Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Happy Friday! 5/7/2010...

Happy Friday! 5/7/2010Outline how monosaccharides are converted into polysaccharides. 2 marks

condensation;involves the removal of water to join monosaccharides together / equation to show this;catalysed by enzymes;consists of many monosaccharides linked (glycosidic) to make polysaccharide;

PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon

Lectures by Chris Romero

Chapter 5Chapter 5

The Working Cell

HOW ENZYMES FUNCTION

5.5 Enzymes speed up the cell’s chemical reactions by lowering energy barriers

http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/assets/interactivemedia/activityshared/ActivityLoader.html?c6e&06&04&5D%20How%20Enzymes%20Function

• For a chemical reaction to begin

– Reactants must absorb some energy, called the energy of activation

Figure 5.5A

EA barrier

Reactants

Products1 2E

• protein catalyst = enzyme

– Can decrease activation energy needed to begin reaction

Figure 5.5B

Reactants

EA withoutenzyme

EA withenzyme

Net changein energy

Products

Progress of the reaction

5.6 A specific enzyme catalyzes each cellular reaction

• Enzymes have unique 3-D shapes

– determine which chem reactions occur in a cell

Figure 5.6

Enzyme(sucrase)Glucose

Fructose

Active site Substrate(sucrose)

1 Enzyme availablewith empty activesite

2 Substrate binds to enzyme with induced fit

4 Products arereleased

3 Substrate is converted to products

• The catalytic cycle of an enzyme

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

5.8 Enzyme inhibitors block enzyme action

• Inhibitors interfere with an enzyme’s activity

• 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

Figure 5.8

Substrate

Enzyme

Active site

Normal binding of substrate

Enzyme inhibition

Noncompetitiveinhibitor

Competitiveinhibitor

CONNECTION

5.9 Many poisons, pesticides, and drugs are enzyme inhibitors

Cool “Fires” Attract Mates and Meals

• Fireflies use light to send signals to potential mates

– Instead of using chemical signals like most other insects

• light comes from a set of chemical reactions

– occur in light-producing organs at rear of insect

• Females of some species

– Produce a light pattern that attracts males of other species, which are then eaten by the female

ENERGY AND THE CELL

5.1 Energy is the capacity to perform work

• All organisms require energy

– Which is defined as the capacity to do work

• Kinetic energy is the energy of motion

• Potential energy is stored energy

– And can be converted to kinetic energy

Figure 5.1A–C

5.2 Two laws govern energy transformations

• Thermodynamics

– Is the study of energy transformations

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

Figure 5.2A

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 5.2B

Chemical reactions

ATP ATP

Glucose

Oxygen

Carbon dioxide

Energy for cellular work

5.3 Chemical reactions either store or release energy

• Endergonic reactions

– Absorb energy and yield products rich in potential energy

Figure 5.3A

Reactants

Energy required

Products

Amount of energy

required

• Exergonic reactions

– Release energy and yield products that contain less potential energy than their reactants

Figure 5.3B

Reactants

Energy released

Products

Amount of energy

released

tial e

• Cells carry out thousands of chemical reactions

– The sum of which constitutes cellular metabolism

• Energy coupling

– Uses exergonic reactions to fuel endergonic reactions

5.4 ATP shuttles chemical energy and drives cellular work

• ATP powers nearly all forms of cellular work

• The energy in an ATP molecule

– Lies in the bonds between its phosphate groups

Phosphategroups

EnergyP P PP P PHydrolysis

Adenine

Ribose

Adenosine diphosphateAdenosine Triphosphate

Figure 5.4A

• ATP drives endergonic reactions by phosphorylation

– Transferring a phosphate group to make molecules more reactive

Figure 5.4B

Chemical work Mechanical work Transport work

Molecule formed Protein moved Solute transported

Product

Reactants

Motorprotein

Membraneprotein Solute

ADP + P

Energy forendergonicreactions

Energy fromexergonicreactions

Hydrolysis

• Cellular work can be sustained

– Because ATP is a renewable resource that cells regenerate

Figure 5.4C

MEMBRANE STRUCTURE AND FUNCTION

5.10 Membranes organize the chemical activities of cells

• Membranes

– Provide structural order for metabolism

• The plasma membrane of the cell is selectively permeable

– Controlling the flow of substances into or out of the cell

Figure 5.10

Cytoplasm

Outside of cell

5.11 Membrane phospholipids form a bilayer

• Phospholipids

– Have a hydrophilic head and two hydrophobic tails

– Are the main structural components of membranes

Figure 5.11A

O O–P

CH2CHCH2

C O C O

Phosphategroup

Symbol

Hydrophilic head

Hydrophobic tails

• Phospholipids form a two-layer sheet

– Called a phospholipid bilayer, with the heads facing outward and the tails facing inward

Figure 5.11B

Hydrophilicheads

Hydrophobictails

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

Figure 5.12

Fibers of the extracellular matrix Carbohydrate

(of glycoprotein)

Glycoprotein

Microfilamentsof cytoskeleton

Phospholipid

CholesterolProteins

Plasmamembrane

Glycolipid

Cytoplasm

5.13 Proteins make the membrane a mosaic of function

• Many membrane proteins

– Function as enzymes

Figure 5.13A

• Other membrane proteins

– Function as receptors for chemical messages from other cells

Figure 5.13B

Messenger molecule

Receptor

Activatedmolecule

• Membrane proteins also function in transport

– Moving substances across the membrane

Figure 5.13C

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

EquilibriumMembraneMolecules of dye

Equilibrium

Figure 5.14B

Figure 5.14A

• Small nonpolar molecules such as O2 and CO2

– Diffuse easily across the phospholipid bilayer of a membrane

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

Figure 5.15

Solutemolecule

Transportprotein

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

Figure 5.16

Lowerconcentration

of solute

Higherconcentration

of solute

Equalconcentration

of solute

H2OSolutemolecule

Selectivelypermeablemembrane

Watermolecule

Solute molecule withcluster of water molecules

Net flow of water

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

Figure 5.17

Plantcell

H2O H2O

H2OPlasma

membrane

(1) Normal (2) Lysed (3) Shriveled

(4) Flaccid (5) Turgid(6) Shriveled (plasmolyzed)

Isotonic solution Hypotonic solution Hypertonic solution

Animalcell

• The control of water balance

– Is called osmoregulation

PP PProtein

changes shapePhosphatedetaches

ATPADPSolute

Transportprotein

Solute binding1 Phosphorylation2 Transport3 Protein reversion4

5.18 Cells expend energy for active transport

• Transport proteins can move solutes against a concentration gradient

– Through active transport, which requires ATP

Figure 5.18

Fluid outside cell

Cytoplasm

Protein

Vesicle

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)

Figure 5.19A

• Membranes may fold inward

– Enclosing material from the outside (endocytosis)

Figure 5.19B

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

Cytoplasm

Plasma membrane

Figure 5.19C

CONNECTION

5.20 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

CytoplasmReceptorprotein

Plasmamembrane

Vesicle

Cholesterol

Figure 5.20

5.21 Chloroplasts and mitochondria make energy available for cellular work

• Enzymes are central to the processes that make energy available to the cell

• 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

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Happy Friday! 5/7/2010...

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