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Lecture 3

Lecture 3- Cell Membranes.docx

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Kathleen Gilmour

Lecture 3- Topic 2 Cell Membranes Pop quiz: Q1: What organelles might be particularly abundant in a cell that produces digestive enzymes for secretion into the intestine? A1: Rough endoplasmic reticulum & golgi complex Q2: what evidence supports the hypothesis that mitochondria originated as free-living aerobic bacteria? A2:_________(look this up) Q3: What is kleptoplasty? Why is it significant? **similar type of 2point question on midterm A3: Organism extracts chloroplasts from algae, and uses it to get energy. Refers to the example of the sea slug ONLY. significant because it explains the endo symbiont relationship Q4: Who proposed the fluid mosaic model of membrane structure? When? A4: Singer and nicholson, in 1972 Q5: Sketch a phosphoglyceride and use your sketch to illustrate its amphipathic nature **type of sketch is fair game for midterm, and final A5: Slide 9 Phospholipids, and sphingolipids have similar structures. -when you put them into water you get hydrophobic interactions. the non-polar tails gather together, and away from water, and the polar heads, are interacting with water. (a non-covalent interaction making it very liquid) Slide10 Glycolipids: similar in structure to phospholipids. main difference is instead of phosphate or R group they have sugars. You can either have single sugar units, or strings of sugars (oligosacharides). -Found primary with the carbohydrate group extending to the outside of the cell. They are commonly used as signals or recognition signals blood groups: the different types refer to the different types of carbohydrates coming off of your red blood cells. Slide 11 Sterols: -type of steroid -presence of a four ringed hydrocarbon skeleton (steroid) -for sterols, you'll have a hydroxyl group at one end (polar), and a hydrocarbon chain at the other end (non- polar) as a whole the molecule is non-polar mostly *this causes it to fit into the membrane quite characteristically -The hydrocarbon rings burry themselves in the fatty acid chain. -the small polar hydroxyl group is oriented towards polar head groups of phospholipids Sterols show different abundances in diff. groups. -Prokayotic cells lack sterols -Eukaryotic cells have it only -Main sterol for animals is cholesterol -Plants don't have cholesterol, have their own unique called phytosterol -fungi have ergosterol. *The four ringed structure is quite rigid in comparison to the fatty chains found on fatty acid tails (phospholipids) slide 12 Answer: B Slide 13 Answer : B Slide 14 -The two halves of the lipid bilayer aren't the same. -composition of each half is different -the lipids rarely flip flop form each side; Hard to pass the hydrophobic center for the polar lipid. -This is what give them different compositions (each lipid) Graph shows the avg distribution of each lipid on either side If we where to add glycolipids they would be biased toward the external side. Because they work as recognition signals Slide 15 as your skin becomes cold membrane becomes less fluid and sensory receptors stop working. sensory receptors cannot work if they cannot move in the membrane. Membrane that is too fluid, is organized enough, and not fluid at all cannot work because sensory systems are mobile. A number of factors affect membrane fluidity: #1Temperature -As temp falls, phopholipids tend to pack together tightly giving a stiff & ri
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