Cellular & Molecular Biology

What are the three key roles/financial decisions of a financial manager?

BIOL 160

Chapter 2

Review 

The Five Big Ideas (FBIs) 

∙ Evolution- populations of organisms and their cellular components have changed  over time through both selective and non-selective evolutionary processes ∙ Structure and Function- all living systems are made of structural subunits, which  impact the functioning of those systems

∙ Information Flow and Storage- DNA is the information code for life’ how it is used  and exchanged within and among organisms is the basis of life on the planet ∙ Transformations of Energy and Matter- all living things acquire, use, and release  matter and energy for cellular functioning

What is a sole proprietorship?

∙ Systems- living systems are interconnected, and interact and influence each  other on multiple levels

Five Scientific Practices (FSPs) 

∙ Link topics and synthesize information, particularly in reference to the FBIs ∙ Ask scientific questions based on models and data If you want to learn more check out quinn mcfrederick

∙ Interpret scientific representations and come to an evidenced conclusion ∙ Summarize information from scientific articles or other sources

∙ Predict the consequences of changes to systems or pathways

Evidence-Based Study of Life 

∙ There are many sources from which scientific problems and questions come from ∙ Biology is studied at many levels of organization

What is a corporation?

Cellular and Molecular Biology 

∙ The cell is the fundamental structural unit of all organisms

What Makes a Cell a Living Organism 

∙ Organisms range from millions of cells to just one

∙ The range of functions for organisms is huge

∙ But they are all alive

Biomolecules 

∙ Biomolecules are unique to the living world

∙ Includes proteins (ch3), nucleic acids (ch4), carbohydrates (ch5), and lipids (ch6)If you want to learn more check out anne arundel comm college

Cellular & Molecular Biology

BIOL 160

Chapter 2

Chemical Elements, Bonds, and Water 

Basic Atomic Structure 

∙ Atoms are composed of protons, neutrons, and electrons

o Protons- have a positive charge and reside in the atomic nucleus o Neutrons- are electrically neutral and also reside in the atomic nucleus o Electrons- have a negative charge and orbit the atomic nucleus in orbitals o

∙ Each element has numbers to describe it

o Mass Number- equal to the number of protons plus neutrons

o Atomic Number- equal to the number of protons If you want to learn more check out icmpv4 header

∙ The number of protons of any given element will always be the same regardless  of charge

Chemical Bonding 

∙ Atoms use their outer electrons to bond to each other

∙ The number of valence electrons usually equals the number of bonds the atom  will form (ex. H????1, C????4, N????3, O????2)

∙ However, there are double and triple bonds that may change this ∙ There are multiple types of bonds

Covalent Bonds

∙ Make atoms more stable by allowing them to share electrons and achieve full  valence shells

∙ Can be polar or nonpolar

o Polar Covalent Bonds- electrons are shared unevenly and result in partial  charges in the atoms (ex. H2, CH4)

o Non-Polar Covalent Bonds- electrons are shared completely evenly (ex.  NH3, H2O)

Cellular & Molecular Biology

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Chapter 2

∙ Electronegativity determines whether bonds will be polar or non-polar o Electronegativity depends on the number of protons in an atom and the  distance between protons and the valence electrons Don't forget about the age old question of vijay vittal asu

o Electronegativity is the greatest in the upper right corner of the periodic  table

o IMPORTANT ???? O>N>C=S~H

Ionic Bonds

∙ Form between ions (typically a metal from the left side of the PT (cation) and a  non-metal from the right side(anion)) (ex. NaCl)

∙ When one atom gives up its electron to another atom so both can form full  valence shells

Non-Polar Covalent Polar Covalent Ionic

Water 

Water as a Solvent 

∙ Water is a very effective solvent (the solvent of life)

∙ Polarity and hydrogen bonds If you want to learn more check out college handwriting

∙ Polar molecules are hydrophilic because the charged atoms will attract the  opposite partial charges in water molecules

∙ Non-Polar molecules are hydrophobic because they do not attract the partial  charges

∙ Water has a unique structure

∙ Small

∙ Bent Shape If you want to learn more check out which party system is most common in a dictatorship

∙ Highly polar bonds

∙ Polar overall

Special Properties of Water 

(primarily due to water’s ability to form hydrogen bonds)

Cellular & Molecular Biology

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Chapter 2

∙ Water is cohesive (water molecules are attracted to each other) ∙ Water is adhesive (water molecules (water molecules hydrogen bonding to other  substances)

∙ Water is denser as a liquid than a solid (ice floats)

∙ Water is able to absorb large amounts of energy

Acids, Bases, and pH 

∙ The concentration of H+is the basis for pH measurement

∙ pH = -log([H+])

∙ [H+] = antilog(-pH) = 10-pH ([H+] = concentration of H+)

Acids 

∙ have [H+] higher than 10-7M

∙ Acidic molecules release H+into the solution

∙ pH 0-7

Bases 

∙ Have [H+] lower than 10-7M

∙ Basic molecules accept (or pick up) H+ions in the solution

∙ pH 8-14

Cellular & Molecular Biology

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Chapter 2

Functional Groups

Functional  Group

Formula 

Family of  

Molecules

Properties 

Example

Amino

Amines

Acts as a base,  tends to attract a  proton

Glycine

Carboxyl

Carboxylic Acids

Acts as an acid,  tends to lose a  proton

Acetic Acid

Carbonyl

Aldehydes

Can react with  certain  

compounds to  produce larger  molecules

Acetaldehyde

Ketones

Acetone

Hydroxyl

Alcohols

Highly polar,  

makes  

compounds more  water soluble,  

can be a weak  acid

Ethanol

Phosphate

Organic  

Phosphates

Multiple  

phosphates can  store large  

amounts of  

energy

ATP

Sulfhydryl

Thiols

Can form  

disulfide bonds in  proteins

Cysteine

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Proteins  

The Structure of Proteins 

∙ A hydrogen atom (H)

∙ An amino functional group (NH2)

∙ A carboxyl functional group (COOH)

∙ A distinctive R-group or side chain

Side Chains 

∙ Side chains can be acidic, basic, polar (but uncharged), or nonpolar ∙ Determining they type of side chain

o Negatively charged? ???? acidic (it has donated H+ions to its surroundings) o Positively charged? ???? basic (it has picked up surrounding H+ions)

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o Is there an O atom? ???? uncharged polar (there is a polar covalent bond) Side Chains, Functional Groups, and Reactivity

∙ Side chains will contain different functional groups, which will affect their  reactivity

∙ Polar side chains will be hydrophilic (polar likes polar)

∙ Non-polar side chains will be hydrophobic

∙ Different functional groups in side chains will also affect formation of entire  proteins

Peptide Bonds 

∙ Proteins form by connecting amino acids with peptide bonds

∙ Peptide bonds form through a condensation reaction between two monomers  (amino acids, in this case)

∙

∙ Peptide bonds can be broken through hydrolysis (putting water in) ∙ Electron sharing from the N makes the peptide bond very similar to a double  bond (more stable)

Important qualities of the Peptide Bond

∙ Side chain orientation- side chains will interact with each other and with water ∙ Directionality- the protein backbone will always have an amino group (NH3+) on  one end and a carboxyl group (COO-) on the other

o The amino end is the N-terminus and the carboxyl end is the C-terminus ∙ Flexibility- the peptide bond itself cannot rotate, but the single bonds on either  side of it can, meaning that protein structure is flexible

What do Proteins Look Like? 

∙ Proteins are incredibly diverse in their structure and function despite there only  being 20 different amino acids

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∙ Due in part to large number of amino acids that make up proteins and the huge  number of interactions that can form between so many side chains ∙ FUNCTION COMES FROM STRUCTURE

Primary Structure

∙ The unique sequence of amino acids in proteins

∙ Absolutely fundamental to the other structure levels

∙ Just one misplaced amino acid can cause a major malfunction (sickle cell) Secondary Structure

∙ Arises from hydrogen bonding between different parts of the amino acids o H-bonding can occur between carbonyl and amino groups of two different  amino acids

∙ Gives rise to either α-helix or β-pleated sheet o α-helix- the backbone of the  

polypeptide coils

o β-pleated sheet- parts of the backbone  bend to fold into the same plane

∙ Depends on the primary structure, especially  the properties of the amino acids involved Tertiary Structure

∙ Arises form side chain interactions including:

α β β

o Hydrogen bonds- between polar side chains and opposite partial charges  in other side chains or the backbone

o Hydrophobic interactions- (in aqueous solution) hydrophilic side chains  interact with H2O molecules, but hydrophobic side chains form globular  masses

o Van der Waals interactions- electrical attractions that occur between all  molecules. Very weak, but helps stabilize hydrophobic side chains that  are very close.

o Covalent disulfide bonds- strong links that connect different distinct  regions of the polypeptide or even two separate polypeptides

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o Ionic bonds- form between groups that have full and opposite charges ∙ All of these different types of interactions can occur in one polypeptide, leading to  very diverse possibilities

Quaternary Structure

∙ Many proteins have multiple polypeptide subunits interacting to make one  structure

∙ The exact bonding that occurs is quaternary structure

Folding and Function 

∙ Folding typically happens spontaneously, the folded form is usually more stable ∙ Proper folding is vital to proper function

∙ Unfolded (or denatured) proteins are pretty much useless

∙ Sometimes proteins spontaneously form incorrectly, in which case molecular  chaperones help them reach the proper formation

∙ Folding is often regulated by the chaperones to ensure the best functioning of the  organism they’re in

What do Proteins Do? 

∙ Catalysis- further explained in the next section

∙ Defense- attack and destroy viruses and disease-causing bacteria ∙ Movement- proteins move the cell itself and different ‘cargo’ inside the cell ∙ Signaling- send and receive signals cell to cell, trigger different enzymes ∙ Structure- compose fingernails and hair, keep blood cells in shape ∙ Transport- allow certain molecules to enter and exit cells

Enzymes and Catalysis 

∙ Catalysis- probably the most vital and fundamental function of proteins ∙ Enzymes- catalytic proteins located in specific sites within the cell ∙ Enzymes bind substrates (reactant molecules)  

∙ Most enzymes are proteins, but some are RNA

DNA and RNA 

DNA 

Structure (some RNA)

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∙ Nucleic acids (DNA and RNA) are made of monomers called nucleotides The Monomers of Nucleic Acids

∙ Phosphate Group- always the same, bonded to the 5’ carbon in the sugar ∙ Sugar- middle part of the NA

o Ribose in RNA

o Deoxyribose in DNA (missing an O on the 2’ C)

∙ Nitrogenous Base- one or two ring structures containing nitrogen, will form the  inside of the double helix

o Purines- have two rings (Guanine [G] and Adenine [A]

o Pyrimidines- only have one ring (Cytosine [C], Thymine [T] (DNA), and  Uracil [U] (RNA))

The Formation of NAs

∙ Phosphodiester Linkage/Bonding- joins two sugars through a phosphate  ∙ The backbone bonding is always directional 5’????3’  

∙ Condensation Reaction

Primary Structure

∙ The sequence of the individual nucleotides bonded in  

the backbone

Secondary Structure

∙ Formed by hydrogen bonds

∙ DNA is a double helix (Watson and Crick, Franklin and Wilkins, Chargaff etc.) ∙ Within the double helix, purines can only pair with pyrimidines

∙ A—T has two H bonds, C—G has three

Function of DNA 

∙ DNA can store and transmit Biological information

∙ Carries information to grow and reproduce

∙ Sequencing of bases contains all the vital information

Replication 

∙ DNA has to be able to replicate itself

∙ It does so through the following process

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o Heating or catalysis cause the molecule to break in half length-wise o Free nucleotides (deoxyribose) base pair with the newly exposed  backbone

o Two identical strands of DNA are produced

Cell Storage of DNA 

Eukaryotes  

∙ The cell keeps DNA within the nuclear envelope

∙ The nucleus contains chromosomes, and is surrounded by a double membrane  that has pore-like openings all over it

∙ Nuclear membrane and ER were probably formed by infolding of the outer  membrane

Prokaryotes

∙ Do not have a nucleus

∙ Keep DNA in the cytoplasm

∙ DNA is circular

RNA 

∙ RNA is more reactive and less stable than DNA

Primary, Secondary, and Tertiary Structure 

∙ Primary Structure- same as DNA, the backbone

∙ Secondary Structure- results from base pairing, but generally forms within the  same strand; hairpin structure; still antiparallel

∙ Tertiary Structure- when secondary structures fold to form more complex  patterns

∙ (Table 4.1 in the book can help with differentiating)

Function of RNA 

∙ Can function as a catalytic molecule

∙ Has some degree of complexity and can catalyze multiple chemical reactions ∙ DNA is not so versatile, its too stable

∙ It’s likely that the first life form began with RNA

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RNA and the Beginning of Life 

∙ The theory- life began with a lone self-replicator with no membrane in a solution ∙ The initial molecule would have to be capable of providing a template that could  be copied and of catalyzing reactions that would link monomers into a copy ∙ RNA is capable of both

Carbohydrates 

Structure 

Monosaccharides 

∙ the building blocks of carbohydrates

∙ Can vary in

o Location of carbonyl (aldose or ketose)

o Arrangement and number of hydroxyls

o Number of Carbon atoms (triose, pentose, hexose, etc)

o Spatial arrangement of atoms

o Shape and form (linear and ring)

▪ Rings form in aqueous solutions

∙ Monosaccharides are unique in structure and function

∙ Of the formula (CH2O)n

∙ Exist in alpha and beta forms (depends on the C1 hydroxyl; alpha down beta up) Glycosidic Linkage 

∙ Links monosaccharides

∙ Condensation reaction

∙ Alpha and beta linkages depend on the plane certain atoms land on ∙ Alpha points down in pictures, beta points up

Function 

Starch 

∙ The sugar/energy storage in plants

∙ Alpha 1-4 and alpha 1-6 glycosidic linkage (1-4 is usual, so when 1-6 occurs it  causes branching in the molecule)

∙ Unbranched helices are called amylose, branched are amylopectin

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Glycogen 

∙ The energy storage in animals (ex. In the liver and muscles)

∙ Alpha 1-4 and 1-6 glycosidic linkage

∙ Much more branched than starch (to hold more energy)

Cellulose 

∙ Structural support of cell walls in plants and algae

∙ Beta 1, 4-glycosidic linkages form parallel strands of monomers that hydrogen  bond with the strands around it

Chitin 

∙ Structural support in cell walls of fungi and exoskeleton of insects and  crustaceans

∙ Beta 1, 4- glycosidic linkage

∙ Monosaccharide monomers have a NHCOCH3 group on one carbon ∙ Parallel strands lined up with hydrogen bonds

Peptidoglycan 

∙ Structural support in bacterial cell walls

∙ Beta 1, 4- glycosidic linkage

∙ Monosaccharide monomers have a NHCOCH3 group on one carbon ∙ Monomers also have 4 amino acids on another carbon

∙ The amino acid chains react with each other to provide parallel structure through  peptide bonds

∙ Lysozyme- an enzyme that can break down peptidoglycan

Overview 

∙ Energy storing carbohydrates (ESC) utilize alpha linkage while structural  carbohydrates (SC) utilize beta linkage

∙ ESCs are helical and often branched

∙ SCs form straight chains that make parallel lines with other chains through  hydrogen bonds

∙ SCs are very difficult to hydrolyze (break apart), while ESCs are easier

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Within the Cell 

∙ Carbohydrates have NO catalytic activity

∙ But they do have many diverse functions

Glycoproteins

∙ Aid in cell identity

o Cell-cell recognition and cell-cell signaling

∙ Display information on the outer surface of the cell

∙ Example- helps sperm cells locate and bind to egg cells

∙ Example- Glycoproteins denote your blood type

Energy Storage

∙ The multitude of C—H and C—C bonds in carbohydrates are prime for energy  storage

∙ The bonds are shared very equally and therefore easy to break to obtain energy  (unlike C—O bonds, for example)

∙ To obtain energy

o Glycogen/Starch is hydrolyzed

o The glucose from the polymers in broken down

o The released energy is captured in the synthesis of ATP (cellular energy  source)

Lipids, Membranes, and Transport 

Lipids 

∙ Lipids are nonpolar, heterogeneous hydrocarbons

∙ They do not have one monomer like the other biomolecules

∙ They serve many purposes

o Fats and Oils- (TAGs) for energy storage, glycerol  

o Phospholipids- cell membranes, phosphate group and 2 FAs

o Steroids- diverse functions (ex. Cholesterol), distinct 4 ring structure Structure 

∙ Fatty acids are the building blocks of lipids

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∙ Although there is much more variation in lipids since FAs bond to things that  aren’t each other

Fatty Acids

∙ Made of chains of carbon and hydrogen with –COOH group on one end (hence  acid)

∙ Can be saturated or unsaturated

o Saturated- has no C—C double bonds, hydrogens with every carbon  (excepting the –COOH)

o Unsaturated- contains at least one C=C double bond, creates a kink in the  chain since the carbons cannot rotate around a double bond

o Saturation affects boiling point

▪ The FA with the LONGEST chain and FEWEST double bonds will  have the HIGHEST boiling point

∙ (When unsaturated) can be cis or trans

o Cis- when the hydrogens attached to the double bonded carbons are on  the same side of the chain (common in natural FAs)

o Trans- when they hydrogens attached to the double bonded carbons are  on opposite sides of the chain (common in hydrogenated oils)

Lipids Found in Cells 

Fats 

Structure

∙ Consist of a glycerol and three FAs

∙ Joined by ester linkages

∙ Form through dehydration reactions

∙ Depending on length and saturation, can be solid or liquid at room temp o Animal fats tend to be solid at room temp (more saturated)

o Plant oils tend to be liquid at room temp (more kinks)

Function

∙ Absorb some vitamins

∙ Energy storage

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∙ Protect organs and bones

∙ Provide insulation

Steroids 

Structure

∙ 4 ring carbon structure

∙ Can be attached to various polar or non-polar side groups (ex. Isoprenoid and  hydroxyl like in cholesterol)

Function

∙ Cholesterol, Vitamin D2, Cortisol, Testosterone  

o All are steroids with very different functions

∙ Cholesterol plays an especially important role in animal cell membranes Phospholipids 

Structure

∙ Composed of three parts

o Polar Head Group- a phosphate and a choline

o Glycerol Backbone

o 2 Fatty Acid chains

∙ Such structure makes the heads hydrophilic and the tails hydrophobic Function

∙ Primarily function as lipid bilayers (membranes) or micelles

Micelles 

∙ Example: soap

∙ Form a circular shape with hydrophilic heads on the outside and hydrophobic  tails on the inside

∙ Tend to form from FAs or other simple amphipathic hydrocarbon chains Membranes 

Phospholipid Bilayer 

∙ Example: cellular membrane

∙ Forms when two sheets of phosphor lipids join together with the heads on the  outside and tails on the inside

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∙ Separates life from non-life

Artificial Membrane Experiments 

∙ Done to learn about the permeability of lipid membranes

o Permeability- a structure’s tendency to allow a given substance to pass  through

∙ Question- how rapidly can different solutes cross the membrane considering  witch phospholipids are used and whether or not proteins or other molecules  have been added

∙ Discovery- phospholipid bilayers are selectively permeable

o Selective Permeability- some substances can cross the membrane easily  while others cannot

What Can Cross a Phospholipid Bilayer?

∙ Small, non-polar molecules can pass the easiest (ex. O2, CO2, N2) ∙ Small, uncharged, polar molecules are next (ex. H2O, glycerol)

∙ Large, uncharged, polar molecules can pass sometimes (glucose, sucrose) ∙ Ions cannot cross (Cl-, K+, Na+)

Factors that Affect Membrane Permeability

∙ Bilayers with short, unsaturated hydrocarbon tails have higher permeability o Easier to pass through because there is more room among the tails ∙ Bilayers with long, saturated hydrocarbon tails have lower permeability o Long straight tails mean the molecules will be more densely packed and  harder to pass through

∙ Cholesterol molecules within the membrane tend to reduce permeability ∙ Temperature also affects the membrane

o Low temps can decrease fluidity and even cause solidification

Transport 

Passive Transport 

∙ Does not require an input of energy

Diffusion

∙ Involves a concentration gradient

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o Concentration Gradient- difference in levels of solute on two sides of a  membrane

∙ Within a concentration gradient molecules and ions move from higher  concentrations to lower concentrations until an equilibrium is reached Osmosis (a type of diffusion)

∙ Water can move across lipid bilayers

∙ Osmosis is the special type of diffusion that involves only water

∙ Primarily occurs when the solute cannot cross the membrane, so water moves  to make the concentrations equal

∙ Only occurs across selectively permeable membranes

∙ Water moves from low solute concentrations to high solute concentrations ∙ Hypertonic, hypotonic, and isotonic

o Words that refer to the amount of solute in one solution compared to  another

o Hypertonic- refers to the solution with more solute particles

o Hypotonic- refers to the solution with fewer solute particles

o Isotonic- when both solutions have the same amount of solute particles Membrane Proteins 

∙ Amphipathic proteins on top of or imbedded in the cell membrane to help  facilitate different functions

∙ May be as many proteins as phospholipids in membranes

∙ Peripheral Membrane Protein- a protein that lies only on the exterior or interior of  the cell membrane, hydrophilic

∙ Integral Membrane Protein- a protein that entirely passes through the membrane,  amphipathic (transmembrane proteins)

Membrane Proteins as Transporters

∙ Ion Channels

o Allow ions (usually unable to pass through the membrane) to pass and  follow the electrochemical gradient

o Form a pore in the membrane

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o Each kind has specific structure

o There can be many different kinds within one membrane

o Water channels are known as aquaporin

o Some channels are gated and require a certain signal or charge to open o Ion and molecule flow is regulated

∙ Carrier Proteins

o Membrane proteins that change shape during transportation

o Interact strongly with cargo

∙ Pumps

o Pumps move molecules AGAINST the concentration gradient

o Requires ATP or an electrochemical gradient (energy sources)

o Pumps set up electrochemical gradients

o The gradients make it possible for secondary active transport to happen  by providing potential energy

Active Transport and Vesicles 

∙ Exocytosis- vesicles containing certain molecules fuse to the membrane from the  inside to release said molecules into the extracellular fluid

Endocytosis- a vesicle buds into the cell to bring in

Inside the Cell 

Prokaryotic Cells 

∙ Prokaryotes do NOT have a membrane-bound nucleus

o Their DNA is kept in a single chromosome (nucleoid)

∙ Prokaryotes DO (almost always) have a plasma membrane, stiff cell wall, and  ribosomes

Eukaryotic Cells 

∙ Considerably larger than prokaryotic cells

∙ Size can make it difficult for molecules to diffuse across the entire cell o A problem partly solved by membrane-bound organelles

Origin of Eukaryotic Cells 

∙ Endosymbiosis Theory- cells engulfed other cells that became mitochondria and  chloroplasts (explains the double membranes surrounding these organelles)

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∙ Eukaryotes likely evolved form prokaryotes (same 20 amino acids and nucleic  acids as hereditary material)

Parts of Eukaryotic Cells 

Ribosomes

∙ (not technically considered organelles)

∙ Structure- large and small subunits containing LOTS of protein molecules; may  be attached to ER or free in the cytoplasm

∙ Function- Synthesize proteins

Nucleus

∙ Structure- double membrane (nuclear envelope), contains many openings;  nucleolus manufacturing RNA and ribosome subunits

∙ Function- stores hereditary information, synthesizes RNA and ribosome parts Endoplasmic Reticulum

∙ Structure- single membrane; branching sacs; rough ER has ribosomes attached,  smooth ER does not; part of the endomembrane system

o Endomembrane System- composed of the ER, Golgi, and lysosomes;  primary system for protein and lipid synthesis

∙ Function- Rough ER creates and processes proteins, smooth ER creates and processes lipids

Golgi Apparatus

∙ Structure- single membrane; stack of flattened membrane sacs ∙ Function- protein, lipid, and carbohydrate processing

Lysosomes

∙ Structure- single membrane; contains protein pumps; contain around 40 different  digestive enzymes; low pH; found only in animal cells

∙ Function- digestion and recycling

Protein Transport in the Cell 

∙ Most proteins are found in the nucleus, peroxisomes, mitochondria, and  chloroplasts

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∙ Proteins will have a target sequence that sends them to the appropriate organelles

∙ Moving proteins in and out of the nucleus requires energy

o Proteins that need to enter the nucleus will have a nuclear localization  signal (NLS) that allows them in

Transport and the Endomembrane System

∙ The endomembrane system (ER, golgi, and lysosomes) manufactures and ships  proteins

∙ Pulse-Chase experiments have been used to track protein movement o Label proteins with radioactive amino acids  

o Wash away excess amino acid leaving labeled proteins

o Follow the tagged proteins to find their path

∙ Pulse-chase found that proteins move from Rough ER to Golgi, to vesicles The Signal Hypothesis

∙ Proteins headed for the endomembrane system have a signal sequence that  sends them in the right direction (20 amino acids long)

o Protein synthesis begins on a free ribosome

o Signal sequence sends the building protein to the appropriate location on  the rough ER thanks to a signal recognition particle (SRP)

o Protein synthesis continues into the rough ER

o When synthesis is complete, the signal sequence is removed and the  ribosome and protein detach from the lumen of the rough ER

∙ After the ER, proteins move to the golgi in vesicles

o Vesicle buds off the ER and travels to the golgi where it binds (on the cis  side) and dumps its contents

o If the protein is to stay within the ER it will have a special retention tag ∙ Once proteins reach the golgi, they are tagged, sorted, and sent in vesicles and  delivered to their specific sites

Delivery to Lysosomes

∙ Autophagy- the lysosome binds to a damaged organelle to be recycled

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∙ Phagocytosis- the phagosome is engulfed by the cell and sent to the lysosome to  extract necessary molecules

∙ Receptor-Meditated Endocytosis- macromolecules bind to receptors and are  engulfed by the cell, the vesicle formed fuses with an early endosome and the pH  lowers, after receiving digestive enzymes, the endosome becomes a lysosome Cytoskeleton 

∙ The cytoskeleton is composed of protein fibers and gives the cell shape and  stability. Also aids in movement of the cell and materials within the cell. Very  helpful with organization of the cell.

∙ Microfilaments- made of actin, resist tension, move cells, divide cells, move  organelles

∙ Microtubules- made of alpha and beta tubulin dimers, resist compression, move  cells (cilia and flagella), move chromosomes, assist cell division, move  organelles, tracks for intracellular transport

∙ Intermediate Filaments- make of keratin among other things, resist tension and  anchor some organelles