Bild1, Mt2

cell signaling: b.t cells next to one another

cells in a multicellular organism communicate by chemical messengers

animal cells communicate by direct contact or cell-cell recognition

e.g. synaptic signaling

messenger molecules that travel only short distances

short distance communication

cell secretes material in close proximity to other cells

short distance communication

neurotransmitter travels across a synapse

long distance communication

travels into blood stream and binds to receptors

*ability of a cell to respond to a signal depends on whether or not it has a receptor specific to that signal

1) reception: signaling molecule binds to the receptor

2) transduction: signal is converted into an intracellular response

3) response: the action that happens

molecules that bind to a specific molecule

shape change that leads to signal transduction

when a signal molecule binds as a ligand to the receptor, conformational change, channel opens, gate allows certain ions to pass through. once ligand disconnects, gate closes.

lungs: relaxes muscle cells, more oxygen to blood

heart: beats faster -> everything moves faster throughout bloodstream

liver: releases glucose into blood

adrenaline/epinephrine binds to receptor, signals molecules

release of glucose is the response (glycogen broken down)

insulin binds to insulin receptor, triggers cascade of phosphorylations

one outcome is that vesicles containing glucose transporters are moved to cell surface; glucose enters the cell

glucose is converted to glycogen

*not all signaling molecules are hydrophilic (some are hydrophobic and can go directly through membrane)

receptors that are inside the cell can then bind to the hydrophobic molecules

e.g. testosterone (steroid)

require energy, yield products rich in potential energy

e.g. photosynthesis

release energy, incr kinetic energy (break chem bonds)

ATP + H2O -> ADP + Pi

exergonic, spontaneous

energy coupling to drive chem rxns

exergonic, but not spontaneous at a high enough rate

need enzymes to catalyze rxn (e.g. sucrase)

dG unaffected, rate affected, activation energy decr

highly specific; active site where enzyme interacts with its substrate

a change in protein structure that the substrate causes

1) enzyme is available with empty active site

2) substrate binds to enzyme with induced fit

3) substrate is converted to products

4) products are released

competitive: blocks substrate binding

noncompetitive: changes shape elsewhere so that substrate cannot bind

molecule binds on another active site and causes a shape change (can be either activators or inhibitors)

enzyme #2 (product) can feedback info into enzyme #1 (reactant) and stop process when no more porduct is needed

responsible for carrying out cellular respiration

outer & inner membrane, intermembranous space

matrix: inside cavity of mitochindrion

cristae: folds that incr surface area of matrix

glucose + O2 -> CO2 + H2O + ATP

occurs in both plants and animals

occurs in two places: cytoplasm & mitochondria (starts in cytoplasm & continues in mitochondria)

occurs in 3 stages: glycolysis, citric acid/krebs cycle, oxidative phosphorylation (electron transport chain and chemiosmosis)

Glucose -> pyruvate

Pyruvate enters mitochondria and is oxidized to CoA

Final products: 2 pyruvate, 2H2O, 2ATP, 2NADH + 2H+

Occurs in mitochondrial matrix

Organic molecules -> CO2, NADH, FADH2, ATP

Occurs in mitochondrial matrix

Chemiosmosis: makes ATP; energy storee in the form of H+ ion gradient across membrane is used to drive cellular work

electron transport chain: located in inner membrane of mitochondria; final electron acceptor O2 -> H2O

ATP synthase

Protein complex; molecular motor

Protons enter, causes motor to spin, creates ATP

Composed of many alpha helices

Chem (potential) energy stored in molecules

Relocation of electrons released energy stored in organic molecules

Electrons transferred from one molecule to another

After each transfer, electrons at a lower energy state

Energy released at each step, used to make ATP

Last electron transfer is to oxygen, forming water

Outer membrane, inner membrane, membranous space (like mitochondria)

Thylakoids: membrane stacks, where the light rxns of photosynthesis occur

Sunlight comes in, H2O comes in, O2 is made

Generates ATP & NADPH, whi h feeds into calvin cycle

Main pigment molecule

Absorbs physical light

First step in the two photosystems

1) photon of light excites electron in pigment molecule. when electron falls back into ground state, energy gets transferred from one pigment molecule to the next.

2) energy eventually gets transferred to a special pair of chlorophyll molecules in the middle. electrons are bumped to a specialized primary electron acceptor molecule

3) electrons are passed on to the electron transport chain

4) electron hole left behind is replenished by pulling electrons from H2O, leaving behind O2 (chlorophyll molecules are strong electron acceptors)

Second step in the two photosystems

Same as photosystem II, but electron hole is refilled by electrons from the electron transport chain

DNA wrapped protein, made up of chromatin

Cell waits in g0 until they get the go-ahead

Cell checks the Stop and Go signals

Cell checks the Stop and Go signals

without full chromosome attachment, stop signal is received

a bunch of microtubules that set up a structure that allows chromosomes to align on them and be pulled apart evenly. chromosomes become condensed, gather toward center

mitosis spindles attach to sister chromatids

Imaginary metaphase plate at middle of the cell where sister chromatids align exactly in a row

Sister chromatids get pulled apart, daughter chromosomes go to either side

Cytoplasm gets indentation (result of microfilaments and other cytoskeletal filaments)

Two nuclei reform with exactly the same complement in both of them

A factor present in the cytoplasm of the S phase or the M phase controls the progression of the cell cycle

chemical factors that will promote cell growth (e.g. platelet-derived growth factor PDGF gives cell the go signal so cells divide)

Anchorage-dependence: need to be attached to a surface to grow

Density-dependent inhibition: when a cell come into contact with other cells, it stops division, forming a monolayer of cells

Cancer cells escape cell cycle controls

Cancer cells divide rapidly, often in absence of growth factors (RAS protein: activating "go" signals)

Growth uninhibited by other cells, tumors form (benign tumors remain at original site, malignant tumors spread to other locations by metastasis)

tumor suppressor; when mutated, doesn't read stop signals