Bio

ch01, ch05

Q: What are the seven vital characteristics that all living organisms share?

A: Reproduction, growth, nutrition (obtaining food), respiration (releasing energy), irritability (detecting and responding to stimuli), movement, and excretion (to maintain homeostasis).

Q: What is the difference between homeostasis and excretion?

A: Homeostasis is the maintenance of a constant internal environment in an organism, while excretion is the removal of metabolic wastes produced by chemical reactions inside the body to help maintain that constant environment.

Q: Why is studying biology important on a broader scale?

A: It develops an appreciation for organisms and the environment, builds scientific problem-solving skills, and helps us understand health, environmental, and social issues.

Q: What is the general sequence of steps in the scientific method?

A: Making observations $\rightarrow$ asking a question $\rightarrow$ proposing a testable hypothesis $\rightarrow$ making a prediction $\rightarrow$ testing via a controlled experiment $\rightarrow$ drawing a conclusion (or revising the hypothesis if falsified).

Q: How do independent, dependent, and controlled variables differ in an experiment?

A: The independent variable is the factor intentionally changed/tested; the dependent variable is the factor measured/observed; controlled variables are all other factors kept constant to ensure a fair test.

Q: What is the purpose of a control set-up?

A: It is identical to the experimental set-up except that the independent variable is absent, ensuring that the observed results are caused only by the factor being tested.

Q: How do accuracy, reliability, and validity differ in scientific investigations?

A: Accuracy is how close a measurement is to the true value (improved by better apparatus/skills); reliability is how consistent repeated results are (improved by larger sample sizes and repetition); validity is whether the experimental design actually tests the intended aim by properly controlling variables.

Q: What are the core principles of the Nature of Science?

A: Science advances through reasonable skepticism, requires creativity and imagination, relies on controlled experiments, involves ongoing inquiry, uses diverse methods, and builds upon the work of previous scientists.

Q: What distinguishes organic chemical constituents (biomolecules) from inorganic ones in organisms?

A: Organic biomolecules are complex carbon-containing molecules built from smaller repeating building blocks (carbohydrates, lipids, proteins, and nucleic acids), whereas inorganic constituents (like water and minerals) generally lack carbon-based backbones.

Q: How are large biomolecules built up and broken down chemically?

A: They are built by condensation (joining smaller molecules together with the release of water) and broken down by hydrolysis (splitting larger molecules using water).

Q: What is the overall structural hierarchy and primary role of carbohydrates?

A: Made of C, H, and O (in a 1:2:1 ratio), they range from simple sweet/soluble monosaccharides and disaccharides to complex, insoluble polysaccharides. They serve as the main immediate energy source, energy reserves (starch in plants, glycogen in animals), and structural support (cellulose in plant cell walls).

Q: What are the three main types of lipids and their big-picture biological roles?

A: Triglycerides (long-term energy reserves, heat insulation, shock absorption, carrying lipid-soluble vitamins), phospholipids (major structural component of cell membranes), and steroids (e.g., cholesterol, used to make certain hormones).

Q: What determines the specific function of a protein?

A: The unique sequence of its 20 types of amino acid building blocks determines how the polypeptide chain coils and folds into a specific 3D shape; if this shape is lost, the protein loses its function.

Q: What are the broad categories of protein functions in the body?

A: Growth and tissue repair (structural components of cell membranes and cytoplasm), functional roles (enzymes, antibodies, hormones, haemoglobin), and acting as a last-resort energy source.

Q: How do DNA and RNA differ in structure and overarching function?

A: Both are polynucleotides, but DNA (containing deoxyribose) carries the genetic blueprint that controls cell activities and organism traits, while RNA (containing ribose) acts as the working instruction manual involved in synthesizing proteins.

Q: How are the seven food substances grouped by their ability to supply energy?

A: Energy-providing: carbohydrates, lipids, and proteins. Non-energy-providing: vitamins, minerals, dietary fibre, and water.

Q: What are the four main biological roles of water in living organisms?

A: It acts as a reactant (in photosynthesis and digestion), an aqueous medium for cellular chemical reactions, a transport medium (in blood and plant vessels), and a cooling agent (via evaporation of sweat).

Q: What are the standard food tests and positive results for glucose, reducing sugars, starch, lipids, and proteins?

A:

• Glucose (Clinistix paper): Pink → purple

• Reducing sugars (Benedict's test + heat): Blue → brick red percipitate

• Starch (Iodine test): Brown → blue-black

• Lipids (Grease spot test): Translucent spot on filter paper that disappears when immersed in an organic solvent

• Proteins (Albustix paper): Yellow → green