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• BIO 202 Exam 1 practice questions and answers cover topics from atoms and molecules to cell study techniques.

Atoms & Molecules

• The three subatomic particles are protons (positive charge), neutrons (no charge), and electrons (negative charge).
• Atomic number signifies the number of protons in an atom.
• Mass number represents the sum of protons and neutrons in an atom.
• Isotopes differ due to varying numbers of neutrons, despite having the same number of protons.
• Radioactive decay involves unstable isotopes releasing radiation over time, applied in carbon dating, cancer treatment, and medical imaging.
• Covalent bonds involve atoms sharing electrons, making them the strongest.
• Ionic bonds occur when electrons are transferred, creating charged ions such as Na⁺ and Cl⁻.
• Hydrogen bonds are weak attractions between partial charges, as seen in H₂O molecules.
• Electronegativity is an atom's capacity to attract electrons, influencing bond polarity.
• High electronegativity, as seen in oxygen (O) and nitrogen (N), results in polar bonds.

Water & Life

• Ice floats because it is less dense than liquid water, due to hydrogen bonds pushing molecules apart in solid form.
• Water's high specific heat helps stabilize temperatures in organisms and environments by absorbing and retaining heat.
• Acids increase H⁺ concentration, resulting in a pH < 7.
• Bases increase OH⁻ concentration, resulting in a pH > 7
• A buffer minimizes pH changes by absorbing or releasing H⁺.
• The bicarbonate system in blood maintains pH ~7.4.

Carbon & Molecular Diversity

• Carbon is vital in biological molecules due to its ability to form four covalent bonds, allowing for diverse organic molecules.
• Carbon skeletons can vary in length, branching, double bonds, and rings.
• Hydroxyl (-OH) groups are polar and found in alcohols.
• Carboxyl (-COOH) groups are acidic and found in amino acids.
• Amino (-NH₂) groups are basic and found in proteins.
• Phosphate (-PO₄) groups are involved in energy storage (ATP).

Macromolecules

• Carbohydrates function in energy storage (starch, glycogen) along with structural support (cellulose, chitin).
• Humans can digest starch, but lack the enzymes to digest cellulose.
• The three main types of lipids are fats, phospholipids, and steroids.
• Phospholipids are important for forming cell membranes, featuring hydrophilic heads and hydrophobic tails.
• A protein's function is determined by its 3D shape (folding), which depends on its amino acid sequence.
• Denaturation causes a protein to lose its shape and function, often due to heat or pH changes.
• The three components of a nucleotide are phosphate group, sugar, and a nitrogenous base.
• DNA is double-stranded with thymine (T) and deoxyribose sugar.
• RNA is single-stranded with uracil (U) and ribose sugar.

Cell Structure & Function

• Prokaryotic cells lack a nucleus, have circular DNA, and are small.
• Eukaryotic cells have a nucleus, possess linear DNA, and are larger.
• Mitochondria is the powerhouse of the cell as it produces ATP.
• Organelles found only in plant cells include chloroplasts, the central vacuole, and the cell wall.
• The nucleus stores DNA.
• Ribosomes synthesize proteins.
• The Golgi apparatus modifies and ships proteins.
• Lysosomes digest waste.
• Mitochondria are responsible for energy production.
• Chloroplasts perform photosynthesis.
• The endosymbiotic theory explains the origin of certain cell organelles.

Cell Organelles & Their Functions

• Chloroplasts, found only in plant cells, function as the site of photosynthesis, where light energy is converted into glucose.
• Chloroplasts have a double membrane like mitochondria.
• Thylakoids are flattened sacs inside chloroplasts where light-dependent reactions occur.
• Grana are stacks of thylakoids.
• The stroma is the fluid surrounding the thylakoids where the Calvin cycle takes place.
• Chloroplasts are only present in plants and algae, not in animal cells.
• The presence of their own DNA and ribosomes in chloroplasts supports the endosymbiotic theory.
• Vacuoles are membrane-bound sacs that store substances and help maintain cell structure.
• Central vacuoles in plant cells store water, ions, and nutrients, providing turgor pressure for structure.
• Food vacuoles, formed by phagocytosis, store engulfed food for digestion in protists and some animals.
• Contractile vacuoles pump out excess water to prevent bursting (osmoregulation) in freshwater protists like Paramecium.
• Nuclear Membrane surrounds the nucleus and controls what enters and exits.
• Nuclear Pores are small holes in the nuclear membrane that allow the passage of substances like RNA.
• Chromatin consists of DNA and proteins that carry genetic information.
• The nucleolus makes ribosomes, which aid in protein production.
• Nucleoplasm is the jelly-like substance inside the nucleus.
• The Nuclear envelope is a double-layered membrane around the nucleus that protects the DNA and controls what enters or leaves the nucleus via pores.
• The endoplasmic reticulum (ER) is a network of membranes connected to the nuclear envelope.
• Rough ER (RER) is studded with ribosomes, which make proteins that are secreted from the cell, incorporated into membranes, sent to lysosomes, or modified and folded before being sent to the Golgi apparatus.
• Smooth ER (SER) lacks ribosomes and does not make proteins.
• SER functions in lipid and steroid synthesis, detoxification of drugs and toxins, and storage of calcium ions.
• Chloroplasts perform photosynthesis, converting light energy into glucose.
• The three main structures inside chloroplasts include thylakoids, grana, and stroma.
• Chloroplasts originated from bacteria, supported by their own DNA & ribosomes, double membrane, and ability to divide like bacteria supporting endosymbiotic theory.
• The central vacuole in plant cells stores water, nutrients, and waste, and provides turgor pressure for support.
• Contractile vacuoles expel excess water in freshwater protists.
• Food vacuoles form by phagocytosis, when a cell engulfs food particles.
• Rough ER has ribosomes attached, while smooth ER does not.
• Smooth ER synthesizes lipids, steroids, and phospholipids.
• Smooth ER detoxifies drugs and poisons, especially in liver cells.
• Proteins made in the rough ER are folded, modified, and sent to the Golgi apparatus for processing.
• Microfilaments facilitate cell movement and changes in cell shape and cytokinesis.
• Intermediate Filaments provide mechanical strength and structural support.
• Microtubules maintain cell shape and rigidity, aid in cell division (mitosis), and serve as tracks for intracellular transport.
• Cilia move fluids or particles along the cell surface and help with cell movement.
• Flagella propel cells through liquid environments and enable whip-like motion.
• The ECM is a network of glycoproteins and other carbohydrates secreted by cells that provides structural support to tissues.
• The intracellular matrix supports organelles and helps maintain cell shape.
• Motor proteins facilitate cell movement and transport materials within cells.
• Plasmodesmata are channels in plant cells that connect cells and allow the sharing of internal chemical environment.
• In animal cells, tight junctions prevent leakage, gap junctions allow for communication, and desmosomes fasten cells together.
• Glycoproteins help with cell recognition and communication.
• Glycolipids help with cell recognition and interaction.
• Peroxisomes break down fatty acids and detoxify harmful substances.
• Defensive proteins protect against disease (e.g., antibodies).
• Storage proteins store amino acids (e.g., casein).
• Transport proteins move substances in a cell (e.g., sodium channels).
• Hormonal proteins signal organism-wide functions (e.g., insulin).
• Structural proteins support cell and organismal shape.
• Contractile and motor proteins coordinate movement.
• Receptor proteins respond to chemical stimuli and trigger cell responses.
• Kinesin moves along microtubules away from the nucleus for intracellular transport and mitosis.
• Dynein moves along microtubules toward the nucleus for intracellular transport and cilia/flagella movement.
• Myosin moves along actin filaments and works in muscle contraction and vesicle transport.

Microscopy & Cell Study Techniques

• The three main parameters of microscopy are magnification, resolution, and contrast.
• Magnification refers to how much larger an object appears.
• Resolution refers to the clarity of an image.
• Contrast refers to the difference in brightness between parts of a sample.
• The two main types of microscopes are light microscopes (LM) and electron microscopes (EM).
• Light Microscopes (LM) use visible light to view specimens.
• Electron Microscopes (EM) use electron beams for much higher resolution.
• The maximum magnification of a light microscope is about 1000x.
• The resolution limit of a light microscope is about 200 nm.
• Two common types of light microscopy are brightfield and fluorescence.
• Electron microscopes use electron beams instead of light for higher resolution.
• The resolution of an electron microscope is approximately ~2 nm.
• Scanning Electron Microscopes (SEM) produce 3D images by scanning a specimen's surface.
• Transmission Electron Microscopes (TEM) are used to study internal structures by passing electrons through thin slices of cells.
• Confocal microscopy uses a laser beam to scan the sample and reduce out-of-focus light for clearer images.
• Cryo-electron microscopy (Cryo-EM) freezes samples at extremely low temperatures to preserve structures without fixatives.
• Super-resolution microscopy uses computational techniques to exceed the resolution limit of traditional light microscopes.
• Cell fractionation involves breaking open cells and separating organelles based on size/density using centrifugation.
• Cell fractionation is useful because it allows scientists to study organelles in isolation to understand their function.
• Ultracentrifuges are tools used for cell fractionation.