Cell Transport

movement of materials (CO2, O2, H2O, glucose, proteins, etc) into or out of cell via cell membrane

2 Types of Cell Transport 1. Active Transport- requires energy 2. Passive Transport- No energy required

Why is Cell Transport Important? Homeostasis- maintaining a steady state Metabolism- chemical reactions that convert “food” into energy Helps cells achieve equilibrium- when concentrations of molecules of a substance are the same everywhere

Brownian Motion All matter is made up of atoms or molecules and these particles are constantly moving. These atoms move in a straight line until they collide with another atom or some barrier then they reflect and move in a straight line until they collide with something else. This movement of atoms and molecules is called Brownian motion.

3 Types of Passive Transport 1.Diffusion 2.Osmosis 3.Facilitated Diffusion

1. Diffusion movement of molecules from areas of higher concentration to areas of lower concentration requires no energy expenditure by cell

Key components of cell that function in cell transport Cell membrane- phospholipids bilayer Cytoplasm- aqueous solution that contains materials Mitochondria- powerhouse of cell (glucose  ATP) RBC- carries protein hemoglobin that transports oxygen and carbon dioxide to and from cells

Example of Cellular Diffusion

Review Solution= Solute + Solvent Solute Solvent Ex: Sugar water Salt water

3 Prefixes for SOLUTES Hypo = Low Ex: Hypothermia, hypoglycemic Hyper = HighEx: Hyperactive, hyperglycemic Iso = Equal

Solution Types 1. Hypotonic Solution- concentration of solute molecules outside the cell is lower than the concentration in cytosol (water moves into cell until equilibrium is reached)

Solution Types 2. Hypertonic Solution- concentration of solute molecules outside the cell is higher than the concentration in cytosol (water moves out of cell until equilibrium is reached) water tends to diffuse from hypo- to hypertonic solutions

Solution Types 3. Isotonic Solution- concentration of solute molecules outside and inside the cell are equal ( water moves in and out of cell but at equal rates)

2. Osmosis process by which water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration Requires no energy expenditure by cell  Passive Transport

Extreme Osmosis Concentration gradient is so far from equilibrium that even after moving water or solutes, equilibrium still will not be reached, and this may result in DEATH of cell 1.Crenation- dehydration of an animal cell 2.Plasmolysis- dehydration of a plant cell 3. Cytolysis- cell bursting, usually occurs in animal cells

Plant Cells and Osmosis Plant cells- usually in a hypotonic environment Water moves into cell via osmosis Cell expands until it presses against cell wall, creating a pressure called turgor pressure

3. Facilitated Diffusion Proteins embedded in cell membrane help molecules that can’t move across membrane rapidly enough, into or out of cell Carrier proteins are specific for one type of molecule Protein changes shape protecting molecule from hydrophobic interior of membrane, then releases molecule on other side

Ion Channels similar to carrier proteins, but are specific for certain ions Examples of ions: Na+, Cl-, K+, Ca+2 These ions are important for many cell functions, but are not soluble in lipids so need to pass through these ion channels Some channels are always open, others close

Active Transport movement of materials up concentration gradient from areas of lower concentration to areas of higher concentration requires cells to use energy works like proteins in facilitated diffusion (bind to specific molecule, changes shape to protect, and releases molecule on other side)

Ex: Sodium/Potassium Pump Many animal cells need higher Sodium concentration outside of cell and higher Potassium concentration inside cell Splits molecule of ATP to change shape of protein to allow this

2 Types of Active Transport 1.Endocytosis-process by which cells ingest external fluid, macromolecules, and large particles, including other cells enclosed by portion of cell that folds in on itself creating a pouch called a vesicle

2 Types of Endocytosis A. Pinocytosis- “cell drinking” –involves transport of solutes or fluids B.Phagocytosis- “cell eating” –movement of large molecules or whole cells into a cell *animal cells ingest bacteria and destroy them via phagocytosis

2. Exocytosis-vesicles in cytoplasm fuse with cell membrane releasing contents into external environment *Remember this is how proteins leave cell Nervous and endocrine systems use exocytosis to release small molecules that control activities of other cells