Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

2. Cell Chemistry & Cell Components

Introduction to Membrane Transport

Anatomy & Physiology

2. Cell Chemistry & Cell Components

Introduction to Membrane Transport

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2:20 minutes

Problem 2

Textbook Question

Add labels to the figure that follows, which illustrates some molecules that can and cannot pass through cell membranes unaided.

Verified step by step guidance

Identify the molecules shown in the images. The first image shows water molecules (H2O) and a large, complex molecule, likely a polysaccharide or protein, which cannot pass through the membrane unaided.

In the second image, identify the different types of transport across the cell membrane. The small molecules like gases (O2, CO2) and water can pass through the membrane via simple diffusion or facilitated diffusion.

Label the first image: The water molecules are shown passing through the membrane, indicating they can diffuse through the lipid bilayer or via aquaporins. The large molecule is shown outside the cell, indicating it cannot pass through the membrane unaided.

Label the second image: The arrows indicate different transport mechanisms. The small molecules passing directly through the membrane represent simple diffusion. The protein structure in the membrane likely represents a channel or carrier protein facilitating transport.

Conclude that small, nonpolar molecules and water can pass through the cell membrane unaided, while larger or charged molecules require specific transport proteins.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cell Membrane Structure

The cell membrane, also known as the plasma membrane, is composed of a phospholipid bilayer that provides a barrier between the inside of the cell and its external environment. This structure is crucial for maintaining homeostasis, as it selectively allows certain molecules to pass while blocking others. The hydrophobic interior of the membrane repels polar molecules, making it essential to understand which substances can diffuse through it unaided.

Selective Permeability

Selective permeability refers to the ability of the cell membrane to regulate the passage of substances in and out of the cell. This property allows the cell to maintain a stable internal environment by controlling the entry of nutrients and the exit of waste products. Small nonpolar molecules, such as oxygen and carbon dioxide, can typically pass through easily, while larger or charged molecules often require specific transport mechanisms.

Transport Mechanisms

Transport mechanisms are processes that facilitate the movement of substances across the cell membrane. These include passive transport, such as diffusion and osmosis, which do not require energy, and active transport, which requires energy to move substances against their concentration gradient. Understanding these mechanisms is essential for identifying how different molecules interact with the cell membrane and whether they can pass through unaided.

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Related Practice

Textbook Question

A molecule that blocks the ion channels lining integral proteins in the plasma membrane would interfere with

(a) Cell recognition

(b) The movement of lipid-soluble molecules

(d) The ability of protein hormones to stimulate the cell

(e) The cell's ability to divide

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Multiple Choice

Which molecule most easily diffuses across a biological membrane's lipid bilayer, without help of a protein?

According to the map above, what kind of large molecule transport is also called the process of cell 'eating'?

Fill in the following concept map to review the processes by which molecules move across membranes.

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Textbook Question

Which of the following processes includes all the others?a. osmosisb. diffusion of a solute across a membranec. passive transportd. transport of an ion down its electrochemical gradient

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Textbook Question

Which of the following groups of amino acid residues (see Ch. 3, Figure 3.2) would likely be found in the portion that crosses the lipid bilayer? a. acidicb. basicc. polar unchargedd. nonpolar

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Textbook Question

How do the components and structure of cell membranes relate to the functions of membranes?

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Textbook Question

Match the term with its appropriate definition.

Osmosis

Secondary active transport

Exocytosis

Phagocytosis

Simple diffusion

Primary active transport

Pinocytosis

Facilitated diffusion

a. Type of endocytosis in which a large particle is ingested

b. Transport across the plasma membrane against the concentration gradient via direct use of energy from ATP

c. Passive movement of solute across the plasma membrane

d. Movement of solvent from a solution of lower solute concentration to a solution of higher solute concentration

e. Passive movement of solute across the plasma membrane via a channel or carrier protein

f. Type of endocytosis in which ECF is brought into the cell in a protein-coated pit

g. Release of large substances from the cell through a vesicle

h. Transport of a substance across the plasma membrane against its concentration gradient using the energy from the 'downhill' movement of another substance

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