Download Cell Biology and Membranes: Understanding Cell Membranes, Nucleotides, and Organelles - Pr and more Quizzes Microbiology in PDF only on Docsity! Key – Quiz #2 – 6:30 lab 1. Define: Cell membrane/ cytoplasmic membrane – The cell membrane or cytoplasmic membrane is the thin, dynamic surface layer surrounding a cell and separating the cytoplasm from the external environment. All cells have cell membranes and their composition is similar in that all contain lipids in a bilayer with integral and peripheral proteins “floating” in it. The cell membrane control what enters and exits the cell, is involved in taxis and other responses, and in prokaryotic cells is the site of ATP synthesis. Positive geotaxis – Taxis is the directed movement of cells in their environment. Geotaxis is movement directed by gravity, and positive movement is toward the stimulus; therefore, positive geotaxis is the movement of cells directed toward the gravitational pull of the earth. Cells in water environments such as ponds show positive geotaxis when they migrate downward toward the mud at the pond bottom. Contractile vacuoles – Contractile vacuoles are membranous organelles produced by freshwater protozoa. Their primary function is to pump excess water out of cells, but because they connect to the endoplasmic reticulum, contractile vacuoles also aid intracellular circulation. They undergo diastole or relaxation, allowing water to enter, and systole or contraction when pumping water out. They also allow cells to excrete liquid wastes such as urea, so function as a primitive excretory system. 2. Nucleotides can have additional phosphate groups attached to them forming nucleoside triphosphates (NTPs) that can be used as energy “currency” within cells (for example, ATP). Nucleotides can be incorporated into coenzymes (enzyme helpers) such as NAD, FAD and NADP. Nucleotides in their cyclic form can serve as regulatory molecules in various cell processes. Examples include cyclic-AMP and cyclic-GMP. 3. Hydrophilic/ integral or intrinsic proteins 4. Simple diffusion/ concentration gradients 5. Active transport 6. Osmosis 7. Phagocytosis – A specific form of endocytosis involving the ingestion of large particles, i.e., those cellular in size./ Lysosomes 8. Quorum sensing
