Danho
ZIMSEC A Level · J2019

Biology Paper 2 June 2019

Questions
12
Total marks
19

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Questions
12
Pass mark
8
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Answer every question in the printed order, get marked at the end, then see the answers.

The questions

Question 101

[1 marks]cell structure and function
Fig 1.1 shows the structure of the cell membrane, with structures labelled A, B and C. What is the name of the molecule labelled A, which forms the bilayer that makes up the basic framework of the membrane?

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Question 102

[1 marks]cell structure and function
In Fig 1.1 showing the structure of the cell membrane, structure B is a protein that spans the full width of the phospholipid bilayer, from the outer surface to the inner surface. What is the general name for this type of protein?

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Question 103

[1 marks]cell structure and function
In Fig 1.1, structure C is a carbohydrate chain attached to a protein on the outer surface of the cell membrane. What is one role of this carbohydrate component?
  1. AIt acts as a recognition marker, allowing the cell to be identified by other cells so that it can attach to them and form tissues.
  2. BIt stores the cell's genetic instructions in a stable form, so that identical copies can be passed on whenever the cell divides.
  3. CIt catalyses the hydrolysis of membrane phospholipids, breaking them down as one way of regulating the overall fluidity of the membrane.
  4. DIt forms extra hydrogen bonds between the two phospholipid layers, holding them tightly together and giving the whole membrane its overall shape.

Question 104

[1 marks]cell structure and function
A cell that secretes large quantities of mucus contains unusually large numbers of a particular organelle, which modifies proteins such as mucin and packages them into vesicles that move to the cell surface and release their contents by exocytosis. Which organelle is this?
  1. AMitochondrion
  2. BRough endoplasmic reticulum
  3. CGolgi apparatus
  4. DLysosome

Question 201

[2 marks]cell structure and function
A structure that is present in a plant cell but absent from an animal cell is
  1. Aa cell surface membrane
  2. Ba cellulose cell wall
  3. Ca mitochondrion
  4. Da ribosome

Question 202

[2 marks]cell structure and function
A structure found in some prokaryotic cells but not in others, so that it can only be described as sometimes present, is
  1. Aa plasmid carrying a few extra genes
  2. Ba ribosome on which polypeptides are built
  3. Ca cell surface membrane enclosing the cytoplasm
  4. Da nuclear envelope surrounding the genetic material

Question 301

[1 marks]water
Two molecules join together to form a larger molecule, and in the process a water molecule is eliminated from between them as a new bond forms. What term describes this type of reaction?

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Question 302

[1 marks]water
The phosphate group of a phospholipid molecule readily attracts and forms hydrogen bonds with surrounding water molecules. What term describes a group that has this water-attracting property?

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Question 303

[1 marks]water
During the light-dependent reactions of photosynthesis, a water molecule absorbs light energy and splits into oxygen, protons and electrons. What term describes this light-driven splitting of water?

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Question 304

[1 marks]water
Water molecules are polar, which allows water to act as a solvent for ions and other polar or charged solutes. Which of the following is a benefit of this property to organisms living in an aquatic environment?
  1. AThe polar water molecules absorb large amounts of heat energy before their temperature rises, keeping the water's temperature relatively stable through the day.
  2. BDissolved mineral ions, such as nitrate, remain in solution in the water, letting plants absorb them and use them to build molecules such as proteins.
  3. CThe polar water molecules form a layer of ice that floats on the surface, insulating the liquid water below during cold weather.
  4. DThe polar water molecules create surface tension strong enough for small insects, such as pond skaters, to walk across the surface without breaking through it.

Question 305

[1 marks]water
A large quantity of heat energy is needed to raise the temperature of water by one degree Celsius, because most of that energy is used to break hydrogen bonds between water molecules rather than to speed up their motion. Which of the following describes the resulting benefit to organisms living in an aquatic environment?
  1. ALarge bodies of water heat up and cool down as quickly as the surrounding air, letting aquatic organisms adjust their metabolism from moment to moment.
  2. BLarge bodies of water release large amounts of stored heat energy, melting any surface ice within minutes of a rise in the surrounding air temperature.
  3. CLarge bodies of water lose their dissolved oxygen rapidly whenever the surrounding air temperature rises even slightly during the day.
  4. DLarge bodies of water resist rapid changes in temperature, giving aquatic organisms a relatively stable thermal environment despite fluctuations in the surrounding air temperature.

Question 306

[1 marks]water
Two water molecules can bond to each other through a weak attraction between the slightly positive hydrogen atom of one molecule and the slightly negative oxygen atom of the other. What is the name of this type of bond?

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