bio sci 93 midterm 1 Exam Questions with Revised Correct Detailed Answers with Rationales Guaranteed Pass

bio sci 93 midterm 1 Exam Questions with Revised Correct Detailed Answers with Rationales Guaranteed Pass Lecture 1 - ● Properties of life: order, regulation, evolutionary adaptation, energy processing, growth and development, response to the environment, reproduction. ● Theme of emergent properties: The biosphere → ecosystems → communities → populations → organisms → organs → tissues → cells → organelles → molecules ● The cell is the basic unit of structure and function and smallest to perform activities of life. All cells are enclosed by a membrane and use DNA as genetic information. ● Structure fits function ● Organisms as open systems ● DNA is the basis of inheritance Lecture 2 - ● Hydrogen bonds: The H atom forms one covalent bond with another atom in the same molecule where it is present, and a second weaker bond (the "hydrogen bond") with an atom in another molecule ● Cohesion: interaction between water molecules → surface tension ● Water can make maximum of 4 hydrogen bonds. ● Hydrophilic substances → Affinity for water, hydrophobic substances → Repel water 2 | P a g e Katelyn Whitman© 2025, All Rights Reserved. ● Water can dissociate into a hydrogen ion and a hydroxide ion. ● Buffers: resist change in pH of a solution ● The main buffer in blood is carbonic acid / bicarbonate Lecture 3 - ● Carbon atoms → building blocks of biological molecules (4 valence electrons and can form four covalent bonds) ● Properties of an organic molecule also depend on the chemical groups attached to the carbon skeleton. ● Chemical groups: hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, methyl and phosphate ● Dehydration reaction → synthesizing a polymer, Hydrolysis → breaking down a polymer * A carbohydrate is a molecule consisting of carbon, hydrogen and oxygen atoms. Examples of it would be sugars, starches and fiber. Simplest carbohydrates are monosaccharides. Disaccharide is 2 monosaccharides joined together by glyosidic linkage (covalent bond). Polysaccharides are Polymers of 100s-1000s of monosaccharides. ● Lipids (not polymers) are diverse group of hydrophobic molecules and are in three forms of fats, phospholipids, and steroids. ● Fats → saturated fats vs unsaturated fats, Phospholipids → glycerol + two fatty acids + phosphate group + choline, Steroids → Carbon skeleton with 4 rings and varying functional groups Lecture 4 - ● Amino acids (monomers) → polypeptides (polymer of amino acids in specific sequence) → proteins (one or more polypeptides with specific 3-D conformation) ● Proteins are all structured from the same set of 20 amino acids. ● Structure of an amino acid contains: amino group, hydrogen, carboxyl group and an R group (variable side chain). Make sure you can identify the polar amino acids vs non polar amino acids based on their structures. 3 | P a g e Katelyn Whitman© 2025, All Rights Reserved. ● Protein folding: - Primary (amino acid sequence) - Secondary (hydrogen bonding, Alpha helix vs Beta pleated sheets) - Tertiary structure (overall shape of polypeptide, R group interactions) - Quaternary structure (Overall protein structure resulting from combined polypeptides of 2 or more, stabilized by R group interactions) ● A single change in the primary structure of a protein can have pleiotropic effects such as different disease or health conditions (ex. Sickle cell anemia) ● Damaged or misfolded proteins are actively degraded by proteasome Lecture 5 - ● Plasma membrane composition: - Lipids (phospholipids which are the main fabric of membrane that form the bilayer) - Cholesterol (regulates membrane fluidity) -Proteins (embedded in bilayer and control the movement of different materials inside and outside of the cell) -Carbohydrates (present on extracellular surface and are mainly responsible for cell-cell recognition). ● Fluid mosaic model of plasma membrane ● The cell membrane is fluid. Lecture 6 - ● Plasma membrane is selectively permeable ○ Can pass through: small, uncharged, nonpolar molecules ○ Cannot pass through: large, charged, polar molecules ● Tonicity ○ Describes the state of the cell based on extracellular environments ○ Hypotonic, isotonic, hypertonic 4 | P a g e Katelyn Whitman© 2025, All Rights Reserved. ● Membrane Proteins ○ Carrier proteins: can change shape when a molecule binds to it (active and passive transport) ○ Channel proteins: opens to allow molecules to pass through (passive) ● Co-Transport ○ Na+/glucose pump (animals) ○ H+/sucrose pump (plants) ● Modes of bulk transport ○ Exocytosis, endocytosis ■ Phagocytosis ■ pinocytosis ■ receptor-mediated endocytosis Lecture 7 - Microfilaments: Composed of: actin Plays a role in phagocytosis via pseudopodia extension Functions: Maintains cell shape, transport of cargo over 5 | P a g e Katelyn Whitman© 2025, All Rights Reserved. short distances, cell motility, cytoplasmic streaming, contraction of muscle (uses myosin and ATP) Intermediate Filaments: Composed of: many different types of IF, depending on the cell type Very stable Functions: Forms nuclear lamina, maintains cell shape Microtubules: Composed of: tubuli