Introduction to the Living Cell

Question 1

What is a cell?

Answer 1

Cells are the fundamental unit of all living thing on earth. They take nutrients and free energy from their surroundings and duplicate. All cells arise from the division of pre-existing cells.

Question 2

What is the history of cell discovery?

Answer 2

• Origin of the word “cells” was by Robert Hooke (1665), after observing slices of cork under a microscope, calling the holes “cells” as they resemble the small rooms of Monks.
• Antonie van Leeuwenhoek was first to see and describe single-celled microorganism, calling them “animalcules”. He observed algae growth in water using a microscope with better lens he made himself. First to observe RBCs, sperm, protozoa and bacteria.

Question 3

How was cell division discovered?

Answer 3

• Theodor Schwann (studied animals) and Matthias Jakob Schleiden (studied plants) came to the conclusion “All living things are composed of cells and cell products.”
• Hugo van Mohl discovered cell division, but Barthélémy du Mortier proceeded him as he observed mid-like partition b/w original and new cells.
• Rudolf Virchow was given credit for “omnis cellula e cellula” (“cells are created through division of pre-existing cells”). Doesn’t credit Robert Remak for stating “binary fission was the means of reproduction of new animal cells”.

Question 4

Define Taxonomy

Answer 4

Taxonomy – Discipline of defining groups of biological organisms based on shared characteristics

Question 5

Define Phylogenetics

Answer 5

Phylogenetics – The study of evolutionary relationships between groups of organisms

Question 6

What are the universal features of cells on earth?

Answer 6

• Phospholipid bilayer
• Exchanging molecules with their environment
• Heredity info stored in DNA
• DNA fragment corresponding to a single protein = a gene
• Translate RNA into protein in the same way
• Cells are made from the same basic building blocks
• Sunlight is the ultimate source of most biological energy
• Role of ATP as the main energy currency (in metabolism)
• “Life is a pattern of flux”
• Homeostasis

Question 7

Explain the meaning of ‘Life is a pattern in flux’

Answer 7

• Cells divide and cells die. Rudolf Schoenheimer discovered molecules in our body are almost continuously being replaced, i..e they have a turnover rate (e.g. water). Some tissues have a higher turnover rate than others, for example the gastrointestinal lining (5 days), compared to red blood cells (120 days), compared to cerebral cortex (close to persons age).
• 98% of human body is replaced in one year.

Question 8

What is the exception to the ‘Life is a patter in flux’ rule?

Answer 8

The exception is DNA. It is conserved (semi-conservative replication).

Question 9

What is compartmentalisation?

Answer 9

Eukaryotic cells are compartmentalized, in other words, they have many organelles performing specific functions which have plasma membranes surrounding them. Prokaryotes do not have this.

Question 10

What are the 3 major domains of a cell?

Answer 10

The three major domains of cells, which evolved in the following order are:
• Bacteria (Eubacteria) — Archaea (Archaebacteria) — Eukaryotes