HewittLyonsSuchockiYeh Conceptual Integrated Science Chapter 15 THE BASIC

This lecture will help you understand: • • • • Characteristics of Life Macromolecules Needed for Life Cell types Tour of a Eukaryotic Cell Membrane Structure and Function Transport Mechanisms: Diffusion, Facilitated Diffusion, Active Transport, Endocytosis, Exocytosis Cellular Communication How Cells Reproduce How Cells Use Energy Chemical Reactions in Cells Photosynthesis Cellular Respiration: Glycolysis, Krebs Cycle, Electron Transport, Fermentation Life Span of Cells History of Science: Cell Theory Math Connection: Diffusion Science and Society: Stem Cells Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Characteristics of Life All living things • use energy • develop and grow • maintain themselves • can reproduce • are part of evolving populations Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Characteristics of Life All living things use energy. • Plants use electromagnetic energy from sunlight. • Animals convert food energy from plants or other animals into chemical energy. • How living things use energy is consistent with the laws of physics. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Characteristics of Life All living things develop and grow, changing over time. Living things also maintain themselves. • They build structures (bones, stems). • They repair damage (immune system). • They maintain an internal environment that is consistent (body temperature, ion balance). Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Characteristics of Life All living things are capable of reproducing. • Asexual reproduction occurs when an organism reproduces by itself. • Sexual reproduction occurs when organisms produce sperm and eggs that join to form new individuals. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Characteristics of Life All living things are part of populations that evolve. • Populations do not remain constant. • Populations change over time, across generations. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

• • Macromolecules Needed for Life Proteins Carbohydrates Lipids Nucleic acids Copyright ©

Cell Types Prokaryotic cells have no nucleus. Prokaryotes are almost always single-celled microscopic organisms. Their DNA is found in a single circular chromosome. They usually have an outer cell wall. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cell Types Eukaryotic cells have a nucleus and may be single celled or multicellular. They • • contain their DNA inside the nucleus have linear chromosomes contain organelles are larger cells than prokaryotes Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Tour of a Eukaryotic Cell Eukaryotic cells contain many parts, including • cell membrane • nucleus • cytoplasm • cytoskeleton • organelles All of the parts of the cell have specific functions. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Tour of a Eukaryotic Cell Plant cells also contain • cell walls to make the cell rigid • chloroplasts that perform photosynthesis Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cell. Membrane Structure and Function The cell membrane • • defines the cell’s border. controls what travels into and out of the cell. functions in communicating with other cells. consists of a phospholipid bilayer, membrane proteins, and short carbohydrates. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cell. Membrane Structure and Function The fluid mosaic model describes the structure of the cell membrane, a mosaic of proteins and phospholipids, almost all of which can move fluidly around the membrane. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Transport Mechanisms Cells take in many materials, including water, oxygen, and organic molecules, and discard wastes such as carbon dioxide. Transport occurs through • • • Diffusion Facilitated diffusion Active transport Endocytosis Exocytosis Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Transport Mechanisms: Diffusion is the tendency of molecules to move from an area of high concentration to an area of low concentration. Diffusion results from the random motion of molecules and requires no energy. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Transport Mechanisms: Diffusion occurs most efficiently (that is, most rapidly and effectively) across small distances, large surface areas, and thin structures. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Transport Mechanisms: Facilitated Diffusion Facilitated diffusion occurs when carrier proteins bind to molecules and move them down a concentration gradient, to an area of lower concentration. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Transport Mechanisms: Active Transport Active transport moves molecules against a concentration gradient, in a direction they would not go without an input of energy. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Transport Mechanisms: Endocytosis Cells use endocytosis when they capture material in a section of cell membrane that pinches off to form a vesicle. This is how some white blood cells engulf invading bacteria. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Transport Mechanisms: Exocytosis In exocytosis, a vesicle fuses to the cell membrane and dumps its contents outside of the cell. The endocrine system releases some hormones into the bloodstream using exocytosis. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Communication Cells communicate with each other via molecular messengers. Communication between adjacent cells occurs in animals via gap junctions, which are like doorways between cells. In plants, plasmodesmata serve as the doorways. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Communication Long-distance communication relies on message molecules traveling through a medium such as the bloodstream. Like a key in a lock, the message molecule eventually finds the right receptor. The key fitting into the lock sets off a series of chemical reactions that cause the target cell’s response. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Communication Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Reproduce In mitosis, one parent cell divides into two daughter cells that have the same genetic information as the parent. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Reproduce Mitosis is part of the cell cycle. During the rest of the cell cycle, called interphase, the cell grows, copies its genetic material (DNA), and builds the machinery necessary for division. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Reproduce • In prophase, the chromosomes condense, and nuclear membranes break down. • In metaphase, the chromosomes line up along the equatorial plane. • During anaphase, the sister chromatids are pulled apart and move to opposite poles of the cell. • In telophase, new nuclear membranes form around each set of chromosomes. • After mitosis, the cytoplasm divides (cytokinesis), and cell division is complete. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Reproduce Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Use Energy • Energy-releasing reactions occur spontaneously. This is consistent with the laws of physics. • For all other reactions, cells rely on the energy of ATP to power them. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Use Energy Even energy-releasing reactions have an activation energy that is necessary for them to happen. A catalyst is a substance that lowers this activation energy, allowing a reaction to happen more quickly. The catalysts in cells are enzymes—large, complex proteins. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Use Energy An enzyme binds to a specific reactant at the active site and releases the products. In the process, the enzyme is not altered or destroyed; it can be used again and again. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Use Energy Cells control enzyme function by synthesizing and degrading enzymes as necessary. In addition, inhibitors can block the function of enzymes. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

How Cells Use Energy • In competitive inhibition, the inhibitor binds to the active site of an enzyme so that the enzyme cannot bind its substrate. • Noncompetitive inhibition occurs when an inhibitor binds to a different part of the enzyme, changing the active site so that the enzyme can no longer bind to its substrate. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Chemical Reactions in Cells • ATP is the energy currency of the cell. • In the ATP reaction, one phosphate group is removed, leaving ADP. Removing the phosphate group releases energy. • Organisms use some of the energy they take in through food to make more ATP. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Chemical Reactions in Cells The sodium-potassium pump uses active transport to control the levels of sodium ions (Na+) and potassium ions (K+) in cells. This process uses one molecule of ATP. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Photosynthesis • Is the process organisms use to convert light energy from the sun into chemical energy • Is conducted in the chloroplasts of plants • Occurs in two stages: the light-dependent reactions and the light-independent reactions • Is the ultimate source of all food on Earth Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Photosynthesis The light-dependent reactions of photosynthesis Copyright © 2007 Pearson Education, Inc. , publishing

Photosynthesis In the light-independent reactions: • The light-independent reactions use the stored energy from ATP and NADPH. • Carbon is fixed, moved from atmospheric CO 2 to the sugar glucose. • These materials are the basis for all of the macromolecules of life. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Respiration Cells break down glucose to produce ATP. This process is aerobic (uses oxygen). This process yields 38 molecules of ATP from every molecule of glucose. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Respiration Cellular respiration occurs in three steps: • Glycolysis • The Krebs cycle

Cellular Respiration: Glycolysis takes place in the cytoplasm of cells. The glucose molecule is split into two molecules of pyruvic acid, releasing two molecules of ATP. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Respiration: Krebs Cycle The Krebs cycle occurs in the cell’s mitochondria. In the Krebs cycle, pyruvic acid is converted to acetic acid and bound to a molecule of coenzyme A. The result—acetyl-Co. A—is broken down into CO 2. Two molecules of ATP are harvested. Additional energy is stored in the molecules NADH and FADH 2. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Respiration: Electron Transport • Electrons carried by NADH and FADH 2 are sent down electron transport chains. • In the process, the electrons lose energy, which is used to pump hydrogen ions across a membrane inside the mitochondria. • At the end of the chain, the electrons combine with O 2 to make water. • The concentration gradient generated by pumping hydrogen ions is used to make ATP. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Cellular Respiration: Fermentation In certain cells, under certain conditions, glycolysis is followed by fermentation. Fermentation uses no oxygen and generates no ATP. But, it regenerates the molecules necessary to keep glycolysis going, so cells can continue to obtain energy through glycolysis. Lactic acid fermentation occurs in muscle cells when there is not enough oxygen for cellular respiration to continue. Alcoholic fermentation by yeast is used to make beer and wine. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Life Span of Cells • Most eukaryotic cells can live for a certain number of cell divisions, not a specific length of time. • Telomeres, lengths of DNA at the ends of chromosomes, get shorter with every cell division. • Eventually, the cell can no longer divide without losing critical genetic information. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Life Span of Cells • Some cells contain a special enzyme— telomerase—that lengthens telomeres. • These cells can divide indefinitely. • Germ cells—those that produce eggs and sperm—contain telomerase and are immortal. • Some tumor cells also contain a lot of telomerase and can divide indefinitely. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

History of Science: Cell Theory • In 1665, Hooke found chambers (actually dried cell walls) in cork and named them cells. • Van Leeuwenhoek was the first to describe many types of living cells. • The central importance of cells was not established until the late 1800 s. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

History of Science: Cell Theory The cell theory states: • All living things are made up of one or more cells. • All cells come from other cells. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Math Connection: Diffusion For a cell with a radius of 1 micrometer, Surface area 4πr 2 4 π(1)2 4π =3 = = = 3 3 Volume 4/3 π r 4/3 π(1) 4/3 π For a cell with a radius of 2 micrometers, Surface area 4 π r 2 4 π(2) 2 4 π (4) = = 1. 5 3 3 Volume 4/3 π r 4/3 π(2) 4/3 π (8) For a cell with a radius of 3 micrometers, Surface area 4 π r 2 4 π(3) 2 4 π (9) =1 = = = 3 3 Volume 4/3 π r 4/3 π(3) 4/3 π (27) Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley

Science and Society: Stem Cells Embryonic stem cells come from human embryos that have yet to differentiate into distinct types of cells. These cells have the capacity to develop into all of the kinds of cells in the body. Although stem cells have great promise for treating many conditions, the use of human embryos is controversial. Copyright © 2007 Pearson Education, Inc. , publishing as Pearson Addison-Wesley