Question
(a) Outline the role of the parts of an alveolus in a human lung.
(b) Explain how antibiotic resistance can evolve in bacteria, such as those causing pneumonia.
(c) Many diseases are caused by bacteria and other pathogens. Explain, using examples,
how other factors can lead to disease in humans.
Answer/Explanation
Ans:
a)
a. the (spherical) wall of an alveolus maximizes/allows gas exchange $\checkmark$
b. pneumocytes I (optimize) gas exchange $\checkmark$
c. pneumocytes II produce surfactant $\checkmark$
d. adjacent capillaries enclose alveolus for efficient gas exchange with blood $\checkmark$
e. surfactant reduces surface tension/prevents collapse of alveolus
f. (alveolar) macrophages/phagocytes help with defense/homeostasis/response to foreign substances $\checkmark$
b)
a. antibiotic resistance exists as a genetic variation (within the population) $\checkmark$
b. (antibiotic resistance) may occur from transfer of genetic material
OR
(antibiotic resistance) may occur through mutation $\checkmark$
c. resistance is specific to one antibiotic $\checkmark$
d. only bacteria with resistance gene reproduce in the presence of antibiotic $\checkmark$
e. frequency of resistant bacteria increases in population $\checkmark$
f. resistant population replaces non-resistant over time $\checkmark$
c)
Since this question is open-ended here is how it may be marked:
For any non-pathogenic disease being addressed, look for the following components
● name of disease/condition.
● factor/category e.g.: genetic, lifestyle, environmental, psychological, multi-factoral.
● description/symptoms of disease.
Question
(a) Draw a labelled diagram to show the fluid mosaic model of the plasma membrane.
(b) Unicellular and multicellular organisms share the same functions of life. Outline four functions of life.
(c) The structure of organisms is based on organic molecules containing carbon.
Explain the cycling of carbon in an ecosystem.
Answer/Explanation
Ans:
a)
a. two correctly oriented layers of phospholipids/phospholipid bilayer shown with heads facing in opposite directions $\checkmark$
b. phospholipids shown with two parts labelled hydrophilic/phosphate head AND hydrophobic/hydrocarbon tail
c. protein (any) shown as a globular structure embedded in one/both layers of phospholipid $\checkmark$
d. peripheral protein, shown as globular structure at the surface of the membrane AND integral protein shown as embedded globular structures $\checkmark$
e. glycoprotein shown as embedded globular structure with antenna-like carbohydrate protruding / carbohydrate shown as a branched/antenna-like structure either on a protein or on a phospholipid
OR
channel protein(s) shown with a pore passing through it
OR
pump protein shown as a transmembrane globular structure $\checkmark$
f. cholesterol shown in between adjacent phospholipids $\checkmark$
b)
a. nutrition: process by which organisms take in and make use of food//nutrients OWTTE $\sqrt{ }$
b. metabolism: conversion of organic molecules/chemical reactions in an organism $\checkmark$
c. growth: increase in size/mass/number of cells within an organism $\checkmark$
d. response/irritability/sensitivity: reactions/responsiveness to stimuli/factors $\checkmark$
e. homeostasis: regulating/maintaining constant/stable interior environment $\checkmark$
f. reproduction: production of similar cells/organisms from existing ones/offspring $\sqrt{ }$
g. excretion: elimination of (metabolic) wastes $\checkmark$
c)
a. autotrophs/producers absorb carbon (dioxide) from atmosphere/air/water $\checkmark$
b. autotrophs make carbohydrates/organic compounds / perform photosynthesis $\checkmark$
c. carbon (compounds) pass along food chains/trophic levels (as consumers feed) $\checkmark$
d. respiration releases carbon (dioxide) into atmosphere/water $\checkmark$
e. carbon (dioxide) is released from dead matter /by decomposition/respiration $\checkmark$
f. methane is produced during anaerobic respiration of organic matter / by methanogens in cattle/herbivores $\checkmark$
g. methane is oxidized into carbon dioxide in the atmosphere $\checkmark$
h. fossil fuels/peat were made from partially decomposed organic matter $\checkmark$
i. combustion of fossil fuels/forest fires/biomass releases carbon (dioxide) into the atmosphere $\checkmark$
j. volcanic eruptions may add large quantities of carbon (dioxide) into the atmosphere $\checkmark$