Untitled Flashcard Set

What does homeostasis refer to?

The maintenance of constant internal conditions in a living organism.

What is the fluid mosaic model?

A model used to describe the cell membrane's structure, consisting of a phospholipid bilayer with embedded proteins and cholesterol.

What key molecules must enter cells for proper function?

Ions and nutrient molecules such as sugars and amino acids.

What must exit the cell to maintain homeostasis?

Waste products such as urea and carbon dioxide.

What property of the cell membrane allows it to control what enters and exits?

Selectivity based on membrane composition and proteins.

What are the three ways substances can move into or out of the cell?

By lipid bilayer solubility, vesicles, or protein transport molecules.

How do phospholipid bilayers assemble in aqueous solutions?

They spontaneously form due to hydrophobic interactions.

What defines passive transport processes?

They do not require energy.

Which transport processes are considered passive?

Simple diffusion, osmosis, and facilitated diffusion.

What is Brownian movement?

The random movement of molecules in solution.

What must a substance do to pass through the cell membrane by simple diffusion?

It must be soluble in the lipid bilayer.

What is facilitated diffusion?

The process where larger, polar molecules move across the membrane with the help of protein carriers.

What happens to glucose once it enters a cell?

It is converted to glucose 6-phosphate, preventing it from leaving the cell.

What is osmosis?

The movement of water across a selectively permeable membrane due to osmotic pressure gradients.

What is a contractile vacuole?

An organelle that helps pump water out of certain cells, helping them survive in hypotonic environments.

What is the sodium-potassium pump?

An active transport mechanism that pumps sodium out of and potassium into the cell using ATP.

What causes molecules to diffuse?

The concentration gradient, moving from high to low concentration.

How does temperature affect the rate of diffusion?

Higher temperatures increase the speed of molecular movement and collision, enhancing diffusion rate.

What are integral proteins?

Membrane proteins that span the lipid bilayer and are involved in transport and communication.

What determines whether a membrane is selectively permeable?

The types and presence of proteins in the membrane.

Which molecules are typically impermeable to the lipid bilayer?

Ionic and large polar molecules.

What is the difference between isotonic, hypertonic, and hypotonic solutions?

Isotonic solutions have equal solute concentrations; hypertonic solutions have higher solute concentrations outside; hypotonic solutions have lower solute concentrations outside.

What kind of transport processes require energy?

Active transport processes.

What is osmotic pressure?

The pressure exerted by solutes in a solution that draws water across a membrane.

What is a semi-permeable membrane?

A membrane that allows some substances to pass while blocking others based on size or charge.

Which of the following are passive transport processes?

Simple diffusion, osmosis, and facilitated diffusion.

What does the rate of diffusion depend on?

Molecular weight and concentration gradient.

What is the main function of the cell membrane?

To protect the cell and regulate the movement of substances in and out.

What is the result of a high osmotic pressure outside a cell?

Water moves out of the cell, potentially causing it to shrivel.

What role do cholesterol molecules play in the cell membrane?

They help maintain fluidity and stability of the membrane.

What process uses ATP to move substances against their concentration gradient?

Active transport.

What do you call the process of engulfing material into a cell?

Endocytosis.

What is the role of proteins in membrane transport?

They facilitate the movement of substances across the membrane.

In what type of solution does water flow into cells?

In a hypotonic solution.

What component of the cell membrane affects its fluidity?

Unsaturated fatty acids in phospholipids.

What process involves the expulsion of materials from a cell?

Exocytosis.

What could happen to a cell in a hypertonic environment?

The cell could lose water and shrink.

What type of molecules can pass directly through the lipid bilayer?

Small, nonpolar molecules.

What effect does the sodium-potassium pump have on a cell's membrane potential?

It creates a charge difference across the membrane, contributing to the cell's excitability.