The sac and the boiling tube shown in the diagram were weighed separately. The sac was then placed inside the boiling tube. After 30 minutes, the sac was removed from the boiling tube and both were weighed again. Which of the following is the most likely result? Mass of Sac (Q) Mass of Boiling tube

P – decreases; Q – increases

P – increases; Q – decreases

P – decreases; Q – increases

P – increases; Q – stays the same

P – decreases; Q – stays the same

A drop of liquid bromine is placed in the bottom of a gas jar. Brown fumes of bromine vapour slowly spread through the whole gas jar. Why does this happen?

Bromine molecules and those in air are always moving around.

Bromine is less dense than air.

Bromine molecules and those in air are always moving around.

Bromine molecules are smaller than those in air.

Bromine molecules move faster than those in air.

Which of the following process does not apply the principle of diffusion?

Water diffuses into root hair cells

Oxygen diffuses from alveolus into blood stream

Carbon dioxide diffuses fro blood stream into alveolus

Digested blood diffuses from villi into blood stream

Water diffuses into root hair cells

During germination, which chemical change takes place in a seed when the enzyme protease becomes active?

Fats into glycerol and fatty acids

Why are enzymes needed during seed germination?

To break down insoluble food to soluble substances

To increase the rate of photosynthesis

What is meaning of optimum temperature?

The temperature where the activity of enzyme is the fastest.

The temperature where the activity of enzyme is the slowest.

The temperature where the activity of enzyme remains the same.

The temperature where the activity of enzyme is the fastest.

The temperature where the enzyme is denatured.

Why does an enzyme stop functioning at about 60oC?

It is made up of protein and is denatured at high temperature.

Its optimum temperature is 50oC.

It is too active and has reached its optimum temperature.

It has yet reached its optimum temperature.

It is made up of protein and is denatured at high temperature.

Diffusion, Osmosis And Enzymes

1.

A student placed five 50 mm strips of potato in dishes containing the following: distilled water 0.1 mol/dm³ sucrose (dilute solution) 0.3 mol/dm³ sucrose 0.4 mol/dm³ sucrose 0.5 mol/dm³ sucrose The length of each strip was measured at regular intervals of time. The results were plotted on a graph. Which line shows the result for the strip of potato in distilled water?
- A.
  
  A
- B.
  
  B
- C.
  
  C
- D.
  
  D
Correct Answer
A. A

Explanation
Osmosis takes place. Distilled water has low water potential than potato strips.

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2.
The sac and the boiling tube shown in the diagram were weighed separately. The sac was then placed inside the boiling tube. After 30 minutes, the sac was removed from the boiling tube and both were weighed again. Which of the following is the most likely result?
1. Mass of Sac (Q) Mass of Boiling tube
- A.
  
  P – increases; Q – decreases
- B.
  
  P – decreases; Q – increases
- C.
  
  P – increases; Q – stays the same
- D.
  
  P – decreases; Q – stays the same
Correct Answer
B. P – decreases; Q – increases

Explanation
Sugar solution is hypertonic to the water in the Visking tube. Water diffuses out of the tubing.

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3.

A drop of liquid bromine is placed in the bottom of a gas jar. Brown fumes of bromine vapour slowly spread through the whole gas jar. Why does this happen?
- A.
  
  Bromine is less dense than air.
- B.
  
  Bromine molecules and those in air are always moving around.
- C.
  
  Bromine molecules are smaller than those in air.
- D.
  
  Bromine molecules move faster than those in air.
Correct Answer
B. Bromine molecules and those in air are always moving around.

Explanation
The movement of molecules is due to their kinetic energy. Bromine molecules and air molecules are constantly moving and colliding with each other. When a drop of liquid bromine is placed in the gas jar, the bromine molecules evaporate and mix with the air molecules. This causes the brown fumes of bromine vapor to slowly spread throughout the entire gas jar.

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4.

What is the process involved in the uptake of water by plants?
- A.
  
  Osmosis
- B.
  
  Diffusion
- C.
  
  Active Transport
- D.
  
  Traspiration
Correct Answer
A. Osmosis

Explanation
The process involved in the uptake of water by plants is osmosis. Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration through a semipermeable membrane. In plants, water is absorbed by the roots and moves through the plant's tissues via osmosis, allowing the plant to maintain its water balance and support various physiological processes. Diffusion and active transport are also involved in nutrient uptake by plants, but osmosis specifically refers to the uptake of water. Transpiration, on the other hand, is the loss of water vapor from the plant's leaves.

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5.

Which of the following process does not apply the principle of diffusion?
- A.
  
  Oxygen diffuses from alveolus into blood stream
- B.
  
  Carbon dioxide diffuses fro blood stream into alveolus
- C.
  
  Digested blood diffuses from villi into blood stream
- D.
  
  Water diffuses into root hair cells
Correct Answer
D. Water diffuses into root hair cells

Explanation
Water diffuses into root hair cells. Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In the given options, oxygen diffuses from alveolus into the blood stream, carbon dioxide diffuses from the blood stream into alveolus, and digested blood diffuses from villi into the blood stream. These processes all involve the movement of substances from an area of higher concentration to an area of lower concentration, which is characteristic of diffusion. However, water diffusing into root hair cells does not involve a concentration gradient, as water moves into the cells due to the process of osmosis, where it moves from an area of lower solute concentration (outside the cell) to an area of higher solute concentration (inside the cell).

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6.

During germination, which chemical change takes place in a seed when the enzyme protease becomes active?
- A.
  
  Protein into amino acid
- B.
  
  Carbohydates into maltose
- C.
  
  Fats into glycerol and fatty acids
- D.
  
  Maltose into glucose
Correct Answer
A. Protein into amino acid

Explanation
During germination, the enzyme protease becomes active and catalyzes the breakdown of proteins into amino acids. This chemical change is essential for the seed to obtain the necessary nutrients for growth and development. Amino acids are the building blocks of proteins and are required for various cellular processes. Therefore, the conversion of proteins into amino acids is crucial for the seed to utilize the stored nutrients and support its growth during germination.

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7.

Why are enzymes needed during seed germination?
- A.
  
  To break down insoluble food to soluble substances
- B.
  
  To increase the rate of photosynthesis
- C.
  
  To make starch for storage
- D.
  
  To speed up water absorption
Correct Answer
A. To break down insoluble food to soluble substances

Explanation
During seed germination, enzymes are needed to break down the insoluble food reserves stored in the seed into soluble substances. These enzymes, known as hydrolytic enzymes, help in the digestion of complex molecules such as starch and proteins into simple sugars and amino acids, which can be easily transported and utilized by the growing embryo. This breakdown of insoluble food into soluble substances provides the necessary nutrients and energy for the seedling to grow and develop.

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8.

Which of the following enzyme works best in the stomach?
- A.
  
  Lipase
- B.
  
  Maltase
- C.
  
  Cellulase
- D.
  
  Pepsin
Correct Answer
D. Pepsin

Explanation
Pepsin is the correct answer because it is an enzyme that is specifically designed to work in the stomach. It is secreted by the gastric glands in the stomach and is responsible for breaking down proteins into smaller peptides. Pepsin works best in the acidic environment of the stomach, where it is activated from its inactive form pepsinogen. Lipase, Maltase, and Cellulase are enzymes that work in other parts of the digestive system, but not in the stomach.

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9.

What is meaning of optimum temperature?
- A.
  
  The temperature where the activity of enzyme is the slowest.
- B.
  
  The temperature where the activity of enzyme remains the same.
- C.
  
  The temperature where the activity of enzyme is the fastest.
- D.
  
  The temperature where the enzyme is denatured.
Correct Answer
C. The temperature where the activity of enzyme is the fastest.

Explanation
The optimum temperature refers to the temperature at which the activity of an enzyme is at its highest or fastest. Enzymes are biological catalysts that speed up chemical reactions in living organisms. Each enzyme has an optimal temperature at which it functions most efficiently. At temperatures lower than the optimum, the enzyme activity is slower, while at temperatures higher than the optimum, the enzyme may become denatured and lose its activity. Therefore, the correct answer is that the optimum temperature is where the activity of the enzyme is the fastest.

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10.

Why does an enzyme stop functioning at about 60^oC?
- A.
  
  Its optimum temperature is 50oC.
- B.
  
  It is too active and has reached its optimum temperature.
- C.
  
  It has yet reached its optimum temperature.
- D.
  
  It is made up of protein and is denatured at high temperature.
Correct Answer
D. It is made up of protein and is denatured at high temperature.

Explanation
Enzymes are biological catalysts made up of proteins. Proteins have a specific three-dimensional structure that is essential for their function. At high temperatures, the increased kinetic energy disrupts the weak bonds that maintain the protein's structure. This causes the protein to unfold and lose its shape, a process known as denaturation. Without its proper structure, the enzyme cannot function properly and its activity is significantly reduced or completely stopped. Therefore, the enzyme stops functioning at about 60°C because it is made up of protein and is denatured at high temperatures.

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