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Biology study guide for first exam

by: Meghan Babington

Biology study guide for first exam Biology 1105

Meghan Babington
Virginia Tech

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first exam notes
Principles of Biology
Dr. Jonathan I. Watkinson
Study Guide
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This 11 page Study Guide was uploaded by Meghan Babington on Saturday September 10, 2016. The Study Guide belongs to Biology 1105 at Virginia Polytechnic Institute and State University taught by Dr. Jonathan I. Watkinson in Fall 2016. Since its upload, it has received 23 views. For similar materials see Principles of Biology in Biology at Virginia Polytechnic Institute and State University.

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Date Created: 09/10/16
MACROMOLECULES IN THE CELL proteins = provide functionality within membranes carbohydrates = only located on the outer surface of the membrane which helps the cell attach  to the extracellular matrix, and these external sugar molecules provide ID markers for cellular  recognition lipids = phospholipids are the main structure of the membrane; hydrophobic  Phospholipids are made of fatty acids and glycerol  Cholesterol helps maintain the cells fluidity  Fatty acids (aka acyl) are long hydrocarbon chains with a carboxyl group on the end of it  glycerol is a 3 carbon polyalcohol with 3 hydroxyl groups. glycerol with 3 fatty acid tails are called triglycerides  SATURATED FATS: lipids with 1 double bond are termed monounsaturated.  Examples are saturated fatty acids. Because they only contain one double bond, the  structure is linear and clean (solid at room temperature)  UNSATURATED FATS: lipids with more than one double bond are termed  polyunsaturated fatty acids. Because they have more than one double bond, their  structure becomes competitive for space and creates not as clean of a structure, making it  appear clustered (liquid at room temperature) TYPES OF LIPIDS  terepens: pigment lipids  steroids: hormones in animals MAIN LIPIDS: phospholipids  hydrophilic heads (polar) hydrophobic tails (non­polar), having both hydrophilic and  hydrophobic properties means it is amphiphilic  CELL TO CELL INTERACTIONS MAIN JOBS: CELL IDENTITY AND MARKERS Cell Identity Cells acquire identity through the expression (turning off and on) of certain genes that code for  certain functions within the cell or between cells. Most of the functions are done by different  proteins. This is important because cells must be able to recognize which cells are part of your  body, and which are intruders/viruses/bacteria etc.  Types of markers  Glycolipids: lipids with carbohydrate heads on the membranes of cells that identify/label  the cell Cell junctions and types Goal of junctions: to serve as the cement and foundation for the house that is the cell  Adhesive junctions: found in external skin and muscle tissue, attaches the cytoskeletons  of neighboring cells  Adherens junctions: based on the protein cadherin, this is a transmembrane protein that  acts with the extracellular domains of cells along with actin (muscle protein) to create  flexible connections between cells  Desmosomes: unique to vertebrates, and interact with intermediate filaments of the  cytoskeletons rather than bonding with the microfilaments of actin, and help support  against mechanical stress on the cell  Hemidesmosomes and focal adhesions: Proteins called integrins that connect cells to  the extracellular matrix via the cytoskeleton.  o In hemidesmosomes, the junctions connect to intermediate filaments o In focal adhesions, the junctions connect to actin  Septate junctions: more modern of the two (septate vs tight), found in both vertebrates  and non­vertebrates, and have the ability to form a barrier around a sheet of cells that  helps protect from leakage within extracellular space  Tight junctions: unique to vertebrates, these junctions act as a wall, or air­tight seal to  keep items on one side of a cell, with the aid of proteins called claudins  Communicating junctions: Junctions that can be found in single­celled organisms that  allow things to diffuse freely between cells (**think of diffusion, or water passing  through a porous object like a sponge)  in animals, these junctions are called gap junctions formed by porous proteins  called pannexins, and is formed when the pannexins in two cells line up with one  another and allow small molecules like sugars and amino acids to pass through.  in plants they’re called plasmodesmata, and they are cytoplasmic connections that  join cell walls together; more complex than gap junctions MEMBRANES: Establish space, act as a barrier to protect what goes into and out of the cell (however it is malleable, it does not have a set shape like cell walls). In eukaryotes, cell membranes are composed of our major parts: WHAT CAN PASS INTO THE MEMBRANE? EASILY: small non­polar molecules like gases SEMI­EASILY: small polar molecules like water DIFFICULT: larger polar molecules IMPOSSIBLE: ions, anything charged A phospholipid bilayer  WHAT IS IT: a semi­permeable membrane that looks like a zipper  WHAT IS IT MADE OF: lipids with a hydrophilic head, and a hydrophobic tail  WHAT DOES IT DO: selectively allows certain substances in and out of the cell, they  also form spontaneously due to their opposite polar/nonpolar “magnetic” attraction Transmembrane proteins   WHAT IS IT: receptors and carrier channels  WHAT IS IT MADE OF: proteins   WHAT DO THEY DO: float freely within the bilayer orchestrating communication  across the membrane Interior protein network  WHAT IS IT: a foundational structure  WHAT IS IT MADE OF: sets of proteins that are more rigid  WHAT DOES IT DO: provide a scaffold or mold for the membrane Cell­surface markers  WHAT ARE THEY: markers that help the cell self­recognize  WHAT ARE THEY MADE OF: glycoproteins and glycolipids  WHAT DO THEY DO: indicate to the cell that certain tissues and molecules are part of  the cell (separates familiar from foreign substances) PROTEIN FUNCTIONS WITHIN THE MEMBRANE  TRANSPORTERS: Selectively pick and carry solutions in and out of the cell via  channels or carriers using active or passive transport  ENZYMES: carry out biochemical reactions in and on the membrane  CELL­SURFACE RECEPTORS: markers that serve as “ID tags” that allow the cell to  recognize its individual parts  CELL­TO­CELL ADHESION PROTEINS: specialized proteins that are used to stick cells  to one another, whether it be temporarily or permanently  ATTACHMENTS TO THE CYTOSKELETON:  proteins on the surface of the cell that  interact with other cells by attaching themselves to the cytoskeleton of other cells via linking proteins  Transmembrane proteins = proteins completely embedded inside the membrane  Peripheral proteins = sit on the edge of the proteins TYPES OF TRANSPORT ACROSS THE CELL MEMBRANE PASSIVE TRANSPORT: no energy required, WITH the concentration gradient ACTIVE TRANSPORT: energy required, AGAINST the concentration gradient DIFFUSION  Direct Molecules float freely from high to low concentrations, no energy and no  channel to pass through other than the membrane itself FACILITATED DIFFUSION channel proteins The movement of polar ions/molecule through an open protein channel in  (think open the membrane (rather than just through the membrane itself) from high to  tunnel) low concentration carrier proteins A molecule binds with a protein inside the protein channel that then carries (think tunnel the item through the channel and into the cell; moving from high to low  with taxi) concentration (down/with the concentration gradient) OSMOSIS Aquaporins Diffusion of water only, via an osmotic gradient (high to low concentration) PROTEIN CARRIERS particles are moved against their concentration gradients using the  Sodium potassium exchange of sodium and potassium in order to open a pump that  pump allows molecules inside the cell (potassium gets pumped out, and  glucose binds with the free sodium outside and then is able to be let  into the cell) ENDOCYTOSIS (transporting items INTO the cell) Phagocytosis mainly solid particles; membrane “eats” the particle and surrounds it  like a bubble, forming a vesicle that takes the particle inside the cell Pinocytosis Mainly liquid particles; fluid is “eaten” by the membrane, forming a  bubble vesicle that takes the liquid inside the cell Receptor­mediated Endocytosis activates a receptor that creates a clathrin­coated vesicle  endocytosis that brings particles inside the cell EXOCYTOSIS (EXpelling items OUT OF the cell) Membrane vesicle Vesicles inside the cell reach the cell membrane, fuse with it, and  thrust particles outside of the cell


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