Introduction To The Living Cell

Question 1

Define a living cell

Answer 1

Fundamental unit of all living things on earth

Take nutrient & free energy from surroundings and make copies of themselves

Question 2

State the range of cell sizes

Answer 2

Smallest cell size = 0.3 micrometers, 10^-4g

Mycoplasma genitalium

Biggest cell size = 20 cm, 2kg

Ostrich egg

Question 3

Organelles of Eukaryotic cells

Answer 3

Nucleus - Directs cell activity e.g protein synthesis & contains genetic material called chromosomes made of DNA

Nucleolus - important role in ribosome production

Mitochondria - important in respiration - they generate ATP from substrates in the presence of oxygen

Ribosomes - make proteins using their RNA and AAs. Involves decoding the info in the mRNA & using AAs to produce required proteins

Golgi Apparatus - Make, process and package proteins

Lysosomes - contains digestive enzymes to help break food down

Endoplasmic Reticulum -
SER - carbohydrate & lipid synthesis, transportation of vesicles
RER - production of antibodies and insulin, transportation of proteins

Question 4

Universal Feature of cells on earth

Answer 4

All cells = surrounded by a plasma membrane
Cells exchange molecule with their surroundings
Cells communicate
All cells = store their hereditary information as DNA
The DNA fragment corresponding to one protein = one gene ( DNA encodes protein - DNA synthesis (replication) , RNA synthesis ( transcription), protein synthesis ( translation) )
Cells translate RNA into protein in the same way
Cells = made from a few simple building blocks
Compartmentalizations of eukaryotic cells

Question 5

Structure of DNA, RNA, Proteins

Answer 5

DNA = 2 strands, held by H bonds, double helix, each strand is an unbranched polymer made of 4 basic units (monomers) , deoxyribose as sugar, maintains protein encoding information

RNA = Uracil instead of Thymine, single stranded, ribosome as the sugar, uses protein encoding information

Protein - Carboxyl group, Amine group, R group

Question 6

General description of transcription ( DNA -> RNA) and translation (RNA -> Protein)

Answer 6

Transcription - uses a strand of DNA as a template - to build RNA

Making an RNA copy of a gene sequence = mRNA - leaves the cell nucleus and enters the cytoplasm - directs synthesis of the protein which it encodes

Translation = process of translating the sequence of a MRNA molecule to a sequence of AAs during protein synthesis

The genetic code describes the relationship - between the sequence of base pairs in a gene & the corresponding AA sequence that it encodes

In the cell cytoplasm - ribosome reads the sequence of the mRNA in groups of three bases to assemble the protein

Question 7

Homeostasis

Answer 7

Ability or tendency of an organism or cell - to maintain internal equilibrium by adjusting its physiology processes

Levels of homeostasis = Chemical, cellular, systematic, populations and biosphere

Question 8

Life is “a pattern in flux”

Answer 8

All constituents of living matter, whether functional or structural - of simple or complex constitution - are in a steady state of rapid flux

Almost all molecules in the human body = continuously replaced ( except DNA)