Molecular & Cellular Biology (35%)

BENCHMARK SC.912.L.14.2

SC.912.L.14.2 Relate structure to function for the components of plant and animal cells. Explain the role of cell membranes as a highly selective barrier (passive and active transport).

BENCHMARK REVIEW

Cells share common structural features, including an outer boundary called the cell membrane. The cell membrane encloses the cell and separates the cell interior, called the cytoplasm, from its surroundings. The cell membrane also regulates what enters and leaves a cell—including gases, nutrients, and wastes.

Movement across the cell membrane that does not require energy from the cell is called passive transport. One kind of passive transport, diffusion, is the movement of a substance from an area of high concentration to an area of lower concentration caused by the random motion of particles of the substance. The diffusion of water through a selectively permeable membrane is called osmosis. In facilitated diffusion, a carrier protein transports a substance across the cell membrane down the concentration gradient of the substance.

Active transport is the movement of a substance against the concentration gradient of the substance. Active transport requires cells to use energy. In animal cells, the sodium-potassium pump uses energy supplied by ATP to transport sodium ions out of the cell and potassium ions into the cell. During endocytosis, substances are moved into a cell by a vesicle that pinches off from the cell membrane. During exocytosis, substances inside a vesicle are released from a cell as the vesicle fuses with the cell membrane.

Within the cytoplasm are many structures, often suspended in a system of microscopic fibers called the cytoskeleton. The cytoplasm includes organelles that carry out various life processes. Organelles are structures that perform specific functions within the cell. Different types of cells have different organelles. The table below summarizes the functions of different organelles.

BENCHMARK PRACTICE

1. The diffusion of water through a selectively permeable membrane is called osmosis. Which description represents the effects of osmosis on a plant cell when the concentration of sugar particles is greater inside the cell than outside?

A. Water diffuses into the cell and the cell swells.B. Water diffuses out of the cell, and the cell

shrinks.C. Water moves into and out of the cell at equal

rates, and cell size remains the same.D. Water is blocked from moving into or out of the

cell, and cell size remains the same.2

2. The illustration below shows a cell and a large particle. Many substances, such as proteins and polysaccharides, are too large to be transported into a cell by carrier proteins. In a process called endocytosis, the large particle is brought into the cell.

Which of the following statements correctly summarizes this process?

A. Waste materials can enter the cell by the same process.

B. The particle passes directly through a protein doorway in the cell membrane.

C. The particle passes directly through the phospholipids that make up the cell membrane.

D. The cell membrane surrounds the particle and forms a vesicle that is brought into the cell.

1. Cells can have two kinds of endoplasmic reticulum (ER): smooth ER, which has no ribosomes, and rough ER, which has ribosomes embedded in its membrane. What would happen if the rough endoplasmic reticulum in the cell of an organism lost all of its ribosomes?

A. ATP production in the cell would stop.B. Protein production in the organism would stop.C. Storage of proteins within the cell would

increase.D. Proteins would no longer be exported from the

cell.E. 4

2. An oxygen molecule comes into contact with the outside of a cell’s lipid bilayer. What process would allow the molecule to move into the cell?

A. osmosisB. active transportC. simple diffusionD. facilitated diffusion

5. Sodium-potassium pumps, endocytosis, and exocytosis all involve active transport. Which of the following is a characteristic of active transport?

A. It involves facilitated diffusion.B. It requires energy from the cell.C. It relies on vesicles that often function as

pumps.D. It moves substances with a concentration

gradient.

Test Practice SC.912.L.14.2

1. A team of biology students performed an experiment to test the effects of four different solutions on a shelled, raw chicken egg. Each raw, unbroken chicken egg of the same size was placed in each of four different solutions. Twenty-four hours later the following results we obtained.

Once the experiment was completed, and the final mass of the eggs were taken, a student increased the concentration of the solute in solution C. What will most likely happen to the mass of the egg in Solution C?

A. The egg will continue to increase in mass.B. The egg will decrease in mass.C. The egg will remain the same mass.D. The egg will initially decrease in mass and then

will start increasing gradually.

2. Look at the diagram of a cross-section of a cell

membrane below.

The cell membrane controls movement of materials into and out of the cell.

Which of the following correctly describes how particles move across the membrane?

A. Lipids actively pump particles across the membrane.

B. Proteins actively pump particles across the membrane.

C. Lipids allow particles to diffuse across the membrane in only one direction.

D. Proteins allow particles to diffuse across the membrane in only one direction.

3. Osmosis occurs when there is a different concentration of solute molecules on each side of the membrane. The drawing below shows a beaker containing a 30% salt solution and a suspended cell containing a 10% salt solution.

What statement best describes the cell after 20 minutes?

A. Water will move from the cell into the beaker, resulting in a smaller cell.

B. Water will move from the beaker into the cell, resulting in a larger cell.

C. Salt will move from the cell into the beaker, resulting in a smaller cell.

D. Salt will move from the beaker into the cell, resulting in a larger cell.

4. One of the main functions of the liver is to detoxify harmful substances from the blood stream. Using your knowledge about organelles, how would you expect the organelles in a liver cell to differ from a standard animal cell?

A. The liver cell would have a larger vacuole than the standard animal cell.B. The liver cell would have more mitochondria than the standard animal cell.C. The liver cell would have smoother endoplasmic reticulum than the standard animal cell.D. The liver cell would have a greater number of Golgi bodies than the standard animal cell.

Molecular & Cellular Biology (35%)

BENCHMARK SC.912.L.14.3

Compare and contrast the general structures of plant and animal cells. Compare and contrast the general structures of prokaryotic and eukaryotic cells. Also assesses SC.912.L.14.2. AA

BENCHMARK REVIEW

The smallest and simplest cells are prokaryotes, which are bacteria. A prokaryote is a single-celled organism that lacks a nucleus and other internal compartments. Prokaryotic cells depend on a strong cell wall to give the cell shape. A prokaryotic cell wall is made of strands of polysaccharides connected by short chains of amino acids. Some prokaryotic cell walls are surrounded by a structure called a capsule, which is also composed of polysaccharides. The capsule enables prokaryotes to cling to almost anything, including teeth, skin, and food. Many prokaryotes have flagella, which are long, threadlike structures that protrude from the cell’s surface and enable movement.

The first cells with internal compartments were primitive eukaryotic cells, which evolved about 2.5 billion years ago. A eukaryote, such as a plant or an animal, is an organism whose cells have a nucleus. The nucleus is an internal compartment that houses the cell’s DNA. Other internal compartments, or organelles, enable eukaryotic cells to function in ways different from prokaryotes. An organelle is a structure that carries out specific activities in the cell.

Many organelles—such as the endoplasmic reticulum, vesicles, Golgi apparatus, lysosomes, and mitochondria—are found in both animal cells and plant cells. However, plant cells have three additional structures that are not found in animal cells:

The cell wall—composed of proteins and carbohydrates, including the polysaccharide cellulose—surrounds the cell membrane of plant cells.

Chloroplasts are organelles that use light energy to make carbohydrates from carbon dioxide and water. The central vacuole is a large membrane-bound space that stores water and may contain many substances,

including ions, nutrients, and wastes; when full, it makes the cell rigid.

Many single-celled eukaryotes use flagella for movement. Short hair-like structures called cilia protrude from the surface of other eukaryotic cells. Flagella or cilia propel some cells through their environment. In other cells, cilia and flagella move substances across the cell’s surface.

BENCHMARK PRACTICE

1. Jorge's class was examining different types of cells under the microscope. Jorge looked at both eukaryotic and prokaryotic cells. Which of the following would the class see when comparing these cells?

A. Only prokaryotes have cell walls.B. Only eukaryotes have a membrane-bound nucleus.C. Prokaryotic cells do not contain DNA.D. Eukaryotic cells do not undergo cell division.

2. Which of the following incorrectly pairs a cell structure with its function for both plant and animal cells?

A. Nucleus: storage area for the cell's genetic materialB. Mitochondria: used to supply energy for the cellC. Vacuole: sac used for storage of waste, water, or materials needed by the cellD. Cell membrane: site of protein synthesis

3. Eukaryotic cells are differentiated from prokaryotic cells because eukaryotic cells

A. are much smaller.B. have permeable membranes.C. have a higher rate of reproduction.D. have nuclei.

4. A biologist studied a cell with an electron microscope. The cell contained an endoplasmic reticulum, chloroplasts, and a cell wall. The biologist observed a cell from which of the following groups?

A. PlantB. AnimalC. FungusD. Bacteria

5. Two cells are shown in the diagram below.

Which statement correctly identifies the cells?

A. Cell 1 is prokaryotic; cell 2 is eukaryotic.B. Cell 1 is eukaryotic; cell 2 is prokaryotic.C. Both cells are prokaryotic.D. Both cells are eukaryotic.

Test Practice SC.912.L.14.2

The diagram below shows a cell.

What type of organism might contain this type of cell?

A. animalB. bacteriumC. plantD. prokaryote

2. Plants play an important role in the carbon cycle by producing carbohydrates. Which of the following organelles enables plants to make carbohydrates from carbon dioxide and water?

A. cell wallB. central vacuoleC. chloroplastD. nucleus

23. The digestive system breaks down materials into

substances the body can use.

What structure inside the cell is most similar to the digestive system in humans?

A. cytoplasmB. lysosomeC. nucleolusD. ribosome

4. The diagram below shows a cell.

What type of organism might contain this type of cell?

A. algaeB. animalC. bacteriumD. plant

5. Cells may have different shapes and different amounts of organelles, depending on their function. Which features do plant cells have that animal cells lack?

A. chloroplast, ribosome, and cell wallB. Golgi apparatus, cytoskeleton, and vesicleC. cell wall, chloroplast, and central vacuoleD. central vacuole, chloroplast, and smooth ER