Diffusion and osmosis 7th grade Life Science

Intro to macromolecules Carbohydrates, lipids, proteins and nucleic acids

Macromolecules macro = big Carbohydrates lipids Organic molecules Supply energy for the cell (break down) Simple (table sugar) and complex carbs (pasta or starch) Examples: sugars, starches and fibers Organic molecules Store energy in cell (even more energy than carbs) major part of cell membrane Do not mix with water Examples: fats and oils

Macromolecules macro = big proteins Nucleic acids Organic molecules Made of smaller molecules called amino acids Used to build and repair many structures Enzymes and scattered in cell membrane Found in eggs, milk, peanut butter, meats and beans Large organic molecules Store important coded info in cells Dna (deoxyribonucleic acid) – genetic material in cells Rna (ribonucleic acid) – needed to make proteins, such as enzymes

To maintain homeostasis, cells must: - exchange materials Homeostasis stability – keep a constant internal state in a changing environment To maintain homeostasis, cells must: - exchange materials - eliminate waste - obtain and use energy - make new cells

Exchange of materials for the cell Cell membranes are semipermeable – only certain particles can move in or out of cell (selective) Passive transport: transport of materials straight through the cell membrane (does not use energy) Active transport: transport of materials through protein channels in cell membrane (requires energy) Protein channel energy

Diffusion and osmosis (passive transport) Movement of molecules from high concentration to low concentration Movement of water through a semipermeable membrane from areas of higher to lower concentration

In Which direction will the particles move or diffuse?

Answer: The particles diffuse from more concentrated to less concentrated!

In Which direction will the water move? (osmosis)

Answer: The water moves from less concentrate to more concentrate!

DIFFUSION and osmosis Concentration gradient: uneven distribution of a substance across a border Solute: particles dissolved in water SOLUTION: MIXTURE OF WATER AND SOLUTE Isotonic: Equilibrium, same concentration in 2 different areas Hypertonic: the area with higher concentration of solute (less water) Hypotonic: the area with lower concentration of solute (more water)

water Essential for cells Water moves across the cell membrane by osmosis it depends on the concentration of water inside and outside the cell

Vesicle transport exocytosis Endocytosis Process in which particles are enclosed in a vesicle in the cell and then released from the cell Opposite of endocytosis Exo = out Process in which cells surround and enclose a particle in a vesicle to bring it into the cell It requires energy Endo = in ENDO EXO

Diffusion lab Groups: A) Warm water x 2 B) cold water x 2 C) room temperature water x 2 d) room temp water with stirring x 2

Instructions Group d only: stir!  Identify people in your group and what group you are in (a, b, c, or D) on your worksheet Add 200 mL of water in your beaker, according to what your group needs (warm - a, cold - b, or room temperature – c and d) Add 1 drop of food coloring in your water – start the timer Group d only: stir!  Stop timer when the food coloring has spread out evenly in the water Write down how long it took for food coloring to be evenly distributed ENTER YOUR INFO ON TABLE AT FRONT

Carrot lab experiments: 1 – fresh water 2 – salt water

Why do you predict this? Give some rationale! instructions Identify people in your group with your group, write a prediction of what is going to happen to the carrot stick in experiments 1 and 2, add an explanation PREDICT: 1. What will happen to a carrot stick that soaks in fresh water overnight? (texture, shape, or other characteristics) 2. What will happen to carrot sticks that soak in salt water overnight? EXPLAIN: Why do you predict this? Give some rationale! OBSERVE: TOMORROW

Bellringer 12/3/15 - answers Too much water enters the cell cell gets swollen, maybe bursts Too much water leaves the cell cell gets shriveled (dehydrated) 2) diffusion; particles will move from area of high concentration to low concentration

Diffusion lab part 2 Which particles will diffuse: iodine, starch or both? Important information: iodine is an “indicator” * it changes color when it encounters starch *

Bellringer 12/4/15 - answers 1) Isotonic more concentrated (more particles, less water) Hypertonic less concentrated (less particles, more water) hypotonic same concentration, equilibrium 2) Cell membrane encloses particles to bring them into the cell 3) Cell membrane encloses particles from the inside of the cell to release them to the outside