Cell Membranes

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Questions and Answers

Which type of transport protein changes shape during the transport process?

Carrier proteins (correct)

Transporters

Pumps

Channels

What is the process called when molecules are transported against their concentration gradient?

Active transport (correct)

Secondary active transport

Facilitated diffusion

Diffusion

Which type of transport protein requires the input of energy?

Transporters

Carrier proteins

Pumps (correct)

Channels

What is the name of the glucose transporter that increases membrane permeability to glucose?

GLUT – 1 Signup and view all the answers

Which type of transport protein allows substances that would not otherwise cross the membrane to pass through?

Channels Signup and view all the answers

What is the term for the concentration and charge gradient collectively?

Electrochemical gradient Signup and view all the answers

What is the term for the passive transport of substances that would not otherwise cross the membrane?

Facilitated diffusion Signup and view all the answers

Which type of transport protein allows ions to diffuse through down their electrochemical gradients?

Channels Signup and view all the answers

What is the name of the membrane protein that uses ATP to transport Na+ and K+ against their concentration gradients?

Sodium – potassium pump Signup and view all the answers

What is the term for the process that makes it possible for cells to engage in secondary active transport?

Diffusion gradient Signup and view all the answers

Which of the following best describes the structure of plasma membranes?

Plasma membranes are made up of selectively permeable bilayers of phospholipids. Signup and view all the answers

What is the term used to describe the movement of water across a plasma membrane?

Osmosis Signup and view all the answers

What is the main function of membranes in cells?

All of the above Signup and view all the answers

What happens to phospholipids when placed in water?

They form lipid bilayers Signup and view all the answers

What is the permeability of phospholipid bilayers?

Selective permeability Signup and view all the answers

Which type of molecules move across phospholipid bilayers quickly?

Small or nonpolar molecules Signup and view all the answers

What is the term used to describe the hydrophilic and hydrophobic regions of phospholipids?

Amphipathic Signup and view all the answers

What is the role of membrane proteins in the passage of substances across the plasma membrane?

They facilitate the passage of substances Signup and view all the answers

What is the term used to describe the formation of phospholipid bilayers without the input of energy?

Spontaneous Signup and view all the answers

What is the function of phospholipids in relation to water molecules?

Phospholipids interact with water molecules Signup and view all the answers

Which of the following factors can influence the behavior of the cell membrane?

Number of double bonds between the carbons in the phospholipid's hydrophobic tail Signup and view all the answers

Which of the following statements about bond saturation and membrane permeability is true?

Unsaturated hydrocarbon chains have at least one double bond Signup and view all the answers

Which of the following factors can decrease membrane permeability?

Increasing the length of the phospholipid tails Signup and view all the answers

Which of the following statements about membrane fluidity is true?

Membrane fluidity is a function of temperature and the structure of the hydrocarbon tails Signup and view all the answers

Which of the following is a form of passive transport?

Diffusion Signup and view all the answers

What happens when there is a difference in solute concentration across a membrane?

Molecules and ions move randomly from high to low concentration regions Signup and view all the answers

Which of the following statements about osmosis is true?

Water moves from regions of high solute concentration to low solute concentration Signup and view all the answers

What happens to a cell in a hypertonic solution?

The cell will shrink Signup and view all the answers

Which of the following is a characteristic of the fluid-mosaic model of membrane structure?

Phospholipids provide the basic membrane structure Signup and view all the answers

What are integral proteins?

Proteins that span the membrane Signup and view all the answers

Study Notes

Transport Proteins and Mechanisms

Transport proteins that change shape during the transport process are called carrier proteins.
Transporting molecules against their concentration gradient is known as active transport.
Primary active transport requires energy input, typically in the form of ATP.
The glucose transporter that increases membrane permeability to glucose is known as GLUT (Glucose Transporter).
Channel proteins allow substances that cannot cross the membrane otherwise to pass through.
The collective term for the concentration and charge gradient is the electrochemical gradient.
Facilitated diffusion describes the passive transport of substances that otherwise cannot cross the membrane.
Ion channels enable ions to diffuse through the membrane down their electrochemical gradients.
The membrane protein responsible for using ATP to transport Na+ and K+ against their concentration gradients is called the Na+/K+ pump.
The process that allows cells to engage in secondary active transport relies on the established electrochemical gradients.

Membrane Structure and Function

Plasma membranes are best described by the fluid-mosaic model, which highlights their dynamic structure composed of lipids and proteins.
The term for the movement of water across a plasma membrane is osmosis.
Membranes function primarily to control the passage of substances in and out of cells, maintaining homeostasis.
When placed in water, phospholipids spontaneously form bilayers with hydrophobic tails inward and hydrophilic heads outward.
Phospholipid bilayers are selectively permeable, allowing certain molecules to cross while blocking others.
Small, nonpolar molecules move across phospholipid bilayers quickly due to their compatibility with the hydrophobic core.
Phospholipids possess hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.

Membrane Dynamics and Factors Influencing Permeability

Membrane proteins facilitate the transport of substances across the plasma membrane by acting as channels or carriers.
The formation of phospholipid bilayers without energy input occurs through spontaneous self-assembly.
Phospholipids interact with water molecules, creating a barrier that separates cellular compartments.
Factors influencing cell membrane behavior include temperature, lipid composition, and cholesterol content.
Increased unsaturation of fatty acid chains in phospholipids generally enhances membrane permeability.
Factors that can decrease membrane permeability include saturation of fatty acids and the presence of cholesterol in certain proportions.
Membrane fluidity is influenced by factors such as temperature and the types of lipids present.
Diffusion, a form of passive transport, occurs naturally along concentration gradients, moving from high to low concentration.
When there is a difference in solute concentration across a membrane, osmosis drives water movement toward the area of higher solute concentration.
In a hypertonic solution, a cell loses water, leading to crenation or shriveling.
Integral proteins are embedded within the plasma membrane and play essential roles in transport and signaling functions.

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Description

Test your knowledge on cell membranes and their key concepts, including phospholipids, selective permeability, diffusion, osmosis, and membrane proteins.