Download 1.1 Introduction to Cells

Topic 1: Cells
1.1 Introduction to Cells
Cell Theory:
 All living organisms are composed of cells
o Cell is a basic unit of life.
o It has a cytoplasm which is surrounded by a plasma membrane which contains a
single nucleus
 Evidence: Robert Hooke: observations of cork material. Microscopes
showed presence of box-like cellular structures.
 All cells come from pre-existing cells
o Cells can be cultured outside body if nutrients and oxygen is present.
o Mitochondria and chloroplast will not survive out of cell.
o Viruses (though smaller than cells) do not count as they do not undergo process
of life.
 Cells are the smallest unit of life
o Evidence : Louis Pasteur broth experiment.
The exceptions to the cell theory:
 Muscle Fibre
o Multinucleate cytoplasm
 Giant Algae
o Extremely large for a single cell
 Fungal Hyphae
o Multinucleate organism
Unicellular organisms
 Carry out all functions of life
 Chlorella, Scendesmus
 Not Eugena
Multicellular Organisms
 Emergent properties (cells form
tissues, tissues form organs etc.)
 The cell contributes to a greater task
 Many cells working together and
world be useless alone.
Functions of Life

Metabolism - chemical reactions that
occur

Reproduction - Living things produce
offspring, sex/asexually


Homeostasis - maintaining constant
internal environment

Excretion -removal of waste materials
from metabolism

Response - the ability to react to
changes in environment

Nutrition - obtaining food to provide
energy & materials for growth
Topic 1: Cells
1.1 Introduction to Cells

Surface Area to Volume Ratio of Cells
 Bigger size/volume
o faster rate of using or making materials in cell (chemical activity per unit of time.
 Bigger surface area
o faster rate of entering and exiting cell (removing waste and allowing reactants to
enter)
 Imbalanced ratio
o cell will eventually die
Therefore, the cell must divide to restore a good ratio.
Magnification:
Unit
Lengths relative to 1m
m
1
cm
100
mm
1000
µm
1000000
nm
1000000000
Topic 1: Cells
1.1 Introduction to Cells
Differentiation of Cells (Multicellular organism)
 All cells of an individual organism have identical genomes, each contains the entire set
of genetic instructions for that organism
 Chemical signals are the instructions for the different genes to differentiate and
become specialized
 Specialized cells are distinct from one another, and serve specific purposes
 Active genes are package in euchromatin, which is expanded and accessible
 Inactive genes are in heterochromatin, which is condensed.
Stem Cells
 Unspecialized cells
 Have the ability to differentiate into a wide range of cells (pluripotent)
Embryonic stem cells
 Blastocyst (one week after fertilization)
o Outer layer = skin, nervous system, face, neck
o Middle Layer = blood, bones
o Inner Layer = respiratory and digestive systems
Adult Stem Cells
 Growth, mantainence, repair
 Some wait for signals, others continuously repair cells which wear out
Stargats disease
 Hereditary disease
 Mutation for vitamin A processing in the eye
 Causes light sensitive cells in the retina (esp. Macula) to deteriorate
 Small yellow spots, blind spots, poor colour vison, wavy vision and problems seeing
with little light.
Stem cell treatments
 Stargat's disease
o Surgeon injects 150microliters of RPE cells under (temporarily detached) retina
o RPE cells support retinas photoreceptors (detect light & pass on information)
 Leukaemia
o Bone marrow transplant from healthy bone marrow is introduced to
bloodstream once abnormal leukocytes are killed.