Introduction to the living cell

Question 1

Definition of a cell

what do they do?

Answer 1

Cells are the fundamental unit of all living things
on earth.

They take nutrients and free energy from their
surroundings and make copies of themselves

Question 2

Taxonomy

Answer 2

Discipline of defining groups of biological organisms based on shared characteristics

Question 3

Phylogenetics

Answer 3

The study of evolutionary relationships between groups of organisms

Question 4

major domains of cells (3)

Answer 4

Bacteria (Eubacteria) —> Archaea (Archaebacteria) —> Eukaryotes

Question 5

Where do cells come from?

earlier vs modern?

Answer 5

• Earlier belief - spontaneously out of nothing
• Reality/modern belief - cells created through division
of pre existing cells

Question 6

What do cells look like?

Answer 6

• Cells may be small, big or fancy shaped

They may be of different shapes
• RBC - round, flat, biconcave
• WBC - amoeboid
• Columnar epithelial - long, narrow
• Nerve cells - long extensions - axons

Question 7

Universal Features of Cells

descended from?
all cells are surronded by? which is made up of?

how do they exchnaged molecules from surroundings?

how do cells communicate?

what do they store? what else do they store?

what builds up a cell?

Answer 7

• Descended from a single common ancestor

• All cells are surrounded by a plasma membrane
plasma membrane made up of phospholipids
this packages them and separates them from the environment

• All cells exchange molecules from their surroundings
using transporter molecules
molecules include sugars, amino acids, peptides, ions etc
this helps regulate metabolism

• Cells communicate
they secrete a signalling molecule
this goes into the blood/lymphatic system
this binds to receptors on other cells
cascade of events takes place

• All cells store hereditory information as DNA
information is stored as nucleotides
there are 4 nucleotides: guanine, adenine, cytosine, tyrosine
these nucleotides are polymerized to form a single strand of DNA
there are non covalent interactions between two strands: H bonds
this then forms a double stranded DNA
this chemical nature is common to everything that lives

• DNA stores protein information
The DNA fragment corresponding to one protein is one gene
transcription of gene takes place
RNA is formed
translation takes place in ribosome
a peptide is formed

• Cells are made up of only a few main building blocks
sugars form polysaccharides
fatty acids form lipids
amino acids form proteins
nucleotides form nucleic acids

ATP as a central currency of energy: Sunlight being the main source

Question 8

Life is a pattern in flux

being in a steady state of rapid flux meaning?

Answer 8

suggest that all constituents of living matter, whether functional or structural, of simple or complex constitution, are in a steady state of rapid flux.”

• an experiment to prove this was conducted after the discovery of isotopes
- animals were fed isotopically marked food
- most isotopes ended up in tissues
- isotopes replaced previous atoms
• cells divide, cells die

• all molecules in the body are replaced quickly except DNA
- eg total water molecules in the body remains same
- however original water molecules goes to zero in 100 days
• GI lining turns over most quickly
• Cerebral cortex lives the longest
• About 98% of all atoms are replaced in a
year