Chapter 7-3 Cell Boundaries Part 1 (of 4)Notes

I.Cell Membranes: ALL cells have one! A. Outer boundary of the cell B. Functions 1) Separates a cell from other cells 2) Protection and support 3) Controls what enters and exits the cell to maintain homeostasis

C. Structure: MOSTLY A LIPID BILAYER, with proteins and carbs scattered throughout. 1) 2 layers of phospholipids a) polar head: forms outsides (bread) of bilayer Described as hydrophilic: water loving, attracts water b) non-polar tail: forms inside (PB&J) of bilayer Described as hydrophobic: water fearing, avoids water (polar)HEAD Hydrophilic (nonpolar) TAIL Hydrophobic

2) Proteins with carbohydrate chains are wedged between Phospholipid molecules. a)Proteins act as pores, channels or pumps to move substances into or out of cell. b)Carbohydrates are markers which are used for cell identification.

D. Selectively permeable: allows CERTAIN substances to pass through The structure allows it to be selective. Protein pores allow small thing insoluble in lipids pass( Ex. H 2 0) Ex. Glucose can pass through Things soluble in Lipids can pass (Ex. Alcohol)

– –Molecules can pass through IF : – –They are soluble in lipids, they can easily pass through bilayer (ex. Alcohol, CO 2, O 2, steroids) – –If they are NOT soluble in lipids (water, gulcose amino acids, ions: May be small enough to get through protein pores (ex. water) May be able to go through a protein channel (ex. Glucose) May be able to get pushed through by a protein pump Ex. Na + (sodium ion), K + (potassium ion)

Examples of substances that need to pass into cell: – –1. water 2. glucose 3.oxygen Examples of substances that need to pass out of cell: – –1. carbon dioxide 2. water

II.Cell Walls A. Found in: 1) Plants 2) Algae 3) Bacteria 4) Fungi (Have both cell membrane AND cell wall) B. NOT IN ANIMAL CELLS C. Function: EXTRA Support and protection, and gives extra strength to cells D. Composed of fibers of carbohydrates: 1. Cellulose in _____________ 2. Chitin in _______________ 3. Peptidoglycan in ___________________ Plants Fungi Eubacteria

REVIEW QUESTIONS How does water move through the cell membrane? _______________ How does water move through the cell membrane? _______________ What does semi-permeable mean? ___________________________________ What does semi-permeable mean? ___________________________________ What molecule is the lipid bilayer made of? ___________ What molecule is the lipid bilayer made of? ___________ Which part is polar? _______Which is nonpolar?_________ Which part is polar? _______Which is nonpolar?_________ How does one cell recognize that a cell is part of that tissue or organ? _____________ How does one cell recognize that a cell is part of that tissue or organ? _____________ What is a substance that is soluble in lipids, that would pass through the lipid bilayer of the cell membrane easily?_______ What is a substance that is soluble in lipids, that would pass through the lipid bilayer of the cell membrane easily?_______ True or False: All cells have cell walls? ______________ True or False: All cells have cell walls? ______________ Through PROTEIN pores Only allows certain substance through Phospholipid Head tail Carbohydrate chain Alcohol False –animal cells don’t

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