Practise IB Biology HL B2.2 organelles through compartmentalization, ribosome location, secretion pathways and cristae, grana and stroma adaptations.
Testis cells are eukaryotic cells. Identify the structures seen under the electron microscope in testis cells that are not present in prokaryotic cells.
a. nucleus/nuclear membrane
b. membrane bound organelles
c. mitochondria
d. rough ER/smooth ER/golgi apparatus
e. lysosomes / centrioles /
f. large/80S ribosomes / ribosomes attached to a membrane
g. linear chromosomes / histones /
4 max
The structure of membranes allows them to carry out many functions in cells.
Discuss the use of membranes for compartmentalization in eukaryotic cells.
a. (membranes divide the cell into) organelles;
b. nucleus/chloroplast/mitochondrion is double membraned/has inner and outer membrane;
c. enzymes/substrates can be concentrated (in the small volume);
d. different/incompatible functions/processes in different organelles (so harm prevented);
e. hydrolytic/digestive enzymes held inside lysosomes/phagocytic vacuoles;
f. pH/conditions can be for optimized for (each) function/process;
g. small spaces/volumes for proton gradient/concentration gradient (to develop quickly);
h. (post- transcriptional) modification of mRNA in nucleus (before it reaches the ribosome);
i. vesicles for transport/transfers;
j. nuclear membrane/envelope protects DNA/chromosomes (from the cytoplasm);
Marking guidance:
Do not award marks
describing the functions of the plasma membrane.
4
max
Draw a labelled diagram of a mitochondrion as seen in an electron micrograph.
Award [1] for each one of the following labelled structures. outer membrane and inner membrane shown as two separate lines;
inter-membrane space / space between inner and outer membranes;
cristae (shown as projections of inner membrane);
matrix;
(70S) ribosomes (shown as dots in the matrix);