BIO Midterm 2 - Unit 4+5 PDF

BIO MIDTERM 2→ UNIT 4+5 when did the first Eukaryotic cells appear on Earth? approximately 2 billion years ago how did Eukaryotic cells appear on Earth? the exact sequence of events that led to the origin of eukaryotic cells is unknown, but it is thought that they had thei...

BIO MIDTERM 2→ UNIT 4+5 when did the first Eukaryotic cells appear on Earth? approximately 2 billion years ago how did Eukaryotic cells appear on Earth? the exact sequence of events that led to the origin of eukaryotic cells is unknown, but it is thought that they had their origins in Endosymbiosis Endosymbiosis a symbiotic relationship where one organism lives inside the cells or body of another organism The Endosymbiotic theory key organelles in eukaryotes, such as mitochondria and chloroplasts, originated from free-living prokaryotes (bacteria) that were engulfed by an ancestral eukaryotic cell How did eukaryotic cells appear? 1) It is thought that ancestral Archaeas lost their cell wall 2) Infoldings of the plasma membrane gave rise to nucleus and the endoplasmic reticulum 3) Endosymbiosis of aerobic bacteria gave rise to mitochondria 4) Endosymbiosis 2) Infoldings of the plasma membrane gave rise to the nucleus and endoplasmic reticulum the nucleus and endoplasmic reticulum may have evolved from internal infoldings of prokaryotic cell membrane, encasing the DNA of prokaryotic cell, giving rise to the nucleus and endoplasmic reticulum Evidence that supports the endosymbiotic theory: many prokaryotes have infoldings of their outer membrane extending into the cytoplasm 3) Endosymbiosis of aerobic bacteria gave rise to mitochondria FIRST: It is thought that an ancient Archaea engulfed (but did not eat) an ancient, aerobic bacteria NEXT: the engulfed bacterial cell remained within the Archaea cell in what have been a mutualistic relationship Over many generations, a symbiotic relationship developed between the 2 organisms so completely that neither could survive on its own the dependents of this ancient engulfed cell are present in ALL eukaryotic cells today as mitochondria what is a mutualistic relationship; how did the engulfed bacterial cell and the archaea cell have a mutualistic relationship? both benefited from the relationship the engulfed bacterium allowed the host Archaean cell to do cellular respiration, and the host cell protected the bacterial cell from predators Origin of Mitochondria scientists proposed that the ancestral eukaryotic cells, which already had an internal system of membranes, engulfed a smaller aerobic bacteria which then became mitochondria→ giving rise to animal cells Origin of Chloroplasts: a 2nd endosymbiotic process ○ later, these bacteria with the “primitive” mitochondria engulfed smaller photosynthetic bacteria (cyanobacteria) which then became the chloroplast→ giving rise to plant cells 1) evidence that supports endosymbiosis: size and shape→ mitochondria and chloroplasts are roughly the same size as bacteria 2) evidence that supports endosymbiosis: mitochondria and chloroplasts are enclosed by a double membrane New cards 15 3) evidence that supports endosymbiosis: Inner membranes of mitochondria+chloroplasts have a similar composition to bacterial membranes ○ the infoldings of the mitochondria are very similar to invagination of the membranes of many prokaryotes 4) Evidence that supports endosymbiosis: mitochondria and chloroplasts contain their own DNA, which is remarkably similar to the DNA of bacteria ○ size= circular DNA ○ replication mechanisms= similar to bacteria ○ their DNA does NOT contain histones→ similar in prokaryotes 5) evidence that supports endosymbiosis: Mitochondria and chloroplasts replicate independently of cell division using binary fission like bacteria New cards 18 6) evidence that supports endosymbiosis: Mitochondria and chloroplasts have ribosomes whose size and structure resemble bacterial ribosomes New cards 19 characteristics of eukaryotic cells typically 100-100 Mm in diameter have membrane-bound organelles have cytoskeleton  larger ribosomes several linear chromosomes 2 types of eukaryotic cells→ animal cells and plant cells Organelles of animal cells (be able to label/identify on diagram) Nucleus ○ Nuclear envelope ○ Chromatin ○ Nucleolus Cytoskeleton ○ Microtubules ○ Centrosome ○ Intermediate filaments ○ Microfilaments Peroxisome Plasma membrane Endoplasmic reticulum ○ Rough ER ○ Smooth ER Lysosome Golgi apparatus Cytoplasm Mitochondria Vacuole organelles of plants cells (be able to label/identify on diagram) Plasmodesmata Endoplasmic reticulum ○ Smooth ER ○ Rough Er Nucleus ○ chromatin ○ nucleolus Cell wall Plasma membrane Cytoplasm Central Vacuole Cytoskeleton ○ microtubules ○ intermediate filaments ○ microfilaments Chloroplast Plastid Ribosomes Golgi apparatus Mitochondria Peroxisome Plasma membrane a selective barrier that allows sufficient passage of oxygen, nutrients, waste to service the volume of every cell composed of: ○ Phospholipid bilayer ○ Proteins ○ Carbohydrates (oligosaccharides attached to phospholipids, and glycolipids and glycoproteins) ○ Cholesterol ( ** ONLY IN ANIMAL CELLS) Nucleus contains most of the cell’s DNA and genes DNA is packed in the form of chromatin→ DNA + histone proteins enclosed by a nuclear envelope; separating it from the cytoplasm the nuclear envelope has 2 membranes+nuclear pores Nucleolus→ area inside the nucleus where rRNA (ribosomes) are made and assembled. They then get out to the cytoplasm or to the surface or the endoplasmic reticulum (RER) Ribsomes protein factories complexes made of ribosomal RNA and protein carry out protein synthesis in 2 locations: ○ 1) in the cytosol (free ribosomes) ○ 2) on the outside of the endoplasmic reticulum (bound membranes) forming the RER Endoplasmic Reticulum a membrane system that forms tubes and sacks within the cytoplasm (gelatinous liquid that fills the inside of a cell) the ER membrane is continuous with the nuclear envelope there are 2 distinct regions of ER: ○ 1) Smooth ER= lacks ribosomes ○ 2) Rough ER= surface is studded with ribosomes ROUGH ER (RER) have ribosomes attached make proteins that later distributes with transport vesicles transport vesicles= secretory proteins surrounded by membranes involved in the synthesis, folding, modification, and transport of proteins synthesis of proteins that are going to be secreted from the cell, that require sugar modification, that are delivered to lysosomes SMOOTH ER (SER) synthesizes (produces) lipids metabolizes carbohydrates contains enzymes that detoxifies drugs and poisons can store calcium ions Golgi Apparatus shipping and receiving center consists of cisternae→ flattened membranous sacs functions: ○ modifies products of the ER ○ manufactures certain macromolecules ○ sorts and packages materials into transport vesicles and distributes to the plasma membrane or to lysosomes Endomembrane system this system regulates protein traffic consists of: ○ Nuclear envelope ○ Endoplasmic reticulum ○ Golgi apparatus ○ Lysosomes ○ Vacuoles ○ Plasma membrane these components are either continuous OR connected via transfer by vesicles Lysosomes digestive compartments membranous sac of hydrolytic (breaking down of a chemical bond by the addition of water) enzymes that can digest macromolecules Lysosomal enzymes work best in the acidic environment inside the lysosome Phagocytosis→ Lysosomes some types of cell can engulf another cell by phagocytosis→ forms a food vacuole; a lysosome fuses w/ the food vacuole and digests the molecules Autophagy→ Lysosomes lysosomes also can use enzymes to recycle the cell’s own organelles and macromolecules Vacuoles large vesicles derived from the ER and Golgi Apparatus perform a variety of functions in different kinds of cells functions vacuoles perform in different kinds of cells: Food vacuoles→ formed by phagocytosis Contractile vacuoles→ found in many freshwater protists: pump excess water out of cells Central vacuoles→ found in many mature plant cells, hold organic compounds+water Mitochondria chemical energy conversion the sites of cellular respiration→ a metabolic process that uses oxygen to generate ATP have 2 membranes: ○ 1) a smooth OUTER membrane ○ 2) a INNER membrane folded into cristae; creates 2 compartments: what are the 2 compartments the inner membrane of the mitochondria create? 1) intermembrane space 2) mitochondrial matrix→ some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Chloroplasts capture of light energy found in: plants and algae= the sites of photosynthesis contain the green pigment→ chlorophyll, and enzymes and other molecules that function in photosynthesis where are chloroplasts found? in leaves green organs of plants/algae what does the structure of a chloroplast include? an outer membrane an inner membrane: ○ thylakoids→ membranous sacs, stacked to form a granum ○ stroma→ the internal fluid Peroxisomes oxidation specialized metabolic compartments bounded by a single membrane what are the functions of peroxisomes? they remove cell toxic substances (excess of toxic oxygen radicals) they break down fatty acids= imp for fat metabolism Cytoskeleton a network of fibers extending throughout the cytoplasm oranizes the cell’s structures/activities; anchoring many organelles composed of 3 types of molecular structures what are the 3 types of molecular structures the cytoskeleton is composed of? 1) Microtubules 2) Microfilaments 3) Intermediate filaments what are the roles of the Cytoskeleton? helps to support the cell+ maintain it’s shape interacts w/ motor proteins to produce motility inside the cell, vesicles can travel along tracks provided by the cytoskeleton Centrioles paired barrel-shaped organelles located in the cytoplasm of ANIMAL cells near the nuclear envelope 2 centrioles form→ the CENTROSOME Centrosome in animal cells: all microtubules ( spindle fiber) in the cell grow out from a centrosome located near the nucleus involved in: the development of microtubules in cell division what do microtubules control? the beating of cilia and flagella→ microtubule-containing extensions that project from some cells beating pattern of flagella one long propeller beating beating pattern of cilia many short windshield wiper beating organelles in just the ANIMAL cell: small vacuole or no vacuole centrioles and centrosomes flagella cilia organelles in just the PLANT cell: cell wall central vacuole chloroplasts organelles in BOTH animal and plant cells: ribosomes peroxysomes endoplasmic reticulum golgi apparatus lysosomes mitochondria cytoskeleton nucleus Cell Plasma Membrane→ FUNCTIONS separates the cell from the outside and provides a barrier to prevent the contents of the cell from escaping and mixing with the surrounding medium what kind of barrier does the membrane act as and not act as? it is NOT a solid barrier, substances NEED to get in and out of the cell the membrane acts as a SELECTIVE barrier→ a barrier that allows the passage of some substances but NOT others Fluid mosaic model of the plasma membrane structure of the plasma membrane MOSAIC of components→ lipids (phospholipids and cholesterol)+proteins FLUID: membrane components can move freely in the plane of the membrane ○ membranes are NOT rigid, but fluid→ they can stretch, bend, and flex in 3D while still maintaining their integrity what happens if you insert a very fine needle into a cell? the membrane will simply part to flow AROUND the needle; once the needle=removed, the membrane will flow back TOGETHER seamlessly Main components of the plasma membrane: 1) LIPIDS→ phospholipid+cholesterol 2) PROTEINS 3) CARBOHYDRATES→ oligosaccharides New cards 58 Lipids→ PHOSPHOLIPIDS PHOSPHOLIPIDS→ amphipathic molecules; 2 layers of phospholipids with their tails(hydrophobic) pointing INWARD and their heads(hydrophilic) pointing OUTWARD, in an arrangement called a → phospholipid bilayer→ forms a STABLE barrier between 2 water compartments phospholipids (& cholesterol) provide the fundamental structure of membranes Lipids→ CHOLESTEROL found alongside phospholipids in the core of the membrane (only in ANIMAL cells) provides stability to the membrane PROTEINS different types of proteins are found embedded in the membrane proteins are INSERTED in a phospholipid bilayer most membrane functions are carried out by membrane proteins FUNCTIONS: ○ transporters ○ anchors ○ receptors ○ enzymes types of membrane proteins transmembrane proteins  peripheral proteins transmembrane protein types: in transmembrane proteins, the polypeptide chain can cross once OR several times ○ SINGLE-pass→ crosses the membrane ONCE ○ MULTI-pass→ crosses the membrane SEVERAL times; cross the membrane with α-helixes containing hydrophobic aminoacids peripheral proteins in or outside of the cell associated w/ phospholipids or proteins CARBOHYDRATES sugar groups (oligosaccharides) are present only on the OUTER surface of the plasma membrane→ facing the outside linked to proteins (glycoproteins) OR to lipids (glycolipids) the cell surface= COATED w/ carbohydrates Carbohydrates→ Oligosaccharides 10 monosaccharides LINKED by glycosidic bonds located→ on the OUTER side of the membrane forming a sugar coating called the CARBOHYDRATE LAYER Functions of the carbohydrate layer helps protect the cell from mechanical+chemical damage absorbs water; gives the cell a slimy surface→ helps MOTILE cells (white blood cells) to squeeze through narrow spaces and prevents blood cells from sticking to one another or to the walls of capillaries FORM distinctive cellular markers→ “molecular id badges”; allow cells to recognize each other examples of cellular markers/recognition involved in the recognition of: ○ an egg by a sperm ○ white blood cell recognition of cancer cells ○ in white blood cell recognition of pathogens (microorganisms→ bacteria, viruses, etc) ○ in early stages of a bacterial infection, the carbohydrate on the surface of white blood cells the transport of substances across the plasma membrane: the membrane represents a barrier for molecules going IN and OUT cells must be able to exchange molecules w/their environment to live which molecules need to be transported in and out of the cell? INTO the cell→ nutrients, ions, oxygen, water OUT of the cell→ wastes, ions, carbon dioxide, water what nutrients need to get INTO the cell? food sugars amino acids salts ions explain the transport of individual molecules across the plasma membrane? the plasma membrane= semipermeable ○ it allows passage of some substances across the membrane so it behaves as a selectively permeable barrier to the passage of substances→ allowing the passage of some substances, but not others why is the membrane impermeable to most substances? the plasma membrane tends to BLOCK the passage of almost all water-soluble molecules BC the interior of the lipid bilayer= hydrophobic (ALL fatty acid tails) the hydrophobic interior of membrane creates a barrier to the passage of hydrophilic molecules which substances can cross the membrane WITHOUT help? small, non-polar molecules: ○ gases→ oxygen, carbon dioxide, nitrogen ○ steroid hormones ○ they readily dissolve in phospholipids and rapidly diffuse across them which substances can’t cross the membrane WITHOUT help? larger molecules polar molecules→ water, glucose, amino acids, proteins= all hydrophilic charged ions→ even if they are small, charged molecules cannot pass at all→ the charge and the strong electrical attraction to water inhibit them from entering the hydrophobic fatty acids in the membrane HOW do these molecules pass? the membrane has several mechanisms to cross these substances the cell can regulate what substances go IN and OUT of the cell diffusion movement of substance from a region where it is more concentrated to a one where it is less concentrated what are the types of transport of substances across the membrane? PASSIVE transport ACTIVE transport PASSIVE transport: types→ simple diffusion + facilitated diffusion  movement of materials across the membrane which requires NO cellular energy (no ATP) due to a difference in concentration, molecules move DOWN a concentration gradient→ from HIGH concentration to LOW concentration Passive transport→ SIMPLE diffusion materials diffuse by inserting THROUGH the phospholipids and going to the other side ○ these MOLECULES include→ gases: oxygen, carbon dioxide, nitrogen, and small lipids: steroid hormones movement of materials go from a HIGH concentration to a LOW concentration of the moelcule diffusion will occur until equilibrium is reached (both sides have the same concentration) Passive transport→ FACILITATED diffusion type of transport which requires the assistance of specialized proteins in the membrane molecules that are transported= hydrophilic, TOO large, polar/charged, CANNOT diffuse through the phospholipids TRANSPORT proteins shield these molecules from the hydrophobic core of the membrane, providing a ROUTE by which they can cross transport goes towards a concentration gradient (from where there is MORE to where there is LESS) ○ transport will STOP→ when an equilibrium is reached which molecules are transported by facilitated diffusion? water large molecules→ glucose, amino acids charged molecules→ ions: Ca2+, Na+, K+, Cl- what are the 2 types of membrane transport proteins? 1) TRANSPORTERS 2) CHANNELS Transporters bind to the molecule to be transferred, and then move it the other side very specific and selective→ glucose transporter ONLY transports glucose, etc carrier proteins can change their shape to move a target molecule from one side of the membrane to the other they move a WIDE variety of water-soluble molecules across membranes but at a much SLOWER rate than channels Channels like a pore; leave a space in the center so the molecules can pass also specific→ discriminate on the basis of size and electric charge ○ Na+ channels ONLY transport Na+ EX of a channel→ Water transport-Osmosis water gets in and out of the cell when= its needed water cannot diffuse through the phospholipids water is transported through facilitated diffusion using a special channel called: AQUAPORIN Osmosis movement of water in and out of the cell depending on the amount of water in both sides Osmosis= passage from HIGH concentration of water to LOW concentration of water Isotonic solution cells are suspended in a isotonic solution→ same amount of SOLUTES, same amount of WATER compared to the cell NO net movement of water volume of cell does NOT change Hypertonic solution cells are suspended in a hypertonic solution→ MORE solutes, LESS water compared to the cell Osmotic pressure is higher INSIDE than out, so water DIFFUSES out cell= shrinks **Hyper-tonic→ hyper person→ runs around a lot→ shrinks energy Hypotonic solution cells are suspended in a hypotonic solution→ LESS solutes, MORE water compared to the cell water diffuses in→ tends to go from where there is more water (HIGH osmotic pressure) to where there is less water (LOW osmotic pressure) cell= swells and bursts **HIPPO-tonic→ swelling Active transport another type of transport across the membrane, but in this case the molecules cross AGAINST the concentration gradient ○ molecules move from a region of LOW concentration to HIGH concentration energy (ATP) is needed to move and pump the substances to be transported transport requires the assistance of membrane proteins→ embedded proteins change shape to open/close passages across the membrane Bulk transport another type of transport→ many substances cross TOGETHER: “in bulk” transport- through membrane through bound vesicles many larger particles get inside the cell this way Bulk movement into the cell→ Endocytosis process of capturing a substance/particle from outside the cell by engulfing it w/ the cell membrane and bringing it into the cell cell captures material “in bulk” from the outside 3 types what purposes does endocytosis serve? taking in nutrients for cellular growth, function & repair capturing pathogens/unknown substances that may endanger the organism:  ○ when pathogens (like bacteria) are identified by the immune system, they are engulfed by immune cells to be destroyed disposing of old or damaged cells→ cells must be safely disposed of when they stop functioning properly to prevent damage to other cells what are the 3 types of endocytosis? 1) Pinocytosis 2) Receptor-mediated endocytosis 3) Phagocytosis New cards 95 Pinocytosis the cell takes IN dissolved substances from the extracellular fluid that it needs to function→ water, some dissolved nutrients ○ “cell drinking” Receptor-mediated endocytosis substances are “trapped” by specific receptors in the plasma membrane a vesicle is formed that invaginates and allows the substances to get inside the cell Phagocytosis the cell takes large particles or even whole cells ○ “food particles” in unicellular organisms ○ damaged cells, bacteria, viruses in animals “cell eating” Bulk movement OUT of the cell→ Exocytosis movement OUT of the cell the process by which cells move materials from inside the cell, across the membrane, and then to the outside occurs when a vesicle FUSES with the plasma membrane, allowing its contents to be released OUTSIDE the cell what purposes does exocytosis serve? removing toxins/waste products from the cell’s interior: cells need to release waste or toxins that must be removed from the cell some cells produce proteins to be released outside (glands) ○ ex→ cells that secrete: antibodies, hormones, digestive enzymes, etc in neurons: cells communicate w/ each other through the release of neurotransmitters that are secreted and allow the transmission of nerve signal