscle, hair, cell membranes, enzymes like insulin)
- Fats (fatty acids & glycerol — cell membranes, hormone storage, long-term energy)

Biochemical Tests

Iodine Test for Starch: Orange/yellow → Blue/black (positive)
Benedict's Test for Glucose: Blue → Brick red (positive)
Biuret Test for Proteins: Blue → Purple (positive)
Ethanol Test for Lipids: Colorless → Cloudy (positive)

Osmosis

Osmosis is the movement of water through a partially permeable membrane from high water potential (dilute solution) to low water potential (concentrated solution).
Effect on Plant Cells:
- Pure water → Water enters, becomes turgid.
- Same concentration → No net movement, flaccid.
- Concentrated solution → Water leaves, becomes plasmolysed.
Effect on Animal Cells:
- Pure water → Water enters, becomes lysed (bursts).
- Same concentration → No net movement, normal.
- Concentrated solution → Water leaves, becomes crenated (shrinks).
Key terms: turgid, flaccid, plasmolysed, osmosis

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Description

This quiz covers key concepts related to enzyme activity and diffusion processes in biological systems. Learn how temperature affects enzyme functionality and explore the mechanisms of diffusion in cells, including gas exchange in lungs and plants. Test your understanding of these fundamental biological principles.