Membrane Proteins 

Transport proteins

May or may not use ATP for energy to move chemicals in or out of the cell

Signal transduction pathway: involves the use of signalling molecules (either protons or lipids that carry messages for the cell; maybe protein an exp is insulin) Which carry the message to target cells (cells that are able to receive the signalling molecules because they have the appropriate receptor) The receptor (protein that accepts the signalling molecule) locate don the target cells will then release a series of chemicals into the cytoplasm to carry the message to the nucleus. 

Extracellular matrix 

Cytoplasm 

Intercellular junctions 

Cell-cell recognition 

Relies on glycoproteins, macromolecules made up of proteins and carbohydrates. To helps cells in multi-cellular organisms identify each other as self  

Enzymatic activity  

Enzymes which are proteins that speed up or facilitate a reaction, can be located in the cell membrane.  

 Molecules are able to move because of their own kinetic molecular energy (KME) 

 What causes molecules to move the way they do? 

Transport proteins 

Channel & carrier → passive 

Pump                   → active 

1. Uniporters 

• Move chemicals in one direction 

• Either in or out of a cell 

• Exp: aquaporin 

2. Ssymporters 

• Move 2 different chemicals in one direction

• Both either into the cell or out 

• Exp: glucose/Na* contransport 

3. Antiporters 

• Move different chemicals in the opposite direction 

• One goes into the cell and the other goes out 

• Exp: Na* / K* pump 

Passive Transport 

Diffusion 

Diffusion 

• Movement of the substances from high [ ] to low [ ] movement of their substances down their concentrated gradient 

• When molecules move from a concentration to a less concentrated area  

• Electrical charge when molecules always move to balance charges 

Osmosis 

Selectively permeable membrane

Controls what goes from one side to another 

Through this membrane, water will move from an area of high concentration to an area of low concentration.

Type of solution when comparing 

1. Isotonic 

• A solution with a similar concentration of solutes 

2. Hypotonic

• A solution with a lower concentration of solutes than the ones around it 

3. Hypertonic 

• A solution with a higher concentration of solutes than the ones around it

Animal Cells 

Hypotonic 

Inside is hyper so H2O rushes in and it bursts, becoming Lysed

Isotonic *

Rate of water going in matches the rate of water going out (ideal)

Hypertonic 

Inside is hypo so H2O leaves making the cell shrivelled 

Plant Cells 

Hypotonic *

Water enters the cell while extra H2O enters the central vacuole creating pressure on the cell wall, making it turgid (ideal)

 Isotonic 

The rate of water going in equals the rate of water going out; leaves will be droopy because of the lack of pressure on the cell wall. The cell becomes Flaccid or deflated; it can survive, but it is ineffective. 

Hypertonic

The water leaves the cell, causing the cell membrane to get ripped off the cell wall, called plasmolysed. 

Facilitated diffusion 

Movement of soluted from high [solute] to low [solute] with the help of transport proteins 

Transport proteins: Allow cell membrane to be selective 

Channel Proteins 

• Create openings or tunnels for specific solutes 

  • Maybe gated 

• The nature & size of the tunnel allow what goes through 

• Exp: Na* channel / Aquaporin (allows water in)

Carrier Proteins 

• Change shape to carry specific solutes across the cell membrane 

• How it works 

  • When it is in the normal conformation, it will face either the outside or inside of the cell 

  • Specific solute enters the binding sight, which causes the carrier protein to flip counter motion and face the opposite side 

    • Binding sight is the region of a protein where a substrate attaches 

  • In the flipped counter motion the solute is repelled out of the character protein into the new region 

  • The carrier proteins will return back to its normal conformation because no solute is in the binding site 

Active Transport 

Cells must supply energy in the form of ATP to move solutes form low [solute] to high [solute], working against the concentration gradient 

Exp: sodium-potassium pump

Two forms of active transport 

Primary active transport 

• A pump uses ATP to move chemicals against their concentration gradient 

• Exp proton pump 

Secondary active transport 

• A carrier proton moves chemicals against their concentration gradient created by primary active transport 

• Exp: sucrose / H* conransporter 

Sodium Potassium Pump 

How does it work?

Bulk Transport

Using ATP, moves either large-size chemicals or large quantities of chemicals across the cell membrane using vesicles. 

Exocytosis

• Takes chemicals out 

• Exp: when Golgi apparatus produces secretory vesicles filled with proteins that are released out of the cell 

Endocytosis 

• Brings chemicals in

• Exp:

  • Phagocytosis 

    • Brings in large-sized substances into the cell 

  • Pinocytosis 

    • Brings in large quantities of solutes into the cell 

  • Receptor-mediated endocytosis

    • Brings in substances once a trigger (single molecule) active the reception on the cell membrane, which could be the solute itself