Cell Membrane Structure and Function

What does the term homeostasis mean?

• the movement of molecules from a low concentration to a high concentration with the use of ATP

• balanced internal chemical and physical conditions of the cell

• a water-loving molecule

• when solutes move from a high concentration to a low concentration

Answer explanation

Homeostasis refers to the balanced internal chemical and physical conditions of the cell, ensuring optimal functioning despite external changes. This distinguishes it from other processes like diffusion or osmosis.

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This simple bacteria cell has some of the same structure as more complex cells. It has a structure that controls what comes in to and leaves the cell and also maintains homeostasis. What is that structure?

• capsule

• cytoplasm

• membrane

• wall

Answer explanation

The structure that controls what enters and exits the cell while maintaining homeostasis is the membrane. It acts as a selective barrier, unlike the capsule, cytoplasm, or wall, which serve different functions.

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In reference to the cell membrane, what does the term "semi-permeable" mean?

• allows certain molecules to pass through but not others

• allows only large molecules to pass through the membrane

• allows only small molecules to pass through the membrane

• allows all molecules to pass through the membrane

Answer explanation

The term "semi-permeable" refers to the cell membrane's ability to allow certain molecules to pass through while restricting others, thus maintaining selective permeability essential for cellular function.

The following image shows the basic structure of the cell membrane. What is the name of the molecules that make up this membrane?

• amino acids

• phospholipids

• glucose molecules

• carbohydrates

Answer explanation

The cell membrane is primarily composed of phospholipids, which form a bilayer that provides structure and regulates the movement of substances in and out of the cell. Other options like amino acids and glucose do not make up the membrane.

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Which of the following macromolecules is NOT present in the cell membrane?

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Answer explanation

Nucleic acids, such as DNA and RNA, are not components of the cell membrane. In contrast, cell membranes primarily consist of lipids, proteins, and carbohydrates, which play crucial roles in structure and function.

Which of the following is NOT a function of the cell membrane?

• Protective barrier

• Regulate transport in & out of cell

• Allow cell recognition

• Contains the cytoplasm

• Prepares DNA for replication

Answer explanation

The cell membrane functions as a protective barrier, regulates transport, and allows cell recognition. However, preparing DNA for replication is not a function of the cell membrane; it occurs in the nucleus.

What part of the cell membrane allows for cell recognition?

• Lipids

• Carbohydrates

• Proteins

• Nucleic Acids

Answer explanation

Carbohydrates on the cell membrane serve as recognition sites for cell communication and interaction. They form glycoproteins and glycolipids, which are crucial for identifying cells and facilitating immune responses.

How many layers of molecules is the cell membrane?

• 1

• 2

• 3

• 4

Answer explanation

The cell membrane consists of two layers of molecules, known as the phospholipid bilayer. This structure is essential for maintaining the integrity and functionality of the cell, making the correct answer 2.

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Match the following

Fatty Acid Tails - (a)  

Phosphate Head - (b)  

• Hyrdrophobic

• Hydrophilic

Answer explanation

Fatty acid tails are hydrophobic, meaning they repel water, while phosphate heads are hydrophilic, meaning they attract water. This dual nature is crucial for forming cell membranes.

_______ regulates what enters and leaves a cell.  

• Cell Membrane

• Nucleus

• Mitochondria

• Cytoplasm

Answer explanation

The cell membrane regulates what enters and leaves a cell by acting as a selective barrier, allowing certain substances to pass while blocking others. This is essential for maintaining homeostasis within the cell.

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