Membranes and Cell Transport Flashcards
Module 1
What is a cell membrane?
A semi-permiable barrier separating the cytoplasm from the extracellular environment.
What does semi-permiable mean?
It allows some substances to pass in/out, and blocks others.
What are cell membranes made up of?
Two inwards-facing phospholipids called a phospholipid bilayer.
Describe the structure of a phospholipid.
A hydrophilic phospholipid head, attatched to two hydrophobic fatty acid chains. These chains face into each other, while the heads face out to the watery cytoplasm.
What is the Fluid Mosaic Model?
The model most often used to describe the cell membrane. “Fluid” describes the ability of molecules to move around, and “mosaic” describes the pattern formed by the phospholipids and proteins in the membrane.
What is passive transport?
The transportation of molecules across the cell membrane without the use of energy.
What is diffusion?
The movement of small, non-polar molecules across the membrane, down the concerntration gradient. This is a passive form of transport and therefore does not require any energy.
What is meant by the phrase “down the concerntration gradient”?
The movement of molecules across the cell membrane, from places of high concerntration, to places of low concerntration.
What is osmosis?
The diffusion of water.
What is facilitated diffusion?
The diffusion of some larger, polar molecules via the help of a protein channel. For example, glucose. This is a passive form of transport.
What is the role of peripheral proteins?
To aid transport and communication.
What is the role of cholesterol in the membrane?
To maintain correct spacing between molecules at different temperatures.
What is a glycoprotein?
A protein with carbohydrate attatched.
What is a glycolipid?
A lipid with carbohydrate attatched.
What is a polar molecule?
A molecule with unevenly distributed electrons, giving it a positive charge on one end, and a negative charge on the other.
