Cells

What is the primary structural component of the plasma membrane?

• Proteins

• Phospholipids

• Carbohydrates

• Nucleic acids

Answer explanation

The primary structural component of the plasma membrane is phospholipids. They form a bilayer that provides the membrane's fluidity and flexibility, allowing for the proper functioning of embedded proteins.

Explain how the structure of the plasma membrane contributes to its function as a selective barrier.

• The rigid structure prevents all substances from passing through.

• The phospholipid bilayer allows only water to pass through.

• The fluid mosaic model allows for selective permeability, enabling certain molecules to pass while blocking others.

• The carbohydrate chains block all foreign substances.

Answer explanation

The fluid mosaic model describes the plasma membrane's structure, allowing selective permeability. This means it can regulate which molecules enter or exit the cell, facilitating essential functions while blocking unwanted substances.

Which of the following best describes diffusion?

• Movement of molecules from an area of low concentration to high concentration.

• Movement of molecules from an area of high concentration to low concentration.

• Movement of water molecules only.

• Movement of molecules against the concentration gradient.

Answer explanation

Diffusion is the process where molecules move from an area of high concentration to low concentration, seeking to equalize concentrations. This is the correct description, as it contrasts with the other options.

How does osmosis differ from simple diffusion?

• Osmosis involves the movement of solutes, while diffusion involves the movement of water.

• Osmosis requires energy, while diffusion does not.

• Osmosis is the diffusion of water across a selectively permeable membrane, while diffusion involves the movement of solutes.

• Osmosis occurs only in plant cells, while diffusion occurs in all cells.

Answer explanation

Osmosis specifically refers to the movement of water across a selectively permeable membrane, while diffusion is the movement of solutes. This distinction is key in understanding how substances move in biological systems.

What is facilitated diffusion and how does it differ from simple diffusion?

• Facilitated diffusion requires energy, while simple diffusion does not.

• Facilitated diffusion involves the use of transport proteins, while simple diffusion does not.

• Facilitated diffusion moves molecules against the concentration gradient, while simple diffusion moves them along the gradient.

• Facilitated diffusion occurs only in plant cells, while simple diffusion occurs in all cells.

Answer explanation

Facilitated diffusion uses transport proteins to help move molecules across the cell membrane, unlike simple diffusion, which allows molecules to pass directly through the membrane without assistance.

If there is a concentration gradient, substances will move from an area of high concentration to an area of ____ concentration.

• equal

• low

Who discovered and named cells? 

• Captain Hook
• Robert Hooke
• Zacharias Janssen
• Rudolf Virchow

What did Hooke first examine? 

• Pond water
• Plant cells
• Cork
• Animal fat

Which is not a part of cell theory?

• All organisms are made of cells
• All existing cells come from preexisting cells
• All matter is composed of living cells
• The cell is the most basic unit of life

Which of the following controls movement of materials in and out of a cell? 

• Cell wall
• Cell membrane
• Cytoplasm
• Nucleus