STM 007: General Biology 1 Comprehensive Reviewer

Comprehensive question-and-answer flashcards covering gametogenesis, membrane transport, biomolecules, ATP energetics, photosynthesis, and cellular respiration based on the General Biology 1 study guide.

What is gametogenesis, and what is the role of meiosis within it?

Gametogenesis is the production of sex cells (gametes). Meiosis reduces the chromosome number from diploid ($2n$) to haploid ($n$), allowing fertilization to restore the diploid number.

Where does spermatogenesis occur, and what does one primary spermatocyte produce?

Spermatogenesis occurs in the testes; one primary spermatocyte undergoes meiosis I and meiosis II to produce four functional haploid sperm cells with relatively evenly distributed cytoplasm.

Where does oogenesis take place, and what are its cellular products?

Oogenesis occurs in the ovaries and divides cytoplasm unequally to produce one large functional ovum and smaller polar bodies that generally degenerate.

What is the key developmental difference between spermatids and polar bodies?

Spermatids are immature cells in sperm development that can develop into functional sperm, whereas polar bodies are small cells formed during oogenesis that generally degenerate.

What components make up the plasma membrane according to the fluid mosaic model?

A flexible phospholipid bilayer containing proteins, cholesterol (especially in animal cells), and carbohydrate chains attached to lipids (glycolipids) or proteins (glycoproteins).

How are phospholipids arranged within the plasma membrane bilayer?

Hydrophilic heads face outward toward watery environments, while hydrophobic tails face inward toward each other.

What cellular role is served by membrane glycolipids and glycoproteins?

They act as surface recognition molecules, aiding in cell recognition, communication, receptor functions, and interactions with neighboring cells.

What is the primary function of cholesterol in animal cell membranes?

It helps regulate membrane fluidity and stability.

How do simple diffusion and facilitated diffusion differ, and what do they have in common?

Simple diffusion is the direct passage of particles through the membrane, whereas facilitated diffusion requires assistance from channel or carrier proteins. Both are passive transport mechanisms moving down a concentration gradient.

By what mechanism do small, nonpolar molecules like $O_2$ and $CO_2$ cross the plasma membrane?

Simple diffusion.

How does glucose commonly move down its concentration gradient across a cell membrane?

Facilitated diffusion through a carrier protein.

What defines active transport, and what is a primary example in animal cells?

Active transport moves substances against a concentration or electrochemical gradient and requires energy; a primary example is the sodium-potassium pump.

How do endocytosis and exocytosis differ in their direction of vesicular transport?

Endocytosis folds the membrane inward to bring material into the cell within a vesicle, whereas exocytosis fuses a vesicle with the membrane to release material out of the cell.

What are the single sugar units of sucrose and lactose?

Sucrose consists of glucose plus fructose; lactose consists of glucose plus galactose.

What are the primary roles of glucose, glycogen, and cellulose?

Glucose serves as immediate fuel for cellular respiration; glycogen provides energy storage in animals; cellulose forms the structural support of plant cell walls.

What causes the symptoms of lactose intolerance?

A deficiency of the enzyme lactase, which leaves lactose undigested into glucose and galactose, causing gas, bloating, or diarrhea.

What is the chemical composition and primary function of triglycerides?

Triglycerides consist of glycerol bound to three fatty acids and function as the major form of stored fat and long-term energy storage.

What structural characteristic defines steroids, and what are two common examples?

Steroids are characterized by a four-ring structure; examples include cholesterol and steroid hormones such as estrogen.

What protective role do waxes play in biological systems?

They provide waterproofing and protection, such as plant leaf cuticles reducing water loss and wax coating honeycombs.

What defines the four levels of protein structure?

Primary: sequence of amino acids; Secondary: local folding patterns like alpha helices and beta-pleated sheets; Tertiary: overall 3D shape of one polypeptide; Quaternary: arrangement of two or more polypeptide subunits.

Why can a single amino acid mutation affect the tertiary or quaternary structure of a protein?

The mutation directly alters the primary sequence, which can disrupt local hydrogen bonding and interactions responsible for higher-level folding and functional activity.

What structural features distinguish DNA from RNA?

DNA contains deoxyribose sugar and thymine (pairing A–T and G–C, typically double-stranded), whereas RNA contains ribose sugar and uracil instead of thymine (typically single-stranded).

How does complementary base pairing support the function of DNA?

Complementary base pairing (A with T, G with C) allows each existing strand to serve as an exact template during DNA replication.

What is the structural difference between ATP and ADP?

ATP contains adenine, ribose, and three phosphate groups, whereas ADP contains adenine, ribose, and two phosphate groups.

How does the ATP–ADP cycle provide usable energy for cellular work?

Hydrolysis of ATP removes a phosphate group to form ADP, releasing usable energy; ADP is recharged back into ATP by adding a phosphate using energy from cellular processes.

Where do the light-dependent reactions of photosynthesis occur, and what do they yield?

They take place in the thylakoid membranes, requiring light directly to produce ATP and NADPH while releasing oxygen ($O_2$) from water splitting.

Where do the light-independent reactions (Calvin cycle) occur, and what do they use?

They take place in the chloroplast stroma, using ATP and NADPH from the light-dependent reactions to build carbohydrates from carbon dioxide.

What are the three main stages of cellular respiration and their locations in eukaryotic cells?

Glycolysis (cytoplasm), Krebs cycle / citric acid cycle (mitochondrial matrix), and the electron transport chain (inner mitochondrial membrane).

What is the role of oxygen in aerobic cellular respiration?

Oxygen serves as the final electron acceptor in the electron transport chain (ETC), the stage that produces the most ATP.

How are photosynthesis and cellular respiration mutually connected?

Photosynthesis uses carbon dioxide, water, and light to produce carbohydrates and oxygen; cellular respiration uses carbohydrates and oxygen to yield energy, releasing carbon dioxide and water.

What is the primary function of fermentation pathways when oxygen is limited?

To regenerate $NAD^+$ so that glycolysis can continue producing small amounts of ATP without oxygen.

What are the end products of alcoholic fermentation in yeast, and what is one common effect?

Ethanol and carbon dioxide ($CO_2$); the carbon dioxide forms bubbles that cause bread dough to rise.

Under what conditions does lactic acid fermentation occur in human muscle cells?

During intense activity when oxygen supply cannot meet cellular demand, allowing continued glycolysis for short-term ATP production.