Cell Biology Chapter - Membrane Functions Quiz

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Questions and Answers

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

Responding to environmental changes and external signals

Synthesizing proteins for intracellular use (correct)

Maintaining intracellular contents and homeostasis

Exchanging nutrients, wastes, and secretions with its surroundings

The cell membrane's fluid mosaic model is described as having a tri-laminar structure. Which of the following best describes this arrangement?

Two layers of phospholipids sandwiching a layer of proteins between them.

Three layers of lipids, with two layers of hydrophilic lipids sandwiching one layer of hydrophobic lipids.

A single layer of phospholipids with proteins embedded throughout.

Two layers of phospholipids with hydrophilic heads facing outwards and hydrophobic tails forming an inner layer. (correct)

The glycocalyx, a layer of carbohydrates on the outer surface of the cell membrane, is composed of which of the following?

Glycolipids and glycoproteins. (correct)

Phospholipids and integral membrane proteins

Transmembrane proteins and cholesterol molecules.

Fibrous proteins such as collagen and elastin.

Which type of cell junction provides strong mechanical attachments between cells, featuring loop and hook-shaped cell adhesion molecules?

Desmosomes (C) Signup and view all the answers

Which of the following best describes the function of membrane-bound enzymes located in the cell membrane?

To catalyze chemical reactions at the cell surface. (D) Signup and view all the answers

How does the extracellular matrix (ECM) contribute to cellular functioning?

It serves as a pathway for diffusion of water-soluble substances and helps regulate cell behavior. (B) Signup and view all the answers

Which membrane component is most responsible for the selective barrier function of the plasma membrane, restricting the passage of water-soluble substances?

Phospholipids (D) Signup and view all the answers

A transmembrane protein that facilitates the passage of water-soluble substances across the plasma membrane is best described as which of the following?

An ion channel or aquaporin (C) Signup and view all the answers

Which type of cell junction is characterized by 'kiss sites' and limits the passage of materials between cells, forcing them to pass through the cells themselves?

Tight Junction (B) Signup and view all the answers

Which cellular junction type contains connexons forming a tunnel between adjacent cells, facilitating the passage of small particles and enabling synchronized action in cardiac and smooth muscle?

Gap Junctions (B) Signup and view all the answers

Which of the following statements accurately describes a property of diffusion?

Diffusion occurs from areas of higher concentration to areas of lower concentration and does not require energy. (B) Signup and view all the answers

Which factors primarily determine the permeability of a plasma membrane?

Lipid solubility and particle size (A) Signup and view all the answers

What is the energy requirement for passive transport across a membrane?

No energy is expended by the cell (B) Signup and view all the answers

Which of the following best illustrates the concept of an electrochemical gradient?

A combined effect of a charge and concentration difference across a membrane (A) Signup and view all the answers

How does osmosis differ from simple diffusion?

Osmosis is the movement of water across a semi-permeable membrane, while diffusion can involve any substance (B) Signup and view all the answers

Which situation best describes when osmosis will cease?

When the osmotic pressure is counter balanced by hydrostatic pressure (A) Signup and view all the answers

What is the primary role of desmosomes or adhering junctions?

To provide mechanical strength by binding cells together and linking to their cytoskeleton (A) Signup and view all the answers

According to Fick's Law, what primarily influences the rate at which diffusion occurs?

The concentration gradient, membrane surface area and membrane permeability (D) Signup and view all the answers

What role do glycoprotein filaments play in the structure of cell junctions?

Helping in anchoring cells together by connecting to the plaque and keratin filaments (C) Signup and view all the answers

Which of the following best describes a condition when water will move from an area of lower solute concentration to one of higher solute concentration?

When it is separated by a membrane that is only permeable to water (semi-permeable) (D) Signup and view all the answers

Which of the following scenarios best exemplifies the function of gap junctions?

The communication of electrical signals in muscle cells (D) Signup and view all the answers

Why must passage through tight junctions occur through the cells, rather than between them?

Because the tight seal prevents movement between cells (D) Signup and view all the answers

What determines the direction of movement of a cation based on an electrical gradient?

Cations move towards a negatively charged area of the gradient (A) Signup and view all the answers

Study Notes

Plasma Membrane Structure and Function

The plasma membrane is a lipid bilayer with embedded proteins.
Phospholipids have a polar head and nonpolar tails.
Cholesterol helps maintain membrane fluidity and stability.
Proteins are embedded within the membrane. Some proteins span the membrane (transmembrane) and others are on one surface.
Carbohydrates are on the outer surface of the membrane only and form glycolipids and glycoproteins.
Glycoproteins and glycolipids act as cell markers, identifying the cell.
The structure of the membrane is known as the "fluid mosaic model" with a tri-laminar structure.
The membrane is selectively permeable, allowing some substances to pass through while preventing others.
Membrane permeability depends on lipid solubility and particle size.
Different forces are involved in membrane transport. Passive transport does not require energy, such as diffusion or osmosis and other such membrane forces.
Active transport requires energy (ATP).
Different types of transport exist (i.e. carrier mediated transport etc): unassisted, facilitated and assisted transport.

Functions of Cell Membranes

Homeostasis and cell survival: maintaining intracellular contents and coordinating activity with other cells.
Providing a mechanical barrier for forming tissues.
Permitting exchange of nutrients, wastes, and secretions.
Responding to environmental changes and signals.
Maintaining ionic gradients for electrical activity.

Cell-Cell Adhesion

Extracellular matrix (ECM) acts as a "biological glue" secreted by cells.
Specialized cell junctions include desmosomes, tight junctions, gap junctions, and cell adhesion molecules.
Cell adhesion molecules are proteins that connect cells - e.g. loop and hook shaped proteins.
These junctions play crucial roles in tissue formation and communication.

Extracellular Matrix

ECM is a meshwork of fibrous proteins in a watery gel.
Collagen provides tensile strength, while elastin flexes the matrix and allows it to stretch, like elastic.
Fibronectin promotes cell adhesion.
ECM components vary to support different cell types and function.

Cell Junctions

Desmosomes are "spot rivets" that link cells together to maintain structural integrity.
Tight junctions create a seal between cells, preventing the passage of materials between them.
Gap junctions allow direct communication and passage of small molecules between cells.

Membrane Transport

Membrane transport is crucial for homeostasis.
Passive transport (diffusion, osmosis) occurs without energy expenditure.
Active transport (e.g., carrier-mediated, vesicular transport) requires energy input.
Membrane permeability is affected by substances and factors such as particle size, and lipid solubility, that determines what can pass.

Diffusion

Diffusion is the movement of molecules from an area of high concentration to low concentration.
Equilibrium is reached when there is no net movement of molecules.
Factors such as concentration gradient, surface area, lipid solubility, and distance influence the rate of diffusion (Fick’s law).

Osmosis

Osmosis is the diffusion of water across a semi-permeable membrane from an area of high water concentration to low water concentration.
The water concentration gradient is determined by the concentrations of solute.
Tonicity describes the osmotic pressure between two solutions.
Tonicity is the concentration of non-penetrating solutes.
Osmolarity is the total concentration of all solute particles in a solution.

Carrier-Mediated Transport

Carrier proteins are important in facilitated transport, and active transport.
They bind to molecules and change shape to move them across the cell membrane.
The carrier proteins undergo a reversible change in shape called flip-flop.
Different types of carrier mediated transport include: uniport, symport, and antiport.

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Description

Test your understanding of cell membrane functions and structures with this quiz. Explore concepts such as the fluid mosaic model, membrane-bound enzymes, and the role of the extracellular matrix. Perfect for students studying cell biology at various levels.