(3 marks) (3 marks)
(3 marks)
Questions
1 Suggest what would happen to the fish if they had no homeostatic mechanism.
2 The branchial MR cells are rich in mitochondria,
a Use information in Figure 1 to suggest the importance of the mitochondria.
b Suggest how the cell maintains a sufficient oxygen supply for the
mitochondria
3 Na /K-ATPase is a protein in the cell membrane. This protein is regulated by pH
changes. Use the information in the diagram to suggest a mechanism for
switching on the Naf/K-ATPase linked to cell surface membrane.
4 Use Figure 1 to predict the changes to the internal environment of the cell when
the Na'/K'-ATPase is active. Suggest a mechanism for maximum sodium uptake
from the water by the cell.
5 Suggest a function for the channel protein B.
6 Bafilomycin A1 is an antibiotic that specifically inhibits V-ATPase.
a What is meant by the term "specific" in this context?
b Predict how the water potential of the blood of the killifish might change in the
presence of this antibiotic.
(4 marks)
(5 marks)
(2 marks)
(1 mark)
(3 marks)

Proteins are the workhorses of the cell, controlling virtually every reaction within as well as providing structure and serving as signals to other cells. proteins are long chains of  amino acids  , and the exact sequence of the amino acids determines the final structure and function of the protein. instructions for that sequence are encoded in  genes  . to make a particular protein, a messenger ribonucleic acid (mrna) copy is made from the gene (in the process called  transcription  ), and the mrna is transported to the  ribosome  . protein synthesis, also called  translation  , begins when the two ribosomal subunits link onto the mrna. this step, called initiation, is followed by elongation, in which successive amino acids are added to the growing chain, brought in by transfer rnas (trnas). in this step, the ribosome reads the  nucleotides  of mrna three by three, in units called  codons  , and matches each to three nucleotides on the trna, called the anticodon. finally, during termination, the ribosome unbinds from the mrna, and the  amino acid  chain goes on to be processed and folded to make the final, functional protein

Its not plagyrisim if you change the wording up.