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Biology Lecture Notes Midterm 1.docx

27 Pages

Biology (Sci)
Course Code
BIOL 115
Robert Levine

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BIO LECTURE NOTES: Midterm 1 Stuff! This course allows us to think critically about Biology in what we read about Science/Biology in news/mags/etc. Being skeptical always, asking questions always, always being ready to change your point of view. What is Science? 1. A way of knowing things 2. A body of Knowledge accumulated through scientific investigation The Scientific Way of Finding Things Out” Observation, then Question, then Hypothesis (informed guess), then Experiments (try to reject some hypotheses), then Conclusion Theory: if hypothesis comes to be recognized as broad and general (like the cell theory). So “a broad intellectual construct, supported by evidence, that has explanatory power”. Scientific method at work” Pasteur tests “spontaneous generation”. Observation: When you start with a sterile flask of sterile meat broth, a growth of living material generally appears in the broth. Question: What is the source of the living material? He had 2 Hypotheses: 1. The living material came from nothing “spontaneous generation”. 2. The living material is derived from living material outside the flask. Pasteur’s experiment: He made an s-curve in the neck of a flask with sterile broth in it, so that any particles from the outside would not contact broth. It remained sterile until he removed trap, or tipped flask to mix trapped dust into broth. The situation where he doesn’t break/tip the flask is called the control. Compares results to this. Conclusion: No growth appears in the broth unless dust is admitted from outside. No spontaneous generation. Example of necessity of control: Hemodynamic idea that if you tie off internal mammilaries in chest it will relieve anginas. Was successful, people had relief, but some guy decided to do a control experiment. Made incisions but didn’t tie off vessels in some patients, tied off vessels in others. Discovered that there was no difference. Attributes of Living things Hierarchy is... (bottom up) Atoms: smallest unit of a molecule Molecule: smallest unit of a compound that still fits the properties of the compound Cell: Smallest unit of a living thing Tissue: a group of cells with a common structure/function Organ: compound of a number of tissues... a bunch of tissues Organism: The entire creature Population: Several organisms of same kind in a particular area Community: interacting populations in a particular area Ecosystem: community plus environment Biosphere: Regions of the Earth’s crust, waters, and atmosphere inhabited by living things. Living things take in energy. Major energy capturers are plants (they capture energy from sun) Plants capture from sun, animals capture from plants, animals/plants die and bacteria/fungi capture that energy (decomposition) (also other animals eat dead animals) Homeostasis – living organisms maintain their internal environment. Maintain constant body temperature (dogs pant, humans sweat, rabbits ears) Living systems respond to the environment: nervous system: smell, vision, hearing, touch, etc. Living organisms change over time. They evolve. Pigeons for example (diff kinds produced with breeding. Darwin). Bacteria (resistant strains) Cavalvade of Organisms (various types of living things) There are three major domains of living things Bacteria (prokaryotes/single celled, earliest organisms), Archaea (prokaryotes/single celled, earliest organisms), and Eukayra (eukaryotes(have a nucleus)). Eukaryotes include plants, fungi, animals, and protista (single celled) EUKARYOTE KINGDOMS: Animalia: Multicellular, Eukaryotic (cells have nucleus), Heterotrophic (ingestion, they eat stuff), have complex organ systems like brain, stomach, heart, digestive tract, etc. Plants: Multicellular, Eukaryotic, cellulose cell walls, Autotrophic (they make their own energy by using sunlight. Photosynthesis), complex organ systems (transport systems, support systems, reproductive organs) Fungi: Tremendous source of pharmaceutical agents, also some poisonous, hallucinations. Most are multicellular, eukaryotic, chitin cell walls (chitin also makes up insect exoskeleton), heterotrophs (not injestion, but absorption. Secrete enzymes and absorb digested material, tissues (but not organ systems), can be pathogenic (can cause disease. E.g. ringworm, athlete’s foot) Protistans: Eukaryotes that are single-celled for the most part. Multicellular ones would be like kelp and seaweed. Can be pathogenic (sleeping sickness, etc.), some are autotrophs (algae, with cell walls), some heterotrophs (ingestion) PROKARYOTES Bacteria:Spherical, rod-shaped, helical. Only some are pathogenic (we are full of non-pathogenic bacteria), unicellular, do not have nucleus (prokaryotes), cell walls, most are heterotrophic, some are autotrophs. Archaea (Extremophiles): Live in extreme conditions (in methane, high temperatures, highly acidic environments, etc). Unicellular, prokaryotes, cell walls, some autotrophic, some chemotrophic (use methane or sulphur compounds to generate energy) VIRUSES Bits of nucleic acid (DNA or RNA) surrounded by a shell of protein. Sometimes they’ll have a bit of cell membrane around them from the last cell they were inside. Can’t do anything on their own. But when they get into a living system, they take it over and use its elements to reproduce, and then burst the cell and enter the environment. One thing they can do is make more of themselves, effectively. Tricky question whether or not they’re living. Most of the ones we know are pathogenic. Prions: proteins that get out of hand and can behave like living organisms (though they’re not) Viroids: bits of naked RNA that can cause disease in plants. (Lecture 2) ATOMS AND MOLECULES: Building Blocks of Living Organisms Elements: materials on Earth that cannot be broken down further. Living organisms are really separate from their environment. Part of being alive means being separate from their environment. Humans and the Earth’s Crust have diff. Concentrations of various elements. Atoms: nucleus contains protons and neutrons, and clouds of electrons around it. In ordinary atoms, the number of protons and electrons are equal (balanced charge). In ions there will be differences. Most of the weight comes from protons/neutrons. Electrons weigh almost nothing. Atomic weight of an atom is the sum of the number of protons and neutrons. Number of protons is atomic number (determines the element). Electrons very broadly dispersed from nucleus which is really tiny. Electrons distributed in electron clouds that have diff energy levels, outside of the nucleus. First shell holds 2e, after than all other shells hold 8e. Isotopes: When the neutrons of an element vary. Diff atomic weight. Isotopes are not stable, don’t like having these extra neutrons. Some of these neutrons break down as radioactivity, so isotopes are often radioactive. When radioactive decay occurs in isotopes, they can become a different element. Isotopes in Biology and Medicine: e.g. PET scans. Radioactive tracer. We can also use isotopes to date fossils. Radiometric Fossil Dating: Most carbon exists as carbon-12. Rays change nitrogen atoms into Carbon-14 atoms. Carbon-14. Extra 2 neutrons. Constantly being produced in the atmosphere by nitrogen/light rays? Carbon that plants get from atmosphere is Co2. Small amount of it is C-14, rest is C-12. Breaks down into Nitrogen. Constantly eating C-14. Except when we die. Then C-14 stops being replenished. After a period of time, the amount of C-14 is half of what it was when it died. This is called the half-life (of the isotope). Half life of C-14 is 5700 years. At the half-life, ratio of C-14 to C-12 is half of what it should be (when alive). After 2 half-lives, ratio would be a quarter of what is should be. Between the present and 40000 years this is an effective method of dating. Potassium breaks down to Argon too. Another Fossil dating thing. Volcanic rocks especially. As long as the rock is molten, argon doesn’t accumulate. As soon as rock hardens, argon collects, and you can determine the age by taking the ratio of argon to potassium. Mendelea?’s table. Part of periodic table. Top left = least electrons, one electron ring. Bottom right: most electrons, 3 electron rings. The nuclei of diff elements attract electrons more/less strongly. This is called electronegativity. Highly electronegative = pulling electrons tightly. Top right = most electronegative. Bottom left = least electronegative. COVALENT BONDS: two non-metals. Stuck together by sharing electrons. Molecular hydrogen = one covalent cond. Molecular Oxygen = two covalent bonds. Water is a compound. Contains than one element. Molecules have strict geometries, btw. Ionic Bonds: electron transfer. Not as strong as covalent. Polar bonds are weak too. Molecules have covalent bonds. NaCl, for example, isn’t a molecule! Water molecule is polar. Electrons spend more of their time around oxygen, not hydrogen. So slight negative charge at oxygen end, slight positive charge at hydrogen end. Hydrogen bonds: polar. Holds water molecules together. Very weak but sufficient to hold water together Since water is weakly polar, it is an excellent solvent. Any ionic substance (any salt) can be dissolved in water. Hydration shells (sphere of hydration) around ions in water. This affects size of ions. Proteins that are small enough can be dissolved in water as well. Hydrophilic: anything that can dissolve in water (anything that has charge on its surface). Loves water. Hydrophobic: can’t dissolve in water. Oil, fat, etc. Lipids. SO, because of hydrogen bonds: 1. Water has high heat capacity. 2. Ice is less dense than water (so floats) 3. Excellent solvent 4. Water is cohesive (water moves up tree, water striders, surface tension) ACIDS AND BASES: based on the idea of hydrogen atoms moving between water molecules. In a body of water, a small number of molecules will lose a hydrogen to produce H30. H+ leaves water molecule, but leaves an electron behind, making it OH-(the proton jumps onto another water molecule that becomes H30+). H3O+ is referred to as H+. OH- is known as hydroxide ion. In regular neutral water, you have equal amounts of H+ and OH-. Acids are solutions with an excess of H+. The less H+ you have, the more basic/alkaline it is. It is crucial for living systems to keep their pH in the proper range. Ours is pH of 7.4. The way to do that is by buffer systems. Buffer systems are found in our blood (suck up H+ or release H+ to maintain pH) Low pH = lots of acid. pH 7= neutral. High pH = low acid. pH scale is logarithmic. pH 5 is 10 times more acidic than pH 6. (Lecture 3) Molecules of Life: Molecules Built on a Carbon Skeleton The major molecules involved in living systems are molecules built on a carbon skeleton. Organic chem. Is the study of stuff that has carbon in it. Carbon skeletons: (always 4 covalent bonds) 1. Carbon can make chains 2. Carbon can make branches 3. Carbon can make double covalent bonds 4. Carbon can make rings This is the molecular structure of living systems Simplest kind of carbon are hydrocarbons. Hydrocarbons are molecules built around carbon atoms. Simply hydrogen and carbon. - Nonpolar, hydrophobic molecules Functional groups: molecular structures that contain more than carbon. When they’re added to carbon skeletons, they change their chemical behaviour. 1. Hydroxyl group (OH- group).. E.G. Ethanol is characterized as a hydrocarbon with a hydroxyl group attached to it. Hydroxyls are polar, so molecules with hydroxyls can make hydrogen bonds. Makes a hydrophobic molecule hydrophilic because of hydrogen bonds too.Polar and water soluble, contribute water solubility to a molecule. 2. Carboxyl group (COOH). An organic acid. Carbon double bonded to oxygen and single bonded to a hydroxyl group. Because of this, this hydrogen can be released into the solution. This is what defines an acid too (a molecule that releases H into environment). Highly polar, acidic, and give up H ions in water. 3. Phosphate group (PO4). Stores useable energy. Breaking one off releases that energy. E.g.ATP  major energy currency in the cell. Because it has these phosphate groups that can be broken. Polar, contribute to water solubility. 4. Amino group (NH2). Polar and basic. Dissolve in water. They can take hydrogen out of water, so they’re basic. Characteristic of amino acids. LOOK UP STRUCTURES OF FUNCTIONAL GROUPS? Carbohydrates: group of organic molecules that play three roles 1. Organic molecules with hydroxyl/alcohol groups on most carbons 2. Involved in generating energy, and storing energy 3. Involved in structural support of living cell/organism. Simple Carbohydrates: monosaccharides. a. Glyceraldehyde: a three-carbon carbohydrate. Energy metabolism. b. Ribose: a five-carbon sugar. Usually in ring form. Involved in structure of DNA (information transfer and storage). Also one of the bases of ATP, so involved in energy transfer/metabolism c. Glucose: a six-carbon sugar. The major source of energy in living system. (ring shape? Sometimes?) Glucose is a fuel. Gives about 4 calories per gram. These monosaccharides can be chemically joined to one another to form disaccharides: a condensation reaction. One of the most common is sucrose. They’re joined together with these two hydroxyls through the loss of a molecule of water. Sucrose is a storage form for glucose and fructose. Can’t be used for energy itself, but can be broken down to gl and fr, and they can go through the energy producing reactions in the body. Sucrose is a storage form of carbohydrate that’s produced in plants. Whenever you have something that’s made of two subunits: - One subunit is called a monomer - Dimer: two put together. - Heterodimer: different subunits put together. Homodimer would be two same subunits stuck together. When you string more than two monomers together, you get a polymer. Homopolymer: all subunits are identical Heteropolymer: two or more diff types of subunits Plants do make dimeric storage units, but major storage for sugar is homopolymers. Glycogen  storage form of glucose that the body can use for energy. Glycogen is stored in muscles/liver of animals. Plants starches are stored in tubers like potatoes, rice, etc. Most plenteous/common form of carbohydrate on the planet, because it is wood. Unlike starches, no animal on the planet can break this starch down.  same subunit (glucose) but put together in a diff way, and now it’s a totally diff compound. ^ all those are homopolymers. Chitin: insect shell. Crustacean shells too. SO, cellulose, plant starches, glycogen and chitin are carbohydrates that are polymers. Shows them as storage for energy and structural support for living shells. Again, carbohydrates, having all those alcohol groups, are highly soluble in water. LIPIDS: hydrophobic organic compounds. Fat. Basic building blocks of fat are fatty acids. These are acids because of the carbodyl group attached on top. Straight long hydrocarbon change with little carboxyl group on it. Still hydrophobic because too big with too small of a carboxyl group. Saturated: straight molecules, no kinks. Since they are straight they can be stacked tightly, making them solid at room temp. Bad for you. Unsaturated: with double-bonded carbon(s). Have kinks in them. Liquid at room temperature. Good for you. Monounsaturated: one double bonded carbon. One kink. Polyunsaturated: more than one double bonded carbon. More than one kink. The fats in our body are called triglycerides. - A molecule of glycerol. Tri-alcohol.3 carbons with alcohol group on each. They condense with 3 fatty acids. Which forms triglycerides, commonly called a fat. Don’t have a lot of free fatty acids in body. - Involved in energy storage. Store twice as much energy as carbohydrates. - Good for thermal insulation too. - Supports your organs (structurally) - When fats are digested you break them back into free fatty acids, and then your body reconnects it. Phospholipids: Amphipathic lipids - Glycerol backbone (3 carbon alcoholic backbone) - Two fatty acids on it - But third alcohol group, instead of being joined to another fatty acid, is joined to a large, hydrophilic functional group. Joined through a phosphate linkage. - Head is hydrophilic, fatty acid tails are hydrophobic. - This is the basis for how your plasma membrane is made. Plasma membrane: two layers of phospholipid chains. Hydrophillic heads pointing to inside of cell, and to outside environment (between the 2 chains). Protective barrier for hydrophobic stuff sandwiched btwn. CHOLESTEROL AND RELATED MOLECULES - An animal lipid - A hydrocarbon with the occasional hydroxyl group - With 4 ring structures - Part of plasma/cell membrane - Important in hormones - Produced in liver mostly, not really from what you eat - Cholesterol is converted to Vitamin D by UV/sunlight. - Derivatives of cholesterol: estrogen, testosterone (steroid hormones) PROTEINS - Molecules built from amino acids - Structural functions: hair and nails - Enzymes: chemical catalysts - Signalling: hormones and their receptors - Movement: muscles and cilia - Amino acid: single carbon as its nucleus, carbosyl acidic group, amino group (and at physiological conditions the carboxyl group has lost a hydrogen but the amino group has bound a hydrogen), and an R group. The R group is all that makes amino acids different, other structures are constant. - 2 types of amino acids: charged and uncharged (but polar, have hydroxyl group) - The third type of amino acids are non-polar and hydrophobic. Just hydrocarbon chains stuck onto the central carbon. This means that that part of the protein can’t be exposed to aqueous environment. So proteins will have both hydrophobic and hydrophilic stretches. BTW, what’s the difference btwn an ion and a polar molecule? Proteins are polymers of amino acids, btw. The way you join amino acids to form proteins: the carboxyl group of one joins to the amino group of the other (through the loss of water) and you get peptide bonds. Runs through the protein. Covalent bonds. The order you arrange the amino acids in is called the primary structure of the protein. Once you have that, the amino acids interact with each other to form diff structures, such as an alpha helix (held in this form by hydrogen bonding), pleated sheet. Those are secondary structures. Then those structures fold together (some pleated sheets, some alpha helix, etc) tangles together. Folded by hydrogen bonding and ionic bonding (if you have an acidic group and a basic group, they’ll form an ionic bond) (electrostatic attraction). Hydrophobic stuff sticks to inside.  tertiary structures. Quaternary structures are when tertiary structures tangle together and it’s crazy. Like yarn. Misfolded proteins are not allowed in living cells. They are broken down. Cystic Fibrosis: a disease of protein misfolding. Denaturing a protein: undoing these proteins. Treating them badly. Done with increasing salt concentration, decreasing pH or adding heat. The things we do to preserve things (canning meats/veggies for ex) is often denaturing the proteins. Hemoglobin only exists as a tetramer (4 subunits) Sickle Cell Anemia: due to mutation of one amino acid in haemoglobin. When these ppl are exposed to low oxygen tension, their red blood cells get stretched out to sickle cells. Blood cells become distorted, can’t get through capillaries. Many harmful effects. NUCLEIC ACIDS/POLYNUCLEOTIDES - Nucleotide polymers that carry information - A nucleotide has a sugar (deoxyribose), a phosphate group, and base. - In DNA sequences (Adenine, Thymine, Guanine, Cytosine) ATP has adenine, ribose, and 3 phosphate groups (LECTURE 4) PRIONS! Kuru: a disease that struck the Fore people of Papua New Guinea. A neurological disorder (affected mostly women and children) - Discoordinated, ataxic (can’t walk properly) - Headaches - Swallowing difficulties - Jerks and tremors Carlton Gadjusek was the answer to this problem. A virologist. He studied it in depth He did autopsies. They showed that people with Kuru had big empty places in their brain, looks spongy. Reminded him of CJD (same sponginess). Weird because CJD is characterized by similar symptoms (seizures, etc). It also looks very much like Scrapie (sheep disease, similar symptoms again). These diseases have: Long incubation time. Don’t know you’re sick till 10-20 years later. They can be transmitted (they are infectious). They are called TSE. Turns out women and kids ate brain soup. They were eating the brains of ppl that died from Kuru. He developed the theory of “slow viruses”, since they have such a long incubation period. He assumed they were viruses because he couldn’t see them CJD (Creutzfeldt-Jakob disease) - Occurs spontaneously (sporadic) 85% of the time - 10% is inherited Fatal Familial Insomnia - Inherited - Usually when people are older, have already had kids Stanley Prusiner tried to discover what causes these diseases These TSE’s are weird because they are contagious through direct brain/brain contact. He discovered that the infectiousness always followed the protein. Weird because it usually follows DNA/RNA (if it was a virus) Resistant to proteases (resistant to digestion) His hypothesis was that the infectious agent is a protein. CRAZY! Turns out the gene is ordinary. Everyone has the Prion gene. It’s a natural, ordinary part of the brain. This explains why there is no immune reaction, no inflammation or anything. When they knocked out that gene in mice, they were unaffected and well. Also, they were not affected by infected brains of others. They called the protein PrP (prion protein). For some reason the ppl who do get sick have the protein folded slightly differently. How do you get it from infected brains? - The Scrapie form of the protein interacts (almost like an enzyme) with normal PrP and converts it, allowing it to shift its shape and become another Scrapie protein. - This was Pruisiner’s idea btw. And we stick to it today. All TSEs have PrP mutations. Overexpressing a normal human TSE prion in a mouse causes TSE BOVINE SPONGIFORM ENCEPHALOPATHY (BSE), also known as: MAD COW DISEASE - Since cows were being fed ground up other cows - They killed about a million cattle, because they were trying to eliminate it - British beef industry in danger - Nothing with the brain and spinal cord was allowed in food - Technically there was no proof that it would affect humans though BUT. A new Variant of CJD (vCJD) was discovered. Affect ppl younger, works faster. In vCJD brain is shrunken. So then is IS transmissible to humans from animals. You can now get vCJD from: spontaneous, familial (mutation), ingestion of infected cows (it is true that the oral route is inefficient though), corneal transplant, pituitary grown hormone extracts, introcerebral electrodes, dual grafts, blood products, etc. Route of vCJD is: 1. Prions are injested 2. Prions are absorbed from small intestines into bloodstream 3. Misfolded prions refold all normal prions in spleen and lymph nodes 4. Refolded prions move to brain and spinal cord, where they refold more proteins. Brain cells die, giving the brain a spongelike appearance. In the prion protein, in a specific place you can have one of two amino acids. Either one is normal, but all of the victims of vCJD had m in both copies of the gene (mom/dad). Suggests that this form of the protein is more succeptible to refolding. (LECTURE 5) Cell Structure and Function: cells are the smallest independent units of life (smallest things that can exist on their own without help from other organisms) Surface to volume ratio is why cells need to be so small. - The amount of oxygen that it gets depends on the surface area - Waste material released is also proportional to amount of membrane - Surface increases as square of linear dimension - Volume increases as cube of linear dimension - As things get bigger and retain their proportion, their surface to volume ration drops Prokaryote structure: small, no nucleus, DNA is just clumped in center (called nucleoid), no internal membranes (only plasma membrane), never multicellular, both aerobic (need oxygen), anaerobic (don’t need oxygen) Eukaryotic structure: have nucleus (membrane bound structure that contains DNA in chromosomes), a lot of membrane structures in cytoplasm (vesicles, mitochondria), much larger than prokaryotes, can exist independently but also make multicellular creatures. Most of our body is composed of prokaryotes, but our cells are made of eukaryotes. Cell is wrapped in plasma membrane Around nucleus, endoplasmic reticulum. Pile of flattened sacs/vesicles. - Both rough (with ribosomes on surface) and smooth. Rough endoplasmic reticulum and golgi complex are responsible for synthesis and processing od proteins Lysosomes: vesicles involved in breaking things down Mitochondria: energy factories of cell. Use oxygen and secrete CO2 - prokaryotes don’t have mitochondria. - Mitochondria are actually former aerobic prokaryotes Cytoplasm: cytosol is just material around organelles. Cytoplasm is that plus organelles. Cytoskeleton: protein polymers that hold cell together. Support cell and are responsible for ell movement. Fre in cytoplasm. Centrosome: small structure in cell involved in mitosis (spindles?) MEMBRANE BOUND ORGANELLES - Membrane made of same stuff as plasma membrane Nucleus: double membrane pierced by channels or nuclear pores (allow large molecules to enter/leave nucleus) - In nucleus are DNA (in form of chromosomes which is DNA+proteins) and different RNAs. - 2 types of RNA, messenger RNA, and ribosomal RNA Endoplasmic Reticulum (ER): - Rough with ribosomes, smooth without - Rough involved in protein synthesis (proteins live in cytoplasm, proteins inserted in membrane, proteins are secreted by hormones) - Proteins in cytoplasm are produced by free floating ribosomes that associate with mRNA - Proteins that are inserted in membrane or secreted are synthesized in and on the rough ER. - Protein is synthesized and strung together/extruded and then go into endoplasmic reticulum (not associated with cytoplasm) - Membrane proteins don’t go into ER, but stay stuck in the membrane - So for the proteins in ER, they get processed, have sugar groups added, get folded properly. Then they’re called glycoproteins. Smooth ER: where lipids are synthesized (like steroids), in liver it’s also involved in detoxifying poisons and drugs. To finish protein processing, part of the Rough ER buds off into vesicles and travels to golgi apparatus and fuses with one of its sheets. It’s then processed in there. Protein is now passed from one piece of golgi to the next (through vesicles), each time it moves it gets processed some more. Finally buds off one last time and moves to plasma membrane, fuses with surface, and releases proteins to the outside(or inserted in membrane). So golgi apparatus: aids in protein processing. When vesicles fuse to membrane and are released it’s called exocytosis. Endocytosis must also happen to balance it out otherwise membrane would just get larger and larger. BUT! There’s another direction it can go from golgi. Vesicles can be released from golgi called lysosomes, they have powerful enzymes, they stay in the cell and digest stuff (like worn out mitochondria and stuff), digested stuff goes like lipids are returned to cytoplasm to be used for more synthesis. These vesicles can also be exocytosed with waste material. Lysosones also fuse with phagocytotic or pinocycotic vesicles (that take up nutritive material from the outside) to digest the nutrients and release them into cytoplasm. Also lysosomes sometimes used as storage depots. But important point is that they break down things in cell that have to be gotten rid of. Gauchers disease: lack of lysosomal enzyme needed to digest certain lipids, so it collects in lysosomes and eventually the person dies. Mitochondrion: outer and inner membrane, and repeated folding of membrane (cristae) inside. Increases surface area. This is where aerobic metabolism occurs (producing ATP). THE CYTOSKELETON Support of cell, look like nerve cells, organizes cytoplasm (mitochondria are there cuz cytoplasm pusts them there, etc), mitosis (structural roles, and moves chromosomes apart from each other) involved in movement inside cell (so those vesicles moving to golgi are moving along a cytoskeleton track), and involved in movement itself (so when we move an arm, etc.) - 3 major parts: o Microfilaments: cell movement, organizing cell structure.muscle contraction. Smallest. Made of protein called actin (homopolymers of actin). o Intermediate filaments: structural. Medium sized. Made of variety of diff subunits. Intermediate filaments differ in diff types of cells (brain cells, muscle cells, etc.) o Microtubules: intracellular transport, mitosis, cilia and flagella. Largest. Made of molecule called tubulin. Move things back and forth in cells. They make up the spindles for mitosis. All microtucules radiate from centrosome. Microfilaments and microfilaments constantly break down, build up, dynamic. Intrermediate filaments are stable. Things move along microtubules using motor proteins. These proteins walk along microtubules carrying vesicles (using ATP to walk) Two ends of microtubules have diff polarity. So some motor proteins walk one way, others that walk diff directions. Cilia and Flagella: filled with double microtubules. CELL JUNCTIONS: specialized structures where two cells touch. 3 major types of junctions - Accluding junctions: bind cells so tightly together that nothing can slip btwn the spaces between them. Called tight junctions. (for example, you don’t want food and stuff to get into bloodstream, in intestine) - Transmitting junctions: communicating junctions, gap junctions. Tiny gap btwn two cells. Protein channels btwn two cells, pores btwn two cells. Allow two cells to communicate directly with one another. - Attaching junctions: junctions like rivets that hold cells together. They’re just physical structures to keep cells in one position, don’t serve another functions. Intermediate filaments hold cells stably together. - Blood-brain barrier: cells outside capillaries form tight junctions, so that blood can’t leak out. Tightly closed off, held together with tight junctions. The only way things in the blood can get into the brain are across the cells. - Gap junctions important in smooth muscle: to control coordination (send signals and stuff). (LECTURE 6) THE PLASMA
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