2 Truths and a Lie
Which statement is FALSE?
A. Diffusion and osmosis are passive processes.
B. Osmosis only occurs across a partially permeable membrane.
C. Active transport moves substances from a higher concentration to a lower concentration using energy.
C. Active transport moves substances from a LOWER concentration to a HIGHER concentration using energy.
Which process moves particles from a region of high concentration to low concentration?
A) Osmosis
B) Diffusion
C) Active transport
B) Diffusion
Which chemical elements are found in carbohydrates?
A) Carbon and hydrogen.
B) Carbon, hydrogen and nitrogen.
C) Carbon, hydrogen and oxygen.
D) Carbon, hydrogen, oxygen and nitrogen.
C) Carbon, hydrogen and oxygen.
Enzymes are a type of...
A) protein.
B) hormone.
C) carbohydrate.
D) lipid.
A) protein.
What is meant by the term concentration gradient?
The difference in concentration between two regions.
Which statement is FALSE?
A. Carbohydrates are mainly used as an energy source.
B. Glucose is soluble in water.
C. Lipids dissolve easily in water.
C. Lipids are INSOLUBLE in water.
They dissolve easily in ethanol.
Which process requires energy from aerobic respiration?
A) Osmosis
B) Diffusion
C) Active transport
C) Active transport
Lipids are made of three fatty acids and …
A) Glycogen
B) Glycerol
C) Glucose
B) Glycerol
Explain what a catalyst is.
A substance that speeds up a chemical reaction without being used up.
Which of the following is the complementary DNA strand for: ATCGTGCTA
A) TACGTACAT
B) ACTAGACTC
C) TAGCACGAT
D) TAGACTCAT
C) TAGCACGAT
Which statement is FALSE?
A. DNA carries genetic information.
B. A DNA molecule is made by a single strand.
C. DNA is made of repeating units called nucleotides.
B. A DNA molecule is made by TWO strands forming a double helix.
Which of the following factors would increase the rate of diffusion?
A) A smaller surface area
B) Lower temperature
C) Thicker membrane
D) Larger concentration gradient
D) Larger concentration gradient
What is the name of the shape formed by the two strands of DNA?
Double helix.
Why is an enzyme only able to catalyse one type of reaction?
Enzymes are specific because its active site has a complementary shape to only one substrate.
Name three factors that affect the rate of diffusion.
- Temperature
- Concentration gradient
- Surface area
- Distance
Which statement is FALSE?
A. The chemical formula of the monomer of a carbohydrate is C₆H₁₂O₆.
B. A lipid molecule is made of one glycerol and three amino acids.
C. The chemical elements found in an amino acid are carbon, hydrogen, oxygen and nitrogen.
B. A lipid molecule is made of one glycerol and three FATTY acids.
A red blood cell is placed in distilled water. What happens?
A) Water enters the cell and swells, possibly bursting.
B) Water enters the cell by osmosis and gains turgor pressure.
C) Water leaves the cell by osmosis and it shrinks.
D) Water leaves the cell and it becomes flaccid or plasmolysed.
A) Water enters the cell and swells, possibly bursting.
Name the monomers of:
- Carbohydrates.
- Proteins.
- DNA.
- Carbohydrates: simple sugar.
- Proteins: amino acid.
- DNA: nucleotide.
Why does enzyme activity increase as temperature rises to the optimum?
A) The substrate changes shape.
B) The active site changes shape.
C) The enzyme denatures as it gains kinetic energy.
D) Molecules move faster and collide more often.
D) Molecules move faster and collide more often.
A root hair cell absorbs mineral ions even when their concentration is lower in the soil than inside the cell.
Explain which process enables this to happen.
Active transport using energy released by aerobic respiration in mitochondria.
Which statement is FALSE? Explain why.
A. Increasing temperature increases enzyme activity until the optimum temperature is reached.
B. Extreme pH can change the shape of an enzyme's active site.
C. Once an enzyme is denatured, cooling it back to the optimum temperature always restores its activity.
C. Once an enzyme is denatured, cooling it back to the optimum temperature DOESN'T NECESSARILY restore its activity.
Explain why a plant cell becomes turgid when placed in distilled water.
Water enters the cell by osmosis. The vacuole fills with water, pushing the cell contents against the cell wall.
A food sample gives these results:
Benedict's test → orange-red
Biuret test → blue
Ethanol test → cloudy white
Which nutrients are present? Explain your answer.
Glucose and lipids.
Positive Benedict's test and Ethanol test.
Negative Biuret test.
Pepsin is an enzyme found in the stomach and works best at an acid pH of 2. Explain why its activity decreases at pH 8.
Extreme pH changes the shape of the active site, which denatures the enzyme, so the substrate no longer fits.
A potato cylinder is placed in a concentrated salt solution. Why does its mass decrease?
Water leaves the potato cells by osmosis because the salt solution has a lower water potential than the cells. The cells lose water, so the potato loses mass.