Diffusion, active transport, endocytosis and exocytosis

Overview

Simple and facilitated diffusion, active transport and the ATP it needs, endocytosis and exocytosis, and which of these processes are passive.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Define diffusion.

   Model answer

   The net passive movement of molecules from a region of higher concentration to a region of lower concentration, down a concentration gradient.

2. 2

   What is facilitated diffusion?

   Model answer

   The passive movement of molecules across a membrane via channel or carrier proteins, down a concentration gradient, without ATP expenditure.

3. 3

   Why do some molecules require facilitated diffusion rather than simple diffusion?

   Model answer

   Large or charged molecules cannot pass directly through the hydrophobic phospholipid bilayer, so they need protein channels or carriers.

4. 4

   Define active transport.

   Model answer

   The movement of molecules across a membrane against a concentration gradient, requiring carrier proteins and ATP as an immediate energy source.

5. 5

   Why is ATP required for active transport?

   Model answer

   Energy from ATP is needed to change the shape of carrier proteins so they can move substances against the concentration gradient.

6. 6

   What is endocytosis?

   Model answer

   The process by which cells engulf substances by infolding of the plasma membrane to form vesicles, requiring ATP.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.