The Cell Membrane: Structure and Function

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Questions and Answers

Which type of molecules can easily cross the cell membrane?

Small and polar lipid-soluble molecules

Large and non-polar lipid-soluble molecules

Large and polar lipid-soluble molecules

Small and non-polar lipid-soluble molecules (correct)

What is the difference between passive and active transport?

Passive transport moves molecules from low to high concentration, while active transport moves molecules from high to low concentration

Passive transport moves molecules along the concentration gradient, while active transport moves molecules against the concentration gradient (correct)

Passive transport uses energy, while active transport does not use energy

Passive transport requires specific carrier proteins, while active transport does not require carrier proteins

What is the characteristic of bulk transport?

It only occurs under specific temperature conditions

It moves small and non-polar molecules into or out of the cell

It requires energy to move molecules across the cell membrane

It involves the movement of large macromolecules such as proteins or polysaccharides (correct)

What is the role of the concentration gradient in determining the movement of molecules across the cell membrane?

It determines whether molecules can cross the cell membrane by passive transport Signup and view all the answers

What is the function of the transport proteins in the cell membrane?

Creating tunnels for selective substance transport Signup and view all the answers

How is the structure of the cell membrane described?

A sandwich of phospholipids with hydrophilic heads and hydrophobic tails Signup and view all the answers

Why is the cell membrane considered semipermeable?

It allows essential molecules to enter and waste products to exit Signup and view all the answers

What is the role of cholesterol molecules in the cell membrane?

Contributing to the fluidity of the cell membrane Signup and view all the answers

What is the term used to describe the movement of water that is a specific type of diffusion?

Osmosis Signup and view all the answers

In which type of solution does a water solution with less solute (more diluted solution) have higher water potential?

Hypotonic solution Signup and view all the answers

What term refers to the strength of a solution in relation to osmosis, and is used when comparing two different solutions?

Tonicity Signup and view all the answers

What does the prefix -iso mean in relation to tonicity?

The same concentration Signup and view all the answers

Study Notes

Molecules and Cell Membrane Transport

Small, nonpolar molecules (e.g., oxygen, carbon dioxide) can easily cross the cell membrane.
Water can also cross due to its small size, even though it is polar, through specialized channels.

Passive vs. Active Transport

Passive transport occurs without energy input, allowing substances to move down their concentration gradient.
Active transport requires energy (ATP) to move substances against their concentration gradient.

Bulk Transport Characteristics

Bulk transport involves the movement of large particles or volumes across the membrane via vesicles.
It includes processes like endocytosis (import) and exocytosis (export).

Concentration Gradient Role

The concentration gradient influences molecular movement; molecules move from high to low concentration areas in passive transport, driving equilibrium.

Transport Proteins Function

Transport proteins facilitate the movement of specific substances across the cell membrane.
They can be channels or carriers, providing pathways for polar or charged molecules.

Cell Membrane Structure Description

The cell membrane is described by the fluid mosaic model, depicting a dynamic arrangement of phospholipids, proteins, and carbohydrates.

Semipermeable Nature of Cell Membrane

The cell membrane is considered semipermeable because it selectively allows certain substances to pass while blocking others based on size, polarity, and charge.

Cholesterol in Cell Membrane

Cholesterol molecules maintain membrane fluidity, stability, and integrity, especially at varying temperatures.
They help prevent the membrane from becoming too rigid or too permeable.

Water Movement and Diffusion

Osmosis refers to the specific movement of water across a semipermeable membrane, driven by concentration differences.

Water Potential in Solutions

A water solution with less solute (more diluted solution) has higher water potential compared to a more concentrated solution.

Osmosis Strength and Comparison

Tonicity describes the strength of a solution in relation to osmosis, comparing solute concentrations between two solutions.

Iso in Tonicity Context

The prefix "iso" means "equal," indicating isotonic solutions have equal solute concentrations, resulting in no net movement of water across the semipermeable membrane.

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Description

This quiz covers the structure and function of the cell membrane, also known as the plasma membrane. It discusses its role as a semipermeable membrane in regulating the passage of substances into and out of the cell, and the composition of the phospholipid bilayer.