Resp & Cell Comm Review

Two main catabolic processes: fermentation: partial degradation of sugars in the absence of oxygen. cellular respiration: uses oxygen to complete the breakdown of many organic molecules. more efficient and widespread Most steps occur in mitochondria. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Introduction Photosynthetic organisms store energy in organic molecules. These are available to themselves, and others that eat them. Fig. 9.1 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

2. Cells recycle the ATP they use for work ATP (adenosine triphosphate): chemical equivalent of a loaded spring. trio of PO - 4 groups are unstable, high-energy. ATP ADP + PO 4 powers most cellular work ATP must be constantly recycled from ADP and PO 4 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

What s different in the electron sharing of the reactants vs. the products? Where does this energy come from? Which atoms got oxidized/reduced? Fig. 9.3 high energy e - positions low energy e - positions Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

glycolysis, the Krebs cycle, the electron transport chain, and chemiosmosis via ATP synthase & H + gradient.

substrate-level phosphorylation generates the few ATP s produced in glycolysis and the Krebs cycle. How is this different from oxidative phosphorylation? no e - transport chain. Fig. 9.7 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

energy investment phase: 2 ATP create reactants with high free energy by phosphorylating glucose. energy payoff phase: 4 ATP via substratelevel phosphorylation NAD + is reduced to NADH. Net Production? 2 ATP + 2 NADH 2 pyruvate NOT used? O 2 Fig. 9.8 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings BIG PICTURE

For each Acetyl CoA that goes in... Lots of high energy electron carriers are produced Know THIS one! Net of 2 NADH 1 FADH 2 Also produced? one ATP Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 9.12

electron transport chain: Thousands of copies in the cristae of each mitochondrion. Most parts are proteins that accept electrons, then pass them along. Electrons drop in free energy as they pass down the chain. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

ATP synthase in the cristae makes ATP from ADP & P i. osmos to push chemiosmosis*: using a chemical s push Push of H + gradient powers ATP synthase http://www.youtube.com/watch?v=xbj0nbzt5kw start at 40 seconds, watch next 3:10 http://www.youtube.com/watch?v=ffbr3anckb4 5 min of Ninja Respiration fun! * vs. substrate level phosphorylation Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 9.14

lactic acid fermentation: Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt. Muscle cells switch from aerobic respiration to lactic acid fermentation to generate ATP if O 2 is scarce. lactate is converted back to pyruvate in the liver. Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 9.17b

Some organisms (facultative anaerobes), including yeast and many bacteria, can survive using either fermentation or respiration. human muscle cells too. Fig. 9.18 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings

ex: phosphofructokinase catalizes 3 rd glycolysis step high ATP levels enzyme inhibition high ADP/AMP levels enzyme activation. inhibition by citrate slows glycolysis until Krebs cycle catches up. Fig. 9.20

Chapter 11 Cell Communication PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Evolution of Cell Signaling Yeast cells Identify their mates by cell signaling 1 2 Exchange of mating factors. Each cell type secretes a mating factor that binds to receptors on the other cell type. Mating. Binding of the factors to receptors induces changes in the cells that lead to their fusion. Receptor a Yeast cell, mating type a a factor factor Yeast cell, mating type Figure 11.2 3 New a/ cell. The nucleus of the fused cell includes all the genes from the a and a cells. a/ Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

In local signaling, animal cells May communicate via direct contact Figure 11.3 (b) Cell-cell recognition. Two cells in an animal may communicate by interaction between molecules protruding from their surfaces. Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

In other cases, animal cells Communicate using local regulators Local signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter Secretory vesicle Neurotransmitter diffuses across synapse Local regulator diffuses through extracellular fluid (a) Paracrine signaling. Target cell is stimulated (b) Synaptic signaling Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

In long-distance signaling Both plants and animals use hormones Long-distance signaling Endocrine cell Blood vessel Why do only certain cells respond? Hormone travels in bloodstream to target cells Target cell Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.4 C (c) Hormonal signaling. Specialized endocrine cells secrete hormones into body fluids, often the blood. Hormones may reach virtually all body cells.

Overview of cell signaling EXTRACELLULAR FLUID Plasma membrane CYTOPLASM 1 Reception 2 Transduction 3 Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Signal molecule Figure 11.5 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

G-protein-linked receptors Signal-binding site Some good animations Segment that interacts with G proteins G-protein-linked Receptor Plasma Membrane Activated Receptor Signal molecule Inactive enzyme CYTOPLASM GDP G-protein (inactive) Enzyme GDP GTP Activated enzyme GTP GDP P i Figure 11.7 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular response

Receptor tyrosine kinases what s happening? Signal molecule Helix in the Membrane Signal-binding sitea Signal molecule osines CYTOPLASM Receptor tyrosine kinase proteins (inactive monomers) Dimer Activated relay proteins 6 ATP 6 ADP P P P P P P P P P P P P Cellular response 1 Cellular response 2 Figure 11.7 Activated tyrosinekinase regions (unphosphorylated dimer) Fully activated receptor tyrosine-kinase (phosphorylated dimer) Inactive relay proteins Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Ion channel receptors Signal molecule (ligand) Gate closed Ions critical in nerve cells Ligand-gated ion channel receptor Plasma Membrane Gate open Cellular response Gate close Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.7

A phosphorylation cascade Signal molecule Receptor Activated relay molecule 1 A relay molecule activates protein kinase 1. Figure 11.8 Inactive protein kinase 1 5 Inactive protein kinase 2 Enzymes called protein phosphatases (PP) catalyze the removal of the phosphate groups from the proteins, making them inactive and available for reuse. Active protein kinase 1 Inactive protein kinase 3 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings P i ATP PP ADP P i ATP Active protein kinase 2 PP ADP Inactive protein 2 Active protein kinase 1 transfers a phosphate from ATP to an inactive molecule of protein kinase 2, thus activating this second kinase. P i P ATP PP 3 Active protein kinase 3 Active protein kinase 2 then catalyzes the phosphorylation (and activation) of protein kinase 3. ADP P 4 Finally, active protein kinase 3 phosphorylates a protein (pink) that brings about the cell s response to the signal. Active protein P Cellular response

2 nd Messenger is a general term, it may actually be applied to a 3 rd or 4 th messenger. 1 A signal molecule binds to a receptor, leading to activation of phospholipase C. EXTRA- CELLULAR FLUID 2 Signal molecule (first messenger) G-protein-linked receptor IP 3 -gated calcium channel Phospholipase C cleaves a plasma membrane phospholipid called PIP 2 into DAG and IP 3. G protein GTP Phospholipase C 3 DAG functions as a second messenger in other pathways. PIP 2 DAG IP 3 (second messenger) Endoplasmic reticulum (ER) Ca 2+ Ca 2+ (second messenger) Various proteins activated Cellular response Figure 11.12 4 IP 3 quickly diffuses through 5 Calcium ions flow out of 6 The calcium ions the cytosol and binds to an IP 3 gated calcium channel in the ER membrane, causing it to open. the ER (down their concentration gradient), raising the Ca 2+ level in the cytosol. activate the next protein in one or more signaling pathways. Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Reception Amplification of a transduced signal: Binding of epinephrine to G-protein-linked receptor (1 molecule) Transduction Inactive G protein Active G protein (10 2 molecules) Inactive adenylyl cyclase Active adenylyl cyclase (10 2 ) ATP Cyclic AMP (10 4 ) Inactive protein kinase A Active protein kinase A (10 4 ) Inactive phosphorylase kinase Active phosphorylase kinase (10 5 ) Inactive glycogen phosphorylase Active glycogen phosphorylase (10 6 ) Figure 11.13 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Response Glycogen Glucose-1-phosphate (10 8 molecules)

Growth factor Receptor Reception Many pathways regulate genes by activating transcription factors that turn genes on or off CYTOPLASM Inactive transcription factor Phosphorylation cascade Active transcription factor P Transduction Response DNA Gene NUCLEUS Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings mrna

Branching and cross-talk further help the cell coordinate incoming signals Signal molecule Receptor Response 1 Relay molecules Response Response Cell A. Pathway leads to a single response Cell B. Pathway branches, leading to two responses 2 3 Cell C. Cross-talk occurs between two pathways Activation or inhibition Response 4 Response 5 Cell D. Different receptor leads to a different response Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Signaling Efficiency: Scaffolding Proteins and Signaling Complexes Scaffolding proteins Can increase the signal transduction efficiency Signal molecule Plasma membrane Receptor Scaffolding protein Three different protein kinases Figure 11.16 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings