BIO EXAM: Second Lecture!

Mattias Schleiden- German botanist

All plants are aggregates of fully individualized, independent,
separate beings, namely the cells themselves

Theodor Schwann, German physiologist

All animal tissues also consist of individual cells

Cell Theory 1

All organisms are composed of one or more cells, and the
life processes of metabolism and heredity occur within
these cells

Cell Theory 2

Cells are the smallest living things, the basic units of
organization of all organisms

Cell Theory 3

Cells arise only from pre-existing cells

Is the statement? “although life likely evolved spontaneously in the environment
of early earth” True?

All cells today represent a continuous line of descent from the
first living cells

Why are most cells relatively small?

Diffusion of substances in and out of cells

Rate of diffusion is affected by

Surface area available, Temperature, Concentration gradient, Distance

IMPORTANT: Why all cells are inevitably small?

Surface area grows by the square, and volume grows by the cube. Surface Area-to-Volume ratio actually decreases.

Surface Area-to-Volume ratio actually decreases.

Is it better to have an organism made of many small cells or an organism composed of fewer, larger cells(Think of wrinkles in the brain)

Organism made of small cells

As a cell’s size increases: Does the volume increase more rapidly or the surface

The volume increases much more rapidly

How do some cells overcome being too large

Some cells overcome limitation by being long and narrow
– like neurons

What cell plays a key role in controlling cell function

Membrane

Resolution

minimum distance two points can be apart and still be distinguished as two separate points

Most cells are less than what size in diameter

50 μm

Objects must be what length apart for naked eye to resolve them
as two objects rather than one

100 μm

Light microscopes

Resolve structures that are 200 nm apart

Electron microscopes

Resolve structures that are 0.2 nm apart

TEM

(Transmission electron microscopes) transmit
electrons through the material

SEM

(Scanning electron microscopes) beam electrons
onto the specimen surface

Is this SEM or TEM

TEM

Is this SEM or TEM

SEM

SEM image of poly grains

Drosophila’s image of eye

SEM image of blood cells

TEM image of Golgi complex

TEM image of mitochondria

Basic Structural Similarities of All cells
(Prokaryote and Eukaryote)

Nucleoid or nucleus where DNA is located, cytoplasm, ribosomes, and plasma membrane

Cytoplasm

Semifluid matrix of organelles and cytosol

Ribosomes

Synthesize proteins

Plasma membrane

Phospholipid bilayer

Cell

Mitochondria

Golgi apparatus

Endoplasmic reticulum

Smooth ER: thin lines inside a cell that is
synthesising steroid hormones & Nearby lipid droplets (dark
circles) supply the cholesterol needed for the biosynthesis of steroids