MCDB 1A: Cell Biology

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epitope

the antigen's binding site -- used in process of finding a protein in a cell

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How do we find a protein in the cell?

an antibody is used to bind to a specific antigen's epitope. A secondary antibody tagged w/a fluorescent cmpd is added and binds to primary antibody. The image can be seen w/a fluorescent microscope.

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Cell theory: what is it and who discovered it

all life comes from preexisting life -- discovered by Louis Pasteur .

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Why are cells so small?

Large SA:V ratio allows for quicker rate of diffusion for monitoring what goes in and out of a cell. We want to bring in nutrients and release waste

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Unicellular

a single cell, like bacteria. Bc they're single cells, they can develop into biofilm or communities like coral

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Multicellular

many cells, like humans. Carry out different functions

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What are the 3 major domains of life?

Bacteria, Archaea, Eukarya BA= prokaryotes E=eukaryotes (fungi, protists, plants, animals)

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What is the cell wall in prokaryotes made of?

peptidoglycan

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How many membranes do prokaryotes have?

some have 2 membranes: the outer and inner

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What is the inner membrane in a prokaryotic cell called?

periplasmic space

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Where is DNA stored for a prokaryotic cell?

the nucleoid contained in the cytoplasm

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What is the flagella?

a tail that allows the cell to swim. Can make bacteria spin: clockwise is a forward motion while counterclockwise is TUMBLING

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What is the pili?

It's used for sex amongst bacteria; allows adhesion to other bacteria or surfaces. It builds bridges between inferiors and exchange cytoplasmic material

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What is another word for bacterial sex?

conjugation

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bacterial sex

  1. the pili connects them together

  2. plasmids that enclose circular DNA are transferred through the pili during replication

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Who discovered penicillin and how?

Alexander Fleming; grew penicillin mold and saw that bacteria couldn't grow near it. Discovered it killed bacterial cells and prokaryotes b/c they tend to have a cell wall

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pencillin

it links peptides to sugars

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What is the nucleolus?

a part of the nucleus with ribosomal genes. It's where ribosomes are made and assembled

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What is the double membrane of the nucleus called and what supports it?

The nuclear envelope; it is supported by the lamina ['laminates"=support] and is contiguous of the ER. Holds different proteins and keeps nucleus from being compressed

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What is the function of nuclear pores?

to regulate what comes in and out of a cell

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What does a mutation in lamin-A cause?

early aging due to a collapsed nucleus

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Describe the nuclear pore complex

it forms channels to allow passage of macromolecules and is important for trafficking. ' it is inside the nuclear envelope

  • mRNAs binded to proteins go out while nuclear proteins go in. They must have a NLS attached in order to be recognized by the pores

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cytosol

Where are proteins sythesized?

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What protein recognizes a NLS?

an importin protein

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NLS are ______ for import of protein into nucleus and __________ to direct a normally cytoplasmic protein into the nucleus

necessary; sufficient

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What is C-myc?

a transcription factor; binds to DNA & turns on transcription of genes associated with replication.

  • if turned back on unnecessarily it leads to cancer due to overexposure

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What size are mitochondria?

about the size of a bacterial cell

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What are the 3 functions of mitochondria?

  1. produce energy, ATP

  2. regulate calcium levels

  3. regulate signals that mediate cell death

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how do mitochondria grow and divide?

binary fission; pinching off in the middle

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describe the structure of mitochondria

  • it has an inner and outer membrane

  • the outer is smooth and semipermeable

  • the inner has a lot of folds (cristae)

  • it has a matrix inside & mitochondrial localization sequence

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what is the matrix?

  • the matrix is the inner part of the mitochondria. It holds rna, trna, ATP synthases, and the electron transport chain.

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a mutation in NADH leads to this

blindness

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how is the pH gradient created and what is its purpose

it is part of the electron transport chain; hydrogen is pumped out to create a gradient across the inner membrane and then hydrogen flows in to create ATP.

  • it is more acidic bc of the hydrogen drive

  • it is a source of energy

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what are plastids?

plants; they have a double membrane

  • serve for photosynthesis and storage

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what is the third membrane of the cytoplasm? Function?

the thylakoid; has proteins to bind chlorophyll & light pigments for photosynthesis

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what is the middle of the cytoplasm called? What is its function?

the stroma; holds DNA & ribosomes

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what are the 2 reactions of chloroplasts?

  1. light --> takes energy from the sun to make O2, ATP, NADPH

  2. dark --> use ATP and NADPH to make CO2 which is then sugar

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endosymbiosis

the belief that mitochondria & chloroplast originated when large eukaryotes ate small prokaryotes

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Peroxisomes

squared granular or crystalline arrays of enzymes that catalase to destroy toxic peroxides

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Chromoplasts

pigment storage

  • attract insects for pollinating

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Plant vacuole (3 functions)

  1. store toxic waste materials, food & nutrients

  2. provide TURGOR aka stiffness for structure

  3. can contain hydrolytic enzymes

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leucoplasts- what and found where?

store starch, lipids or proteins found in roots/nonphotosynthetic tissue

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amyloplasts

store starch in potatoes

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diabetes: 2 types

  • high blood sugar, weakness, lethargy, and weight loss

  • Type 1: juvenile--lack of insulin. The own immune system attacks beta cells of pancreas

  • Type II: lack of insulin responsiveness

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insulin: what and discovered by who

  • peptide hormone secreted into blood by beta cells in pancreas

  • binds to cell surface of muscle & fat cells : signals to import and store glucose

  • discovered by Banting and Best

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Endomembrane system

  • network of closed membrane tubules, closed vesicles, and closed sacs

  • divides cytoplasm in 2 (inside and outside membrane sacs)

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3 Functions of Endomembrane System (STC)

Sequestration: of molecules/particles into cysternal space of vesicles Transport: of sequestered molecules/particles from place to place w/in cytoplasm or to nucleus Chemical modification

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What makes up the endomembrane system?

  1. Rough ER

  2. Smooth ER

  3. Golgi Complex

  4. Vesicles

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Rough ER

  • has ribosomes attached

  • is where integral membrane proteins & proteins that are secreted are made

  • they're then translocated across the membrane into cysternal space

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Smooth ER

  • lipid synthesis

  • detoxification of hydrophobic toxins

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Golgi complex (post office)

  • modifies carbs/proteins and ships them to the cell surface

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Vesicles

  • lysosomes, peroxisomes, secretory ; move to cell surface

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Secretory pathway

rough ER --> golgi --> vesicles

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Integral Membrane proteins

  • secreted proteins with signal sequence at N-terminus

  • direct ribosome to rough ER signal removed in lumen of ER

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Golgi apparatus

  • has a cis/trans region

  • vesicles from ER fuse with the cis region

  • pinch off and fuse with medial and trans region

  • pinch off trans and fuse with plasma membrane

  • proteins inside vesicle secreted outside cell

  • proteins in vesicle membrane inserted in plasma membrane

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lysosomes

pinched off the golgi

  • cells recycling center

  • has digestive enzymes break down old cellular materials

  • digest ingested bacteria

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Tay-Sachs Disease

  • lysosomal storage disease

  • mutation in gene for hexose-aminidase A prevents lysosomes from breaking down certain membrane glycolipids

  • leads to blindness, dementia, death

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Phagocytosis

  • when macrofuge ingests bacteria

  • the phagosome fuses with lysosome to kill bacteria

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Randy Schekman (schek, shake)

  • isolated yeast cells that had secretion defects

  • called them sec genes encode membrane proteins that are involved in membrane traffic

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The eukaryotic cytoskeleton's 3 different skeletal fibers

  1. Microfilaments

  2. Intermediate Filaments

  3. Microtubules

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Microfilaments

  • made up of actin monomer

  • polarization on plus end

  • depolarization on minus end

  • assembled by noncovalent bonds at the end of filaments

  • partakes in treadmilling

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Intermediate filaments

  • build similar cable like filaments

  • very stable NOT DYNAMIC

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Cell shape of microfilaments

  • Stress fibers: bundled actin, maintain skin cell shape attach to focal adhesion -Microvili: project from cell surface most found in intestine

  • actin join integrin

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Movement of Eukaryotic Cytoskeleton

  • DUE TO MICROFILAMENTS proven bc of amoeba experiment where Cytochalisin B blocks formation of microfilaments leading to movement

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An example of intermediates

nuclear lamins

  • support nucleus, attachment points for DNA keratin filaments

  • support skin, hair

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Microtubules

  • made of alpha beat tubulin dimers

  • both ends have different properties

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Two functions of microtubules

  • Dynamic instablity: switching b/w growth and shortening ends

  • Treadmilling

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Function of microtubules in animals

centrioles surrounded by pericentriolar matrix

  • centriole = set of 9 triplet microtubules

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Dynein motor proteins

  • help move the cilia and flagella

  • negative directed

  • make microtubules slide past each other

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Type of microtubules vesicles use to move

  • dynein and kinesin motors

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How microtubules move

using the cilia or flagella!

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Lipid rafts

-high in cholesterol --> less fluidity

  • more rigid

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3 types of molecule transportation

  1. Passive diffusion

  2. Carrier mediated diffusion

  3. Active transport

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Passive diffusion

  • no ATP required

  • from high concentration to low

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Type of molecules that can't diffuse passively

  • most water soluble

  • any with a positive or negative charge ex. sugars, AA, proteins

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How do molecules that can't diffuse passively get across the membrane?

  • channel proteins ex. Ion channels

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Carrier mediated diffusion

ex. glucose carrier protein NO ENERGY REQUIRED

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Active transport

  • needs energy and ion gradient

  • moves molecules against their concentration gradient

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Uniporter

  • active transport: moves one substance in one direction

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Symporter

  • active transport: two substances in same direction

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Antiporter

  • active transport: two substances moving in opposite directions

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Types of gated ion channel

ligand binding and voltage

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Endocytosis & exocytosis

moving complex molecules into cells fusion of membrane vesicle to plasma membrane

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3 types of endocytosis

  1. Phagocytosis: large particles and small cells engulfed inside vesicles

  2. Pinocytosis: cell drinking; taking up water into vesicles

  3. Receptor mediated endocytosis: specialized form--takes in certain kinds of macromolecules into cells

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