Keystone Practice

Living organisms can be classified as prokaryotes or eukaryotes. Which two structures are common to both prokaryotic and eukaryotic cells?

plasma membrane and cytoplasm

A scientist observes that, when the pH of the environment surrounding an enzyme is changed, the rate the enzyme catalyzes a reaction greatly decreases. Which statement BEST describes how a change in pH can affect an enzyme? A. A pH change can cause the enzyme to change its shape. B. A pH change can remove energy necessary to activate an enzyme. C. A pH change can add new molecules to the structure of the enzyme. D. A pH change can cause an enzyme to react with a different substrate.

A

Which statement best describes how antibiotics affect cellular homeostasis?

Antibiotics interfere with the transport of intracellular and extracellular materials.Homeostasis is maintained by different processes to regulate an organism's internal environment. The antibiotic action described in the scenario causes the cell wall to rupture and the cell to burst, so there can no longer be regulation of transport across the plasma membrane.

Which statement best describes how antibiotics affect cellular homeostasis?

Antibiotics remove chloroplasts from plant cells to cause starvation.

Carbohydrates and proteins are two types of macromolecules. Which functional characteristic of proteins distinguishes them from carbohydrates? A. Large amount of stored information B. Ability to catalyze biochemical reactions C. Efficient storage of usable chemical energy D. Tendency to make cell membranes hydrophobic Correct Answer

B

Photosynthesis and cellular respiration are two major processes of carbon cycling in living organisms. Which statement correctly describes one similarity between photosynthesis and cellular respiration? A. Both occur in animal and plant cells. B. Both include reactions that transform energy. C. Both convert light energy into chemical energy. D. Both synthesize organic molecules as end products.

B

Using a microscope, a student observes a small, green organelle in a plant cell. Which energy transformation MOST LIKELY occurs first within the observed organelle? A. ATP to light B. Light to chemical C. Heat to electrical D. Chemical to chemical

B

Which statement correctly describes how carbon's ability to form four bonds makes it uniquely suited to form macromolecules? A. It forms short, simple carbon chains. B. It forms large, complex, diverse molecules. C. It forms covalent bonds with other carbon atoms D. It forms covalent bonds than can exist in a single plane

B

Which statement BEST describes an effect of the low density of frozen water in a lake? A. When water freezes, it contracts, decreasing the water level in a lake. B. Water in a lake freezes from the bottom up, killing most aquatic organisms. C. When water in a lake freezes, it floats, providing insulation for organisms below. D. Water removes thermal energy from land around the lake, causing the lake to freeze.

C

Carbon can combine with many different elements but frequently combines with oxygen, hydrogen, and nitrogen to form organic molecules. Which statement best explains why carbon is able to form a large number of different molecules?

Carbon can form four covalent bonds.Key: Carbon can form four covalent bonds with its four valence electrons.

Which characteristic of life is best shown by this diagram?

Changes occur in an organism as it grows and develops.The life cycle diagram shows four stages in the life of a moth. The growth and development of this organism is best represented by this diagram.

Which characteristic of life is best shown by this diagram? A. DNA is the genetic code in an organism. B. An organism is made of one or more cells. C. An organism responds to changes in its environment. D. Changes occur in an organism as it grows and develops.

D

In order for medicine X to produce the effects that the researchers observed, it must have entered into which part of the targeted cells?

Golgi apparatus

Which statement best explains why these cells have structural differences?

The cells have different functions.The differences in cellular structure between each cell type are directly related to the specific functions of each cell type.

Which statement best describes a difference between prokaryotic cells and eukaryotic cells?

The presence of membrane-bound organelles in eukaryotic cells indicates that they are more complex than prokaryotic cells.Eukaryotes are more complex because they have organelles that are membrane bound, such as the nuclei which contain their DNA. Prokaryotes have DNA, but it is not bound by a membrane as in eukaryotes.

Alveoli are microscopic air sacs in the lungs of mammals. Which statement best describes how the structure of the alveoli allows the lungs to function properly?

They increase the surface area of the lungs, allowing efficient gas exchange. The millions of alveoli in mammals greatly increase the surface area of the lungs, thereby providing a larger surface area for gas exchange.

1. Cellular respiration and photosynthesis both involve water. 2. Cellular respiration uses sugar, and photosynthesis produces sugar. 3. Cellular respiration and photosynthesis both use light to produce energy. 4. Cellular respiration requires light energy, and photosynthesis requires chemical energy Which two statements correctly describe one similarity and one difference between cellular respiration and photosynthesis? A. statements 1 and 2 B. statements 1 and 4 C. statements 2 and 3 D. statements 3 and 4

a

A. The cells have different functions. B. The cells evolved in different organisms. C. One of the cells develops into the other type of cell. D. One of the cells is more primitive than the other cell.

a

Life functions are performed at many levels of biological organization. Which level of biological organization is the simplest level at which a structure can support life functions? A. cell B. tissue C. organelle D. organ system

a

Proteins are embedded within the cell membrane. Which of the following is the most likely purpose of these proteins? A. It allows passage of particles into and out of the cell. B. It manufactures phospholipids to repair membrane damage. C. It releases stored chemical energy in membrane carbohydrates. D. It attracts unbalanced electrical charges in the cell's environment.

a

The opening of the stomata allows water to evaporate from inside the leaf in a process known as transpiration. As this occurs, water molecules cling to one another and pull water in a continuous stream up the stem of the plant from the roots to the leaves. Which property of water makes this movement possible? A. cohesion B. freezing point C. high specific heat D. temperature-dependent density

a

Which statement best describes how active transport differs from passive transport? A. Only active transport requires ATP. B. Only active transport moves small particles. C. Only active transport relies on a plasma membrane. D. Only active transport allows substances to leave a cell.

a

Which statement describes the formation of a protein molecule? A. Amino acids combine to form a protein chain. B. Fatty acid monomers dissolve to form a protein chain. C. Fatty acid monomers combine to form a protein chain. D. Amino acids dissolve monomers to form a protein chain.

a

Which characteristic is shared by all prokaryotes and eukaryotes?

ability to store hereditary information

Which of the following is a property of water that allows a water strider to walk on the surface of water? A. solubility B. cohesion C. high specific heat D. low freezing point

b

All living organisms must maintain homeostasis in order to survive. Which statement best describes one way humans maintain homeostasis? A. Temperature is regulated by giving off carbon dioxide. B. Water content is regulated by giving off carbon dioxide. C. Temperature is regulated by sweating. D. Water content is regulated by sweating

c

Plant cells use sunlight to make their own food. Which structure allows plant cells to perform this function? A. nucleus B. vacuole C. chloroplast D. mitochondrion

c

Which statement best explains why cellular respiration in plants and other organisms is dependent on photosynthesis? A. Photosynthesis is one of the final steps in cellular respiration. B. Photosynthesis provides the materials that fuel cellular respiration. C. Photosynthesis absorbs excess energy produced by cellular respiration. D. Photosynthesis absorbs materials that are catalyzed during cellular respiration.

c

Life functions are performed at many levels of biological organization. Which level of biological organization is the simplest level at which a structure can support life functions?

cell,A cell is the smallest functional unit that can reproduce and survive independently.

Which characteristic is shared by both prokaryotes and eukaryotes?

contain genetic material.Key: Both prokaryotes and eukaryotes contain genetic material (DNA).

A jackrabbit has large ears containing blood vessels that help it maintain a constant body temperature by adjusting heat exchange with the surrounding environment. Which characteristic of life is best described by this example? A. growth B. energy use C. organization D. homeostasis

d

Carbonic anhydrase is an enzyme involved in the reaction of carbon dioxide with water to form a molecule that dissolves well in the liquid part of blood. How does carbonic anhydrase affect this reaction? A. by making the reaction reversible B. by changing chemical products of the reaction C. by increasing the time needed for the reaction to occur D. by decreasing the amount of energy needed to complete the reaction

d

The function of which human organ is most like the cell walls of bacteria? A. heart B. liver C. pancreas D. skin

d

Which component of the cell membrane contains a hydrophobic region and acts as the primary barrier to MOST foreign substances? A. Protein B. Cholesterol C. Carbohydrate chain D. Phospholipid bilayer

d

Which example is an activity that a fish MOST LIKELY uses to maintain homeostasis within its body? A. Using camouflage to avoid predators. B. Feeding at night to regulate body temperature. C. Moving to deeper water to regulate metabolic wastes. D. Exchanging gases through its gills to regulate oxygen levels.

d

Given the properties of the medicine Y molecule, which mechanism is most likely responsible for medicine Y's entry into cells?

exocytosis.Exocytosis moves materials out of a cell.

A scientist observes a single-celled organism with several long, whip-like tails. Which function do the whip-like tails most likely perform for the organism?

movement through an environment.Key: The cell uses flagella for movement.

The function of which human organ is most like the cell walls of bacteria?

skin.Key: The cell walls of bacteria act as regulatory structures similar to the skin of humans.

Which characteristic is shared by all prokaryotic and eukaryotic organisms?

the need for a source of energy. All prokaryotic and eukaryotic cells require a source of energy to survive.