Within the fluid mosaic of a plasma membrane, what is the role of transport and channel proteins?
A) They identify the cell.
B) They may set off cellular changes such as cell division or hormone secretion.
C) They prevent the passage of amino acids.
D) They are cell-surface connection sites.
E) They permit ions and water molecules to move through the plasma membrane.
E
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According to the Baltimore system, there are ______ major groups of viruses
A. 4 B. 5 C. 6 D. 7 E. 8
Answer the following statements true (T) or false (F)
1. Catabolic and anabolic reactions in living cells involve the transfer of electrons from one molecule to another in reduction-oxidation reactions. 2. Metabolism refers to only those reactions that release energy. 3. The half-life of a molecule is the time it takes for 50% of the molecule to be broken down and recycled. 4. Autophagy is an important process that removes worn-out organelles, recycles components, then releases them into the cytosol.
Ribosomes that do not anchor on the surface of the rough endoplasmic reticulum during translation most probably
A) are synthesizing cytoplasmic proteins. B) have a defect in ribosomal proteins that allow attachment to the surface. C) have a signal peptidase error. D) do not make the appropriate anchor protein. E) All of the above are probable reasons.
An excess number of chromosomes in a gamete results from
A. mutation. B. nondisjunction. C. crossing-over. D. fertilization.