Gas Exchange I
What is the enzyme that catalyzes the reversible hydration of CO₂?
What is carbonic anhydrase
What metal does hemoglobin use to bind O₂?
Iron (Fe²⁺)
What are the four classic signs of inflammation?
Rubor, calor, tumor, dolor (redness, heat, swelling, pain)
What are the two main communication systems in animals?
Nervous (fast) and endocrine (slow)
What structure links the nervous and endocrine systems?
The hypothalamus
What evolutionary event allowed for the rise of aerobic respiration?
What is The Great Oxidation Event/Oxygen Revolution (2.5 BYA)
What is the Bohr effect?
Decreased pH (higher CO₂) lowers Hb’s O₂ affinity, enhancing release to tissues.
What distinguishes innate from adaptive immunity?
Innate is fast and non-specific
Adaptive is slow, specific, and provides memory.
Which class of hormones binds intracellular receptors?
Lipophilic (steroid) hormones
What are the two major hormones regulating blood glucose
Insulin and glucagon
Why does nitrogenase need to be protected from oxygen, and how do plants achieve this?
O₂ inactivates nitrogenase; legume hosts produce leghemoglobin to isolate O₂
Why do fetal and adult hemoglobins have different sensitivities to 2,3-BPG?
Fetal Hb binds O₂ more tightly (less affected by 2,3-BPG) to extract O₂ from maternal blood.
Evolutionary benefit because babies cannot breathe on their own
Explain how pattern recognition receptors (PRRs) like Toll-like receptors detect pathogens.
They recognize conserved microbial motifs (PAMPs) and trigger innate immune responses.
A mutation disables a plant’s auxin transport proteins. Predict two growth defects.
Loss of phototropism (growth towards light) and failure of apical dominance
No auxin gradient to suppress lateral buds.
A patient shows lethargy, cold intolerance, and weight gain. Which axis is affected and how?
HPT axis → hypothyroidism (low thyroid hormone, reduced metabolism)
Rubisco can bind both CO₂ and O₂. Explain how carbon-concentrating mechanisms (CCMs) compensate for this problem
CCMs increase CO₂ concentration near Rubisco to outcompete O₂, improving photosynthetic efficiency (e.g., C₄ and CAM pathways)
Explain how fish gills maximize O₂ extraction from water.
Countercurrent exchange maintains a gradient favoring O₂ diffusion along the entire capillary.
Why is clonal deletion essential in the adaptive immune system?
It prevents autoimmunity by removing self-reactive B and T cells.
Explain how negative feedback maintains homeostasis using an endocrine example.
Insulin lowers high blood glucose, reducing its own stimulus (high blood sugars)
Explain why chronic stress can suppress the immune system.
Prolonged cortisol (HPA axis) reduces inflammation and immune cell activity.
Nitrogenase, the enzyme that fixes atmospheric nitrogen, is easily inactivated by oxygen. Explain why this is a problem for cyanobacteria that also perform photosynthesis, and describe one way they solve it.
Photosynthesis produces oxygen, which can inactivate nitrogenase by oxidizing its metal cofactors. Cyanobacteria solve this by separating the two processes
This separation protects nitrogenase while allowing both processes to occur.
In hypoxic environments, predict how Hb’s dissociation curve might shift and explain the physiological benefit
Shifts right (lower affinity) to enhance O₂ unloading to tissues; adaptation improves survival at low O₂.
Compare RNA interference (RNAi) and CRISPR-Cas as antiviral systems and discuss how these ancient mechanisms have been repurposed in biotechnology.
Both detect and degrade foreign nucleic acids; RNAi silences viral RNA in eukaryotes, CRISPR cuts viral DNA in bacteria; now tools for gene editing and knockdown.
Auxin promotes stem elongation but can inhibit root growth at high concentrations. Explain how differences in auxin concentration lead to these opposite effects.
In shoots, moderate auxin levels stimulate cell wall loosening and elongation (the “acid growth” response).
In roots, high auxin levels trigger stress hormones like ethylene, which slow cell expansion and growth. Thus, the same hormone has different effects depending on its local concentration and tissue sensitivity.
Compare the mechanisms of short-term and long-term stress responses and predict which would dominate in chronic psychological stress.
Short-term: SNS releases epinephrine, rapid fight-or-flight response
Long-term: glucocorticoids, sustained energy mobilization, but immune suppression → dominates under chronic stress (high cortisol levels for a prolonged period).