Topic 1.2 and 1.3 Review

1.2 Ultrastructure of cells Essential Idea: Eukaryotes have a much more complex cell structure than prokaryotes Nature of science: Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8) Understandings Prokaryotes have a simple cell structure without compartmentalization Eukaryotes have a compartmentalized cell structure Electron microscopes have a much higher resolution than light microscopes

1.2 Ultrastructure of cells Applications and skills Application: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll of the leaf Application: Prokaryotes divide by binary fission Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs Skill: Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells

U 1.2.1 Prokaryotes have a simple cell structure without compartmentalization The first cells most likely to evolve were prokaryotic cells Prokaryotes are not compartmentalized and simple A- 70S ribosomes B- nucleoid region (DNA) C- plasma membrane D- cell wall E- pili F- flagella G- cytoplasm C D E B A F G

S 1.2.1 Drawing of the ultrastructure of prokaryotic cells based on electron micrographs

S 1.2.1 Drawing of the ultrastructure of prokaryotic cells based on electron micrographs

A 1.2.2 Prokaryotes divide by binary fission What is binary fission? Binary fission is a simple process where the bacteria splits into two identical cells Benefits? Quick, easy Negatives? They are all genetically the same

U 1.2.2 Eukaryotes have a compartmentalized cell structure What are some differences between eukaryotes and prokaryotes? Eukaryotic cells contain a nucleus whereas prokaryotic cells lack a true nucleus Eukaryotic cells have compartmentalization, why is this important? It allows for enzymes and substrates to be located in areas of optimum pH, temperature, etc.

U 1.2.2 Eukaryotes have a compartmentalized cell structure F A- rough endoplasmic reticulum B- smooth endoplasmic reticulum C- lysosomes D- Golgi apparatus E- vesicles F- mitochondria G- nucleus H- nuclear membrane I- nuclear pore J- 80S ribosomes J Single membrane A G H I C Double membrane D B E

U 1.2.2 Eukaryotes have a compartmentalized cell structure Plant cells have: Chloroplasts Double membrane Large vacuole Single membrane Cell wall

S 1.2.2 Drawing of the ultrastructure of eukaryotic cells based on electron micrographs

S 1.1.2 Drawing of the ultrastructure of eukaryotic cells based on electron micrographs

S 1.2.3 Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells What do you notice in these micrographs of pancreas cells? A lot of ER and Golgi Thus it will be making and shipping lots of proteins A 1.2.1 Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll of the leaf

A 1.2.1 Structure and function of organelles within exocrine gland cells of the pancreas (last slide) and within palisade mesophyll of the leaf What do you notice in these micrographs of palisade mesophyll cells? Chloroplasts Cell wall Plasma membrane Free ribosomes Nuclear membrane What does the micrograph tell us about the function of the palisade mesophyll? Functions in photosynthesis

U 1.2.3 Electron microscopes have a much higher resolution than light microscopes Resolution- ability of a microscope to show two close objects separately in the same image Electron microscopes emit shorter wavelengths so produce a higher resolution Light microscope Electron Microscope Resolution 0.25 μm 0.25 nm Magnification X 500 X 500,000

U 1.2.3 Electron microscopes have a much higher resolution than light microscopes Transmission electron microscopes (TEM) Use electrons Non-living specimen (ultra thin sections) Electrons transmitted through so can see into cells Scanning electron microscopes (SEM) Non-living specimen Electrons not transmitted, surface image produced

U 1.2.3 Electron microscopes have a much higher resolution than light microscopes

1.3 Membrane structure Essential idea: The structure of biological membranes makes them fluid and dynamic. Nature of science: Using models as representations of the real world—there are alternative models of membrane structure. (1.11) Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model. (1.9) Understandings Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules Membrane proteins are diverse in terms of structure, position in the membrane and function Cholesterol is a component of animal cell membrane

1.3 Membrane structure Applications and skills Application: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutions Skill: Drawing of the fluid mosaic model Skill: Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model Skill: Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model

S 1.3.2 Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model Developed by Davson-Danielli in the 1930s States there was a bilayer of phospholipids in the center and a layer of proteins on the outside Why did they develop this model? Chemical analysis showed the membrane was made of proteins and phospholipids Red blood cells membrane analysis showed there was twice as many phospholipids as membranes- supporting the phospholipid bilayer Membranes let things in and out

S 1.3.3 Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model Electron micrographs of cell membranes were produces in the 1950s Showed two dark lines separated by a lighter line Evidence against Davson-Danielli Globular proteins located in center of phospholipid bilayer as seen in freeze fracture electron micrographs Protein analysis showed proteins could extend from one side to the other due to hydrophobicity Fluorescent-tagged membrane proteins were shown to move within the membrane This lead to the Singer-Nicolson Model or Fluid Mosaic Model

U 1.3.1 Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules Phospholipid structure Phosphate head- hydrophilic (water loving) Two fatty acid tails- hydrophobic (water hating) They are amphipathic Why do they form a bilayer? Due to their amphipathic nature when phospholipids are placed in water they form a bilayer with the hydrophobic tails facing away from the water and hydrophilic head facing toward the water- micelle

S 1.3.1 Drawing of the fluid mosaic model Integral proteins Embedded in the bilayer Peripheral proteins Attached to one of the outer surfaces Glycoproteins Proteins with a sugar unit attached

U 1.3.2 Membrane proteins are diverse in terms of structure, position in the membrane and function Hormone binding sites Has a specific shape that binds a hormone, causes a change in shape, allows for a message to be sent to the interior of cell Ex: Insulin receptor Enzymatic activity Can be exterior or interior and catalyze reactions, sometimes working in metabolic pathways Ex: Cytochrome oxidase Cell adhesion Can provide permeant or temporary connections between cells (junctions- tight junctions or gap junctions) Ex: Cadherin Cell-to-cell communication Proteins can have carbohydrates attached that allow for cellular recognition Ex: Glycoproteins Passive transport channels Proteins that span the membrane and allow for movement from high to low concentrations Ex: Nicotinic acetylcholine receptor (receptor for a neurotransmitter) Active transport pumps Proteins that move molecules across the membrane with the use of ATP Ex: Calcium pump

U 1.3.3 Cholesterol is a component of animal cell membrane Cholesterol is a steroid It is hydrophobic but had one hydrophilic end Thus it can fit in the membrane Cholesterol limit the movement of the phospholipids Allows membranes to function at a wider temperature range

A 1.3.1 Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutions Since they limit the movement of phospholipids cholesterol reduces the fluidity of membranes It also reduces permeability of the membrane to some hydrophilic particles like sodium and hydrogen ions This allows animals to maintain concentration differences of these ions Plant cells do not have cholesterol in their cell membranes They depend on saturated and unsaturated fatty acids to maintain fluidity in their membranes

Topic 1.5 Review Origins of Cells Essential Idea: There is an unbroken chain of life from the first cells on Earth to all cells in organisms alive today

1.5 The origins of cells Nature of science: Testing the general principles that underlie the natural world—the principle that cells only come from pre-existing cells needs to be verified. (1.9) Understandings: Cells can only be formed by division of pre-existing cells The first cells must have arisen from non-living material The origin of eukaryotic cells can be explained by the endosymbiotic theory Applications and Skills: Application: Evidence for Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth

U 1.5.1 Cells can only be formed by division of pre-existing cells What are the parts of the cell theory? Cells come from preexisting cells Cells are the basic unit of structure and function All living organisms are composed of one or more cells What DNA evidence supports this? Most organisms use the 64 codons of the genetic code What process did scientist originally think was how cells formed? Spontaneous generation

U 1.5.1 Other evidence to support this: Cells are complex and no other natural mechanisms for producing cells has been suggested Populations of cells cannot increase without cell division Viruses do not consist of cells so they can only reproduce inside of host cells

U 1.5.2 The first cells must have arisen from non-living material Unless cells came from somewhere else in the universe they must have come from non-living material Hypothesis for how life might have started Miller-Urey Experiment- production of carbon based compounds (amino acids and sugars) Deep sea vents- assembly of carbon compounds into polymers Membrane formation- naturally molecules would form bilayers DNA as a molecule of inheritance

U 1.5.3 The origin of eukaryotic cells can be explained by the endosymbiotic theory What is the endosymbiotic theory? Mitochondria and chloroplast were once free living and were incorporated into a prokaryotic cell through what process? Endocytosis What type of symbiotic relationship was this? Mutualistic What are some special things mitochondria and chloroplast have that support this theory? They have their own circular DNA They have their own 70S ribosome They transcribe their own DNA They can only reproduce from pre-exiting mitochondria and chloroplasts Double membranes

A 1.5.1 Evidence for Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth What famous experiment did Louis Pasteur perform? Swan-neck flask Experiment Explain Conclusion- swan-neck prevented organisms in the air from entering thus no organisms appeared spontaneously