Review Cell Membrane Cell membrane selectively permeable phospholipid

Review: Cell Membrane Cell membrane – selectively permeable phospholipid bilayer • Controls what enters and leaves a cell • Cell communication (carbohydrate chains) • Protective barrier for cell from its surroundings • Provides anchoring (peripheral proteins) for the cytoskeleton

How does a Cell Maintain Homeostasis All cells/organisms require a certain internal environment to function properly • This is called homeostasis Main concerns for homeostasis include: • Temperature • p. H levels • Ions/salinity • Water levels • Nutrient availability *these conditions can very minute-to-minute or hour-to-hour*

Most bodily functions aim at maintaining homeostasis, and the inability to maintain it leads to disease and often death Temperature • Body prefers 98. 6⁰ F • Cold = shake; Pull blood and water into your core area • Hot = sweat; Send blood and water to your skin (red color) • Controlled by enzymes unless extreme temps (denatures the enzyme)

p. H levels • Acids = 0 -6; Bases = 8 -14 (7 = neutral) • Blood p. H level very narrow (7. 35 -7. 45) • Maintained by buffers in the blood (proteins usually) • Affected by oxygen levels • Body p. H maintained by lipid buffers, alkaline salts, calcium from bones and muscles, lymphatic system Buffers – substances that can balance out too acidic or basic environments **yeast, molds, fungus, parasites thrive in an acidic body lacking oxygen (anaerobic). They feed on your proteins and fats and poison us with their waste**

Ions, water, nutrients, and large particles are moved/controlled by cellular transport Two types of Cellular transport • Passive transport – Does not require energy – Moves from area of high concentration to low concentration – Ex. diffusion, osmosis, facilitated diffusion • Active transport – Requires energy (ATP) – Moves from an area of low concentration to high concentration – Ex. pumps, endocytosis, exocytosis, ion channels