Ch. 1: Cell Structure &

Function

Sect. 1: Types of Unicellular

Organisms - Recap

Sect. 2: How Cells Work

Types of Unicellular Organisms

There are many different types of

unicellular organisms, all of which fall

into two general categories: prokaryotic

organisms (also called bacteria) and

eukaryotic organisms. In general,

eukaryotic cells are more complex than

prokaryotic organisms, because

prokaryotes don't have membrane-

bound organelles.

Classifications Prokaryotes and eukaryotes also differ

in the chemical composition of some of

their structures as well as in the

organization of their DNA. Below is a

chart which highlights the important

differences between the two types of

cells. Although you probably aren't yet

familiar with the terms on the chart, you

may find it helpful to return back to this

page as you learn new information later

on.

Classification Operations - Prokaryote

Eukaryote

cell membrane yes yes

nucleus no

membranes surrounded by two membranes

endoplasmic

reticulum no yes

Golgi bodies no yes

mitochondria no yes

vacuoles no yes

lysosomes no yes

ribosomes yes yes

chromosomes

circular

without

histones

linear with histones

Classifications Cont. -

In addition to this classification, organisms

may also be classified be their method of

nutrition. Heterotrophs are organisms

which obtain food from the environment,

whereas autotrophs have a method of

producing their own food. Also, aerobes

are organisms which require oxygen to

survive, whereas anaerobes do not

need oxygen.

We have discussed the main 4 types of

unicellular organism that we are required

to, but we get into more detail with

vocabulary in plant and animal

chapters which describe the

differences mentioned in the charts

above on cellular organelle operation.

This way, you will first have an

understanding of the what the terms above

mean before you learn which cells have

what.

How the Cells Work!

During Plant and Animal cell observation

we explain all of the details about how a

cell works, but here is a general

explanation to get you started. Cells have

tiny structures inside of them called

organelles. Organelles are very similar to

human organs in that they help perform

specific functions. However, cells don't

have organelles called "the liver" or "the

heart."

Some of the names of cell organelles

include the mitochondria, lysosomes,

and the endoplasmic reticulum. Don't

get scared by the strange names; Later

we focus on cell organelles so that you

can understand them completely. The cell

organelles float around in a fluidic

substance called the cytoplasm. The

cytoplasm is similar to very watery jelly.

As the cytoplasm moves around within

the cell, organelles can come into

contact with one another, allowing

certain processes to occur. This

movement of the cytoplasm is called

cyclosis. Just like humans, cells need to

perform certain processes similar to our

processes for eating, breathing, and

reproduction.

These processes have some very

interesting names: phagocytosis,

glycolysis, mitosis.