High School Biology : Cell Structures and Organelles

Study concepts, example questions & explanations for High School Biology

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Understanding The Cell Membrane And Cell Wall

What does it mean when a cell membrane is "selectively permeable?"

Possible Answers:

Harmful compounds cannot enter the cell

The shape of the membrane will change, depending on the environment

Some compounds can cross the membrane, while others cannot

Compounds can only enter the cell through channels

Correct answer:

Some compounds can cross the membrane, while others cannot

Explanation:

The cell membrane is composed of a phospholipid bilayer. Polar regions of the membrane face outward and shield a hydrophobic interior. Only certain compounds can cross both regions of the membrane. Polar compounds and ions will be able to interact with the polar regions of the membrane, but be unable to cross the hydrophobic interior. Similarly, large compounds will be unable to fit between the phospholipids. Only small, nonpolar molecules can cross the membrane freely.

Protein channels are placed in the membrane to allow polar and large molecules to cross, further adding to the selective nature of the membrane. Harmful compounds can still enter the cell from time to time, but the selectivity of the membrane helps prevent the potency of these attacks.

Example Question #5 : Understanding The Cell Membrane And Cell Wall

Which of the following does not contain a cell wall?

Possible Answers:

All cells have a cell wall

Plant cells

Some protists 

Some fungi

Animal cells

Correct answer:

Animal cells

Explanation:

A cell wall is a tough, and rigid layer of polysaccharides lying outside of the plasma membrane in plants, some fungi, and some protists. The cell wall provides these cells with structural support and protection. It also prevents over-expansion when water enters the cell. Animal cells lack a cell wall, and only have a plasma membrane.   

Example Question #52 : Cell Biology

Which of the following controls what enters and leaves the cell?

Possible Answers:

Cytoplasm

Nucleus

Cell membrane

DNA

Correct answer:

Cell membrane

Explanation:

The cell membrane controls what enters and leaves the cell. The cell membrane is a selectively permeable phospholipid bi-layer, which admits molecules by passive and active transport into the interior of the cell. The DNA is the genetic code found in the nucleus while cytoplasm is the liquid inside the cell.

Example Question #6 : Understanding The Cell Membrane And Cell Wall

What is the best description of the fluid-mosaic model for a cell's membrane?

Possible Answers:

A double layer of phospholipids with embedded proteins

A double layer of phospholipids

A single layer of phospholipids

A single layer of phospholipids with embedded proteins

Correct answer:

A double layer of phospholipids with embedded proteins

Explanation:

The fluid-mosaic model for the cell membrane is a double layer of phospholipids with embedded proteins.  The proteins do active transport in pumping molecules across the membrane.  The phosphates are on the outside and the lipid chains are on the inside of the membrane.

Example Question #11 : Understanding The Cell Membrane And Cell Wall

Which of the following are true of cell walls?

Possible Answers:

They provide support and protection for the cell

They are made of lipids

They are made only of carbohydrates

They are a double layer of phospholipids

Correct answer:

They provide support and protection for the cell

Explanation:

The cell wall provides support and protection for the cell.  Most are made from carbohydrate and protein.  They are not made of phospholipids or lipids.

Example Question #11 : Understanding The Cell Membrane And Cell Wall

Which of the following is another name for the cell membrane?

Possible Answers:

All of these

Plasma membrane

Semipermeable membrane

Phospholipid bilayer

Cytomembrane

Correct answer:

All of these

Explanation:

All these answers are correct and can be used interchangeably, so it's good to be aware of all of them. All cells have a cell membrane, regardless of organism, to separate their internal environment from their external environment. The term plasma membrane refers to the cytoplasm within the cell that the membrane is separating from the external environment. Phospholipid bilayer describes the molecular makeup of the cell membrane as it is composed of a double layer of amphiphilic (something that is both hydrophobic/lipophilic and hydrophilic) phospholipids. Semipermeable membrane refers to the ability of the membrane to allow certain substances cross from one side to the other, while restricting the passage of other substances. Cytomembrane uses the Greek root "cyto", meaning cell, to create a compound word that in the end means the same thing as cell membrane.

Example Question #11 : Understanding The Cell Membrane And Cell Wall

The major component of cell membranes is __________.

Possible Answers:

starch

amino acids

glucose

galactose

phospholipids

Correct answer:

phospholipids

Explanation:

Cell membranes are composed of a phospholipid bilayer. Phospholipids have hydrophilic heads and hydrophobic tails. The tails come together to form the hydrophobic inside of the membrane, whereas the hydrophilic heads face the outside of the cell and the inside aqueous cytoplasm. 

Example Question #51 : Cell Biology

Which of the following organelles has only one membrane?

Possible Answers:

Nucleus

Lysosomes

Chloroplasts

Mitochondria

Correct answer:

Lysosomes

Explanation:

Lysosomes are specialized vesicles that bud off of the Golgi apparatus and house digestive enzymes within the cell. Lysosomes have only one outer membrane, made of a phospholipid bilayer, similar to the plasma membrane surrounding the cell.

In contrast, the nucleus, mitochondria, and chloroplasts all have two outer membranes. Each of these is made of a lipid bilayer, for a total of four layers of phospholipids around these structures.

Example Question #52 : Cell Biology

Which of the following structures is not made up of tubulin?

I. Flagella

II. Mitotic spindle

III. Microfilament

Possible Answers:

II only

III only

I and II

II and III

Correct answer:

III only

Explanation:

A cell’s cytoskeleton is made up of three types of filaments: microfilaments, intermediate filaments, and microtubules. Microfilaments are made up of actin, whereas microtubules are made up of tubulin. Flagella, cilia, and the mitotic spindle of the cell are made from microtubules. The only filament given that is not made up of tubulin is microfilament.

Example Question #2 : Understanding Other Cell Structures

The lumen of which of the following organelles contains the highest concentration of hydrogen ions?

Possible Answers:

Golgi apparatus

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Lysosomes

Correct answer:

Lysosomes

Explanation:

The question states that the lumen of the organelle contains a high concentration of hydrogen ions. Recall that a high concentration of hydrogen ions results in a low pH. Lysosomes are organelles that contain degradative, hydrolytic enzymes that break down the cell’s waste products. These enzymes need a low pH to be functional, therefore, the lumen of lysosomes has a low pH (around a pH of 5). Lysosomes are known for having a high concentration of hydrogen ions to facilitate this acidic environment.

The other organelle known for sequestering hydrogen ions is the mitochondria. In mitochondria, hydrogen ions are used to create the gradient in the intermembrane space that is used to make ATP.

Learning Tools by Varsity Tutors