AP Biology Practice Test 6: Internal Environments

The correct answer is (C). Ribosomes are responsible for polypeptide synthesis and are located both free in the cytoplasm and on the rough endoplasmic reticulum. The smooth endoplasmic reticulum synthesizes lipids and detoxifies drugs and poisons.

The correct answer is (D). Plasmodesmata are channels in cell walls of plant cells.

The correct answer is (A). The mitochondria are responsible for cellular respiration.

The correct answer is (C). The plasma membrane controls molecular traffic into and out of the cell. It is selectively permeable, meaning it allows some substances to enter the cell, but not others. This is essential because it call keep many harmful or dangerous substances from entering and destroying the cell while still allowing the necessary substances to enter.

The correct answer is (C). The diagram is showing a plant cell (notice the cell walls). If a cell is immersed in an isotonic solution, there will be no net movement of water. In other words, water will move in and out of the cell at an equal rate.

The correct answer is (A). There is a net movement of solutes across membranes from an area of high concentration to an area of low concentration until they reach equilibrium.

The correct answer is (C). The sugar molecules are too large to move across the selectively permeable membrane. The water molecules move from an area of high water concentration (low solute concentration) to the area of low water concentration (high solute concentration) until the solution reaches equilibrium.

The correct answer is (A). The plasma membrane’s phospholipid bilayer is made up of two layers of phospholipids. Phospholipids have a hydrophilic (water loving) head and a hydrophoboic (water hating) tail. The hydrophilic heads are attracted to water, and therefore make up the outer part of the phospholipid bilayer.

The correct answer is (D). Membrane proteins are made of protein, Answer (D) describes a carbohydrate.

The correct answer is (C). The sodium-potassium pump exchanges sodium for potassium across the plasma membrane of animal cells by pumping ions against steep concentration gradients.

The correct answer is (B). Endocytosis is the process by which a cell takes in substances by engulfing them in new vesicles formed from the plasma membrane.

The correct answer is (A). Phagocytosis is the process by which cells engulf a particle by wrapping pseudopodia around it and packaging it into vacuoles.

The correct answer is (A). Mitochondria generate ATP by extracting energy from sugars, fats and other fuels to make energy available in animal cells. Chloroplasts convert solar energy into chemical energy to make sugar available for plant cells. Thus, they both convert energy into a form that the cell can use.

The correct answer is (D). All other choices are part of the endomembrane system. The mitochondria are the site of cellular respiration.