CELLULAR RESPIRATION Both photosynthesis and cellular respiration provide energy for metabolism = life’s processes Photosynthesis traps sunlight energy and converts it to energy in chemical bonds of sugar Cellular respiration makes ATP for the organism by breaking apart the chemical bonds of sugar The “big picture” ---

Photosynthesis uses solar energy In an Ecosystem: CO2 H2O Glucose O2 ATP ECOSYSTEM Sunlight energy Photosynthesis in chloroplasts Cellular respiration in mitochondria (for cellular work) Heat energy + Photosynthesis uses solar energy To produce glucose and O2 from CO2 and H2O Cellular respiration uses glucose to make ATP Produces CO2 and H2O from glucose and O2

Cells trap energy in ATP – ADP + Pi  ATP by two (2) different processes: 1. By directly coupling ATP synthesis to a specific exergonic reaction “Substrate-level phosphorylation” By indirectly coupling ATP synthesis to exergonic reactions “Oxidative Phosphorylation” “Chemiosmosis” “Electron-transport Pathway” - Trap energy from breaking bonds in glucose - High-energy electrons carried by NADH & FADH2 - Energy transferred to ATP synthesis enzyme on a membrane

Organic molecule (substrate) 1. ATP made by substrate-level phosphorylation A phosphate group is directly transferred from an organic molecule to ADP Directly couple an exergonic reaction to the endergonic reaction than makes ATP, all on an enzyme Enzyme Adenosine Organic molecule (substrate) ADP ATP P

2. ATP made by Oxidative Phosphorylation / Chemiosmosis Uses diffusion of a H+ across a membrane to provide energy for the synthesis of ATP So – Let’s take a look at how membranes transport substances to see how this works:

MEMBRANE STRUCTURE AND FUNCTION Membranes organize and compartmentalize the chemical reactions in cells Membranes Provide structural order for metabolism Provide an efficient way for making ATP using energy from electrons in the chemical bonds of your food Use enzyme-like proteins and other organic chemicals for transporting substances across the membrane

Membrane Structure and Function © 2015 Pearson Education, Inc. 7

The plasma membrane of the cell is selectively permeable Controlling the flow of substances into or out of the cell Cytoplasm Outside of cell TEM 200,000 

VISUALIZING THE CONCEPT: Membranes are fluid mosaics of lipids and proteins with many functions Biologists use the fluid mosaic model to describe a membrane’s structure, a patchwork of diverse protein molecules embedded in a phospholipid bilayer. The plasma membrane exhibits selective permeability. The proteins embedded in a membrane’s phospholipid bilayer perform various functions. Teaching Tips You might wish to share a very simple analogy that seems to work well for some students. A cell membrane is a little like a peanut butter and jelly sandwich with jelly beans poked into it. The bread represents the hydrophilic portions of the bilayer (and bread does indeed quickly absorb water). The peanut butter and jelly represent the hydrophobic regions (and peanut butter, containing plenty of oil, is generally hydrophobic). The jelly beans stuck into the sandwich represent proteins variously embedded partially into or completely through the membrane. Transport proteins would be like the jelly beans that poke completely through the sandwich. Analogies are rarely perfect. Challenge your students to critique this analogy by finding exceptions. (For example, this analogy does not include a model of the carbohydrates on the cell surface.) © 2015 Pearson Education, Inc. 9

The membrane is a fluid mosaic of phospholipids and proteins proteins and other molecules embedded in a phospholipid bilayer Fibers of the extracellular matrix Carbohydrate (of glycoprotein) Glycoprotein Microfilaments of cytoskeleton Phospholipid Cholesterol Proteins Plasma membrane Glycolipid Cytoplasm

Membrane phospholipids form a bilayer Have a hydrophilic head and two hydrophobic tails Are the main structural components of membranes CH2 CH3 CH N + O O– P C Phosphate group Symbol Hydrophilic head Hydrophobic tails

Phospholipids in water form a two-layer sheet Called a phospholipid bilayer, with the heads facing outward and the tails facing inward Water Hydrophilic heads Hydrophobic tails

Small nonpolar molecules such as O2 and CO2 and even ethanol and some organic solvents – Diffuse easily across the phospholipid bilayer of a membrane Water can’t “grab onto” small molecules that don’t have a charge, so they can move into the fatty acid chains in the middle of the membrane These molecules always cross cell membranes

Passive transport is diffusion across a membrane In passive transport, substances diffuse through membranes without work by the cell Spreading from areas of high concentration to areas of low concentration Equilibrium Membrane Molecules of dye

Transport proteins may facilitate diffusion across membranes Many kinds of molecules do not diffuse freely across membranes For these molecules, transport proteins provide passage across membranes through a process called facilitated diffusion Solute molecule Transport protein

Osmosis is the diffusion of water across a membrane In osmosis, water travels from a solution of lower solute concentration to one of higher solute concentration Lower concentration of solute Higher concentration of solute Equal concentration of solute H2O Solute molecule Selectively permeable membrane Water molecule Solute molecule with cluster of water molecules Net flow of water

The control of water balance in organisms Is called osmoregulation Some definitions: solute = chemical dissolved in a solvent solvent = chemical that dissolves a solute solution = a solute dissolved in a solvent hypotonic = less concentrated solution hypertonic = more concentrated solution isotonic = two solutions of equal concentrations

Water balance between cells and their surroundings is crucial to organisms Osmosis causes cells to shrink in hypertonic solutions and swell in hypotonic solutions In isotonic solutions, animal cells are normal, but plant cells are limp Plant cell H2O Plasma membrane (1) Normal (2) Lysed (3) Shriveled (4) Flaccid (5) Turgid (6) Shriveled (plasmolyzed) Isotonic solution Hypotonic solution Hypertonic solution Animal cell

The membrane is a “fluid mosaic” of phospholipids and proteins proteins and other molecules embedded in a liquid phospholipid bilayer Fibers of the extracellular matrix Carbohydrate (of glycoprotein) Glycoprotein Microfilaments of cytoskeleton Phospholipid Cholesterol Proteins Plasma membrane Glycolipid Cytoplasm

Proteins give the membrane a great variety of functions Many membrane proteins function as enzymes

Other membrane proteins Function as receptors for chemical messages from other cells Messenger molecule Receptor Activated molecule

Membrane proteins also function in transport Moving substances across the membrane ATP Active Transport Requires energy Concentrates a chemical Runs diffusion in reverse Passive Transport Requires no energy input Relies on diffusion “Facilitated” Uses proteins

Cells expend energy for active transport Transport proteins can move solutes against a concentration gradient that needs ATP “Pumps” = pump a chemical across a membrane P Protein changes shape Phosphate detaches ATP ADP Solute Transport protein Solute binding 1 Phosphorylation 2 Transport 3 Protein reversion 4

Active Transport - “Bulk” transport Exocytosis and endocytosis transport large molecules and/or large amounts of molecules To move large molecules or particles through a membrane, a vesicle may fuse with the membrane and expel its contents (exocytosis) Fluid outside cell Cytoplasm Protein Vesicle

Membranes may fold inward, enclosing material from the outside (endocytosis) Vesicle forming

Endocytosis can occur in three ways Phagocytosis Pinocytosis Receptor-mediated endocytosis Pseudopodium of amoeba Food being ingested Phagocytosis Pinocytosis Receptor-mediated endocytosis Material bound to receptor proteins PIT Cytoplasm Plasma membrane TEM 54,000 TEM 96,500  LM 230

CONNECTION Faulty membranes can overload the blood with cholesterol Harmful levels of cholesterol can accumulate in the blood if membranes lack cholesterol receptors LDL particle Protein Phospholipid outer layer Cytoplasm Receptor protein Plasma membrane Vesicle Cholesterol

Review: Proteins make the membrane a mosaic of function Many membrane proteins function as enzymes Membrane proteins also function in transporting substances across the membrane ATP

Membranes are Selectively Permeable The membranes that form the plasma (cell) membrane And organelles like ER, nucleus, Golgi body, lysosome Are BARRIERS to certain chemicals and molecules They won’t let solutions on opposite sides of the membrane mix together – So -

So, why you need to know about membranes: The most efficient mechanism to make ATP is Chemiosmosis, or the Electron transport pathway, or Oxidative phosphorylation ----- Terms for the same process ----- Takes place on the inner mitochondrial membrane & depends on the diffusion of H+ across that membrane

Electron transport chain Electron Transport Pathway H2O NAD+ NADH ATP H+ Controlled release of energy for synthesis of ATP Electron transport chain 2 O2 2e + 1

In oxidative phosphorylation, the mitochondrion – transfers energy in electrons removed from the chemical bonds in your food, and uses that energy to concentrate H+ on one side of a membrane. Then the H+ diffuses across the membrane through a protein channel next to an enzyme that makes high energy bonds of ATP.

Then, diffusion & phosphorylation of ADP Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron flow Electron carrier NADH NAD+ FADH2 FAD H2O ATP ADP ATP synthase H+ + P O2 Electron Transport Chain Chemiosmosis . OXIDATIVE PHOSPHORYLATION + 2 1 2