BIOL 120 1st Edition Exam 2 Study Guide Lectures 8 11 Lecture 8 Cell Structure Cell Theory All organisms are composed of cells cells are the basic unit of life cells arise only from pre existing cells Cell size is limited by o Surface area available o Temperature o Concentration Gradient o Distance Prokaryotic Cells lack a membrane bound nucleus o All lack a membrane o Bacteria Lack a membrane bound nucleus Possesses a single chromosome nucleoid Contains a long strand of DNA with a few supportive proteins Has ribosomes A stiff cell wall Some contain plasmids small supercoiled circular DNA Has an internal photosynthetic membrane o External Structures Flagella tail like features that spin around to move the cell Most have a cell wall Many have an additional layer outside of the cell wall called a capsule Eukaryotic Cells compartmentalized cells o Differences from Prokaryotic Eukaryotic chromosomes are inside the nucleus membrane bound Eukaryotic cells are larger Eukaryotic cells have membrane bound compartments Eukaryotic cells have a diverse and dynamic cytoskeleton o Animal Cell o Plant Cell o Nucleus Store genetic information Nucleolus region where ribosomal RNA is synthesized Nuclear envelope a double membrane surrounding the nucleolus with nuclear pores to control what goes in and out of the nucleus Linear chromosomes Chromatin chromosomes and proteins which are in charge of folding o Endomembrane System a series of membranes throughout the cytoplasm divides cell into compartments a distinction between eukaryotes and prokaryotes o Rough ER a network of membrane bound tubes and sacs studded with ribosomes interior is called the lumen synthesize proteins o Smooth ER Similar to rough ER but lacks ribosomes Enzymes within the Smooth ER synthesize fatty acids and phospholipids used for membranes Also breaks down poisonous lipids and stores calcium ions o Golgi Apparatus a flattened stack of interconnected membranes Function transport system Packs molecules into package vesicles Distributes molecules synthesized at one location ot be used at another o Ribosomes are non membranous and not considered organelles large and small subunits containing RNA molecules and protein made of rRNA Functions Protein synthesis o Microbodies Enzyme bearing membrane enclosed vesicles Peroxisomes contain enzymes involved in oxidation of fatty acids hydrogen peroxide produced as a by product that is broken down by catalase in plants it is glyoxysomes use enzymes that oxidize fats to form a compound used to store energy o Lysosomes single membrane bound structures containing about 40 different digestive enzymes Found in animal cells Function used for digestion and waste processing Delivered through Phagocytosis bringing in matter to the cell to be broken down Autophagy breaking down material inside of the cell Receptor mediated endocytosis brings material into the cell through receptors Endocytosis a process by which the cell membrane can pinch off a vesicle to bring outside material into the cell Pinocytosis a process that brings fluid into the cell o Vacuoles Found in plants Functions Storage Contain digestive enzymes Most are used for water and ion storage Types Central storage contractile o Mitochondria Inner and outer membrane Cristae finger like projections that give more surface area Have their own DNA and make their own ribosomes o Chloroplast Found in plant and algae cells double membrane and contain their own DNA Thylakoids membrane bound flattened vesicles Grana thylakoids stacked into piles Stroma the solution surrounding the grana and thylakoids Function convert light energy to chemical energy o Cell Wall Found in plants fungi and many protists o Cytoskeleton A network of protein fibers that support the shape of the cell and keeps organelles in fixed locations Three types microfilaments actin filaments two protein chains loosely twined together microtubules dimers of alpha and beta tubulin subunits intermediate filaments very stable o Centrosomes Found in animal cells and most protist region surrounding centrioles help move chromosomes during cell division o Extracellular matrix Animal cells lack a wall secrete a mixture of glycoproteins into the area around them i e collagen which forms a protective layer over the cell surface o Connections Tight junction Connect the plasma membrane of adjacent cells Anchoring junction attaches cytoskeletons of neighboring cells Communication junction chemical or electrical signal passes directly from one cell to an adjacent cell Plasmodesmata specialized openings in cell walls similar to communication junction in animal cells Membrane Proteins o hydrophobic interior of membrane makes it hard for molecules to pass through proteins function as transport proteins o Functions Transporters Enzymes Cell surface receptors Cell surface identity markers Cell to cell adhesion proteins Attachments to the cytoskeleton o Types Passive transport no energy input needed goes with gradient Sodium Potassium pump goes against gradient Active Transport requires energy directly or indirectly Needs selective carrier proteins o Uniporters o Symporters o Antiporters Carrier protein gradient goes from high to low o Channel protein act as gates ion channels and gated channels o Endocytosis movement of substances into the cell o Exocytosis the discharge of materials out of the cell Cell Division Cell Cycle o Key facts Chromosomes are duplicated during the S phase from 46 to 92 Diploid 46 chromosomes 2 sets Haploid 23 chromosomes 1 set for reproduction o Bacterial cell division Divide through binary fission Circular chromosomes o Meiosis and Mitosis Meiosis leads to the production of gametes egg and sperm Mitosis leads to the production of all other cell types somatic cells Functions o Growth o Wound repair o Asexual reproduction o G1 S G2 Interphase G1 and G2 do not have DNA synthesis During this phase organelles replicate and additional cytoplasm is created o Chromosomes Chromosomes contain a single long double helix of DNA wrapped around proteins Gene a section of DNA that encodes a specific protein or RNA when mitosis starts the chromosomes condense into compact structures that are easy to move around the cell at the end of mitosis the copied chromosomes are divided between two daughter cells o Replication Chromatid the DNA copies in a replicated chromosome Centromere where chromatids are joined together during mitosis Sister chromatid chromatids from the same chromosome o