Cell Membrane Functions and Transport Quiz

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Questions and Answers

What is the primary function of the cell membrane?

To regulate the movement of substances in and out of the cell. (correct)

To produce energy for cellular functions.

To provide structural support to the cell.

To transport nutrients across the cell wall.

Which of the following components makes up the largest percentage of the cell membrane?

Carbohydrates

Proteins (correct)

Nucleic acids

Lipids

Which mechanism of transport involves movement against an electrochemical gradient?

Osmosis

Simple diffusion

Facilitated diffusion

Active transport (correct)

What thickness is the cell membrane approximately?

7.5 nm (B) Signup and view all the answers

Which ion does the cell membrane help to control in both the intracellular and extracellular fluids?

Sodium (C) Signup and view all the answers

What is NOT a function of the cell membrane?

Generating food for the cell (B) Signup and view all the answers

What type of transport includes molecules moving down their electrochemical gradient?

Passive transport (B) Signup and view all the answers

Which component accounts for only 3% of the cell membrane's structure?

Carbohydrates (B) Signup and view all the answers

What type of transport uses energy directly from the hydrolysis of ATP?

Primary active transport (C) Signup and view all the answers

Which of the following statements is true regarding active transport?

It requires a transport carrier protein. (D) Signup and view all the answers

How does secondary active transport primarily generate its energy?

From the Na concentration gradient (D) Signup and view all the answers

Which of the following correctly distinguishes active transport from simple diffusion?

Active transport requires carrier proteins. (A) Signup and view all the answers

What is a defining characteristic of vesicular transport?

It enables large substances to cross cell membranes. (D) Signup and view all the answers

What process involves the trapping of extracellular material within vesicles formed by the cell membrane?

Endocytosis (B) Signup and view all the answers

What occurs during exocytosis?

Vesicles fuse with the cell membrane to release their contents. (D) Signup and view all the answers

Which transport mechanism exhibits saturation and competition?

Active transport (D) Signup and view all the answers

What process involves the engulfment of large-sized substances by the cell membrane?

Vesicular transport (D) Signup and view all the answers

Which statement is true regarding simple diffusion?

It occurs down the electrochemical gradient. (C) Signup and view all the answers

What characterizes facilitated diffusion compared to simple diffusion?

Both A and B are correct. (B) Signup and view all the answers

Which of the following best describes osmosis?

Diffusion of water across a membrane. (D) Signup and view all the answers

What is a key feature of active transport?

It requires energy to move substances against the gradient. (C) Signup and view all the answers

How does water primarily enter the cell by osmosis?

Through the lipid bilayer due to its small size. (A) Signup and view all the answers

What distinguishes facilitated diffusion from simple diffusion?

Facilitated diffusion is limited by carrier proteins. (D) Signup and view all the answers

Which characteristic is NOT true for simple diffusion?

It is rate-limiting and saturable. (C) Signup and view all the answers

Study Notes

Cell Membrane

A thin, elastic, semi-permeable membrane surrounding every animal cell
7.5 nm thick
Controls what enters and exits the cell

Functions of the Cell Membrane

Separates the cytoplasm from the extracellular fluid (ECF)
Maintains the cell's internal environment
Transports macromolecules into and out of the cell
Controls the distribution of ions like sodium and potassium
Generates transmembrane potentials
Contains receptors for hormones and transmitter substances, important for signal transduction

Components of the Cell Membrane

Composed of lipids, proteins, and carbohydrates
42% lipids, 55% proteins, 3% carbohydrates

Transport through the Cell Membrane

Three main mechanisms: passive transport, active transport, and vesicular transport

Passive Transport (Diffusion)

Movement of substances across the cell membrane down its electrochemical gradient
Requires no energy
Three types: simple diffusion, facilitated diffusion, and osmosis

Simple Diffusion

Movement of substances across the cell membrane without the need for carrier proteins
Occurs through the lipid bilayer or watery protein channels
Characterized by:
- Occurs down an electrochemical gradient
- No energy is required
- Not rate-limiting
- Not saturable

Facilitated Diffusion

Diffusion of substances across the cell membrane down an electrochemical gradient, requiring carrier proteins
Characterized by:
- Occurs down an electrochemical gradient
- No energy is required
- Requires the presence of a transport carrier protein
- Rate-limiting and saturable

Osmosis (Diffusion of Water)

Water diffuses through the lipid bilayer very rapidly due to its small size and high kinetic energy
Water moves from high to low concentrations of water

Active Transport

Movement of substances across the cell membrane against its electrochemical gradient
Requires energy
Two types: primary and secondary active transport

Primary Active Transport

Obtains energy directly from the hydrolysis of ATP
Example: Sodium-Potassium Pump

Secondary Active Transport

Uses energy stored in a concentration gradient (like sodium)
Example: Sodium-Glucose co-transport

Active Transport Characters

Occurs against the electrochemical gradient
Requires energy
Requires the presence of a transport carrier protein
Exhibits saturation and competition

Vesicular Transport

Mechanism by which large sized substances can cross the cell membrane
Two types: endocytosis and exocytosis

Endocytosis

Extracellular material is trapped within invaginations of the cell membrane
Forms vesicles
Active process requiring energy

Exocytosis

Intracellular material is trapped within vesicles
Vesicles fuse with the cell membrane, releasing their contents into the ECF
Active process requiring energy (e.g. release of hormones, digestive enzymes)

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Description

Test your understanding of the cell membrane's structure, functions, and transport mechanisms. This quiz covers key concepts related to passive and active transport, the composition of the membrane, and its role in maintaining cellular integrity. Perfect for biology students looking to reinforce their knowledge.