BIOL 1003 Ch 2.6, 3.1-3.4 Lipids, Cells, and Organelles PDF

Ch 2.6, 3.1-3.4: Lipids, Cells and Organelles Copyright © 2020 Nelson Education Ltd.  2.6 Lipids Lipids are an essential component of our bodies and are used by our cells for vital functions: e.g. myelin sheath to insulate nerve, cell m...

Ch 2.6, 3.1-3.4: Lipids, Cells and Organelles Copyright © 2020 Nelson Education Ltd.  2.6 Lipids Lipids are an essential component of our bodies and are used by our cells for vital functions: e.g. myelin sheath to insulate nerve, cell membranes, lung surfactant, cell signaling molecules. Fats are necessary for absorbing fat-soluble vitamins. 2  2.6 Lipids: Triglycerides Triglycerides have two main parts: H 1. Glycerol H C OH 2. Fatty acids H C OH Fatty acids attach at these OH groups H C OH H Glycerol is the triglyceride backbone. Glycerol Fatty acids have chains of C and H atoms: OH H H H H H H H H H H H hydrocarbons. HO C C C C C C C C C C C C C H H H H H H H H H H H H H C-H bonds store energy and are non-polar. A fatty acid The FA chain ends with a carboxyl (-COOH) group. 3 2.6 Lipids: Triglycerides Triglycerides are long-term energy storage molecules, in fat cells (adipocytes). Adipocytes are found in adipose tissue or subcutaneous fat. Triglycerides can be broken down and used for energy (ATP production). Copyright © 2020 Nelson Education Ltd.  2.6 Lipids: Fats vs. Oils Fats are triglycerides which are usually solid at room temperature, while oils are triglycerides that are liquid are room temperature. The difference is mostly due to saturation of the fatty acid chains Saturated fats: no double bonds in the fatty acid chains. Straight chains, orderly, pack well together – makes them solid e.g.) animal fats. Unsaturated fats: one or more double bonds in the chain. Makes the fatty acids less orderly, can’t pack well – makes them liquid. Most vegetable oils. One double bond: monounsaturated fat Two or more double bonds: polyunsaturated fat Coconut and palm oil are interesting because they are saturated vegetable oils. 5 Copyright © 2020 Nelson Education Ltd. 2.6 Triglycerides: Trans Fats In unsaturated cis fatty acids, the hydrogens are on the same side of the double bond. Most naturally o occurring fats. In unsaturated trans fatty acids, the hydrogens are on opposite sides of the double bond. Notice all trans fats must be o unsaturated Trans fats are more stable than cis, so became popular in packaged food. Copyright © 2020 Nelson Education Ltd. 6  2.6 Lipids: Triglycerides: Trans Fats Trans fats are made by partial hydrogenation. Partially hydrogenating vegetable oils makes them more stable and less likely to spoil. Trans fats can increase LDL (“bad” cholesterol) and decrease HDL (“good” cholesterol). Research in the 1990s began showing adverse health effects of trans fats. Adding partially hydrogenated oils to food products was banned by Health Canada in Sept of 2018. Some trans fats occur naturally in meat and milk products from ruminants and most plant oils contain 400 °C) or for long periods (> 90 minutes) may moderately increase trans fats e.g.) commercial deep-frying. 7  2.6 Lipids: Triglycerides: Essential Fatty Acids 3 2 1 Essential fatty acids must be obtained from our diet since our bodies can’t manufacture them. is an omega-3 because the 3rd carbon has the first double bond They are are polyunsaturated. 6 5 4 3 2 1 Omega-3 and omega-6 are essential, they are named for the is an omega-6 because the 6th carbon carbon with the first double bond. has the first double bond NB: When counting carbons in a fatty acid, count from the end opposite of the carboxyl group Omega-9: we synthesize them, but poorly, so some consider them essential. Copyright © 2020 Nelson Education Ltd. 8  2.6 Lipids: Cholesterol Cholesterol is in animal cell membranes. Most of the cholesterol in the body is synthesized by the liver. Liver and brain cells contain the most cholesterol. Functions of cholesterol: Note the shape of cholesterol – 1. Maintain cell membrane flexibility it’s used to make several important hormones 2. Used to produce steroid hormones 3. Produce bile (used to break down fats) 4. Help transport fats through bloodstream (HDLs and LDLs) 9 Copyright © 2020 Nelson Education Ltd.  2.6 Lipids: Phospholipids Are the primary component of cell membranes, along with some cholesterol and proteins. Have two non-polar fatty acid This simplified chains (tails) and a polar “head” drawing above is that contains a phosphate usually what you will see in group. drawings of cell membranes The fatty acids are often unsaturated. Having a polar and a non-polar group in one molecule: amphipathic. Copyright © 2020 Nelson Education Ltd. 10  2.6 Lipids: Cell Membranes Cell membranes are composed of phospholipids, cholesterol, and proteins. Note the membrane is made by two layers of phospholipids: the non- polar “tails” point toward each other. Called the phospholipid bilayer. This one picture has 3 of 4 Copyright © 2020 Nelson Education Ltd. macromolecules we’ve been looking at! 11 KAHOOT! Chapter 3: Cells  3.1 Cell Theory Most human cells are between 5 and 20 µm in diameter. They’re small because nutrients need to diffuse across the cell. Some cells have special modifications to increase surface area. neurons are very long and thin. cells lining the digestive tract have microvilli—fingerlike projections that make more surface area. microvilli The microvilli increase surface area available for nutrients to enter the cell Copyright © 2020 Nelson Education Ltd. To become larger, multicellular organisms increase cell number, rather than cell size, because cells are limited by diffusion of nutrients and waste to about 100 µm. 14  Example: Cells in culture These are cell that line the inside of blood vessels. They’ve been grown in a flask in my lab. Each cell is about 45 micrometers wide, but each cell is only about 2-5 micrometers tall. The nuclei are about 10-12 micrometers wide. Resemble a fried egg. Inside each nucleus you can usually see 2-4 nucleoli, which we’ll talk about later.  3.1 Cell Theory 1. All living things are composed of cells. 2. The cell is the basic unit of all living organisms and is the smallest single unit that can survive independently. 3. All cells come from pre-existing cells. 4. All cells contain genetic material, DNA, which is passed on to new cells that arise from cell division (red blood cells expel their nucleus just before release into blood). 5. All cells are either prokaryotic or eukaryotic. 16  3.2 Plasma Membrane The plasma membrane forms the boundary of the cell. Controls the permeability of the cell to water and dissolved substances. Most hydrophilic molecules can’t pass the hydrophobic core of the plasma membrane by themselves: need channels or transporters. Cytoplasm is everything inside the cell and includes the organelles. Cytosol is the fluid component of the cytoplasm. Nucleus Plasma membrane Cytoplasm 17 Copyright © 2020 Nelson Education Ltd.  3.2 Plasma Membrane The plasma membrane is conceptualized by the fluid mosaic model: it contains a mosaic of mostly phospholipids with some proteins and cholesterol. Plasma membrane phospholipids contain mostly unsaturated fats that give it a somewhat fluid consistency, and many proteins and cholesterol can “float” around in it. Figure 4.9 from https://openstax.org/books/biology-2e/pages/4-3-eukaryotic-cells 18 CC-BY  3.2 Plasma Membrane Remember: A phospholipid has an outer polar (hydrophilic) head and two inner nonpolar (hydrophobic) tails. While the plasma membrane is the most obvious, many organelles are made of or surrounded by membranes. Note: While many diagrams of organelles depict their membrane as a solid line, they are still made of some kind of phospholipid bilayer (or two!). Copyright © 2020 Nelson Education Ltd. 19  3.2 Plasma Membrane Note the inner and outer “leaflets” of the phospholipid bilayer. Membrane proteins may pass through the entire membrane, or only one leaflet. Copyright © 2020 Nelson Education Ltd. 20  3.2 Important Types of Membrane Proteins Receptors: bind to Self Antigens: are substances outside of Enzymes: catalyze membrane proteins that the cell and affect the chemical reactions. act as markers, such as function of that cell, such ACE2 (angiotensin blood-type proteins and as hormones. Targets of converting enzyme 2) MHC. many pharmaceuticals. Transporters: allows substances to cross the Gap junctions: allow Adhesion: connects membrane, such as ion cells to directly cells together. channels or carrier communicate. proteins. 21 KAHOOT!  3.3 Prokaryotic and Eukaryotic Cells Prokaryotic Eukaryotic Lack a nucleus and do not have Has a nucleus and internal an extensive system of internal membrane-bound organelles membranes (organelles) Protists, fungi, plants, and Eubacteria and Archaebacteria animals 23  3.3 Prokaryotic Cells Nucleoid region: contains single, circular DNA molecule, but no membrane Cytoplasm: no internal framework, contains ribosomes for protein synthesis Cell membrane: composed of phospholipids, cholesterol, and proteins Cell wall: 2 general types, both very different from a plant cell wall. Gram-positive: composed a mix of carbohydrate and protein called peptidoglycan (unlike cellulose in plant cell walls) Gram-negative: composed of peptidoglycan and an outer membrane with lipopolysaccharide (LPS) Capsule: composed of protein and is an extra layer of protection for the cell Copyright © 2020 Nelson Education Ltd. 24  3.3 Prokaryotic Cells Other structures sometimes found in prokaryotes Flagellum (plural, flagella): whip-like protein fibre that extends from the cell surface May be one or many Aids in locomotion and feeding Pilus (plural, pili): short hair-like structure coming out of the plasma membrane Aids in attaching to substrates and in exchanging genetic information between cells Figure 4.5 from Openstax Biology: https://openstax.org/books/biology-2e/pages/4-2- prokaryotic-cells#fig-ch04-02-01 25 CC-BY Study Suggestion: Make a chart outlining the differences: Prokaryotes Eukaryotes Draw a Picture of a typical prokaryotic cell and a eukaryotic cell.26  3.3 Eukaryotic Cells Eukaryotic cells are larger and more complex than prokaryotic cells. They have a plasma membrane encasing a cytoplasm. Internal membranes form compartments called organelles. The cytoplasm is semi-fluid and contains a network of protein fibres that form a scaffold called a cytoskeleton. 27  3.3 Eukaryotic Cells Plasma membrane: composed of phospholipids, cholesterol, and proteins Cytoplasm: contains cytosol, organelles, and cytoskeleton Nucleus: membrane-bound organelle that contains DNA Cell wall? found in fungi, some protists, and plants, but not in animal cells 28 Copyright © 2020 Nelson Education Ltd.  3.4 Organelles: Nucleus Nucleus contains DNA: 46 chromosomes in humans (called chromatin here and is less condensed than during mitosis) Nuclear envelope is a double membrane (2 lipid bilayers). Outer membrane is continuous with the endoplasmic reticulum Nuclear pores allow molecules to move into and out of nucleus, e.g mRNA Nucleolus is site of transcription of ribosomal RNA 29 Copyright © 2020 Nelson Education Ltd.  3.4 Organelles: Endoplasmic Reticulum It is continuous with the outer nuclear membrane Rough endoplasmic reticulum contains ribosomes and is a site of protein synthesis (translation). Especially membrane proteins! Smooth endoplasmic reticulum is site of lipid (phospholipids and cholesterol) and carbohydrate (glycogen) synthesis. Smooth ER in muscle cells stores calcium 30 Copyright © 2020 Nelson Education Ltd. 3.4 Organelles: Golgi Bodies Golgi bodies (also called Golgi complex or Golgi apparatus): flattened membranes that collect, modify, package, and distribute molecules manufactured in the cell Modification example: adding carbohydrates to proteins to form glycoproteins Packaging: proteins bound for export from the cell to the blood stream Vesicles are small bits of membrane that bud off one organelle to move to another or perform a specialized function Copyright © 2020 Nelson Education Ltd. 31  3.4 Organelles: Mitochondria Thought to be derived from ancient bacteria that were assimilated by early eukaryotes. Mitochondria produce energy in the form of ATP through oxidative phosphorylation Made of an outer membrane and an inner membrane. Inner folds called cristae. Contain ribosomes and their own DNA (but not all the genes they need). Can self-replicate Important role in cell cycle, programed cell death, and cellular aging Copyright © 2020 Nelson Education Ltd. 32  3.4 Organelles: Ribosomes The cell’s protein factories: site of protein synthesis (translation) Some are free in cytoplasm, some are attached to rough ER Receive the messenger RNA and translate it to protein Made of a mixture of ribosomal RNA (rRNA) and protein Made of 2 subunits (large and small) NOT a membrane-bound organelle Copyright © 2020 Nelson Education Ltd. 33 3.4 Lysosomes and Peroxisomes Appear as small round vesicles (surrounded by membrane) floating in cytoplasm Lysosomes: contain digestive enzymes that break Peroxisome down macromolecules and old organelles (recycling and disposal) and a low pH. Immune cells have lots of these to break down ingested pathogens. Aid in apoptosis or “programmed cell death”. Many genetic diseases result from missing lysosome enzymes. Copyright © 2020 Nelson Education Ltd. Peroxisomes: break down long-chain fatty acids for ATP production (mitochondria) contain molecules that help to detoxify harmful metabolism byproducts (lots in liver). 34  3.4 Organelles: Centrioles Centrioles are found in most eukaryotic cells except for plants and fungi. Involved in the organization of spindle fibres (microtubules) that transport chromosomes during cell division. Not a membrane-bound organelle Copyright © 2020 Nelson Education Ltd. 35 Organelles Summary Copyright © 2020 Nelson Education Ltd. KAHOOT!