Post on 26-Jan-2016
description
Movement of substances across the
plasma membrane
Chapter 3
• Many biochemical reactions take place in a cell.
• The cells require many substances to carry out these biochemical reaction.
• Waste products that are formed during biochemical reactions within the cells must be eliminated because they are poisonous.
• There is movement of substances across the plasma membrane so that the cell can
Obtain nutrients and gases
Excrete metabolic wastes
Maintain a suitable pH and ionic concentration with the
cell for enzyme activity
Red Blood Cell Near Some Body cell
Moving in Moving out
Carbon dioxide
Oxygen
Photosyntesising Plant Cell
Moving in Moving out
Carbon dioxide
Oxygen
Water
Glucose
Plant Cell With No Chloroplast
Carbon dioxide
Oxygen
Glucose
Water
Moving in Moving out
Liver cellCarbon dioxide
Oxygen
Glucose
Water
Amino acids
Urea
Moving in Moving out
The structure of the plasma membraneThe plasma membrane has 3 components
1. Double layer of phospholipids molecules.
2. Pore
3. Carrier Proteins
A phospholipid molecule
Hydrophilic head
Hydrophobic tails
Phospholipid bilayer
Outside of cell
Inside of cellP
hosp
holip
id la
yer
• The phospholipids bilayer, proteins and other parts are not rigid or static, but form a dynamic and flexible structure.
• The protein molecules float about in the phospholipid bilayer to form a mosaic pattern that is always changing like fluid.
• Singer and Nicolson call it ‘fluid-mosaic model’
The plasma membrane is generally described as semi-permeable or selectively permeable because it only lets certain substances through.
Fat soluble molecules and small molecules such as oxygen are able to pass through unaided.
Water soluble substances such as glucose and amino acids and ions need to aided by carrier protein.
Water molecules can move across plasma membrane.
Which of these substances can pass through phospholipids layer or carrier protein?
Na+ Sodium ion
K+ Potassium ion
Carrier Protein
Channel Protein
Movement Of Substances Across The Plasma Membrane
Passive transport Active transport
Simple diffusion
Facilitated diffusion
Osmosis
The differences between PT and AT
Does not require energy
Substances move with concentration
gradient
Will continue until an equilibrium is
reached
Require energy from cell respiration
Substances move against concentration
gradient
Process leads to accumulation or elimination of the
substance from the cell
Passive Transport Active Transport