Question

reviously unknown single-celled organism that lacks a nuclear envelope and cochondria has just been discovered. Which of the following cell components would this organism most likely possess? a) lysosomes b) actin filaments c) ribosomes d) endoplasmic reticulum e) all of these components are equally possible 6) Autophagy is a process by which: a) Human macrophages find and consume foreign invaders such as infecting bacteria in the human body b) Peroxisomes break down long chain fatty acids into shorter lengths that mitochondria can consume for energy production c) Lysosomes fuse with damaged organelles to break them down d) Viruses replicate themselves in host cells and then continue to infect new hos cells 7) True or False: the "B-barrel" structure of transmembrane proteins is made up primaril of multiple a-helical domains that pass through the lipid bilayer membrane. a) True b) False 8) Which of the following represents the most reduced form of carbon? a) CH4 b) COOH c) CHO d) CH2OH e) CO2 9) All proteins: a) are enzymes b) contain at least one a-helix c) are water-soluble d) a) and b) above e) bind to other molecules

Answer 1

5) c) ribosomes

• the given cell in question is prokaryotic and as prokaryotes lack membrane bound organelles, ribosomes are the only organelles that are non membrane bound and present both in prokaryotes as well as eukaryotes.
• all the other components are membrane bound and hence more likely to be absent.

6) c) lysosomes fuse with damaged organelles and break them down

• this is a form of macroautophagy in which lysosomes are involved in removing the dysfunctional components of the cell.
• lysosomes are also known as the suicidal bags of the cell.

7) b) False

• beta barrel structure of protein is made up of many beta barrels that are arranged in an anti parallel fashion.
• It is a closed structure with hydrogen bonds involved in binding.

8) a) CH4

• reduction: addition of hydrogen/ removal of oxygen/ gain of electrons
• in CH4 there are 4 hydrogen atoms and hence it is the most reduced form of carbon among the given options

9) e) bind to other molecules

• These molecules are termed ligands
• most enzymes are proteins, but ribosomal enzymes are also found
• not all proteins are water soluble, it depends on the side chains
• proteins may contain an alpha or beta structure

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