Biology Exam 2 — Master Flashcards (Campbell Biology: Concepts & Connections, 10th Edition)

Comprehensive vocabulary flashcards covering Chapters 16, 24, 6, 7, 5, and 21 from Campbell Biology: Concepts & Connections (10th Edition) for Biology Exam 2 preparation.

Prokaryotic cell

A cell without a nucleus or membrane-bound organelles. Bacteria and Archaea are prokaryotes.

Main structures of a prokaryotic cell

The plasma membrane controls what enters and leaves; cytoplasm is where reactions occur; ribosomes make proteins; DNA stores genetic information; and the cell wall provides support. Some prokaryotes also have capsules, pili, and flagella.

DNA in prokaryotes

DNA is found in the nucleoid region, which is not surrounded by a membrane. Some prokaryotes also contain small DNA circles called plasmids.

Binary fission

Asexual reproduction in which one prokaryotic cell copies its DNA and divides into two cells.

Prokaryote shapes and Gram staining

Cocci are spherical, bacilli are rod-shaped, and spirilla are spiral-shaped. Gram-positive bacteria have thick peptidoglycan walls and stain purple; Gram-negative bacteria have thinner peptidoglycan walls, an outer membrane, and stain pink or red.

Bacteria vs. Archaea

Both are prokaryotes, but they differ in cell chemistry and genetics. Bacterial cell walls usually contain peptidoglycan; archaeal cell walls do not. Archaea share important molecular and genetic features with eukaryotes.

Prokaryotic energy and carbon sources

Phototrophs obtain energy from light; chemotrophs obtain energy from chemicals. Autotrophs use $CO_2$ or another inorganic carbon source to make organic molecules; heterotrophs obtain carbon from organic molecules. These categories can be combined, such as photoautotrophs and chemoheterotrophs.

Oxygen requirements

Aerobes require oxygen for their energy-producing processes. Anaerobes do not require oxygen; some are harmed or killed by it.

Temperature adaptations

Psychrophiles grow best in cold environments; mesophiles grow best at moderate temperatures; thermophiles grow best at high temperatures.

Extreme archaea

Halophiles thrive in high-salt environments; thermophiles thrive in hot environments; methanogens produce methane and live in oxygen-free environments.

Biofilms and quorum sensing

Biofilms are communities of microbes attached to a surface and protected by a surrounding material, making them difficult to eliminate. Quorum sensing is chemical communication that helps bacteria coordinate group behaviors based on how many nearby cells are present.

Helpful roles of bacteria

Bacteria help decompose waste, treat wastewater, break down pollutants through bioremediation, and support digestion and health as part of the gut microbiome.

Pathogenic bacteria and Koch’s postulates

Pathogens cause disease. Mycobacterium tuberculosis causes tuberculosis; Staphylococcus aureus can cause skin infections and other illnesses. Koch’s postulates are traditional criteria for linking a microorganism to a disease by finding it in diseased hosts, isolating it, testing whether it causes disease, and recovering it again.

Exotoxins vs. endotoxins

Exotoxins are harmful substances released by certain bacteria. Endotoxin refers to LPS in the outer membrane of Gram-negative bacteria; its lipid A portion can trigger strong inflammation.

Antibiotics, resistance, and viruses

Antibiotics kill bacteria or stop their growth but do not directly treat viruses. Antibiotic resistance occurs when bacteria survive medicines that would normally kill them or stop their growth. Viruses are noncellular agents containing DNA or RNA in a protein coat; they require host cells to reproduce and are generally not considered alive. In the lytic cycle, new viruses are made and released; in the lysogenic cycle, viral genetic material persists with the host’s genetic material and may later enter the lytic cycle.

Innate immunity vs. adaptive immunity

Innate immunity is a fast, broad defense against many pathogens. Adaptive immunity targets specific antigens using B cells and T cells and can form memory cells for future protection.

Physical barriers and chemical defenses

Skin and mucous membranes help block pathogens. Mucus traps microbes, cilia move trapped material, stomach acid damages many microbes, and enzymes in tears and saliva help destroy pathogens.

Macrophages and phagocytosis

Macrophages are innate immune cells that engulf and digest pathogens and debris through phagocytosis. They can also present antigens to help activate adaptive immunity.

Inflammatory response

When tissue is damaged or infected, signaling chemicals are released, blood vessels widen and become more permeable, and fluid and immune cells enter the tissue. Phagocytes attack microbes and remove debris, followed by tissue repair. Common signs are redness, heat, swelling, and pain.

Lymphatic system and lymph nodes

Lymph vessels return excess tissue fluid to the blood. Lymph nodes filter lymph and provide places where immune cells can encounter antigens and activate an immune response.

Antigen, antibody, and vaccine

An antigen is a molecule recognized by the immune system. An antibody is a protein that binds a specific antigen and helps neutralize or mark targets. A vaccine exposes the immune system to an antigen or instructions for making one, helping build protection and immune memory.

B cells, plasma cells, and memory B cells

B cells recognize specific antigens. When activated, they can become plasma cells, which release antibodies, or memory B cells, which help the body respond faster to the same antigen in the future.

Helper T cells and memory helper T cells

Helper T cells coordinate immune responses by signaling to B cells, cytotoxic T cells, and other immune cells. Memory helper T cells remain after an infection or vaccination and help the body respond faster to the same antigen later.

Cytotoxic T cells and memory cytotoxic T cells

Cytotoxic T cells recognize and kill infected or abnormal body cells, including many virus-infected cells. Memory cytotoxic T cells remain to support a faster response if the same antigen appears again.

B-cell and T-cell development

B cells mature in the bone marrow. T cells originate from stem cells in the bone marrow and mature in the thymus. Activated B cells can produce plasma and memory B cells; activated T cells can become helper, cytotoxic, or memory T cells.

Clonal selection

An antigen activates the B cell or T cell with a matching receptor. That cell multiplies to form a group of cells recognizing the same antigen, including effector cells and, often, memory cells.

Humoral immunity

Adaptive immunity involving B cells and antibodies in body fluids. It is especially important for targeting pathogens and toxins outside body cells.

Cell-mediated immunity

Adaptive immunity involving T cells. Cytotoxic T cells kill infected or abnormal body cells, making this defense especially important against pathogens such as viruses that reproduce inside cells.

Humoral vs. cell-mediated immunity

Humoral immunity uses B cells and antibodies to target antigens outside cells. Cell-mediated immunity uses T cells to coordinate defenses and destroy infected body cells.

Primary vs. secondary immune response

The primary response happens the first time the body encounters an antigen and is usually slower. The secondary response occurs after another exposure and is usually faster and stronger because of memory cells.

Vaccination and immune memory

Vaccines activate an adaptive immune response and help produce memory B and/or T cells. When the same antigen appears again, these cells help the body respond more quickly and effectively.

Herd immunity

When enough people in a population are immune to an infectious disease, its spread becomes less likely, indirectly protecting some people who are not immune. The level needed depends on the disease; vaccination helps build population protection.

Cellular respiration

The process cells use to extract energy from molecules such as glucose and transfer much of that energy to ATP.

Cellular respiration equation

$C_6H_{12}O_6 + 6\,O_2 \rightarrow 6\,CO_2 + 6\,H_2O + \text{energy}$, which is captured in ATP and released as heat.

Photosynthesis vs. cellular respiration

Photosynthesis uses light energy to make sugars and releases oxygen. Cellular respiration uses sugars and oxygen to make ATP, releasing carbon dioxide and water. The products of one process are the reactants of the other.

ATP

The main immediate energy-carrying molecule used by cells. When ATP is converted to ADP and phosphate, usable energy is released for cellular work.

NADH and FADH₂

Electron carriers that collect high-energy electrons during cellular respiration and deliver them to the electron transport chain to help produce ATP.

The four stages of cellular respiration

Glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation. The first three harvest electrons and make some ATP; oxidative phosphorylation produces most ATP during aerobic respiration.

Glycolysis

Occurs in the cytosol. One glucose molecule is split into two pyruvate molecules, producing a net of $2$ ATP and $2$ NADH per glucose.

Pyruvate oxidation

Occurs in the mitochondrial matrix in eukaryotic cells. Per glucose, two pyruvate molecules are converted into two acetyl-CoA molecules, producing $2$ NADH and $2\,CO_2$. No ATP is produced directly in this stage.

Citric acid cycle

Occurs in the mitochondrial matrix in eukaryotic cells. Per glucose, it produces $2$ ATP (or equivalent), $6$ NADH, $2$ FADH₂, and $4\,CO_2$.

Oxidative phosphorylation

Occurs at the inner mitochondrial membrane. The electron transport chain helps build an $H^+$ gradient, and $H^+$ flows through ATP synthase to make ATP. This stage produces most of the ATP in aerobic respiration.

Approximate ATP yield

Aerobic cellular respiration typically produces about $30\text{--}32$ ATP per glucose in eukaryotic cells. The exact amount can vary; most ATP comes from oxidative phosphorylation.

Redox reactions

Reactions involving electron transfer. Oxidation is loss of electrons; reduction is gain of electrons. During respiration, glucose is oxidized, while NAD⁺ and FAD are reduced to NADH and FADH₂.

Final electron acceptor

Oxygen is the final electron acceptor in aerobic cellular respiration. It accepts electrons and $H^+$ to form water. Without oxygen, the aerobic electron transport chain cannot continue normally.

Locations and destinations in cellular respiration

Glycolysis occurs in the cytosol; pyruvate oxidation and the citric acid cycle occur in the mitochondrial matrix; the electron transport chain and ATP synthase are in the inner mitochondrial membrane. Pyruvate enters pyruvate oxidation, while NADH and FADH₂ deliver electrons to the electron transport chain.

Photosynthesis

The process by which plants, algae, and some bacteria use light energy to make organic molecules from carbon dioxide and water.

Photosynthesis equation

$6\,CO_2 + 6\,H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6\,O_2$. Light energy is stored as chemical energy in sugars, and oxygen is released from water during the light reactions.

Chloroplast, thylakoids, and stroma

The chloroplast is where photosynthesis occurs. Thylakoid membranes contain the machinery for light-dependent reactions. The stroma is the fluid surrounding the thylakoids and is where the Calvin cycle occurs.

Chlorophyll

A pigment that absorbs light energy, especially red and blue wavelengths, to help power photosynthesis.

Light-dependent reactions

Occur in the thylakoid membranes. They use light energy to split water, release oxygen, and produce ATP and NADPH.

Water splitting in photosynthesis

Light energy helps split water molecules, supplying electrons and $H^+$ and releasing oxygen as a by-product.

Photosynthetic electron transport chain and H gradient

Energized electrons pass through proteins in the thylakoid membrane. Their energy helps build an $H^+$ gradient, which powers ATP synthase to produce ATP.

ATP and NADPH in photosynthesis

ATP provides energy, and NADPH provides high-energy electrons used by the Calvin cycle to build organic molecules.

Calvin cycle (light-independent reactions)

Occurs in the stroma. It uses $CO_2$, ATP, and NADPH to produce G3P, a small sugar molecule used to build glucose and other organic molecules. It does not directly require light but depends on products of the light reactions.

Light-dependent reactions vs. Calvin cycle

Light-dependent reactions occur in thylakoid membranes and produce ATP, NADPH, and oxygen. The Calvin cycle occurs in the stroma and uses $CO_2$, ATP, and NADPH to produce G3P.

Potential energy

Stored energy based on an object's position or structure. Chemical bonds and concentration gradients can store potential energy.

Exergonic reactions

Reactions that release free energy. Their products have less free energy than their reactants.

Endergonic reactions

Reactions that require an input of energy. Their products have more free energy than their reactants.

Exergonic vs. endergonic reactions

Exergonic reactions release free energy; endergonic reactions require energy. Cells can couple energy-releasing reactions to energy-requiring reactions.

Activation energy

The initial energy needed to start a chemical reaction by bringing reactants to the transition state.

Enzymes and activation energy

Enzymes are biological catalysts, usually proteins, that speed up reactions by lowering activation energy. They are not used up and do not change the overall free-energy difference between reactants and products.

Reading an activation-energy graph

The vertical height from the reactants to the peak represents activation energy. An enzyme-catalyzed reaction has a lower peak than an uncatalyzed reaction, but the starting and ending energy levels stay the same.

Substrate and active site

The substrate is the reactant an enzyme acts on. The active site is the region where the substrate binds and the reaction occurs.

Competitive vs. noncompetitive inhibition

A competitive inhibitor binds to the active site and competes with the substrate. A noncompetitive inhibitor binds elsewhere and changes the enzyme’s activity; adding more substrate generally does not overcome this inhibition.

Feedback inhibition

The final product of a metabolic pathway inhibits an enzyme earlier in the pathway, preventing the cell from making more product than it needs.

Nutrient, Calorie, metabolism, and digestion

A nutrient is a substance needed for energy or normal body function. A food Calorie equals one kilocalorie of energy. Metabolism is all chemical reactions in the body. Digestion breaks food into smaller molecules that can be absorbed.

Four stages of food processing

Ingestion is taking in food; digestion breaks it down; absorption moves nutrients into the body; elimination removes undigested material.

Alimentary canal and accessory organs

The alimentary canal is the continuous tube from mouth to anus through which food passes. Accessory organs, such as the salivary glands, liver, gallbladder, and pancreas, help digestion without food passing through them.

Mechanical vs. chemical digestion

Mechanical digestion physically breaks food into smaller pieces, such as chewing and stomach churning. Chemical digestion uses chemical reactions, often enzymes, to break large food molecules into smaller molecules.

Food pathway through the digestive system

Mouth → pharynx → esophagus → stomach → small intestine → large intestine → rectum → anus.

Peristalsis

Waves of smooth muscle contractions that push food through the digestive tract.

Mouth and salivary glands

The mouth takes in food and begins mechanical digestion through chewing. Saliva moistens food, and salivary amylase begins breaking down starch.

Pharynx and esophagus

The pharynx directs swallowed food toward the esophagus. The esophagus moves food to the stomach through peristalsis.

Stomach

Stores food temporarily, churns it, and mixes it with gastric juice. Hydrochloric acid helps kill many microbes and denatures proteins; pepsin begins protein digestion.

Small intestine

The main site of chemical digestion and nutrient absorption. Digestive enzymes and bile help complete digestion, and nutrients pass through its lining into blood or lymph.

Villi and microvilli

Tiny projections in the small intestine that increase surface area and allow nutrients to be absorbed efficiently.

Large intestine

Absorbs remaining water and electrolytes and compacts undigested material into feces. It contains bacteria that can produce certain vitamins.

Rectum and anus

The rectum stores feces before elimination. The anus is the opening through which feces leave the body.

Liver

Produces bile, processes nutrients absorbed from the intestines, stores certain nutrients, and helps detoxify substances in the blood.

Gallbladder

Stores and concentrates bile made by the liver and releases it into the small intestine when needed.

Pancreas

Releases digestive enzymes into the small intestine to break down carbohydrates, proteins, and fats. It also releases bicarbonate to help neutralize acidic material from the stomach.

Bile

A fluid made by the liver and stored in the gallbladder. It emulsifies fat into smaller droplets so lipase can digest it more effectively. Bile is not an enzyme.

Carbohydrate digestion

Amylases begin breaking starch into smaller carbohydrates. Enzymes in the small intestine finish breaking carbohydrates into simple sugars, such as glucose, that can be absorbed.

Protein digestion

Proteases, including pepsin in the stomach and enzymes in the small intestine, break proteins into smaller peptides and amino acids.

Lipid (fat) digestion

Lipases break fats into smaller molecules, mainly fatty acids and monoglycerides. Bile helps by emulsifying fats but does not chemically digest them.

Nutrient absorption and transport

Most nutrients are absorbed in the small intestine. Many water-soluble nutrients enter blood capillaries and travel to the liver; most absorbed fats enter lymph vessels first and later reach the bloodstream.

What happens to absorbed nutrients?

Cells use nutrients for energy, growth, repair, and making molecules. Extra nutrients may be stored, such as glucose as glycogen or excess energy as fat.

Why the small intestine is adapted for absorption

It is long and has folds, villi, and microvilli that provide a large surface area. Its thin lining and blood and lymph vessels help nutrients move away efficiently.

Small intestine vs. large intestine

The small intestine completes most chemical digestion and absorbs most nutrients. The large intestine mainly absorbs remaining water and electrolytes and compacts waste into feces.