Cell Transport How substances move into and out

Cell Transport How substances move into and out of cells

What types of things need to get in & out of cells? • Organic compounds lipids, proteins, & carbohydrates) • Water • Cellular waste (CO 2, ammonia) • Solutes/inorganic molecules (salts, vitamins, minerals) How do these things get across the cell membrane?

Cell Membrane • Composed of a lipid bilayer (two-layered) embedded with proteins • The cell membrane is selectively permeable or semi-permeable: some things can pass freely through it while others cannot

Internal & External Cell Environment • Every cell is filled with water and solutes (cytoplasm) and surrounded by water and solutes • Solute: Substance that is dissolved in a liquid • Solutes includes both organic compounds (fats, proteins, amino acids, starches) and inorganic compounds (salt, vitamins, minerals) • Water and solutes cross the cell membrane

Two ways a cell transports substances across its membrane

Passive Transport • Movement of substances across membranes without adding energy • Substances naturally move from areas of HIGH to LOW concentration • Small particles/water go through the lipid bilayer • Larger particle go through protein channels

Two types of passive transport

Tonicity • Comparison of solute concentration inside and outside the membrane • Hypertonic- the area with the higher concentration of solute • Hypotonic- the area of lower solute concentration • Isotonic- equal concentration of solutes

Hypertonic Outside

Hypotonic Outside

Isotonic

Equilibrium/Homeostasis • Occurs when the concentration of a substance is the same across an area • Dynamic Equilibrium: Even though substances are equal in concentration on either side of the membrane, they continue to move back and forth.

Active Transport • When the cell must use energy (ATP) to get substances across the membrane • Movement of substances from LOW to HIGH concentration levels • Movement of large particles

Three ways cells move large particles in and out:

Phagocytosis- Extensions of cytoplasm wrap around and engulf large particles

Endocytosis- Cell pinches off membrane bound packets into cell Exocytosis- Cell expels membrane bound packets out of cell

Finger Mini-Lab • Question: After soaking two fingers in fresh water and two fingers in salty water for 15 minutes, how will they look different? Hypothesis: • 1. If I soak my fingers in salty water, they will look _____. 2. If I soak my fingers in fresh water, then they will look _____. • Conclusion: Were you hypotheses right? Explain the results, using the following words: • Hypertonic, hypotonic, osmosis, diffusion, solute