Biological Science: All About Cells

BIOLOGICAL SCIENCE
ALL ABOUT CELLS
NSC043 Lecture 3

What is a CELL?
— Basic

structural unit of all living organisms — microscopic — “all life forms are composed of cells and product of cells” — All functions essential to life occur at the cellular level

1

Phagocytosis, Pinocytosis, and microvilli

CYTOPLASM
— Collective

term for cytosol and organelles contained within — Colloidal suspension — Cytosol mainly composed of water with free-floating molecules — Viscosity constantly changes — “Cytoplasm is like egg whites It’s very fluid and jelly —like Parts in the cytoplasm — organelles Are like baby organs inside of a cell”

ORGANELLES
— Numerous

membranous compartments

◦ Compartmentalized = doesn’t interfere with others ◦ But there is still communication
— “Little

organs” — Contains chemical systems that perform a variety of functions

"Cells Are Us" — Cells contain certain smaller structures, known as organelles. — They perform the work of cells. — Organelles are thus one level of organization for life functions.

2

Animal & Plant CELL

comparison

PROKARYOTIC vs. EUKARYOTIC
—

Cells with NO definite membrane & membrane systems

—

Cells WITH membranes and a definite nucleus

3

How do cells divide?
— PROKARYOTES

◦ Binary Fission
– Prokaryotic chromosome contains mostly DNA and some associated proteins Asexual reproduction requires a single parent; offspring are genetically identical to parent.

EUKARYOTES Meiosis and Mitosis
—

MEIOSIS
—

Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes

—

MITOSIS — process in which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei. — It is generally followed immediately by cytokinesis which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing roughly