BIL 150 Lecture Notes (Up until Exam 1)
BIL 150 Lecture Notes (Up until Exam 1) BIL 150
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This 19 page Bundle was uploaded by Casey O on Tuesday September 27, 2016. The Bundle belongs to BIL 150 at University of Miami taught by Malancha Sarkar in Fall 2016. Since its upload, it has received 4 views. For similar materials see General Biology in Biology at University of Miami.
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Date Created: 09/27/16
What is Life? There are 1.8 million named species, but there are between 10 million to over 200 million total species. New species are constantly arising. Barcoding: Every species have 1522 nucleotides. The sequence of nucleotides is unique for each species; able to identify. Cytochrome coxidase. Concepts: The Laws of Nature. Newton’s law of gravitation, his three laws of motion, etc. Physical laws work on living organisms as well. Properties of Life: The order of things. Organisms are not random. Emergent property: it can move together. Living Organisms evolve over time, but there are exceptions to the rule (i.e. cockroaches). Things mutate and adapt which provides an evolutionary advantage; they will survive. Response to the environment, to a stimulant. Regulations. Maintain homeostasis. Stable internal environment. Hormones, physical features. Energy processing. Organisms use energy and cans tore energy. Stored as different things depending on the organism. Growth and Development. Repairing the cells, constantly. There is development after birth. Reproduction. All organisms will reproduce, sexually and asexually. Cell Theory: All living organisms are made up of cells. Living, basic unit of life. Has all properties of life. Atoms→small molecules→proteins→viruses→prokaryotes→eukaryotes. Scales of Biology: Microscopic to Global scale. Form the entire living planet. Hierarchy of biological organization. Atoms→ Molecules→ Organelles→ Cells→ Tissues→ Organs & Organ Systems→ Organisms→ Populations→ Communities→ Ecosystems→ The Biosphere Central Dogma: DNA→ RNA→ Proteins Evolution: Living organisms evolve with time. Evolution of skin color. Depends on the amount of melanin within our skin. Human skin tone originates as light skin, but became darker due to loss of hair and selective pressures from the environment (UV rays). Evolution is a change of gene pool. Change of allele frequencies. Organisms evolve and adapt to their specific environment. Natural Selection: Variation: the organisms in the population vary with regard to a trait. Heredity: Variation in the trait has a genetic component transmissible to offspring. Evolution cannot happened in a single generation. There needs to be a DNA component. Selective Pressure and Differential Reproductive Success. Those organisms with favorable traits will survive and pass on the favorable traits to their offspring. Natural is the process that leads to the outcome of an adaptive individual. Vitamin D is an essential to healthy life, provided by UV Rays. Those who live in a place with short hours of sunlight are able to absorb more Vit D from the sun (light skin). Those who live in a place with long hours have darker skin, and do not absorb as much Vit D from UV. Folate is important for DNA synthesis. Folic acid is used for DNA replication. Mother’s often take Folic acid to help the growth of her baby and reduce problems at birth. Both of these are selection pressures. Folate may be destroyed wherever UV light is present. The selective pressure to maintain a dark skin near the equator is stronger than light skin. Folate can explain why dark skin evolved, but it has more difficulty explaining the evolution of light skin (which doesn’t have any reproductive advantage). Vitamin D Increased risk of death from cardiovascular disease. Cognitive impairment in older adults. Severe asthma in children. Cancer. Insufficient amount of Vit D during childhood results in rickets, a condition that often leads to bowing of the long bones of the legs and deformation of the pelvis. How is Vitamin D linked to Natural Selection? Many laws found in physics and chemistry are applicable in Biology. Only 25 elements are essential to life C, H, O, N: 96% of living matter. Remaining: Ca, P, K, S, and few others (trace elements). Water is necessary for all life. Isotopes Two atoms of an element that differ in the number of neutrons. Radioactive Isotopes are used in medicine Cancer mostly (tracing atoms, tracing processes). Also used to date fossils. Stable isotopes and Unstable Isotopes (i.e. halflife) Stable Isotopes Carbon and Nitrogen are two essential elements in biochemistry of life. Both elements occur 12 14 naturally ccer in two stable isotopic forms in their number of neutrons: light ( C and N) and heavy ( C and N). Organisms preferably metabolize the light isotopic forms. As a result the isotope ratios of carbon and nitrogen, systematically increase as one moves up the food chain. Non metabolized ions are dangerous/toxic to the human body. Energy Levels of Electrons Energy: capacity to cause change. Potential Energy: energy the matter has because of location or structure. Electron orbitals (shells) are where electrons rotate around the center of the atom. In the outermost shell an electron has high energy. Energy depends on which electron shell it is in. Valence electrons are those in the outermost shell, or valence shell. The chemical behavior of an atom is determined by valence electrons. Elements with full valence shell is chemically inert. If not full, the atom is UNSTABLE. Valence electrons are the ones to create chemical bonds in order to become stable. (Give, Take or Share electrons). Bonds and Interactions Covalent bond (Electronegativity). Ionic Bonds. Hydrogen Bonds in living cells. (EXTREMELY IMPORTANT). Van der Waals interactions. Covalent Bonds can form between atoms of same element or different. Atoms in a molecule attract to various degrees. Electronegativity is an atom’s attraction for the electrons in a covalent bond. The more electronegative an atom is, the more strong it pulls shared electrons towards itself. In a nonpolar covalent bond, the atoms share the electron equally. In a polar covalent bond, one atom is more electronegative and the atoms do not share the electron equally. Unequal sharing of electrons cause a partial positive or negative charged for each atom or molecules. Ionic Bonds. Atoms sometimes strip electrons from their bonding partners. After the transfer of an electron, both atoms have charges. One gives, One takes. Most of the strongest bonds are covalent. Weak chemical bonds are ionic and hydrogen bonds.Weak chemical bonds reinforce shapes of large molecules and help molecules adhere. Hydrogen Bond. When an hydrogen atom bonded to one electronegative atom is also attractive to another electronegative atom. In living cells the electronegative parents are usually oxygen or nitrogen. Found in DNA. Van der Waals Interactions. If electrons are distributed asymmetrically in molecules or atoms. They result in “Hot spots” Positive or NEgative Change. Prefers a particular area in the electron cloud. Orbitals Preferred areas in space with high probabilities of finding an electron. Molecular Shape and Function.Shape is important to its function. Shape determined by the position of an atom's valence orbitals. In covalent bonds s and p orbitals by hybridize, creating specific shapes. Structure of enzyme receptors allows a particular molecule to pass through. Structure is important. Chemical Reactions They make or break chemical Bonds. Chemical equilibrium is reached when the forward and reverse reaction rates are equal. Water Required more than any other substance. No enzyme will function without water. Cells are 70 to 95% water. Four emergent properties of water that affect life. ● Expands when freezes ● Cohesion ○ Adhesion (sticking to something other than itself) ○ Surface tension (sticking to itself, other water molecules) ● High specific heat, evaporative cooling ○ Lot of time to heat and lot of time to cool; evaporation takes heat ● Solvent of life ○ Water dissolves many things, i.e. salts, sugars. Universal solvent. ○ This is due to its polarity, allows hydrogen to forms bonds easily. ○ When Ionic Compounds dissolve, ions are surrounded by a sphere of water molecules. Hydration shell. This is mostly because of hydrogen bonds. Moderation of Temperature Amount of heat needed to change temperature (Water: 1 cal/g/ C)o Temperature changes slowly. Evaporating Cooling. Cooling effect due to evaporation of liquid. ● Hydrophilic (Affinity for Water) ● Hydrophobic (No Affinity for Water) Acids and Bases + ● Acids: increased H concentration ○ Donates to aqueous solutions ● Bases: reduced H concentration + ○ Donates OH and accepts H in solutions Our bodies need both to function. Even the smallest of changes can cause enzymes to stop working and would become very sick. Buffers ● Substances that minimize changes in pH ○ If something is becoming more acidic, buffers produce some basic ion. + ● Most consist of acid base pair that reversibly combines with H Carbon and the Molecular Diversity of LIfe ● All major macromolecules contain carbon. ● Cells 7095% water but the rest are carbon based carbon. ● Can bond with 4 other molecules. ● Organic Chemistry: Study of Carbon Compounds ○ Simple molecules to colossal ones ○ Most contain hydrogen atoms ● Can make a diverse groups of compounds. ● Depending on how carbon molecules bond, the shape of the molecule will change. ● Electro configuration provides carbon to bond to many things. ● Valences or carbon and frequent partners (hydrogen, oxygen, nitrogen) are the building code for most living molecules. Molecular Diversity of Carbon Skeleton ● Carbon chains form skeletons of organic molecules. ● Chains vary in length and shape. ● Hydrocarbons ○ Organic Molecules with only C and H ○ Components of many organic molecules (e.g., fats) can undergo reactions that release large amount of energy. Isomers ● Compounds with the same molecular formula but different structures. ○ Structural Isomers have different covalent arrangements of atoms ○ CisTrans Isomers have sam covalent bonds but differ in spatial arrangement ○ Enantiomers are Isomers that are mirror images of each other. Chemical Groups Important to Life ● Functional Groups ○ Components of organic molecules involved in chemical reactions ■ Provide properties to a molecule. ○ Hydroxyl group ■ Polar. Forms hydrogen bond with water. ■ Alcohol ○ Carbonyl group ○ Carboxyl group ■ Acts as an acid. ■ Organic Acid ○ Amino group ■ Acts as a base. ■ Amine ○ Sulfhydryl group ■ Thiol ○ Phosphate group ■ Organic Phosphate ■ Found in DNA. Plasma Membranes. ○ Methyl group ■ Methylated Compound Macromolecules ● Polymers: Large (long) molecules consisting of many Monomers (building blocks). ○ Lipids do not have any polymeric form. Just bulky big molecules. ○ A dehydration reaction occurs when two monomers bond together through the loss of a water molecules. ○ Polymers are disassembled by hydrolysis; water being put in. Opposite of dehydration reaction. ○ Carbohydrates: Fuel and Building Material ■ Monosaccharides (simple sugars) ● Multiples of C (n O2 n ● Glucose are the most common ■ Polysaccharides ● Polymers of sugars specifically Storage and Structural Roles. ● The structure and function of a polysaccharide are determined by sugar monomers and position of glycosidic linkages. ■ Starch ● Stored form of carbohydrates (energy) in plants. ● Made of amylose. ● Unbranched and somewhat branched (some soluble) ■ Glycogen ● Stored form of carbohydrates (energy) for animals. ● Located in muscle tissue and some in liver. ● All branched. ■ Cellulose ● Humans can not digest. ● Hydrogen bonds between the molecules. Source of strength. ● Makes the cell wall. ■ Structural Polysaccharides ● Cellulose is major component of tough plant cell walls. ● Glycosidic linkages differ from starch. ■ Chitin ● Forms the exoskeleton of arthropods. Provides strength and protection. ● Used to make flexible and flexible surgical thread. ● NAcetylglucosamine Lipids: ● Most biologically importance: fats, phospholipids and steroids. ● Forms when: ○ Glycerol combines with fatty acid through dehydration reactions ○ Create triglyceride. ● Major functions: ○ Energy storage in adipose cells. ○ Adipose tissue also cushions vital organs and insulates. ○ Our body requires fat. ○ Does not stick to water because of long, nonpolar, tails. ■ Hydrophobic ● Bonds: ○ Single Bond in the tail is Saturated fat. Solid at Room Temperature. ○ Double Bond in the tail is Unsaturated fats. Liquid at Room Temperature. ■ More than one double bond is a polyunsaturated fat. ■ Creates a kink in the molecule. ● Diets rich in saturated fats contributes to heart disease ● Hydrogenation: Manmade. COnverting unsaturated fats to saturated fats by adding hydrogen ○ Oils get rancid with time, so by hydrogenating it creates a longer shelf life. Adds to flavor. ○ Transfats are worse than saturated fat. No enzymes to digest transfats. ● Omega 3 Fatty Acids: ○ Commonly found in marine and plant oils. ○ Polyunsaturated fatty acids with a double bond. ○ Have two ends COOH and CH3 end. ● Phospholipids: ○ Major structure of your cells. Cell membrane. ○ Hydrophilic end and hydrophobic end (farry acid end) ○ Two chains of fatty acids and hydrophilic head. ○ Double layer of phospholipids make your cell membrane Steroids: ● Characterized by carbon skeleton of 4 fused rings. ● Cholesterol: component of animal cell membranes. Proteins: ● Types: ○ Enzymatic Proteins ○ Defensive Proteins ○ Storage Proteins ○ Transport Proteins ■ Present in cell membranes. Receptors. ○ Hormonal Proteins ○ Receptor Proteins ○ Contractile and Motor Proteins ○ Structural Proteins ● Polypeptides: ○ Polymer built from same set of 20 amino acids. ○ Proteins are 1 or more polypeptides. ○ Amino Acids: monomers or polypeptides. ■ Different side chains, called R groups. ■ Put together by dehydration Reaction creates a peptide bond between amino acids. ● Structure ○ Specific activities of proteins result from their 3D architecture. ○ Functional Protein consists of one or more polypeptides, warped into a unique shape. ○ Four Levels: ■ Primary structure is a unique sequence of amino acids. ● Unfolded, Denatured, Protein. ■ Secondary Structure, found in more proteins, consist of coils and folds in the polypeptide chain. ● I.e. Alpha Helix, Pleated Sheet ■ Tertiary structure is determined by interactions in the R Groups. ● Gives the protein it’s 3D shape. ● R groups with slightly positive or slightly negative molecules may form ionic bonds with nearby R groups. ● R Groups may interact with Hydrogen to form Hydrogen Bonds. ● Sometimes Covalent Bonds are made. ■ Quaternary structure is when a protein has multiple chains. ● Two of more polypeptide chains. ● Stabilized by same interactions that stabilize tertiary structures. ○ Always have an amino end and a carboxyl end. ○ All Amino Acids have the same backbone, but the R groups change what it is. ● SickleCell Disease: Change in Primary Structure ○ Slight change can affect a protein’s ability to function. ○ Sickle Cell Disease, inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin. ■ Sickle Cell helps to prevent Malaria. ○ Polar with Polar may not change the structure. Polar with nonpolar may change the structure. ● What Determines Structure ○ Physical and Chemical condition can affect structure. ■ PH, salt concentration, temperature, environmental factors. ■ Loss of native structure > Denaturation ● Biologically inactive. ● Something acidic will denature a protein. ● Many can not revert after denaturation. ○ Chaperonins ■ Protein molecules that assist in the folding of proteins. ● Secreted when something bad happens to the body to help protect other proteins. ■ Polypeptide enter the cylinder. When it comes out, it is fully folded. Nucleic Acids ● Nucleic Acids: store and transmit hereditary information. ○ Gene (unit of inheritance) Programs a sequence of a polypeptide ■ Genes are made of DNA, a nucleic acid ○ Types: ■ Deoxyribonucleic Acid DNA ● Found in complex organisms. ● Stable. ■ Ribonucleic Acid RNA ● Found in both simple and complex organisms. ● Many different functions. ○ DNA > Genes > Chromosomes > Genome ○ Structure: ■ Polymers call polynucleotides. ● Monomers called nucleotides. ■ Has a nitrogenous base, pentose sugar and phosphate group. ■ Nucleoside has same structure without the phosphate group. ● Deoxyribose in DNA ○ Phosphate backbone. ● Ribose in RNA ○ Folded on itself, not double helix. ■ Purines: ● Adenine ● Guanine ■ Pyrimidines: ● Cytosine ● Thymine ● Uracil ● DNA Double Helix ○ Molecule: 2 polynucleotides spiraling around an axis. ○ Antiparallel: DNA double helix, two backbones run in opposite 5′ → 3′ directions from each other ○ A>T, G>C ● ATP ○ Provides energy to our body ■ Primitive molecule ● Present is simple organisms and complex organisms. ○ Nucleoside triphosphate. ○ Reacts with water to get energy. Cells: Different type of cells for different functions. All living organisms are made up of cells. Cells arise from cells. Most plant and animal cells are between 10100 picometers. Light microscopy allows you to see cells at a basic level. Electron microscope allows you to see things such as organelles and cillia. Prokaryotic and Eukaryotic: ● Prokaryotes do not have a nuclear membrane. ○ Chromosomes are circular. ● Eukaryotic cells have a nucleus ● Basic Features of all cells: ○ Plasma membrane ○ Cytosol ○ Chromosomes ○ Ribosomes Domains of Life: ● Archaea ○ Prokaryotes ○ Closer to Eukaryotes ○ Can survive under extreme conditions. EXTREMOPHILES ■ Halophiles: Highly saline environments ■ Thermophiles: Thrive in very hot environments. ● Used to isolate enzymes for PCR. ■ Methanogens: Swamps and marshes and produce methane. ● Bacteria ○ Prokaryotes ■ No nucleus, or membrane bound organelles. ■ DNA in unbound region called the nucleoid. ■ Cytoplasm bound by plasma membrane. ■ Capsule > Cell Wall > Plasma Membrane ■ Most of unicellular. Some species form colonies. ■ Most cells are .55 picometers. ■ Common Shapes: ● Spherical ● Rod ● Spiral ■ Highly adaptive, mutate fast; found everywhere. ■ Autotrophs make their own food. ■ Heterotrophs can use outside energy sources, but do need organic compounds to survive. ● Eukarya ○ Eukaryotes ■ Have nuclear membrane and membrane bound organelles. ■ Cytoplasm between plasma membrane and nucleus. ● Plasma Membranes separate Cell from outside. ● Prevents things from entering and leaving the cell. ● Phospholipid bilayers. ● Cholesterol is found in the plasma membrane on animal cells. Embedded. Provides fluidity to membrane. ● Proteins integrated in the plasma membrane sometimes have carbohydrate side chains attached to them. Move in the membrane. ■ Larger than Prokaryotes. ● Size and Evolution. ○ Cells have become larger over years for predatory purposes. ○ Smaller cells can take and expel substances quicker. ○ Became multicellular for easier exchange of materials. ● Organelles ○ Mitochondria used to be individual prokaryotes. ■ Consumed by larger cell and integrated. ■ Has its own DNA. ■ Lost genes to live in symbiosis. ■ Cannot live independently. ○ Lysosomes ■ Recycling agent of the cell. Cleaning. ● Reabsorb the one it destroys. ● Some cells can engulf another by phagocytosis, forming a food vacuole. ○ Lysosome fuses with food vacuole and digest molecules. ○ Recycles and Helps in protection. ■ Has bags of hydrolytic enzymes to destroy old or dead organelles. ○ Golgiapparutus ■ Decides the destination of a protein. ● Tags a protein and tells it what to do. ■ Modifies proteins. ○ Cytoskeleton ■ Microfilaments ■ Intermediate Filaments ■ Microtubules. ● Play important role in cell division. ● Can’t divide it destroyed. ■ Helps in cell division. ■ Acts as tracks for travel across the cell. ○ Ribosomes ■ Help in synthesis in proteins. ● Synthesis in cytosol (free ribosomes) outside of endoplasmic reticulum or nuclear envelope (bound ribosomes). ■ Made of ribosomal RNA. ■ May be attached to Endoplasmic Reticulum. ● Rough when Ribosomes are attached. ○ Protein Synthesis ● Smooth when no ribosomes are attached. ○ Lipid Synthesis ■ Consists of: ● Large subunit. ○ RNA get’s attached. ● Small subunit. ○ Cell Wall ■ Made of cellulose. ■ Provides strength and prevents attacks from fungal spore or bacteria. ○ Chloroplasts ■ Contain pigment: Chlorophyll. ■ Used to be independent prokaryote before living symbiotically. ■ Has its own DNA. ○ Central Vacuole. ■ Storage for minerals, hormones and other molecules. ○ Nucleus ■ Contain the cell’s genes (DNA) ● Organized into chromosomes ● Proteins of chromosomes are called chromatin. ○ Condenses to form discrete chromosomes as cell prepares to divide. ● Nucleolus is located in the nucleus. Site of RNA (rRNA) synthesis. ○ Stores it before use. ● Regulates gene expressions. ■ Nuclear Envelope ■ Double membrane (Lipid Bilayer) with Pores to allow materials in and out. ● Proteins guard the pores. ○ Endomembrane Systems ■ regulates protein traffic; performs metabolic functions. ■ Components: ● Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane. ■ Components are either continuous or connected via transfer by vesicles. ● Responsible for connecting everything. ■ Pinch of the ribosomes and transport them to Golgi Complex. ○ ER ■ Smooth ER ● Synthesis lipids. ● Metabolize Carbohydrates. ● Detoxifies Drugs and poisons ● Stores Calcium Ions ■ Rough ER ● Bound ribosomes. Secrete glycoproteins. ● Distributes transport vesicles, proteins surrounded by membranes ● Membrane factory for the cell. ○ Golgi Apparatus ■ Flattened membranous sacs called cisternae ■ Functions ● Modifies products of the ER ● Manufactures certain macromolecules ● Sorts and packages materials into transport vesicles. ■ Vesicles transport to plasma membrane to release the product. ○ Vacuoles ■ Present only in plant cells and fungal cells ■ Used to store minerals, water, hormones, etc. ■ Contractile Vacuoles ● Present in protists. Pump excess water out of the cell. ■ Central Vacuoles found in mature plant cells, hold organic compounds and water. ■ Food Vacuoles formed by phagocytosis ■ Cells may have one or several vacuoles. ○ Mitochondria and Chloroplasts ■ Responsible for transformation of energy. ■ Mitochondria ● Generates ATP ● Cellular Respiration ■ Chloroplasts ● Present in plants and algae ● Site of photosynthesis ● Gelatinous matrix: stroma ● Thylakoid is one stack in the cell, granum is many stacks. ● Chlorophyll is the pigment that converts and traps sunlight, made into chemical form. ■ Not part if endomembrane system, was once individual organisms ■ Double membrane ● Mitochondria: Smooth outer membrane, folded inner membrane. ■ Proteins made by free ribosomes>Like prokaryotes ■ Own DNA ■ Peroxisomes: ● Oxidative Organelles. ● Bound by a single membrane ● Produce Hydrogen peroxide and convert to water. ● Catalays, which destroy hydrogen peroxide. ● Helps in degradation of amino acids, lipids, uric acid. ● Peroxisomes can’t replicate by themselves, they divide. No DNA. ■ Endosymbiosis: ● Single nonphotosynthetic eukaryote engulfed a prokaryotic which utilizes photosynthesis and continued to use the genes. ○ Septoplasty ■ Found in Seas slugs. ■ They eat algae but cannot digest chloroplasts. ● Distributes the chloroplasts all over the body. ● Won’t eat for next few months ● Swims on surface of the ocean and traps sunlight for energy. Cytoskeleton ● Network of fibers extending through cytoplasm. ● Organizes cell structure and activity. ○ Keeps organelles in a particular space. ○ Maintain shape. ● Three types: ○ Microtubules ■ Helps in chromosome movement. ● Attached. ● Moves them to the pole in cell division. ■ Organelle movement ■ Tubulin Protein Subunits. ○ Microfilaments ■ Two intertwined strands of actin. ■ Helpful in muscle contraction. ■ Directs movement of cytoplasm in the cell. ○ Intermediate Filaments. ■ Fibrous proteins supercoiled in thick cables. ● Keratin ■ Moves materials in the nucleus. Scaffold. Structure. ● Interactive with motor proteins. ● Vesicles travel along the “monorails” of the cytoskeleton. ● Centrosomes ○ Help in cell division. ○ Consists of two centrioles ○ Move to either end of cell when cells are dividing. ○ Anchor for the microtubules. Cilia and Flagella ● Core of microtubules sheathed by plasma membrane ● Basal Body that anchors them. ● A motor protein, dynein, drives the bending movements of a cilium or flagellum ○ Maintains the structure. ○ Keep the microtubules in proper place. ○ “Walk” on the microtubules. Extracellular Components: Connections between and Cellular Activities ● Synthesize and secrete materials. External to plasma membrane ● Structure include: ○ Cell walls ○ Extracellular matrix (ECM) of animal cells ○ Intercellular junctions ■ Communication between cells. ■ Putting two cells together to form a strong structural component. ■ Many types of junctions. ● Active as “cement” to bring cells together. ● Effect genomes. Cell Walls ● Present exclusively in certain proteins and plants. ○ Prokaryotes ○ Fungi ○ Some protis ● Animal cells do not have cell wall. ● Protects cell, maintains shape. Prevents excess water uptake ● Cellulose fibers embedded in other polysaccharides and proteins. ECM of Animal Cells ● Lack cells walls so they have ECM ● Made up of glycoproteins ○ Collagen, proteoglycans and fibronectin ■ Collagen triple helix, provides structure ● Ecm bind to receptor proteinsIntegrins ○ Present in all animals cells ○ Help in attaching cells to the base; come together. ○ Communicate within themselves. ● Functions: ○ Support – Adhesion – Movement – Regulation ● Regulate gene expressions. Cell Adhesion ● Sponges were broken down into individual cells. ● Cells from both sponges were swirled together. ● The cells from each sponge sorted themselves out. ○ The ECM recognizes each other. ○ Therefore it brings them together. Intercellular Junctions ● Neighboring cells interact and communicate through direct physical constance. ● Intercellular junctions facilitate the contact. ● Types: ○ Plasmodesmata ○ Tight Junctions ■ Prevents leakage of fluid in intermembrane space. ○ Desmosomes ○ Gap Junctions ■ Molecules can pass through; from one cell to another. Fluid Mosaic Model ● Amphiphilic Molecules ○ Containing hydrophobic and hydrophilic regions ○ Phospholipid Bilayer ■ Phospholipids 7 ● Move laterally ~ 10 times per second ● Flip positions ~ Once per month ○ Integral Proteins and Peripheral Proteins (attached to cytoskeleton to keep cell in place). ● Hydrocarbon Tails ○ Unsaturated tails prevent packing. ○ Saturated Tails pack together tightly. ○ Cholesterol in an animals cell membrane reduces membrane fluidity at moderate temperatures. At low temperatures it hinders solidification. ■ Maintains the fluid nature of the plasma membrane ■ Important for maintenance of the structure of plasma membrane. ● Proteins ○ Determine most membrane functions. (Diverse) ○ Six Major Functions ■ Transport ● Act as “doors” ■ Enzymatic Activity ● Cellular respiration ■ Signal transduction ● How cells know what is around it. ● Picked up by receptors pass on information chain of signals ■ CellCell Recognition ● Use Glycoproteins to recognize one another. ● Attach to Glycoprotein to communicate ■ Intercellular joining ● Cemented together by proteins. ■ Attachment to the cytoskeleton & extracellular matrix (ECM) ● Maintain cell shape. Membrane Structure ● Regulates materials in and out of the cell ● Allows only certain materials. ○ Selectively permeable. ● Nonpolar molecules can pass through lipid bilayer easily ○ Gases ○ Small, uncharged polar molecules ■ Water (Slightly Permeable) ● Polar molecules have a hard time crossing the plasma membrane ○ Need special transport proteins. ○ Large uncharged polar molecules ○ Ions ○ Charged polar molecules ● Transport Proteins ○ Aquaporins facilitate the passage of water through the membrane ○ Passive Transport ■ Diffusion of a substance. ● Spread evenly, forms an equilibrium ○ Do not stop once equilibrium is reached, just moves slowly. ● No more concentration Gradient. ● Move from high concentration to low concentration. ■ No energy is required for transport. ■ Molecules move randomly ○ Osmosis ■ Diffusion of Water across selectively permeable membrane. ■ Water molecules only. ■ Low Solute Concentration > HIgh Solute Concentration ● Water Balance of Cells ○ Tonicity Ability of solution to cause cell to swell or shrink. ■ Isotonic Solution: Concentration is same as inside of the cell, no net water movement ■ Hypertonic: Solute concentration is greater than inside the cell, cell loses water ■ Hypotonic: Solute Concentration is less than inside the cell.
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