Human Phys. Notes for Week of February 1st - 5th (M & W Lectures)
Human Phys. Notes for Week of February 1st - 5th (M & W Lectures) Biology 207
Long Beach State
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This 6 page Class Notes was uploaded by Cristina Villagran-Gonzalez on Tuesday February 2, 2016. The Class Notes belongs to Biology 207 at California State University Long Beach taught by Dr. Balwant Khatra in Spring 2016. Since its upload, it has received 35 views. For similar materials see Human Physiology in Biology at California State University Long Beach.
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Date Created: 02/02/16
Lecture – 2/1 Proteins Most important macromolecule – proteins have a large variety of functions in our body (almost limitless amount of functions) Each protein has a unique 3D structure – determined by DNA Structure: acid group + amino group + functional group, which varies among proteins Proteins are made by dehydration synthesis H is stripped from amino end and OH is stripped from carboxyl end o Forms a peptide bond (bond btwn the amino acids) Covalent bond – very strong, not easily broken Backbone is made up of Nitrogen – Carbon – Carbon bonds Backbone produces 3D shape – R groups are hanging out 2 terminals – amino terminal & carboxyl terminal Have certain areas for molecules to bind onto 4 levels of Protein Structure o Primary structure = sequence of amino acids (Polypeptide strand) o Secondary Structure = caused by weak H bonding of adjacent polypeptide bonds Results in alpha helix or beta pleated sheet structure due to these hydrogen bonds Due to backbone of protein determined by the interactions of the R groups which can bond with each other o Tertiary Structure = the specific 3D shape of the protein which is very important to its function Forming of polypeptide Differ among amino acids due to varying structures Folding & bending of the amino acid chains There are hydrophobic bonds, ionic bonds, & covalent bonds present Since it is held together by weak bonds, proteins can easily become denatured by changes in pH or temperature o Quaternary structure = multiple polypeptide chains covalently bonded to each other Polypeptides are attracted to each other due to hydrogen, ionic, hydrophobic and sulfide bonds Conjugated Proteins – ex: glycoproteins, lipoproteins Protein functions: structural, enzymes, antibodies, receptors, carriers Chapter 4 – Enzymes & Energy “All enzymes are proteins, but not all proteins are enzymes” Enzymes Serve as catalysts – speed up rate of reaction, but remain unchanged at end of reaction o Do not change nature of reaction o Increase rxn by lowering activation energy Most of them are proteins A + B C + D Reactants (substrates) Products Ways to increase energy for activation: heat, pH o However, heat has negative effect on cells – enzymes allow rxns to occur at lower temps Enzymes increase proportion of molecules that have enough energy to react Mechanisms Function of enzyme dictated by structure Enzymes have a specific 3D structure w/ pockets where substrate can bind to enzyme (called active site or catalytic center) Lock and key fit form enzyme – substrate complex Enzymes can only accommodate one type of substrate – Very specific Enzymes allow for new bonds to form between substrate Naming Name based on enzyme function o Usually end in ase o Can also contain name of substrate and activity Isoenzymes Enzymes that do the same job in two different organs o Have the same o Molecules may be slightly different Control of Enzyme Activity Enzyme activity measured by rate at which substrate is converted to product o Influenced by pH, temp, concentration of cofactors, conc. Of enzyme & substrate, possible stimulatory or inhibitory effects of products on enzyme function Must be in optimal range (pH & temp) for maximal activity of enzyme – 3D structure is affected when outside of this range Ex: pepsin has optimal pH of 2 bc it works in our stomach which produces hydrochloric acid Depends on environment of the cell o Coenzymes – additional small molecules which aid the enzyme activity Transport hydrogen atoms and other small molecules btwn enzymes Organic molecules derive from watersoluble vitamins o Cofactors – metal ions Help from active site through conformational change of the enzyme or help in enzyme – substrate binding o Substrate Concentration Rate of product formation increases as substrate conc increases Continues until rxn reaches a plateau – at this point, enzyme is said to be saturated (reaches its maximum rate) Some enzymes produced in an inactive form and activated when they are needed (ex: pepsinogen pepsin) Some enzymes are activated by other enzymes through phosphorylation or dephosphorylation Activity can be controlled by turnover – degrading enzymes Sometimes, single enzymes can have a reversible rxn o Depends on substrate/product concentration o Called Law of Mass Action Metabolic Pathways Series of rxns linked together which convert an initial substrate into a product Most metabolic pathways are branched – they can produce several products o Product of one enzyme rxn becomes substrate for the next Each step is an intermediate & catalyzed by different enzymes Regulation o End Product Inhibition: occurs when 1 product in a divergent pathway inhibits activity of the branch point enzyme Prevents final product accumulation; causes rxn to favor alternate pathway Occurs by allosteric inhibition – product binds to enzyme causing it to change to an inactive shape Prevents earlier rxns from occurring o Inborn Errors of Metabolism: due to inherited defects in genes for enzymes in metabolic pathways Metabolic disease can occur from: Increases in intermediates formed prior to the defective enzyme Decreases in products normally formed after defective enzyme All intermediates before error will accumulate product Bioenergetics Deals with transfer of energy Energy comes in many different forms (light, chemical, electrical, etc) o Can be transferred from one form to another form, but cannot be created o Follows laws of thermodynamics 1 law of thermodynamics: energy cannot be created nor destroyed, only transformed o Conversion of light energy to glucose (plants) nd 2 law of thermodynamics: energy is lost with each transformation as heat, so available organized energy (free energy) decreases o Entropy = degree of disorganization Increases at each step of energy transformation o Relates to endergonic & exergonic rxns Endergonic: chemical rxn which requires input of energy Lecture 2/3 Chapter 3 – Cell Structure & Genetic Control Cells Smallest unit in our bodies that provide functions Large variety; Common features o Plasma membrane & associated proteins Cells in diff tissues have different proteins All cells surrounded by membrane – has various functions including aid in communication, acting as a barrier, etc – must know composition of membrane o Cytoplasm & organelles Fluid within cell; contains organelles inside it – will need to know functions of different organelles o Nucleus (not all cells have them) Surrounded by membrane; contains all genetic material Plasma Membrane Structure of phospholipid plays a role in structure of membrane o Hydrophobic parts (fatty acid tails) vs hydrophilic parts (phosphate head) Membrane made up of two layers of phospholipids – phospholipid bilayer o Tails are in middle, heads are both outside the cell and inside the cell (outside layer of membrane) o Primarily hydrophobic – which is why membranes are selectively permeable Small hydrophobic molecules can pass through easily o Cholesterol molecules embedded within membrane – to fill in holes o Not a rigid structure – phospholipids are essentially fluid fluid mosaic model Proteins do not have a set pattern (not stationary) – moving all the time o Peripheral proteins embedded in membrane, but portion is sticking out or in o Integral proteins are both inside and sticking outside membrane Membrane Proteins o Integral proteins span membrane o Peripheral proteins embedded on just one side of the membrane Functions: Structural support, transport, enzymatic control of cell processes, receptors for hormones & other molecules (molecule that can identify signal and respond appropriately), “self” markers for immune system Also have carbs (glycoproteins & glycolipids) on part of outer surface which help mark the cell – impart negative charge Cilia: small extension from surface of the cell – tiny hair like structures composed of microtubules that project from plasma membrane o Help cell move (motile cilia) through hollow organs o Primary cilium may have a sensory function – found on almost every cell in body o Covered by plasma membrane Flagella: single whip like structure that propels a cell to move forward o Sperm Microvilli: folds in PM that increase surface area for rapid diffusion Transport o Bulk transport: a way cells move large molecules and particles across PM Exocytosis vs endocytosis Whole membrane of cell participates in these types of transport 3 types of endocytosis Phagocytosis: cell eating – membrane surrounds material to take into cell using a vacuum o Pseudopods are formed Pinocytosis: cell drinking – bringing dissolved material into the cell – mostly fluid accumulates o nonspecific Receptormediated Endocytosis: receptors used to bring specific material into cell – material binds to these receptors then forms indentation to bring them in Exocytosis: large cellular products are moved out of cell Golgi apparatus packages proteins into vesicles that fuse with plasma membrane Cytoplasm & Organelles Material within a cell o Includes organelles, fluid (cytosol), microtubules & microfilaments (long structure made by combing proteins together) & intermediate filaments called cytoskeleton o Cytoskeletal proteins Extremely dynamic Continuously made and dissolved Localize different organelles in different parts of cytoplasm Help in transporting molecules from one side of cell to another (act as highways) Form spindle apparatus that pulls chromosomes apart in mitosis Lysosomes o Organelles filled w. digestive enzymes – digestive system of cell Digest any material which is not needed by the cell o Fuse w/ food vacuoles after an immune cell engulfs a bacterium or dead cell o Primary lysosome: only contains digestive enzymes o Secondary Lysosome: contains partially digested contents of food vacuole o Residual Lysosome: lysosome filled with waste which can leave cell through exocytosis or recycled o Carry out apoptosis – death of a cell & autophagy Peroxisome o Vesicle like organelles (similar to lysosomes) which contains oxidative enzymes which are involved in detoxification in liver & lipid breakdown Ex: detoxification of alcohol Mitochondria o Powerhouse of the cell o Where all energy is produced o Have inner & outer membrane separated by intermembrane space Inner membrane is folded into cristae o Believed to have originated from symbiotic bacteria o Inside of mito: matrix – contains all enzymes responsible for breaking down nutrients o Have their own DNA comes from mother Ribosomes o Protein factories of the cell mRNA takes genetic info to ribosome so protein can be assembled o very small – found free in cytoplasm, but most are attached to rough E.R broken into 2 subunits composed of proteins & ribosomal RNA while not in use Endoplasmic Reticulum o System of membranes specialized for synthesis or degradation of molecules o Rough Contains ribosomes Main function: protein synthesis & protein modification o Smooth Contains enzymes for synthesis of lipids such as steroids; Ca storage & detoxification No ribosomes attached Golgi Apparatus (Complex) o Consists of stacks of flattened sacs One side receives proteins from ER Modifies them & sorts them – then packaged in vesicles & bud off to fuse with the plasma membrane for exocytosis Nucleus Most cells have one nucleus o Muscle cells have hundreds; RBC’s have none Enclosed by nuclear envelope made of 2 membranes o Outer membrane: continuous w/ rough ER o Inner membrane: often fused with outer membrane o Nuclear pores: allow material to go in and out of nucleus – allow small molecules to diffuse through them Nucleolus contained in center of nucleus o Important for making ribosomes DNA & Genes Nucleus contains chromosomes which are made up of genes – small part of chromosome that codes for a specific protein o Gene on DNA is transcribed as mRNA, which can leave the cell o mRNA then translated at ribosome to assemble proper amino acid sequence these two steps = Genetic Expression Genome & proteome o Genome: all the genes in a particular individual or all the genes of a particular species Humans: ~25000 genes o Proteome is all the proteins produced from the genome More than 150000 proteins produced in the human body Chromatin o DNA in nucleus packaged w/ proteins called histones – form chromatin Euchromatin: active in transcription, looser. Changes in histones allow molecule access to DNA during gene expression Heterochromatin: inactive regions
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