Cell structure and microscopy & Disease
What is the name of the circular DNA found in bacterial cells?
Plasmid
What term describes the loss of a protein's 3D structure?
Denaturation
What is the name of the model that describes the structure of cell membranes?
Fluid mosaic model
During which phase of mitosis do chromosomes line up at the equator?
Metaphase
Which chamber of the heart pumps blood to the lungs?
Right ventricle
Compare the structure and function of rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).
RER: Studded with ribosomes, involved in protein synthesis and modification
SER: No ribosomes, involved in lipid synthesis
Describe the biochemical test for non-reducing sugars and the expected results for sucrose.
First perform Benedict's test → negative result (remains blue)
Boil sample with dilute hydrochloric acid to hydrolyze glycosidic bonds
Neutralize with sodium hydrogencarbonate
Perform Benedict's test again → positive result (brick red precipitate forms)
Sucrose gives negative then positive; glucose gives positive immediately.
Explain why gas exchange surfaces need to be moist.
Oxygen and carbon dioxide dissolve in water before diffusing across membranes
What are Okazaki fragments and where are they found?
Short DNA segments on the lagging strand during replication
Explain how both cohesion and adhesion are involved in the transpiration stream.
Cohesion: Water molecules stick together → form continuous column in xylem
Adhesion: Water molecules stick to xylem walls → helps pull water upward
Together: Create capillary action and maintain water column under tension
Explain how inappropriate antibiotic use contributes to antibiotic resistance, including the concepts of selective pressure and horizontal gene transfer.
Inappropriate use (wrong drug, incomplete course) kills susceptible bacteria → selective pressure favors resistant strains → resistance genes spread via plasmids (conjugation) → multi-resistant strains emerge
Explain how pH affects enzyme activity, using pepsin (optimum pH 2) and trypsin (optimum pH 8) as examples.
Answer:
Enzymes have an optimum pH where they work best.
Extreme pH disrupts ionic bonds and hydrogen bonds in the enzyme, changing the active site shape.
Pepsin works in acidic stomach conditions; trypsin works in alkaline small intestine.
Explain how root hair cells are adapted for water and mineral ion uptake.
Large surface area: Long extensions increase absorption
Thin walls: Short diffusion distance
Many mitochondria: Provide ATP for active transport of ions
Carrier proteins: For specific ion uptake against concentration gradient
Describe 3 differences between DNA replication and transcription
. Purpose/Function:
DNA Replication: Creates an exact copy of the entire DNA molecule for cell division
Transcription: Produces a complementary RNA copy of a specific gene for protein synthesis
2. Enzyme Involved:
DNA Replication: Uses DNA polymerase
Transcription: Uses RNA polymerase
3. Product Formed:
DNA Replication: Produces two identical DNA double helices
Transcription: Produces single-stranded mRNA (plus other RNA types like tRNA, rRNA)
See page 5
(pulmonary) semilunar valve
Explain how the microtubules are involved in: a) cell division, b) organelle movement, and c) cell shape maintenance. Include specific cytoskeletal components in your answer.
a) Cell division: Microtubules form spindle fibers that separate chromosomes; actin filaments form cleavage furrow in cytokinesis
b) Organelle movement: Microtubules serve as tracks for motor proteins (kinesin, dynein) to transport vesicles/organelles
c) Cell shape: provide mechanical strength; form microvilli and maintain cell cortex
At a picnic, 3 people eat wild mushrooms. One dies (Death cap) , one gets sick(False morel) , one is fine. All mushrooms contain enzyme inhibitors. Explain the different outcomes using enzyme kinetics.
Death cap: Irreversible inhibitor of RNA polymerase (α-amanitin) → stops transcription → cell death.
False morel: Reversible inhibitor of succinate dehydrogenase → less severe.
Edible: No inhibitors or not absorbed.
Antarctic fish survive in -1.8°C water without freezing. Their membranes remain fluid while human cell membranes would solidify. Explain three specific biochemical adaptations these fish have evolved, and predict what would happen if you transplanted their membrane lipids into tropical fish.
More unsaturated fatty acids: Double bonds create kinks → prevents tight packing
Shorter fatty acid chains: Reduce hydrophobic interactions → lower melting point
Altered cholesterol content: Adjusts to maintain optimal fluidity (varies by species)
Transplant consequence: Tropical fish membranes would become too fluid at higher temperatures → lose integrity → cell lysis
During protein synthesis, how many tRNA molecules can be bound to a ribosome at the same time at most
2
See page 7
see page 1
page 2
See page 3
See page 4
"Cystic Fibrosis (CF) is a genetic disorder caused by mutations in the CFTR gene, which codes for a chloride ion channel protein found in epithelial cell membranes. These channels normally regulate the movement of chloride ions and water across cell membranes.
Normal CFTR function: In healthy individuals, CFTR channels transport chloride ions out of cells. Water follows the chloride ions by osmosis, keeping secretions (like mucus, sweat, and digestive fluids) thin and watery.
Why CF patients have thick mucus in their lungs (refer to osmosis and chloride transport)
Why their sweat is salty (refer to epithelial transport in sweat glands)
Thick mucus: Defective CFTR → reduced Cl⁻ secretion → less water moves into airways by osmosis → mucus becomes thick and sticky → impaired ciliary clearance
Salty sweat: Sweat glands normally reabsorb Cl⁻ (and Na⁺) from sweat; defective CFTR prevents reabsorption → Cl⁻ (and Na⁺) remain in sweat → salty sweat
Explain how mutations in two different types of genes can lead to cancer?
Proto-oncogenes → when mutated become oncogenes (e.g., growth factor genes that are always "ON") → excessive cell division.
Tumor suppressor genes → when mutated become inactive (e.g., p53 which normally stops damaged cells from dividing) → damaged cells keep dividing.
see page 8
page 9