Biology Chapter 7 Flashcards

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Questions and Answers

What is the function of a cell membrane?

It separates the cell from its surroundings, exhibits selective permeability, and forms additional compartments in eukaryotic cells.

What is the cell membrane mostly made up of?

Lipids and proteins, although some carbohydrates.

What is the fluid mosaic model?

It describes the cell membrane as a phospholipid bilayer with embedded proteins that can move laterally.

What is the purpose of cholesterol in the membrane?

It acts as a temperature buffer, preventing packing in cold temperatures and reducing fluidity in warm temperatures. Signup and view all the answers

Do proteins move within the cell membrane?

True Signup and view all the answers

What are the two integral transmembrane protein types?

Integral proteins and peripheral proteins. Signup and view all the answers

What are integral proteins?

Proteins that penetrate the hydrophobic core of the lipid bilayer. Signup and view all the answers

What are peripheral proteins?

Proteins that are inside or outside of the membrane, attached to integral proteins. Signup and view all the answers

What are the six major functions of membrane proteins?

Transport, catalyze chemical reactions, signal transduction, recognition, intercellular connections, connections to cytoskeleton and ECM. Signup and view all the answers

What is signal transduction?

Proteins accept chemical messengers from other cells. Signup and view all the answers

What is recognition in cell membranes?

Identifies the cell as belonging to a specific type. Signup and view all the answers

What is the membrane naturally permeable to?

Nonpolar molecules and small molecules like oxygen and carbon dioxide. Signup and view all the answers

Is the membrane permeable to water?

True Signup and view all the answers

Is the membrane permeable to polar molecules?

False Signup and view all the answers

Is the membrane permeable to ions or charged particles?

False Signup and view all the answers

Which two protein types help transport across the lipid bilayer?

Channel proteins and carrier proteins. Signup and view all the answers

What are channel proteins?

Integral proteins that have hydrophilic tunnels allowing certain polar ions to pass through. Signup and view all the answers

What are carrier proteins?

Integral proteins that hold onto their passengers and change shape to shuttle them across the membrane. Signup and view all the answers

What is passive transport?

Movement across the membrane that requires no energy. Signup and view all the answers

What is diffusion?

Movement of molecules from high to low concentration. Signup and view all the answers

What does diffusion do?

It tends to equalize solute concentrations on both sides of the membrane. Signup and view all the answers

What is osmosis?

Diffusion of solvent, usually water, across a semipermeable membrane. Signup and view all the answers

What is tonicity?

The ability of a solution to cause a cell to gain or lose water. Signup and view all the answers

What is isotonic?

When solute concentration is the same inside and out. Signup and view all the answers

What is hypotonic?

When solute outside is smaller than inside, causing water to flow in. Signup and view all the answers

What is hypertonic?

When solute outside is greater than inside, causing water to flow out. Signup and view all the answers

A solution that has relatively high solute and low free water is?

Hypertonic. Signup and view all the answers

A solution that has relatively low solute and high free water is?

Hypotonic. Signup and view all the answers

A solution that has equal solute and equal free water is?

Isotonic. Signup and view all the answers

What happens to water in a U tube with hypotonic solution on one side?

Water will flow from the hypotonic side to the hypertonic side. Signup and view all the answers

Water moves by osmosis from the _ solution into the _ solution.

hypotonic, hypertonic. Signup and view all the answers

What is osmoregulation?

The regulation of water internally in animal cells. Signup and view all the answers

What is facilitated diffusion?

Diffusion aided by channel and carrier proteins. Signup and view all the answers

What is diffusion in channels?

Movement through specific integral proteins like aquaporins. Signup and view all the answers

What is diffusion in carriers?

Carrier proteins shuttle substances across the membrane, usually slower than channels. Signup and view all the answers

What is active transport?

The use of ATP to move solutes against their concentration gradient. Signup and view all the answers

What allows cells to maintain internal solute concentrations different from their environment?

Active transport via carrier proteins. Signup and view all the answers

What is an example of active transport?

Sodium/Potassium pump. Signup and view all the answers

How does the sodium potassium pump work?

Binds Na+, phosphorylates with ATP, changes shape, releases Na+, binds K+, and reverts to its original shape. Signup and view all the answers

When open to ECM, what can go into sodium potassium pump?

2K+. Signup and view all the answers

When open to cytoplasm, what can go into Na+/K+ pump?

3Na+. Signup and view all the answers

How large is the voltage across the membrane?

-50 to -200 mV. Signup and view all the answers

How do ions react to the potential of the membrane?

Negative ions are attracted to positive voltage outside, positive ions to negative voltage inside. Signup and view all the answers

What are the two types of bulk transport mechanisms?

Exocytosis and endocytosis. Signup and view all the answers

What is exocytosis?

Cell releases substances to the outside via vesicles. Signup and view all the answers

What is endocytosis?

Ingest food or liquid, involving processes like phagocytosis and pinocytosis. Signup and view all the answers

What is phagocytosis?

Ingestion of particles through cell membrane folding. Signup and view all the answers

What is pinocytosis?

Ingestion of liquids and dissolved particles. Signup and view all the answers

What is receptor-mediated endocytosis?

A specific form of endocytosis involving membrane receptors. Signup and view all the answers

Study Notes

Cell Membrane and Structure

The cell membrane separates the cell from its environment, allowing for selective permeability and compartmentalization in eukaryotic cells.
Composed predominantly of lipids (phospholipids) and proteins, it forms a bilayer structure.
The fluid mosaic model describes the dynamic nature of the membrane, where proteins can move laterally while flip-flopping occurs infrequently.

Role of Cholesterol

Cholesterol serves as a temperature buffer for the membrane, preventing freezing at low temperatures and reducing fluidity at high temperatures due to its rigid structure.

Protein Types and Functions

Integral Proteins: Penetrate the lipid bilayer, often spanning the entire membrane; they typically have hydrophobic regions in the center and hydrophilic regions at the ends.
Peripheral Proteins: Located on the inner or outer membrane surfaces, they are attached to integral proteins and play roles in cell structure and signaling.
Membrane proteins perform diverse functions including transport, catalyzing reactions, signal transduction, recognition, intercellular connections, and linking to the cytoskeleton.

Transport Mechanisms

Passive transport requires no energy and includes simple diffusion and facilitated diffusion.
Diffusion: Movement from high to low concentration, equalizing solute concentrations across membranes.
Osmosis: A specific type of diffusion involving water moving across a semipermeable membrane towards a hypertonic solution.
Tonicity describes a solution's ability to affect cell water levels: isotonic (equal solute), hypotonic (lower outside), and hypertonic (higher outside).

Water Movement and Regulation

Water flows from hypotonic solutions into hypertonic solutions, dictated by the concentration gradient.
Osmoregulation: Essential for animal cells without cell walls, involving structures like contractile vacuoles to manage internal water levels.

Active Transport

Active transport utilizes ATP to move solutes against their concentration gradient via carrier proteins.
The Sodium/Potassium pump is a key example, exchanging sodium and potassium ions across the membrane.

Membrane Potential and Ions

The voltage across the membrane ranges from -50 to -200 mV, generating a negative interior and positive exterior.
Ions respond to this electrochemical gradient, with negative ions attracted to the positive outside and vice versa for positive ions.

Bulk Transport Mechanisms

Exocytosis: The process of expelling substances from the cell using vesicles.
Endocytosis: The intake of substances through the membrane, encompassing phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis (specific internalization using receptors).

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Test your knowledge of cell membranes with these flashcards focusing on their function, composition, and structure. Ideal for students looking to reinforce their understanding of biological membranes in eukaryotic cells.