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Notes - Chapter 5 - PPT

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Christopher Luther

on 12 November 2012

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Transcript of Notes - Chapter 5 - PPT

Receptor mediated Endocytosis Plasmolysis Chloroplasts carry out photosynthesis
Using solar energy to produce glucose and oxygen from carbon dioxide and water
Mitochondria consume oxygen in cellular respiration
Using the energy stored in glucose to make ATP 5.21 Chloroplasts and mitochondria make energy available for cellular work
Enzymes are central to the processes that make energy available to the cell Cholesterol Vesicle Plasma membrane Receptor protein Cytoplasm Phospholipid outer layer Protein LDL particle Figure 5.20 A cell using receptor-mediated endocytosis to take up an LDL Receptor Proteins 5.20 Faulty membranes can overload the blood with cholesterol
Harmful levels of cholesterol
Can accumulate in the blood if membranes lack cholesterol receptors CONNECTION LM 230 TEM 96,500 TEM 54,000 Plasma membrane Cytoplasm PIT Material bound to receptor proteins Receptor-mediated endocytosis Pinocytosis Phagocytosis Food being ingested Pseudopodium of amoeba Figure 5.19C Three kinds of endocytosis Pinocytosis Phagocytosis Endocytosis Endocytosis can occur in three ways
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis Vesicle forming Figure 5.19B Endocytosis Vesicle Protein Cytoplasm Fluid outside cell Figure 5.19A Exocytosis 5.19 Exocytosis and endocytosis transport large molecules
To move large molecules or particles through a membrane
A vesicle may fuse with the membrane and expel its contents (exocytosis) Intro to Endocytosis & Exocytosis Active Transport 5.18 Cells expend energy for active transport
Transport proteins can move solutes against a concentration gradient
Through active transport, which requires ATP The control of water balance
Is called osmoregulation
5.17 Turgid Elodea 5.17 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 Net flow of water Solute molecule with
cluster of water molecules Water molecule Selectively permeable membrane Solute molecule H2O Equal concentration of solute Higher concentration of solute Lower concentration of solute Figure 5.16 Osmosis Osmosis 5.16 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 Transport protein Solute molecule Figure 5.15 Transport protein providing a pore for solute passage 5.15 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 Small nonpolar molecules such as O2 and CO2
Diffuse easily across the phospholipid bilayer of a membrane Molecules of dye Membrane Equilibrium Figure 5.14A Passive transport of one type of molecule Diffusion 5.14 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 ATP Figure 5.13C Transport ATP Figure 5.13C Membrane proteins also function in transport
Moving substances across the membrane Activated molecule Receptor Messenger molecule Figure 5.13B Signal transduction Activated molecule Receptor Messenger molecule Figure 5.13B Other membrane proteins
Function as receptors for chemical messages from other cells Figure 5.13A Enzyme activity 5.13 Proteins make the membrane a mosaic of function
Many membrane proteins
Function as enzymes Figure 5.12 The plasma membrane and extracellular matrix of an animal cell Cytoplasm Glycolipid Plasma membrane Proteins Cholesterol Phospholipid Microfilaments of cytoskeleton Glycoprotein Carbohydrate (of glycoprotein) Fibers of the extracellular matrix 5.12 The membrane is a fluid mosaic of phospholipids and proteins
A membrane is a fluid mosaic
With proteins and other molecules embedded in a phospholipid bilayer Phospholipids form a two-layer sheet
Called a phospholipid bilayer, with the heads facing outward and the tails facing inward TEM 200,000X Outside of cell Cytoplasm Figure 5.10 Plasma membrane in cross section TEM 200,000  Outside of cell Cytoplasm Figure 5.10 The plasma membrane of the cell is selectively permeable
Controlling the flow of substances into or out of the cell Membrane Structure 5.9 Many poisons, pesticides, and drugs are enzyme inhibitors CONNECTION Competitive inhibitor Noncompetitive inhibitor Enzyme inhibition Normal binding of substrate Active site Enzyme Substrate Figure 5.8 How inhibitors interfere with substrate binding A competitive inhibitor
Takes the place of a substrate in the active site
A noncompetitive inhibitor
Alters an enzyme’s function by changing its shape 5.8 Enzyme inhibitors block enzyme action
Inhibitors interfere with an enzyme’s activity 5.7 The cellular environment affects enzyme activity
Temperature, salt concentration, and pH influence enzyme activity
Some enzymes require nonprotein cofactors
Such as metal ions or organic molecules called coenzymes H2O Substrate (sucrose) Active site Substrate is converted to products Products are released Fructose Glucose Enzyme (sucrase) Substrate binds to enzyme with induced fit Enzyme available with empty active site 2 3 4 1 Figure 5.6 The catalytic cycle of an enzyme The catalytic cycle of an enzyme 5.6 A specific enzyme catalyzes each cellular reaction
Enzymes have unique three-dimensional shapes
That determine which chemical reactions occur in a cell Progress of the reaction Energy Products Net change in energy EA with enzyme EA without enzyme Reactants Figure 5.5B The effect of an enzyme on EA A protein catalyst called an enzyme
Can decrease the energy of activation needed to begin a reaction Enzyme 2 1 Products Reactants EA barrier Figure 5.5A For a chemical reaction to begin
Reactants must absorb some energy, called the energy of activation 5.5 Enzymes speed up the cell’s chemical reactions by lowering energy barriers HOW ENZYMES FUNCTION How Enzymes Work Cellular work can be sustained
Because ATP is a renewable resource that cells regenerate 0 ATP drives endergonic reactions by phosphorylation
Transferring a phosphate group to make molecules more reactive 0 5.4 ATP shuttles chemical energy and drives cellular work
ATP powers nearly all forms of cellular work Cells carry out thousands of chemical reactions
The sum of which constitutes cellular metabolism
Energy coupling
Uses exergonic reactions to fuel endergonic reactions Potential energy of molecules Amount of energy released Products Energy released Reactants Figure 5.3B Exergonic reaction Exergonic reactions
Release energy and yield products that contain less potential energy than their reactants 5.3 Chemical reactions either store or release energy
Endergonic reactions
Absorb energy and yield products rich in potential energy Energy for cellular work + Carbon dioxide water Oxygen + Glucose ATP ATP Chemical reactions Heat Figure 5.2B Energy transformations in a cell The Second Law of Thermodynamics
The second law of thermodynamics
States that energy transformations increase disorder or entropy, and some energy is lost as heat Figure 5.2A The First Law of Thermodynamics
According to the first law of thermodynamics
Energy can be changed from one form to another
Energy cannot be created or destroyed 5.2 Two laws govern energy transformations
Thermodynamics
Is the study of energy transformations Figure 5.1C Potential energy being converted
to kinetic energy Figure 5.1B Potential energy Figure 5.1A Kinetic energy Kinetic energy is the energy of motion
Potential energy is stored energy
And can be converted to kinetic energy 5.1 Energy is the capacity to perform work
All organisms require energy
Which is defined as the capacity to do work ENERGY AND THE CELL A female firefly devouring a male of another species Unnumbered Figure p.71 Females of some species
Produce a light pattern that attracts males of other species, which are then eaten by the female Cool “Fires” Attract Mates and Meals
Fireflies use light to send signals to potential mates
Instead of using chemical signals like most other insects 0 The Working Cell Chapter 5 Energy from exergonic reactions P ADP  Energy for endergonic reactions ATP ATP cycle Unnumbered Figure page 86 Hypertonic solution Hypotonic solution Isotonic solution (6) Shriveled (plasmolyzed) (5) Turgid (4) Flaccid (3) Shriveled (2) Lysed (1) Normal Plasma membrane H2O H2O H2O H2O H2O H2O H2O H2O Plant cell Animal cell Figure 5.17 How animal and plant cells behave in different solutions Equilibrium Figure 5.14B Passive transport of two types of molecules Hydrophobic tails Hydrophilic heads Water Water Figure 5.11B Phospholipid bilayer 5.10 Membranes organize the chemical activities of cells
Membranes
Provide structural order for metabolism MEMBRANE STRUCTURE AND FUNCTION Enzyme 2 1 Products Reactants EA barrier Figure 5.5A Jumping-bean analogy for energy of activation (EA) and the role of enzymes Hydrolysis Phosphorylation Energy from exergonic reactions Energy for endergonic reactions P + ADP ATP Figure 5.4C The ATP cycle Figure 5.4B How ATP powers cellular work + Solute Membrane protein Motor protein Reactants Product + ADP Solute transported Protein moved Molecule formed P P P P P P P Transport work Mechanical work Chemical work ATP 0 Figure 5.4A ADP + + Adenosine Triphosphate Adenosine diphosphate H2O Ribose Adenine Hydrolysis P P P P P P Energy ATP Phosphate groups The energy in an ATP molecule
Lies in the bonds between its phosphate groups Amount of energy required Products Energy required Reactants Potential energy of molecules Figure 5.3A Endergonic reaction Figure 5.2A Energy lost as heat during the conversion of chemical energy to kinetic energy The light comes from a set of chemical reactions
That occur in light-producing organs at the rear of the insect Vesicle forming Figure 5.19B Membranes may fold inward
Enclosing material from the outside (endocytosis) Transport protein Solute ADP ATP Phosphate detaches Protein changes shape P P P 4 3 2 1 Protein reversion Transport Phosphorylation Solute binding Figure 5.18 Active transport of a solute across a membrane ADP + + Adenosine Triphosphate Adenosine diphosphate H2O Ribose Adenine Hydrolysis P P P P P P Energy ATP Phosphate groups Figure 5.4A ATP structure and hydrolysis Hydrophobic tails Hydrophilic head Symbol Phosphate group O O O C O C CH2 CH CH2 O P O– O O + N CH3 CH3 CH3 CH2 CH2 CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 Figure 5.11A 5.11 Membrane phospholipids form a bilayer
Phospholipids
Have a hydrophilic head and two hydrophobic tails
Are the main structural components of membranes Hydrophobic tails Hydrophilic head Symbol Phosphate group O O O C O C CH2 CH CH2 O P O– O O + N CH3 CH3 CH3 CH2 CH2 CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 Figure 5.11A Phospholipid molecule
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