Biology ( Transport )

Passive / Active Transport

Passive transport

Movement of material across the cell membrane

Recall

Cell membrane is selectively permeable / allow certain molecules and ions to pass while blocking others

Adenosine Triphosphate

ATP, the energy cells use

Diffusion

Random motion from an area with high concentration to low

Molecules that can pass through the plasma membrane

Very tiny non-polar molecules ( oxygen / carbon dioxide / water )

Molecules that cannot pass through the plasma membrane

Large molecules, charged ( the cell membrane has a negative charge )

Channel proteins

Opens and closes creating a corridor for specific molecules / ions to pass, bi-directional

Example of a channel protein

Aquaporin, allows water to diffuse the membrane more rapidly

Carrier proteins

Takes up particles on the high concentration side of the plasma membrane, changes shape, and releases them on the lower side

Osmosis

Special type of diffusion involving water

Chemical solution

Mixture of two or more chemical substances

Chemical solution

Mixture of two or more substances

Involves the solvent ( dissolves others ) and the solute ( dissolves )

Nature’s tendency

Equalize the concentrations when they are uneven

Hypotonic

A solution with a low solute concentration

Causes the cell to swell / burst

Hypertonic

A solution with a high solute concentration

Causes the cell to shrivel / shrink

Isotonic

A solution with a equal solute concentration

Perfect for the cell

Osmosis in plant cells

Plant cells don’t burst when water enters through osmosis due to their cell wall

Osmosis in animal cells

Don’t have vacuoles

Cells do not pop in hypotonic conditions due to extracellular fluid keeping it isotonic

Two types of transport

Passive and active transport

Active transport

Movement of molecules / ions across a membrane against concentration gradient by ATP

Charge of a cytoplasm

Negative charge

Charge of a extracellular

Positive charge

Sodium Potassium Pump

Requires ATP to work

Transports 3NA+ out of the cytoplasm for every 2K+ and creates an electric signal

Electrical Potential

The electric signal in the cell membrane

Endocytosis

Cellular process where cells engulf outside materials in

Phagocytosis

Eats large / solid particles ( like bacteria, debri, and harmful pathogens )

Pinocytosis

Drinking extracellular fluid containing dissolved nutrients / molecules

Exocytosis

Transportation of cellular products inside to outside

Factors of the rate of diffusion

Relative concentration on each side and temperature ( high = faster, low = slower )

Cytoplasmic streaming

Organelles / cytosol flow in a circular pattern in the cell

SA : V ratio

Relationship between surface area of the membrane and the volume of the cytoplasm

Large SA : V ratio

Reduces distance from the membrane to the center allowing cells to efficiently supply substances / remove waste

Lower SA : V ratio

Less efficient at exchanging substances

Factors determining if / how they cross a membrane

Characteristics of the selectively permeable membrane and chemical / physical properties of a substance

Chemical factors of exchange

Charged particles can only pass through transport proteins while uncharged particles can readily pass ( if small enough )

Physical factors of exchange

Large / irregular particles can only pass through transport proteins / endocytosis / exocytosis while small particles can readily pass ( if uncharge )