Question
(a) Label X and Y on the diagram of the heart.
b. Explain how the circulatory system is able to transport the blood under high pressure from the heart to the rest of the body.
c. The heart responds quickly to physical activity. Describe how heart rate is controlled to meet the increased circulatory demands.
Answer/Explanation
Ans:
a) X: pulmonary artery
Y: left atrium Accept auricle
b)
a. contraction of ventricle creates high pressure Features require an explanation, a list is inadequate b. blood at high pressure is carried out of the heart through arteries
c. thick muscular walls of arteries resist pressure/prevent leaks
d. elastic recoil of arterial walls helps to push blood
e. narrow lumen of arteries maintain pressure
c)
a. nerve impulse from medulla/brain acts on heart/right atrium
b. pacemaker/sinoatrial node/SAN increases/controls contraction of heart
Question
(a) The structure of prokaryotic cells has been investigated using electron microscopy.
Draw a labelled diagram to show prokaryotic cell structure.
(b) Outline the reasons for differences between the proteomes of cells within a multicellular organism.
(c) Discuss the cell theory and its limitations.
Answer/Explanation
Ans:
a)
a. cell wall — a uniformly thick wall
b. pili — hair-like structures connected to cell wall
OR
flagellum — at one end only, longer than pili
c. plasma/cell membrane — represented by a continuous single line
d. «70S» ribosomes — drawn as small discrete dots not circles
e. naked DNA/nucleoid — region with DNA not enclosed in membrane
f. cytoplasm — the non-structural material within the cell
b)
a. all the genome is the same in all the cells of an organism
b. the genome/DNA/genes instructs the production/expression of proteins/proteome
c. the proteome is all the proteins produced by a cell
d. the proteome varies with the function/location/cell differentiation/environmental conditions of the cell
e. specific genes are expressed/turned on/off in different cells
f. «turning on/off» according to a required function
c)
cell theory:
a. cell theory is the accepted explanation of life
b. organisms are composed of «one or more» cells
c. cells are the basic/fundamental/smallest units of life
d. cells can only come from pre-existing cells
e. spontaneous generation of life has been disproven
limitations:
f. striated muscle cells contain many nuclei «while most eukaryotic cells have one nucleus»
OR
red blood cells have no nucleus «while most eukaryotic cells have one nucleus»
g. giant algae have complex single cell structure
OR organisms as large as giant algae would be expected to be multicellular, but they have only one cell with one nucleus
h. aseptate fungal hyphae are tube-like structures that contain no cell membranes between the many nuclei
OR
slime molds contain many nuclei
i. viruses have some characteristics of living organisms but are not cells