Unit 5

What is the fluid mosaic model?

A model describing the cell membrane as a flexible phospholipid bilayer with moving proteins, lipids, and cholesterol embedded within it

Having both hydrophilic and hydrophobic regions

Amphipathic

How does cholesterol affect membrane fluidity?

It prevents the membrane from becoming too rigid or too fluid.

A protein permanently embedded in the cell membrane, often spanning the entire membrane

Integral protein

What is the function of a channel protein?

It selectively allows certain substances or ions to pass through the cell membrane

A protein temporarily attached to the inner or outer surface of the membrane

Peripheral protein

What is a glycoprotein?

A protein with attached carbohydrate molecules used for cell recognition

A carbohydrate-rich coating around the cell formed by glycoproteins and glycolipids

glycocalyx

What are the functions of the glycocalyx

Cell recognition, cell adhesion, receptors for hormones, and protection

What types of molecules can pass directly through the phospholipid bilayer?

Small nonpolar molecules such as oxygen, carbon dioxide, alcohol

What is passive transport?

Movement of substances across the membrane without using ATP

A difference in the concentration of substance across a space

Concentration Gradient

Movement of particles from an area of high concentration to low concentration

What is simple diffusion?

Passive movement of small nonpolar molecules directly through the lipid bilayer

Passive transport using membrane proteins to move substances across the membrane

Facilitated diffusion

What is the function of carrier protein?

It binds specific molecules and changes shape to transport them across the membrane

How does glucose usually cross the cell membrane?

By carrier-mediated facilitated diffusion using glucose transport proteins

Facilitated diffusion through a membrane channel protein

Channel-mediated facilitated diffusion

Membrane channel proteins that allow water to cross membrane

Aquaporins

Passive movement of water across a semipermeable membrane

Osmosis

A solution with the same solution concentration as the cell

Isotonic solution - cells maintain their normal shape and function

A solution with a higher solute concentration than the cell

Hypertonic solution - water leaves the cell and the cell shrivels

A solution with a lower solute concentration than the cell

Hypotonic solution - water enters the cell, causing swelling and possible bursting

Movement of substances across a membrane using ATP energy, usually against the concentration gradient

Active transport

What does sodium-potassium pump do?

It pumps Na+ out of the cell and K+ into the cell using ATP

How many ions are moved by the Na+/K+ pump per ATP?

3 Na+ out and 2 K+ in

What is primary active transport?

Transport directly powered by ATP hydrolysis

What is secondary active transport?

Transport powered indirectly by concentration gradients created by ATP-driven pumps

Why are sodium and potassium gradients important?

They are essential for nerve signaling, muscle contraction, and cell function и

The process of bringing substances into the cell using vesicles formed from the cell membrane

Endocytosis

A form of endocytosis that brings extracellular fluid into the cell

Pinocytosis

Selective endocytosis using membrane receptors specific for certain substances

Receptor-mediated endocytosis (iron - transferrin)

The process of exporting substances out of the cell using vesicles

Exocytosis

What substances are commonly secreted by exocytosis

Hormones, digestive enzymes, histamine