Cell Biology Exam 4 Study Guide

function of integrin proteins

-attachment of cell to EMC/signal transduction

structural features of cadherins proteins

-calcium dependent -large extracelular segment, small cytoplasmic segment, and a transmembrane domain

function of selectin proteins

-immune recognition (cell-cell binding functions in leukocytes migration and clotting) -recognizes the carbs on other cells and binds to them

selectins

-integral membrane glycoproteins that recognize and bind to specific arrangements of carbohydrate groups projecting from the surface of other cells -has a small cytoplasmic domain, a single membrane spanning unit, and a large extracellular segment has L-selectin, P-selectin, E-selectin -present in leukocytes and involved in platletes migration -binding of selectin to ligands require Ca2+

structural features of tight junctions

-integral proteins of 2 adjacent membranes meet -interconnected strands of integral proteins

function of gap junctions

-intracellular communication -sites of cell-cell communication -integrate the activities of one cell of tissue into function unit

rubisco

-large multisubunit enzyme, converts inorganic carbon to useful biological molecules; ribulose bisphosphate caroxylase oxygenase -can only fix 3 CO2 molecules per second, super slow that's why we need a lot of it

photosystem I & II

-large pigment protein complexes; PSII promotes electrons from below water to midway; PSI promotes electrons promotes electrons from midway to above NADP+

Chloroplast

-membrane bound organelle; main site of photosynthesis -found in meophyll cells -has an inner and outer membrane

function of plasmodesmata junctions

-sites of cell-cell communication in plants

stroma

-space inside chloroplast inner membrane but outside thylakoids -less acidic than the lumen -where ATP synthesis happens

function of desmosomes junctions

-used to maintain epithelial structure -sensitive to mechanical stressors

describe the structural and functional differences between LHC chlorophylls and reaction center chlorophylls

LHC: complexes of subunit proteins that join to form complexes of photosystems; Absorbs energy to donate to the Reaction Centers Reaction center: P680 or P700; • Transfers electrons to an electron acceptor (Pheophytin in PSII, and A0 in PSI)

absorption spectrum

actual wavelength that varying pigments in a molecule can absorb

major role of gap junctions

creates a connection accros a distance between cytoplasm of cells

plasmodesmata

cytoplasmic channels that connect most plant cells and extend between adjacent cells directly through the cell wall. Lined with plasma membrane and usually contain a dense central structure (desmotubule) derived from the endoplasmic reticulum of the two cells.

major role of hemidesmosome junctions

helps with cell attachment

interaction type of collagen protein

main protein interacting with the ECM

major role of tight junctions

makes it difficult for molecules to pass paracellularly

what is the relationship between the light-dependent and light-independent phases of photosynthesis in terms of chemicals that link the two

the light-dependent reactions produce NADPH and ATP which are the molecules used in the Calvin Cycle to produce the GAP -> F16bP -> sucrose

know the major roles of the individual proteins below including whether they are involved in cel-cell or cell-ECM interations: collagen fibronectin integrins catenins laminins

(see study guide)

know the major roles of the junctions below, including whether they are involved in cell-cell, cell substrate, or cell-ECM interactions: hemidesmosome tight junctions gap junction focal adhesion plasmodesmata

(see study guide)

know the unique structural features of collagen and connexins

*Collagen: 3 polypeptide alpha chains coiled around each other to form a triple helix configuration. Each of the chains has ~1000 amino acid residues. Undergo hydrogen bonding. *Connexins: four-pass transmembrane proteins with a C & N cytoplasmic terminus, a cytoplasmic loop, and two extra-cellular loops. Assembled in groups of 6 to form hemichannels. Average lenght ~380 amino acids.

light-independent reactions

- second series of reactions of photosynthesis where carbohydrates are made from CO2 using energy from ATP and NADPH -the calvin cycle

structural features of integrin proteins

-2 covalently linked glycoprotein subunits (1 alpha and 1 beta) -NH2 head

structure of gap junctions

-6 connexin=1 connexon -2 connexon = 1 gap junction

relate the absorption spectrum of a plant extract to the action spectrum of photosynthesis

-Action Spectrum -Indicates the relative efficiency with which light of various wavelengths is able to promote photosynthesis -Identifies the wavelength that are more effective in bringing about physiological response. -Absorption Spectrum -The intensity of light absorbed relative to its wavelength -Measures wavelength of light absorbed by pigment -The presence of pigments with varying absorption properties ensures that a greater percent of incoming photons will stimulate photosynthesis -The action spectrum for photosynthesis follows the absorption spectrum of chlorophylls and carotenoids fairly closely!

carotenoids (B-carotene)

-An accessory pigment in photosynthesis. Unlike chlorophyll, it is unable to do anything with the light it takes it, but it can pass along its energy. -contains a linear system of conjugated double bonds absorb light in the blue and green regions of the spectrum, so they give off orange color function as secondary light collectors, also they draw excess energy of exicted electrons and dissipates it as heat

know the variety of the 2 proteins that make up tight junctions and how they relate to tight junction differences in permeability

-Claudins and Occludins are used to make TJ's -They have many different isoforms which lead to different combinations of binding. -The amount of complexes made between the membranes by these proteins changes how selective the membrane is. -distribution of certain claudins in an area changes depending on the tissue and what its needs are

what structural features make the cholorphyll molecule a colored pigment

-Consists of porphyrin ring with magnesium ion in center -Long hydrocarbon tail -Rings = delocalization of electrons forming a cloud -Chlorophyll a is present in all oxygen-producing photosynthetic organisms. -Ring = light absorbing -Tail = keeps chlorophyll embedded in the photosynthetic membrane.

explain the circumstances for and the molecular mechanism of control of certain calvin cycle enzymes by the redox state of thioredoxin

-Ferrodoxin, which is the final acceptor of PSI, transfers electrons to NADPH, but it also transfers some to Thioredoxin. Thioredoxin reduces disulfide bridges (causing conformational change) to activate the enzymes in the Calvin Cycle. -Also, the pH of the stroma plays a role. If it is more alkaline, then the enzymes move more quickly. This would make sense in light reactions because H+ are being pulled out of the stroma and in to the thylakoids when light reactions are occuring at the PS's.

explain the operation of a light-harvesting complex, including the role of accessory pigments

-LHCII proteins bind both chlorophyll and carotenoid pigments -LCH contains chlorophylls, proteins, pigments antennas -antenna pigments absorb protons of various wavelengths and transfers energy to pigment molecules at the reaction center -accessory pigments: other pigments that increase the wavelength absorption of the chlorophyll molecule (carotenoids, chlorophyll b)

what determines the absorption spectrum of a pigment

-Pigments only absorb light at a particular wavelength -Alternating single and double bonds along porphyrin ring -Conjugation = strong absorbers of light -Conjugation broadens absorption peaks and increases the range of wavelength -Absorbed energy causes a redistribution of electron density of the molecule -Loss of electron to its electron acceptor

explain the mechanism of photolysis: starting with oxidation of P680; explain the mechanism of its reduction by the oxygen complex adn the subsequent oxidation of water to O2

-The overall reaction is 2e + PQ + 2H -> PQH2 (Happens twice) Steps 1. Photons come in and excite an electron in P680, which is in PSII 2. The electron is transferred to Pheophytin and P680 is oxidized to P680+ 3. P680+ is so strong that it pulls electrons from water 4. The electrons from the water are found in the Oxygen Evolving Complex (MnCa cluster involved here) 5. An intermediate tyrosine carries the electrons to the P680+ 6. Water splits up and P680+ is reduced back to P680 7. The process repeats, and overall it takes 4 photons to make the reaction go as described

visible light

-a form of electromagnetic radiation...the wavelenght ranges that are visible to our eyes... -the visible spectrum ranges from 350nm to 750nm

fibronectin

-a glycoprotein that binds to integrins. -Binds collagen. -Helps in cell adhesion/maintaining the structure of extracellular matrix.

hemidesmosome

-adhesive structure at basal surface of epithelial cells, contains dense plaque on inner surface of plasma membrane with keratin containing filaments extending into the cytoplasm -the signals transmitted from the ECM affect the shape and activity of the cell

focal adhesions

-adhesive structures containing integrins in the region the plasma membrane portion of the integrins are connected by various adaptive proteins -they are sensory structures that collect information about physical and chemical properties in the env. can create mechanical forces

describe the functions of plastmodesmata

-allow cell communication between plant cell walls they are cytoplasmic channels that pass through teh cell walls of adjacent cells -lined by plasma membrane and contain a dense central structure (desmotubule) -cell-cell communication as substances pass through the annulus surrounding the desmotubule

function of tight junctions

-barrier to free diffusion of water and solutes -helps maintain polarity of cells -different permeabilities

light harvesting complex I and II

-bind chlorophylls and carotenoids and are situated outside the core of the photosystems -the excitation energy is passed from the anetenna pigment in the light harvesting complex to the chlorophyll molecule in PSII, then from there to the PSII reaction center.

P700

-chlorophyll dimer known as photosystem I present in the reaction center, once it receives the excitation energy it transfers an electron to the molecule A0 (aka chlorophyll a)

P680

-chlorophyll dimer known as photosystem II a reaction center pigment that gets the excitation energy from chlorophyll molecule and responds by transferring a single electron to pheophytin

photosynthesis

-converts sunlight to chemical energy that can be used chemical energy produced is stored in the form of carbohydrates -in the process, low energy electrons are removed from -a donor and converted into high energy electrons using light energy

structure of plasmodesmata junctions

-cytoplasmic channels -lined by plasma membrane -dense central structure derived by ER of the two cells

wavelength

-distance between two wave crests -as the wavelength increases, the energy decreases so longer wavelengths have lower energy

cadherins

-family of glycoproteins that mediate Ca2+ dependent cell-cell adhesion -transmit signals from ECM to cytoplasm -they join cells to one another by binding to the cadherin on that cell

phenophytin

-first electron carrier in PSII -a primary electron acceptor, it receives electrons from P680 and transfers them to plastiquinone

light-dependent reactions

-first series of reactions of photosynthesis where sunlight energy is converted to chemical energy stored as ATP and NADPH -occurs in the thylakoid membrane

thylakoid

-flattened, membranous sacs inside the chloroplast; have machinery for photosynthesis -place within the thylakoid is called lumen -the place outside the thylakoid but within the chloroplast membrane is called the stroma

function of cadherin proteins

-form adherin binding sites

know the size (and molecular weight) selectivity of gap junctions

-mammalian gap junctions allow the diffusion of molecules having a molecular mass below approx. 1000 daltons (1 kDa) -relatively nonselective -gated: -closure probably triggered by phosphorylation of connexin subunits -closure also triggered by voltage changes across the junction or abnormaly high Ca+ cytosolic concentrations

excited state

-molecule with a promoted electron following photon absorption -when light is absorbed, the electron gets pushed from the inner to the outer orbital

tight junctions

-occur at apical end of junctional complexes between adjacent epithelial cells; adjoining membranes make contact at intermittent points where integral proteins of two adjacent membranes meet

structural features of adherens junctions

-occur in belts hat encircle each of the cells -cells are held together by Ca dependent linkages formed by the extracellular domains of cadherins proteins

describe the molecular weight selectivity of plasmodesmata

-recent studies suggest that plasmodesmata allow much larger molecules 50,000 daltons (up to 50 kDa) through -plasmodesmata is capable of dilation -plants produce their own movement proteins that regulate the flow of proteins and RNAs from cell to cell allowing for the dilation of the plasmodesmata

describe what is known (from the text) about regulation of opening of gap junctions

-regulation differs depending on the specific connexins forming the connexon -in some cases, connexons in neighboring cells that are composed of different connexins are able to dock, but not in other cases -compatibility differences: promoting or preventing communication between types of cells

structural features of selectins protein

-single pass -calcium dependent -N terminus on the outside -EGF sequence -large extracellular domain and a small cytoplasmic domain

adherens junctions

-specialized adhesive junctions common in epithelia. -The plasma membranes in this region are separated by 20-35 nm and are sites where cadherin molecules are concentrated. The cells are held together by linkages between the extracellular domains of cadherin molecules that bridge the gap between neighboring cells.

major role of laminin proteins

-stimulates mammary cells -by binding to the cell surface integrins and activating the kinases they are connected to on the inside

NADPH

Electron carrier that is very similar to NADH. It is created in the light dependent part of photosynthesis, and then it is used in the Calvin cycle which makes glucose.

know the epithelial location of tight junctions and their functions in those issues

Locations: Skin, lining of arteries, lining of organs Function: Retention of certain molecules. Skin for pretty much everything, arteries so the blood actually gets places, and organs to make sure that the stomach doesn't burn up everything and whatnot -keep molecules from passing paracellularly

primary electron acceptor

Molecule that receives the photoexcited electron from reaction-center pigments in both photosystems.

connexins/connexons

Multisubunit complex of a gap junction formed from the clustering within the plasma membrane of an integral membrane protein called connexin. Each connexon is composed of six connexin subunits arranged around a central opening (annulus).

describe the structural and function differences between P680 and P700

P680: • Reaction center of PSII • 680 = wavelength absorbed most strongly • Excites electron • Electron transferred to pheophytin P700: • Reaction enter of PSI • 700 = wavelength absorbed most strongly • Excites electron • Electrons transferred to A0 • A0 = very strong reducing agent

describe the structural and functional differences between PSI and PSII

PSI: Has Ferrorodoxin used to reduce NADP+ to NADPH • Reduces molecule of NADP to NADPH PSII: Has the Oxygen Evolving Center for Photolysis • Catalyzes the light driven oxidation of water • Catalyzes the transfer of electrons from H20 → Plastoquinone (PQ) • Major contributor in forming H+ gradient.

what are the starting and ending carbon-containing molecules of the Calvin Cycle

Start: RbuP and CO2 End: Glucose/Sucrose/Fructose and RbuP (takes 6 cycles to completely make glucose)

cellulose microfibrils

a fiber made up of celluose. These microfibrils are laid down in the inner surface of the primary cell wall (cell absorbs water=increase volume=separation of existing microfibrils & new ones form to help increase cell strenght)

laminin

a protein of the extracellular matrix.Active part of basal lamina (helps with cell differentiation)

major role of plasmodesmata junctions

allows plant cells to pass molecules through without having to deal with the cell

occludins/claudins

an integral plasma membrane protein located at tight junctions (helps with tight junction stability/ barrier function) -not all TJs have occludins, but they have claudins

major roles of fibronectins proteins

binding for parts of the ECM to create a network -binds to the cell surface to hold ECM in stable attachment to the cell -attaches cells to the ECM

interaction type of focal adhesion junctions

cell substrate/ECM

interaction type of fibronectins proteins

cell-ECM

interaction type of hemidesmosome junctions

cell-ECM

interaction type of integrin proteins

cell-ECM (Ca+ dependent)

interaction type in gap junctions

cell-cell

interaction type in tight junctions

cell-cell

interaction type of catenins proteins

cell-cell

interaction type in plasmodesmata junctions

cell-cell (plants)

pigments

compounds that appear colored because the only absorb light of one wavelength

porphyrin ring

conjugate acids of ligands that bind metals to form complexes (one example is heme (cofactor of hemoglobin))

major role of the catenins proteins

connects cadherins to the cytoskeleton

gap junctions

connects the cytoplasm of two cells (allowing different molecules/ions to pass through a regulated gate (spanned by connexons) between cells).

major role of integrin proteins

connects to the extracellular matrix by going through the membrane -cell signalling (binding ligands and influencing events within the cell)

electromagnetic spectrum

contains all possible frequencies of electromagnetic radiation (radio waves (long wavelenght/low frequency)->Gamma Rays (short wavelenght, high frequency)....

desmosomes

disk-shaped adhesion junctions found in epithelia basal to the adherens junction

action spectrum of photosynthesis

effective wavelengths for photosynthetic reactions to occur because not all pigments in a plant do photosynthesis

reaction center

energy jumps from pigment to pigment until it arrives at the reaction center. An electron acceptor traps a light excited electron from the reaction center chlorophyll (the single chlorophyll molecule that actually transfers electrons to an e- acceptor)

interaction type of laminins proteins

extracellular glycoproteins that influences the cells around it -cell-cell

integrins

family of integral membrane proteins that bind extracellular molecules

collagen

fibrous glycoprotein known for high tensile strength

non-cyclic photophosphorylation

formation of ATP during oxygenic photosynthesis, electrons move from linearly from H2O to NADP+

chlorophyll

light absorbing photosynthetic pigment

extracellular matrix

organized network of of extracellular materials present beyond the plasma membrane; may determine shape and activity of cell

photon

packet of light energy

Calvin cycle

path converting CO2 to carbohydrate happens in the stroma

cyclic photophosphotylation

process carried out by PSI independent of PSII

proteoglycan

protein polysaccaride complex with protein core and attached glycosaminoglycans; can bind cations, which draws in water; form porous hydrated gel

major role of collagen protein

provides structural stability of the cell

function of adherens junctions

signal transduction

structural features of desmosomes junctions

specialized rope-like cadherins that create a disk shaped connection

photolysis

splitting of water during photosynthesis the process that produces O2 in plants

granum

stack of thylakoids in chloroplast

ground state

unexcited state of an atom or molecule

major role of focal adhesion junctions

used for in vitro studies (locomotion)