HardBiologyHigh School (11–12)Cell Biology › Cell Structure and OrganellesConceptualA-LevelAPBoard ExamIB
A student finds that a mature red blood cell of a cow has no nucleus…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student finds that a mature red blood cell of a cow has no nucleus. A cell of the pancreas, which makes digestive enzymes, has large and many nucleoli. Name another mature cell with no nucleus, and explain the large nucleoli of the pancreatic cell.
Need a reminder? The key ideaShow
The nuclear envelope has two membranes and pores. Nucleoli have no membrane and make rRNA. Chromatin is DNA, histones, non-histone proteins and RNA. The centromere sits in the middle (metacentric), a little off the middle (sub-metacentric), near one end (acrocentric) or at the end (telocentric).
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. No nucleus. The red blood cells of many mammals lose their nucleus as they mature. So do the sieve tube cells of vascular plants.
Step 2. The nucleolus. It is the site of active synthesis of ribosomal RNA.
Step 3. The pancreatic cell. Enzymes are proteins, and ribosomes make proteins. A cell making much protein needs many ribosomes, so its nucleoli are larger and more numerous.
Answer: sieve tube cells have no nucleus. The pancreatic cell makes much protein, so it needs much rRNA for its ribosomes, and its nucleoli are large and many.
Discussion (0)
Log in to join the discussion.
Loading…