The most valuable lipid ever?

Transcription

1 The most valuable lipid ever? Spermaceti whale oil Used by sperm whales in a special organ in the huge head cavity Largely comprised of cetyl palmitate ww.thisrecording.com

2 Peer Instruction Are membranes with straight lipid tails more or less permeable than membranes with kinked tails? Are membranes with long tails more or less permeable than membranes with short tails? Are warmer membranes more or less permeable than colder membranes?

3 Clicker Question #6 (An over-simplified question) Imagine a pure membrane from only one of these four phospholipids: Which membrane will be the most permeable to ethanol?

4 Tuesday January 10 th, 2017 Class 6 Learning Goals Transmembrane Transport and Organelles After this class, you should be able to: Predict the polarity of any part of an integral membrane protein For each of three types of membrane transport, Describe the logic for the cell of that transport type Describe the mechanism Be able to identify the type of transport from a scenario Name and predict the enzymatic components inside any of the organelles in the given table Identify membrane movements necessary for organelle function the sorting/production/delivery of non-cytoplasmic proteins Trace the path of transport and development for a protein or lipid moving through the endomembrane system.

5 Is the membrane of this cell semi-permeable? 1. Yes, because molecules can cross the membrane easily 2. Yes, because molecules can t cross the membrane easily. 3. Yes, because some molecules cross the membrane easily, but other molecules do not cross easily. 4. No, it is not semi-permeable. Clicker Question #1

6 Clicker Question #2 What is the difference between Cell A and Cell B? 1. Cell A actively transports molecules across the membrane. 2. Cell B creates a door to allow molecules to go down their concentration gradient and come into the cell. 3. Cell B uses passive diffusion to push molecules out of the cell. 4. Cell B actively transports molecules up a concentration gradient and out of the cell.

7 Clicker Question #3 Why is Cell C using so much ATP? 1. Cell C must spend energy to create transport proteins. 2. Cell C must spend energy to actively drive each star molecule out of the cell. 3. Cell C must spend energy to actively pull star molecules in through the green transport proteins. 4. Cell C must both create transport proteins and fuel them with ATP to drive star molecules into the cell.

8 Clicker Question #4 A permeable poison is added to the water around bacterial cells. Which adaptation is most likely to help a cell survive? 1. Facilitated diffusion: The cell creates a transport protein that will passively allow poison to flow out of the cell. 2. Active transport: The cell uses ATP to pump the poison out of the cell through a costly transport protein. 3. Passive diffusion: The cell waits for the poison to diffuse out of the cell into the water. 4. Active transport: The cell uses ATP to pump a wide variety of molecules out of a large but inexpensive transport protein.

9 Orientation for Page 2: What does this image show? Clicker Question #5 1. A cross section of a transport protein taken within the hydrophobic area of a membrane. 2. A cross section of a lipid membrane. 3. A hollow tube of multiple cells. 4. A protein floating outside of the hydrophilic layer of phospholipids.

10 Clicker Question #6 Q7: Which of these R-groups is most likely to be in direct contact with the substrate molecule as it travels through the transport protein?

11 Clicker Question #7 The transport protein is hit with a chemical cross-linking agent. This makes the protein extremely rigid. What is the most likely result of this cross-linking? 1. The transport protein allows the same specific molecules to pass through the membrane more quickly. 2. The transport protein allows many different large molecules to pass through very quickly. 3. The transport protein loses the ability to transport molecules through the membrane.

12 1) Draw in the missing steps: Vesicles can form from membranes: Peer Instruction Vesicles can be absorbed into membranes: This can be spontaneous, but is usually guided by proteins. 2) How can a motor protein help to move a vesicle?

13 Vesicle video

14 Peer Instruction 1) Explain these three mechanisms for cellular digestion. (One sentence each, maximum) Lysosome Lysosome Endosome Damaged organelle Vesicle from Golgi apparatus 2) How could vesicles be used to send signals?

15 Organelles: A General Definition What is an organelle? An organelle is a specific location within a cell characterized by compartmentalized structures Eukaryotes have some membrane-bound organelles Why separate regions in the cell? Molecules don t diffuse easily throughout the entire cell. Concentration can drastically increase reaction rates. Some organelles create unique microenvironments for special reactions.

16 Eukaryotes: Animal and Plant Cells Generalized animal cell Nucleolus Nuclear envelope Chromosomes Nucleus FICTION Centrioles Generalized plant cell Cell wall Chloroplast Rough ER Ribosomes Peroxisome Smooth ER Golgi apparatus Lysosome Mitochondrion Cytoskeletal element Plasma membrane Nuclear envelope Nucleus Nucleolus Chromosomes Rough ER Ribosomes Smooth ER Golgi apparatus Vacuole (lysosome) Peroxisome Mitochondrion Plasma membrane Cytoskeletal element

17 Organelles: The Lysosome Lysosomes are singlemembrane-bound centers for storage and/or waste processing. Microenvironment: Acidic Material being digested within lysosomes Materials are delivered to the lysosomes by three processes: -phagocytosis, -autophagy, and -receptor-mediated endocytosis. (Peroxisomes are very similar, with a Peroxide-based microenvironment)

18 Clicker Question #8 Why is the lysosome useful? In other words, why not simply do lysosome-like digestion in the cytoplasm using the same digestive enzyme? 1. The lysosome provides needed structure for the cell 2. The lysosome helps to concentrate enzymes and cofactors to help reactions happen more quickly 3. They lysosome needs to have a membrane in order to contain enough lipids for the cell 4. The lysosome is where enzymes are polymerized from amino-acid monomers 5. The lysosome restricts dangerous digestion reactions to a safe and secure location in the cell.

19 Organelle Cellular Role Specialized components Microenvironment Nucleus (Covered in great depth in 355) Lysosome Peroxisome Vacuole Mitochondria (Covered in depth in Week 5) Chloroplast (Covered in great depth in 220) Rough ER Smooth ER Golgi Apparatus Ribosomes (Covered in depth next week) Cytoskeleton Plasma membrane (Covered in depth yesterday)

20 Clicker Question #9 The nucleus is the organelle in which DNA is stored and used. Which is most likely about the chemical microenvironment of the nucleus in most cells? The nuclear microenvironment: 1. Contains all of the proteins in a cell because the protein-building instructions are located therein 2. Has a diversity of mutation-causing chemicals 3. Allows import of DNA 4. Is relatively protective against mutation-causing rays and chemicals

21 Problem: Some proteins need to be in the plasma membrane Some proteins need to be sent outside the cell but proteins are far too big to go through even one side of the plasma membrane

22 The EndoMembrane System: The protein & lipid factory Nucleus Comprised of the rough ER, the smooth ER, and the Golgi apparatus, The EMS is the primary system for protein and lipid synthesis. This system allows production, processing and transport of specific and diverse molecules.

23 EMS Organelles: The Rough ER A Protein Synthesis and Processing Complex The rough ER is contiguous with the nuclear membrane New proteins are directly inserted into the ER Microenvironment: noncytoplasmic molecular conditions for protein folding After processing, proteins are transported to other destinations by controlled vesicle budding Lumen of rough ER Ribosomes on outside Free ribosomes in cytoplasm

24 Clicker Question #4 Many functional proteins are translated in the cytoplasm with no need for the Endomembrane System. What is a good reason to use the EMS? 1. To make proteins that are delivered to a specific organelle 2. To make proteins that are delivered to the plasma membrane 3. To make proteins that fold differently than they would if they were translated in the cytoplasm 4. To make proteins with lipid modifications 5. All of these are good reasons to use the EMS for translation

25 EMS Organelles: Smooth ER A Lipid-Handling Center and Storage Site The smooth ER is the major processing zone for lipids Smooth ER lacks ribosomes, naturally ER hosts non-cytoplasmic molecular conditions and specialized enzymes After processing, lipids are transported to other destinations by controlled vesicle budding Lumen of smooth ER Smooth endoplasmic reticulum

26 EMS Organelles: The Golgi Apparatus A Site of Protein Processing The cis face is oriented towards the rough ER A site for carbohydrate modification of proteins Packaging and transport to cellular locations with vesicles Formed by a series of stacked flat membranous sacs called cisternae. Receives products from the rough ER and sends finished products to the cell surface in vesicles. Vesicle Lumen Cisternae The trans face is oriented away from the rough ER cis face Golgi apparatus Vesicles trans face

27 Golgi Video

28 Clicker Question #5 What is a reasonably hypothesis about the microenvironment of the Smooth Endoplasmic Reticulum? 1. It is more hydrophobic than the rest of the cell 2. It would be worse for protection of nucleic acids than the microenvironment in the nucleus 3. It is good for breaking down protein 4. It is the same as the cytoplasm.

29 Key Concepts Why do you expect amino acid side chains on the outside of an integral membrane protein (but within the bilayer) to be hydrophobic? Explain the matches between three possible transport situations facilitated diffusion, active transport, and passive diffusion and three cellular situations a need for extreme rapid transport, intake of a common large molecule, letting a rare waste molecule out of the cell What specialized enzymes would you expect in a mitochondrion? In the Rough ER? What microenvironment is unique to the nucleus? To the peroxisome? Imagine: 1) a lipid destined to become part of the plasma membrane, and 2) a protein that will be released outside of the cell. Describe the differences in the pathways taken by each molecule. Where or when does each pathway utilize the joining of lipid membranes? Bonus question: Where does the energy come from to move Golgi vacuoles to different parts of the cell? There are two very different answers