Midterm Exam: The Basics - General Biology | BIOL 1001, Study notes of Biology

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CHAPTER 4
The Basics:  The cell is the smallest living unit  Genetic material in cells is deoxyribonucleic acid (DNA)  Prokaryotes-don’t have nucleus, store in the nucleoid region  Eukaryotes-have a nucleus, and internal membranes called organelles  Nuceloid is a dense region of DNA in a prokaryotic cell  Cytoplasm is the entire region inside the cell membrane and outside the nucleus in cells that have a nucleus (i.e.., most eukaryotic cells)  Eukaryotes are much more complex (fig 5-3) o The inside of the eukaryotic cell is compartmentalized into organelles o Organelles are one of several compartments suspended in the cytoplasm of eukaryotic cells  Some of the cellular organelles o Nucleus o Endoplasmic reticulum o Golgi complex o Vesicles o Mitochondrion o Chloroplasts  The nucleus is the compartment that contains the cell’s genetic library Nucleus is a (usually) membrane-bound cellular organelle in eukaryotic cells.  Ribosomes build the cell’s proteins o Ribosomes are cytoplasmic complexes which are the sites of protein synthesis o Ribosomes contain rRna (ribosomal RNA) and many proteins  Made up of two subunits  In the prokaryotes the ribosomes are free in the cytoplasm  In eukaryotes the ribosomes are either free, or attached to a membrane (usually the membrane of the endoplasmic reticulum) The endoplasmic reticulum o Found in two forms: smooth ER and rough ER  Smooth ER (because there are no bound ribosomes attached  Functions-synthesis of lipids (especially phospholipids and steroids)  Rough ER (because of the presence of bound ribosomes)  Functions  Manufacture of membranes  Synthesis of secretory proteins  The golgi complex (apparatus) finishes, sorts, and ships many cell product  One type of vesicle which “leaves” from the Golgi complex is the lysosome (fig 5.10)  Lysosomes are membrane-bound organelles which are digestive compartments that digest all major classes of macromolecules o Functions of lysosomes:  1. Intracellular digestion  food vacuoles are formed by phagocytosis (fig 5.10) of a food particle. Lysosomes fuse with these food vacuoles to digest the food.  Phospholipids are molecules which can form membranes naturally.  Cell membranes are phospholipid bilayers o Evidence: the phospholipid content of red blood cells is just enough to cover the cell with two layers o The red blood cell has no internal membranes  Biological Membranes contain proteins o Evidence: membranes isolated from red blood cells contain proteins in addition to lipids o Singer and Nicolson proposed the Fluid Mosaic Model (Fig 4.1)  Membrane made of phospholipids, proteins, and cholesterol  Fluidity in membranes means there is lateral two-dimensional movement of the lipids and some proteins in the plane of the membrane. o However, transverse (flip/flop) across the membrane is rare o Lateral movement about 107 times per second o Flip-Flop movement about once a month  Mosaic-aspects of membranes means that there are proteins interspersed within the lipid bilayer  Some functions of membrane proteins o Transport proteins  Channel proteins-pores  Carrier proteins-selective revolving doors o Receptors o Cell-to-cell recognition Some of the recognition keys on the surface of the cells are glycoprotein o Glycoproteins are proteins which have carbohydrate attached to them
Transport Across Membranes  Transport is movement  Movement of molecules requires two factors o 1.movement must be through a fluid  liquid or gas o there must be a concentration gradient  difference in the amount of molecules from one place to another o Molecules in a fluid always move  If there is a concentration gradient then the movement has a specific direction  Passive transport: movement down a concentration gradient  Concentration gradient is a concentration change over a distance in a particular direction  Diffusion is the net movement of a substance down a concentration gradient  1. Movement is from greater concentration to lower concentration  2. The greater the concentration difference, the faster the diffusion  net movement continues until the system reaches equilibrium  usually occurs over short distances  Much of the movement of substances across membranes occurs by diffusion and therefore is a form of passive transport.  Passive transport is diffusion of substance across a biological membrane  Does not require the cell to expend energy  Depends on the permeability of the membrane  Membranes are built to be selectively permeable  Selective permeability is the property of biological membranes which allows some substances to cross more easily than others.  Two factors which influence permeability o Solubility characteristics of the substance crossing the membrane o Facilitated diffusion by a carrier protein or a channel protein  Specific proteins facilitate diffusion of selected solutes  Facilitate diffusion is diffusion across a membrane with the help of a protein  Three types of facilitated diffusion  1. Bind and release  2.Selective channel o a pore the size of the solute  3. Gated channel o like a selective channel only with a door.  Osmosis is the passive transport of water  Osmosis is the diffusion of water across a differentially permeable membrane  Influence by factors which govern diffusion  Osmosis :the tendency of water to move through a membrane from an area of lower concentration into an area of higher concentration solution, diluting it, until there is equal concentrations of fluid on both sides of the cell membrane  The principles of Osmosis  1.Osmosis is the diffusion of water across a differentially permeable membrane  2. Water moves from a low concentration of solute to high concentration of a solute  3. Dissolved substances decrease the amount of free water molecules  Note these are relative terms comparing one solution to another
CHAPTER 6
Some basics  Matter is anything that takes up space and has mass o The physical material of the universe  Energy is the capacity to do work Potential Energy-the energy stored in matter because of its position or location Kinetic Energy-the energy of motion o Potential energy in biological systems can be stored in chemical bonds o First law of thermodynamics-states that energy can be transferred and transformed, but it cannot be created or destroyed (i.e., the energy of the universe is constant) o The planet is an open system o Energy is constantly flowing in from the sun.
Coupled reactions
Chemical reactions which release energy can be coupled to chemical reactions which require energy. Coupled reaction: glucose breakdown and protein synthesis(fig 6.5) CONTROLLING THE METABOLISM OF LIVING CELLS ---Metabolism is the total of an organism’s chemical processes
-Uptake of matter and energy
-Conversion to usable form
-Synthesis of cellular materials -Elimination of waste products The chemistry of life is organized into metabolic pathways
Two types of metabolic pathways: Catabolic pathways and anabolic pathways ---Catabolic pathways are metabolic pathways which release energy by breaking down complex molecules to simpler compounds.
-degradation, releases energy
Anabolic pathways are metabolic pathways which consume energy to build complicated molecules from simpler ones -synthesis, energy requiring
Enzymes speed up metabolic reactions by lowering energy barriers (fig. 6.8)  Catalysts are chemical agents that accelerate a reaction without being permanently changed in the process (i.e., a catalyst is reusable and is not destroyed by the reaction)  Enzymes are biological catalysts which are usually protein  Enzymes are substrate-specific o Substrates are the substances which enzymes act on. o In the presence of the appropriate enzyme the substrates become more reactive.  An enzyme binds to its substrate and catalyzes the conversion of the substrate (reactants) to the product  The enzyme is unchanged by the process  The substrate binds to the active site of an enzyme o The active site is the restricted region of an enzyme molecule where the substrate is bound (fig 6.9) Active Site o Usually a pocket or groove on the surface of the protein o Usually formed by only a few amino acid R-groups o The shape, size, and binding ability of the active site confer specificity for the substrate (i.e., the substrate has to fir the active site)  Some enzymes require coenzymes to function o Coenzymes are small non-protein organic molecules that are required for proper enzyme catalysis (e.g., vitamins)  Regulating Metabolic Reactions o Metabolic pathways are regulated by controlling enzyme activity o Feedback inhibition is the regulation of a metabolic pathway by its end product, which inhibits an enzyme at an earlier point in the pathway. o Fig 6-10  Prevents the cell from making something it has enough of already  Allosteric regulation (fig, 6-11 a) o Allosteric sites are specific receptor site on some part of the enzyme molecules other than the active site. o Allosteric enzymes have two conformations, on is active and the other is inactive o Binding of an inhibitor to an allosteric site stabilizes the inactive conformation o Allosteric enzymes are often found at key regulatory positions in metabolic pathways, meaning at places where these enzymes can turn the pathway ON or OFF  The Catalytic ability of enzymes may also be inhibited by competitive inhibitors  Competitive inhibitors are chemical that resemble an enzyme’s normal substrate and compete with it for the active site. o Competitive inhibition  Block the active site by binding but no reacting  Reversible(fig. 6-11c)  which is not a an example of intercellular connection- vacuole
Bonus-A