Comprehensive Biology Review: Cell Structure, Genetics, Ecology, and Biochemistry

Which of the following statements is false?

a. Tissues exist within organs which exist within organ systems.

b. Communities exist within populations which exist within ecosystems.

c. Organelles exist within cells which exist within tissues.

d. Communities exist within ecosystems which exist in the biosphere.

c

Genetics

The study of heredity and the variation of inherited characteristics.

Ecology

The branch of biology that deals with the relationships of organisms to one another and to their physical environment.

What genetic mutations cause uncontrolled cell division?

Mutations in genes that regulate cell growth and division, such as oncogenes and tumor suppressor genes, can lead to uncontrolled cell division.

How can these mutations be targeted to treat cancer?

Targeted therapies can inhibit the specific pathways or proteins affected by these mutations, thereby slowing down or stopping the growth of cancer cells.

How does homeostasis keep your body healthy on a hot day?

Homeostasis maintains health by regulating body temperature through sweating, dilating blood vessels to release heat, and stimulating thirst to encourage water intake.

Microscopic study in biology

Involves studying DNA, cells, and bacteria at a cellular level.

Organismal study in biology

Focuses on studying organ systems or the behavior of individual organisms.

Ecosystem study in biology

Involves studying food webs and energy flow within ecosystems.

Global study in biology

Focuses on understanding climate change and biodiversity loss on a global scale.

Ionic bonds

Forms through the transfer of electrons creating charged ions that attract each other

Covalent Bond

When atoms share electrons

Why are hydrogen bonds and van der Waals interactions necessary for cells?

They allow molecules to interact weakly and reversibly, which is essential for protein folding, DNA base pairing, membrane structure, and cell signaling.

How do buffers help prevent drastic swings in pH?

Absorb excess H⁺ or OH⁻ ions, keeps pH stable even when acids or bases are added

What property of carbon makes it essential for organic life?

Carbon can form four covalent bonds, allowing it to build complex, diverse, and stable molecules.

What are the characteristics of saturated fats?

Saturated fats have no double bonds, straight chains, are solid at room temperature, and often come from animal sources.

Saturated fats

No double bonds, straight chains, solid at room temperature, come from animal sources.

Unsaturated fats

One or more double bonds, bent chains, liquid at room temperature, come from plant or fish sources.

What is studied in microscopic biology?

DNA, cells, and bacteria.

What is studied in organismal biology?

organ systems or behavior.

What is studied in ecosystem biology?

food webs and energy flow.

What is studied in global biology?

climate change and biodiversity loss.

Why are biological macromolecules considered organic?

They are carbon-based molecules with C-H bonds.

What role do electrons play in dehydration synthesis and hydrolysis?

Electrons are rearranged as bonds form or break between monomers.

What are the similarities and differences between glycogen and starch?

Both are glucose polymers. Glycogen: highly branched, animals. Starch: less branched, plants.

Why is it impossible for humans to digest cellulose?

We lack the enzyme cellulase to break β-glycosidic bonds.

What are three functions of lipids in plants and animals?

Energy storage, Cell membrane structure, Hormones/signaling molecules.

Why have trans fats been banned from some restaurants?

They increase heart disease risk and are made by hydrogenating oils.

Why are fatty acids better than glycogen for storing energy?

They have more C-H bonds, storing more energy per gram.

How does cortisol pass through the plasma membrane?

Cortisol is hydrophobic, so it diffuses through the lipid bilayer.

What happens if one amino acid is substituted in a polypeptide chain?

It can alter protein shape and function (ex: sickle cell anemia).

What are the differences in the four protein structures?

Primary: amino acid sequence, Secondary: α-helices & β-sheets, Tertiary: 3D folding, Quaternary: multiple subunits.

What are the key features of aquaporins?

They are channel proteins with hydrophilic interiors allowing water through.

What are antibiotics?

Medicines used to fight bacterial infections by targeting prokaryotic cells without harming human cells.

What part of bacterial cells do antibiotics target?

Structures unique to bacteria, such as the cell wall, ribosomes, or enzymes involved in DNA replication.

Why are not all microbes harmful?

Some aid in digestion, producing vitamins, and recycling nutrients.

In which cells are ribosomes abundant?

In cells that produce large amounts of protein, (pancreatic cells, plasma cells, and muscle cells)

What are the similarities between mitochondria and chloroplasts?

Both have double membranes, contain their own DNA, and produce energy.

What are the differences between mitochondria and chloroplasts?

Mitochondria perform cellular respiration to generate ATP, while chloroplasts carry out photosynthesis and contain chlorophyll.

Why are plasma membranes arranged as a bilayer?

To protect the hydrophobic tails from water.

What are the similarities between centrioles and flagella?

Both are made of microtubules.

What are the differences between centrioles and flagella?

Centrioles organize the mitotic spindle, while flagella are involved in cell movement.

How do cilia and flagella differ?

Cilia are short and numerous, moving fluid across a cell's surface, while flagella are long and few, moving the cell itself.

How do microfilaments and microtubules assist in phagocytosis?

Microfilaments help the macrophage change shape to engulf pathogens, while microtubules transport the phagosome within the cell.

What boundaries do plant, animal, and bacterial cells use?

Plant cells have a plasma membrane and cellulose cell wall; animal cells have a plasma membrane only; bacterial cells have a plasma membrane and peptidoglycan cell wall.

What is the function of the extracellular matrix?

It provides structural support, anchors cells, and regulates cell signaling.

How do pathogenic E. coli gain an advantage by degrading tight junction proteins?

It allows bacteria to break down barriers between epithelial cells, facilitating spread, nutrient access, and evasion of immune defenses.

Why is it advantageous for the cell membrane to be fluid in nature?

Fluidity allows membrane proteins to move, enables vesicle fusion, helps cells change shape

Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane?

They are amphipathic: hydrophilic heads face water, and hydrophobic tails avoid water, causing them to self-assemble into bilayers.

How can a cell use an extracellular peripheral protein as the receptor to transmit a signal into the cell?

It can bind a ligand outside the cell and interact with integral membrane proteins that transmit the signal across the membrane.

How do molecular size, temperature, solution density, and distance affect the rate of diffusion?

Smaller molecules diffuse faster; higher temperature increases kinetic energy; denser solutions slow diffusion; shorter distances increase diffusion rate.

Why does water move through a membrane?

To equalize solute concentrations on both sides of the membrane (osmosis).

Why is it important that normal saline and lactated Ringer's solution are isotonic?

To prevent red blood cells from swelling (lysis) or shrinking (crenation).

How does decreasing temperature affect the rate of diffusion of molecules across a cell's plasma membrane?

It slows molecular movement and reduces membrane fluidity, limiting permeability.

What happens to a cell with a mutation in its potassium channels that prevents potassium from leaving?

Potassium accumulates, making the cell hypertonic, water enters via aquaporins, causing the cell to swell and possibly lyse.

Where does the cell get energy for active transport processes?

ATP (directly) or stored ion gradients (indirectly).

How does the sodium-potassium pump contribute to the net negative charge of the interior of the cell?

It pumps 3 Na⁺ out and 2 K⁺ in, exporting one net positive charge per cycle.

Why would intestinal cells use active transport for glucose absorption?

To absorb glucose even when its concentration is lower inside the cell than in the intestinal lumen.

Why is the sodium/calcium exchanger classified as secondary active transport?

It uses the energy stored in the sodium gradient (created by ATP-powered pumps) rather than ATP directly.

Why is it important to have different types of proteins in plasma membranes for transport?

Different substances vary in size, charge, and polarity, requiring specific transport mechanisms.

Why do ions have difficulty getting through plasma membranes despite their small size?

They are charged and hydrophilic, making them incompatible with the hydrophobic core of the lipid bilayer.

What is the activation energy for ATP hydrolysis?

The activation energy is high.

How does enzyme feedback inhibition benefit a cell?

It prevents waste by shutting down a metabolic pathway when enough product has accumulated.

What is the relationship between a genome, chromosomes, and genes?

A genome is the complete set of DNA in an organism; chromosomes are compacted DNA molecules within the genome; genes are specific sequences of DNA on chromosomes that code for proteins or functional RNAs.

What occurs during the G1 phase of the cell cycle?

The cell grows and performs normal functions.

What happens during the S phase of the cell cycle?

DNA is replicated.

What is the purpose of the G2 phase in the cell cycle?

The cell prepares for mitosis by producing proteins and organelles.

How do chromosomes fit inside a eukaryotic nucleus?

DNA wraps around histones to form nucleosomes, coils into chromatin fibers, and further loops and folds to compact the DNA.

How does cytokinesis differ in animal and plant cells?

In animal cells, cytokinesis occurs via a contractile ring forming a cleavage furrow; in plant cells, it occurs via a cell plate formed by Golgi vesicles.

Why might a cell enter the G0 phase after cytokinesis?

Cells may enter G0 if they are fully differentiated, have reached the end of their functional lifespan, or are not receiving signals to divide.

What happens if a cell produces mutated cohesin protein?

Sister chromatids may separate prematurely during mitosis, leading to chromosome missegregation and aneuploidy.

What are the criteria for the G1 checkpoint?

Adequate size, nutrients, DNA integrity, and growth signals.

What does the G2 checkpoint ensure?

Complete and accurate DNA replication, sufficient cell size, and functional organelles.

What is the purpose of the M checkpoint?

To ensure all chromosomes are properly attached to spindle fibers before anaphase.

What do positive regulators do in the cell cycle?

They promote cell cycle progression.

What is the role of negative regulators in the cell cycle?

They halt the cell cycle when errors occur or signals are missing.

What is a proto-oncogene?

A gene that promotes cell division; mutation can lead to an oncogene.

What is the function of a tumor-suppressor gene?

It inhibits cell division; mutation can lead to loss of control.

How does p53 benefit a multicellular organism?

It prevents damaged or mutated cells from dividing, protecting the organism from cancer.

What are the common components of eukaryotic cell division?

DNA duplication, segregation, cytokinesis.

What components are involved in prokaryotic cell division?

FtsZ ring and no nucleus.

How are duplicated bacterial chromosomes distributed into daughter cells?

Chromosomes attach to the cell membrane and are pulled apart as the cell elongates.

What is a silent mutation?

A mutation that causes no change in the amino acid.

What is a missense mutation?

A mutation that changes one amino acid, which may affect function.

What is a nonsense mutation?

A mutation that introduces a premature stop codon, truncating the protein.

What is a frameshift mutation?

A mutation that alters the reading frame, drastically changing the downstream sequence.

How does degeneracy of the genetic code make cells robust to mutations?

Silent mutations often occur in the third codon position without changing the amino acid, reducing harmful effects of point mutations.