Chapter1: Biology: Exploring Life • Levels of biological organization from smallest

to largest: molecules organelles cells tissues organs organ systems organisms populations communities ecosystems biosphere

• The basis of life’s unity and diversity is the genetic information in DNA molecules.

• Biologists organize the diversity of life into three domains: (1) Bacteria and (2) Archaea consist of single-celled prokaryotic organisms; (3) Eukarya includes protists, plants, fungi, and animals. Protists are primarily single-celled eukaryotes. Plants, fungi, and animals are mostly multicellular eukaryotes that differ in how they obtain nutrients.

• Darwin’s theory of evolution based on natural selection is the core theme of biology.

• Discovery science draws conclusions form descriptions and measurements. Hypothesis-based science follows five basic steps:

Chapter 2: The Chemical Basis of Life • Matter consists of elements. Elements can

combine to form compounds. • Twenty-five elements are essential for life.

Oxygen, carbon, hydrogen, and nitrogen are the most abundant.

• Atoms are the smallest units of matter that retain the properties of an element. Atoms consist of protons (+1 electrical charge), neutrons (no charge), and electrons (-1 charge). Different isotopes of an element have varying numbers of neutrons.

• Atoms with incomplete electron shells tend to gain, lose or share electrons, forming chemical bonds with other atoms.

• Ionic bonds are attractions between ions of opposite charges.

• Atoms in covalent bonds complete their outer electron shells by sharing electrons.

• Water is a polar molecule; unequal electron sharing results in a slightly negative O end and two slightly positive H ends:

• Weak attractions between slightly charged H and

negatively charged areas of molecules are called hydrogen bonds. Water’s polarity and hydrogen bonding explain most of its life-supporting properties.

• Acidic solutions have more H+ ions than OH- ions and a pH < 7.

• Chemical reactions rearrange matter as reactants are converted to products.

Chapter 3: The Molecules of Cells • Organic compounds vary in (1) the size and

shape of the carbon skeleton, and (2) the presence and location of functional groups.

• Cells make a huge number of polymers from a small set of monomers, linked together by dehydration reactions.

• Carbohydrates. Monosaccharides provide cells with energy and molecular building blocks. Polysaccharides store energy in animals (as glycogen) and in plants (as starch). Cellulose in plant cell walls provides structure.

• Lipids are hydrophobic. They include fats (energy storage), phospholipids (cell membrane component), waxes, and steroids (such as cholesterol and some hormones). Most animal fats are saturated. Plant oils are mostly unsaturated (have less hydrogen because of double bonds in the carbon skeleton).

• Proteins are important structural elements of cells and participate in most cellular activities. Amino acids, the monomers of proteins, come in 20 varieties and are linked by peptide bonds to form polypeptides.

• A peptide bond joins the carboxyl end of one amino acid with the amino group of the next:

(–) (–)

(+) (+)

O

HH

The Semester at a Glance

• A protein consist of one or more polypeptides

folded into a specific shape that determines the protein’s function. Four structural levels may contribute to this shape: (1) the amino acid sequence (primary structure); (2) coiling or pleating held by hydrogen bonds (secondary structure); (3) the overall shape held by interactions among R groups (tertiary structure); and (4) association of more than one polypeptide (quarternary structure).

• Nucleic acids are polymers of nucleotides. DNA, the molecule of inheritance, is a double helix: two polynucleotide strands held together by hydrogen bonds between bases. DNA is transcribed into RNA, a single- stranded nucleid acid, which is then translated into the primary structure of proteins.

Chapter 4: A Tour of the Cell • Prokaryotic cells are small and structurally

simple: • Eukaryotic cells are larger and more complex,

with a nucleus and membrane-bounded organelles.

• An animal cell:

• A plant cell: • Within the nucleus, DNA and proteins make up

chromatin fibers. Each fiber is a chromosome. • The endoplasmic reticulum (ER) consists of a

network of membranes. Rough ER (with attached protein-manufacturing ribosomes) makes membranes and secretory proteins. Smooth ER synthesizes lipid and aids in detoxification.

• The Golgi apparatus refines ER products and packages them in transport vesicles.

• Lysosomes, sacs containing digestive enzymes, function in digestion within the cell and chemical recycling.

• Plant cells have a large central vacuole, chloroplasts (organelles that convert solar energy to chemical energy), and plasmodesmata (channels between adjacent cells).

• Mitochondria, the sites of cellular respiration, convert food energy to ATP.

• Microfilaments, intermediate filaments, and microtubules are protein fibers that make up the cytoskeleton, the cells’ structural framework.

• Cilia and flagella are motile appendages made primarily of microtubules.

• Junctions between animal cells help hold them together, and some provide communications between cells.

Chapter 5: The working Cell • Energy is the capacity to perform work. • Kinetic energy (energy of motion) can be

converted to potential energy (stored energy) and vice versa. Energy cannot be created or destroyed. Every energy transfer or transformation increases entropy (disorder).

• Endergonic reactions require a net input of energy, and the products contain more energy than the reactants. Exergonic reactions release energy.

H

H

N C C N C C

R H R OH

O

Peptidebond

H O H

• Energy coupling, with ATP as the energy shuttle, uses and exergonic process to drive an endergonic one.

• Enzymes are biological catalysts that lower the activation energy of reactions, thereby speeding them up.

• How an enzyme works: • Enzyme function is altered by temperature, pH,

and competitive and noncompetitive inhibitors. • A membrane is a fluid mosaic of proteins

floating in a phospholipid bilayer. • Membrane proteins serve a variety of functions,

such as enzyme activity, signal transduction, and transport.

• Molecules tend to diffuse down their concentration gradients. Diffusion across a biological membrane is called passive transport.

• Osmosis is the passive transport of water across a selectively permeable membrane. Water balance between cells and their environment is crucial to organisms.

• Transport proteins may function as membrane pores or carriers that facilitate diffusion.

• Active transport requires energy; cells use ATP and membrane proteins to pump solutes against ther4i concentration gradients.

• Exocytosis releases cell products when vesicles fuse with the plasma membrane. Cells take in large molecules via the reverse process, endocytosis.

Chapter 6: How Cells Harvest Chemical Energy • Cellular respiration breaks down glucose to

provide usable energy in the form of ATP. Glucose is oxidized and O2 is reduced. Energy is released in small quantities during the transfer of electrons from glucose to hydrogen carriers (NAD+) to the electron transport chain to oxygen.

• ATP is generated by two mechanisms: (1) Oxidative phosphorylation involves the electron transport chain and chemiosmosis and (2) substrate-level phosphorylation transfers a phosphate group from a substrate to ADP.

• Cellular respiration has three stages: 1. Glycolysis. In the cytosol, a molecule of glucose is split into two molecules of pyruvate. Two ATP and 2 NADH are produced. 2. The citrus acid cycle. In the mitochondria, pyruvate is converted to acetyl CoA, which enters the citric acid cycle and is broken down to CO2. Electrons are transferred to make NADH and FADH2. 3. Oxidative Phosphorylation. In the inner mitochondrial membrane, electrons are passed through the electron transport chain to oxygen, forming water. H+ is pumped into the intermembrane space and diffuses back through ATP synthesases, producing ATP. About 34 ATP are created per glucose molecule. • Diagram of cellular respiration: • If oxygen is absent, pyruvate is converted to

lactate or ethanol and NAD+ is regenerated. This process of fermentation allows glycolysis to continue to generate some ATP.

• Cells use organic molecules as fuel. Food molecules as well as intermediate molecules form glycolysis and the citric acid cycle are used as raw materials for biosynthesis.

• The fuel for cellular respiration ultimately comes from photosynthesis.

Chapter 7: Photosynthesis: Using Light to Make Food • The summary equation for photosynthesis:

Lightenergy

PHOTOSYNTHESIS

6 CO2 6+ H2O

Carbon dioxide Water

C6H12O6 6+ O2

Glucose Oxygen gas

• Photosynthesis, which occurs mainly in chloroplasts in leaf cells, is a redox process in which water is oxidized and carbon dioxide is reduced.

• Photosynthesis occurs in two stages: 1. Light reactions. Solar energy is absorbed and converted to chemical energy in the form of ATP and NADPH within a network of membranous structures called thylakoids. 2. The Calvin cycle. This cyclic series of chemical reactions in the stroma of a chloroplast uses ATP and NADPH to make the energy-rich sugar G3P from O2. • Plants use the sugars they produce for cellular

respiration and or producing their other organic molecules. Plants and other photosynthesizers are the ultimate source of food for virtually all other organisms.

• Photosynthetic adaptations of C4 and CAM plants enable sugar production to continue even when stomata are closed, thereby reducing water loss in arid environments.

• Atmospheric CO2 in the atmosphere traps heat and warms the planet – a process commonly called the greenhouse effect. Levels of CO2 in the atmosphere are increasing, raising concerns about global warming.

Chapter 20: Unifying Concepts of Animal Structure and Function • Structure and function are correlated at each

level: cell, tissue, organ, organ system, and whole animal.

• Animals have four kinds of tissue: (1) epithelial (covers body and its parts); (2) connective (binds and supports other tissues); (3) muscle (functions in movement); and (4) nervous (relays information).

• An organ system is a group of organs that work together to perform a vital function. There are 12 major organ systems: digestive, respiratory, circulatory, immune, lymphatic, excretory,

endocrine, nervous, integumentary, skeletal, muscular, and reproductive.

• All animals exchange materials with the environment. Larger animals have extensively branched internal structures and a circulatory system that facilitates exchange between the environment and body cells (via interstitial fluid).

• Homeostasis is the body’s tendency to maintain relatively constant internal conditions despite external fluctuations:

• Negative feedback is a control mechanism in

which a change triggers mechanisms that counteract the change.

Chapter 21: Nutrition and Digestion • Herbivores eat plants or algae; carnivores eat

animals; and omnivores eat animals and plants or algae.

• There are four stages of food processing: ingestion, digestion, absorption (into the body’s cells), and elimination (of undigested materials).

• Digestion, the breakdown of food macromolecules into monomers, occurs in compartments housing hydrolytic enzymes. Simple animals such as a hydra have a gastrovascular cavity with one opening. Most animals have an alimentary canal, running from mouth to anus, that includes specialized regions such as a crop, gizzard, or stomach.

• Human digestion begins in the oral cavity, where teeth and digestive enzymes start to break down food. Using peristalsis, the esophagus squeezes food along to the stomach, where food is stored and broken down further with acid and enzymes. Virtually all chemical digestion and nutrient absorption occurs in the small intestine. The pancreas and the liver provide digestive enzymes and bile, respectively. The large intestine reclaims water and compacts the feces.

Homeostaticmechanisms

Externalenvironment

Internalenvironment

Smallfluctuations

Largefluctuations

• The human digestive tract (digestive glands in blue):

• An animals’ diet provides fuel for its activities,

raw materials for making the body’s molecules, and essential nutrient that the body cannot make itself. For humans, these nutrients include eight essential amino acids, 13 vitamins, and essential minerals.

Chapter 22: Gas Exchange • Gas exchange involves breathing, transport of O2

and CO2 by the circulatory system, and the servicing of tissue cells.

• Animals require a moist surface for diffusion of gases between their cells and the surrounding air of water. There are four types of gas exchange mechanisms:

1. Skin: entire outer skin used as respiratory organ, as in earthworms. 2. Gills: outfoldings of the body surface in fish and aquatic invertebrates. Countercurrent exchange maximizes oxygen transfer from water to blood. 3. Tracheal system: tiny branching air tubes in insects. 4. Lungs: internal sacs in terrestrial vertebrates. • The human respiratory system:

• Negative pressure breathing ventilates the lungs

of mammals. Muscle contractions expand the rib cage and lower the diaphragm, crating a negative pressure, and air rushes into the lungs (inhalation). During exhalation, muscles relax and air is pushed form the lungs.

• Alveoli are the respiratory surfaces in the lungs. Inhaled O2 diffuses into capillaries, binds to hemoglobin in red blood cells, and is transported to body cells by the circulatory system. Hemoglobin also helps transport CO2 and buffers the blood.

Chapter 23: Circulation • The circulatory system transports nutrients and

O2, transports wastes, and plays a key role in homeostasis.

• The pulmonary circuit carries blood between the heart and lungs. The systemic circuit transports blood between the heart and body (systemic) capillaries.

• Blood flow though the human cardiovascular system:

• Arteries carry blood under high pressure from the

heart. Exchange between the blood and interstitial fluid occurs across the thin walls of capillaries. Blood moves back to the heart via veins with one-way valves.

• The cardiac cycle is controlled via electrical signals from the pacemaker (SA node); it has two phases: systole (contraction) and diastole (relaxation).

• Diseases of the heart and blood vessels – including heart attack and stroke – kill more

Americans than any other type of disease. Atherosclerosis is the buildup of lipid and other substances in the arteries.

• Blood consists of plasma (water and dissolved salts and proteins) and cells: red blood cells (erythrocytes), which transport oxygen; white blood cells (leukocytes), which aid in defense; and platelets, which aid in clotting.

Chapter 24: The Immune System • The innate defenses include the skin, mucous

membranes, phagocytic cells, antimicrobial proteins, and the inflammatory response.

• The lymphatic system is a network of fluid-collecting vessels and organs, including the lymph nodes that fight infections.

• The immune system is a large collection of cells that present a specific response to infection and produce an acquired immunity. Antigens are molecules that elicit immune responses.

• Two kinds of lymphocytes carry out the immune response:

1. B cells provide humoral immunity. They secrete antibodies, which attack foreign antigens in body fluids. 2. T cells provide cell-mediated immunity. They attack body cells infected with pathogens. • Antibodies recognize antigens through specific

binding and can trigger destruction of a molecule or cell.

• Antigens activate only lymphocytes with complementary receptors, a process called clonal selection. In the primary response (see figure), the selected lymphocytes multiply into clones of effector cells and memory cells. Memory cells mount a rapid secondary immune response upon subsequent exposures.

• Helper T cells and cytotoxic T cells are the main effectors of cell-mediated immunity. When a helper T cell encounters an antigen-presenting cell, it releases signals that activate itself and cytotoxic T cells and help to stimulate B cells. Cytotoxic T cells attack infected body cells that are displaying foreign antigens attached to self proteins.

• Malfunction of failure of the immune system can cause autoimmune and immunodeficiency diseases. HIV, the AIDS virus, attacks helper T cells. AIDS is a worldwide epidemic.

• Allergies are abnormal sensitivities to antigens (allergens) that produce uncomfortable inflammatory responses.

Chapter 25: Control of the Internal Environment • Thermoregulatory mechanisms, which help to

maintain body temperature within narrow limits, include increases in metabolic rate; shivering; fur and feathers; changes in blood flow to the skin; sweating; panting; and behavioral responses such as basking in the sun, burrowing, or migrating.

• Osmoregulation is the control of the gain and loss of water and dissolved solutes in and organism. The excretory system plays a role in osmoregulation and rid the body of nitrogenous wastes, in the form of ammonia, urea, or uric acid.

• The liver performs many homeostatic functions. • The nephron is the functional unit of the human

kidney. • Major functions of the excretory system: Chapter 26: Chemical Regulation • The endocrine system consists of a collection of

hormone-secreting cells. A hormone is a regulatory chemical that travels via the bloodstream to target cells, where it may trigger changes by two main signaling mechanisms: (1) binding a plasma-membrane receptor; or (2) binding an intracellular receptor:

• The vertebrate endocrine system consists of more

than a dozen glands, secreting over 50 hormones. The hypothalamus is the master control center, secreting some hormones that are stored and released from the posterior pituitary gland. It also regulates the anterior pituitary’s production of hormones, many of which regulate the activity of other endocrine glands.

• Hormones from the thyroid gland regulate development and metabolism. Blood calcium level is balanced by calcitonin and parathyroid hormone.

• The pancreas secretes insulin and glucagons, which have opposing effects in the control of blood glucose level.

• Hormones from the medulla and cortex of the adrenal glands help to maintain homeostasis by mediating short-term and long-term responses to stress, respectively. Estrogens, progestins, and androgens are steroid sex hormones produced by the ovaries and testes.

Chapter 28: Nervous System • The nervous system receives sensory input,

interprets it, and sends out appropriate motor commands.

• Neurons are the functional units of the nervous system. The structure of a motor neuron:

• A neuron maintains a membrane potential across

its membrane, with the interior of he cell negatively charged.

• In a nerve signal, called an action potential, ions move in and out of a neuron, crating a rapid change from resting potential to a positive potential and back again. Action potentials are self-propagated in a one-way chain reaction along a neuron.

• A nerve signal may be passed to another neuron across a synapse. Chemical synapses make complex information processing possible. A variety of small molecules serve as neurotransmitters.

• The vertebrate central nervous system includes the brain and spinal cord.

• Functional divisions of the peripheral nervous system:

• The hindbrain, midbrain, and the thalamus and

hypothalamus of the forebrain function in conducting information to and form higher brain center, keeping track of body position, regulating homeostatic functions, and sorting sensory information.

• The cerebrum of the forebrain is the largest and most complex part of the brain.

• The cerebral cortex contains interactive regions responsible for language, reasoning, personality traits, and integration of sensory information and motor responses.

• The hypothalamus, medulla, pons, and reticular formation regulate sleep and arousal.

• The limbic system is involved in emotions, memory, and learning.

Chapter 29; The Senses

• In sensory transduction, sensory receptors convert stimuli into electrical signals, which are transmitted via sensory neurons to the central nervous system.

• There are five categories of sensory receptors: (1) pain receptors; (2) thermoreceptors; (3) mechanoreceptors (touch, pressure, and sound); (4) electromagnetic receptors (such as photoreceptors).

• The cornea and lens focus light on photoreceptor cells in the retina. The lens changes shape to bring objects at different distances into sharp focus.

• Photoreceptor cells called rods are extremely sensitive to light; cones are photoreceptors that distinguish color.

• The single-lens eye of a vertebrate: • The outer ear channels sound waves to the

eardrum, which passes the vibrations though a chain of bones in the middle ear to the fluid in the cochlea. Vibrating fluid bends hair cells in the organ of Corti, triggering nerve signals to the brain. The semicircular canals and the utricle and saccule are organs of balance located in the inner ear.

• Olfactory (odor) receptors lining the nasal cavity and taste receptors located on the tongue detect and respond to different categories of chemicals.

Chapter 30: How Animals Move • All the divers means of animal locomotion

(swimming, hopping, walking, running, crawling, and flying) must overcome the forces of friction and gravity.

• The skeletal system functions in support, movement, and the protection of internal organs.

• The human endoskeleton is composed of cartilage and bone. A bone is a living organ containing several kinds of tissues.

• Skeletal muscles pull on bones, which act as levers rotating at joints to produce movements. Antagonistic pairs of muscles produce opposite movements.

• Each skeletal muscle cell, or fiber, contains bundles of myofibrils that contain bundles of overlapping thick (myosin) and thin (actin) protein filaments. Repeating units of thick and thin filaments are called sarcomers.

• Sarcomeres, the muscle fiber’s contractile units,

shorten when myosin pulls the actin filaments toward the center of the sarcomere.

© 2008, adapted from “Biology” Campbell et al.