Transcript Unit: Cell Structure & Function

Unit: Cell Structure & Function
Lecture #1 Life is Cellular
Why study Cells?
All Critical processes which take place in
Living organisms take place in cells.
In the human body, cells are responsible for many
things including sight, hearing, smell, memory,
pain and pleasure
In order to understand how living things perform
life’s activities, it is essential to understand how
the cell functions.
Question
How did we first learn about cells?
Answer
Microscopes!
Early Microscopy
– It was not until the mid-1600s that
scientists began to use microscopes to
observe living things.
– Robert Hooke (1665) was n English
scientist who used a crude microscope
to look at a nonliving thin slice of cork, a
plant material.
– Under the microscope, cork seemed to
be made of thousands of tiny, empty
chambers that Hooke called “cells”. The
term cell is used in biology to this day.
– Today we know that living cells are not
empty chambers, but contain a huge
array of working parts, each with its
own function.
Cork Cells
Anton van Leeuwenhoek - 1675
• Dutch scientist
who used a
microscope to view
living organisms
found in pond
water.
• We know now that
these are actually
single celled
organisms.
• He also looked at a
sample taken from a
human mouth.
• He drew the
organisms he saw in
the mouth—which
today we call
bacteria
It took scientists 150 years to fully appreciate
the discoveries of Hooke and Leeuwenhoek.
Cell -
The smallest unit that can perform
all the life processes.
• It is the basic structural, functional, and
developmental unit of life.
• There are different types of cells within an
organism due to the fact that they are
specialized for specific functions.
Example - We have about 250 different
types of cells in our body; such as blood
cells, muscle cells, epithelial (skin) cells, etc.
Types of Cells
The Cell Theory
Work contributions from other scientists
eventually led to the Cell Theory.
The theory states:
1) All living things are made of one or more cells
2) Cells are the basic units of structure and
function in organisms.
3) All cells arise from preexisting cells.
Cell Size
All cells need to take in substances such as
nutrients, ions & oxygen & they need to
Remove waste that builds up within the cell.
The only way in or out is for substances to
Pass through the cells surface (cell
membrane).
Question: Cells are SMALL. Why is this
important?
Answer
• Small cells exchange substances much
more rapidly because substances do not
need to travel as far to reach the center of
a smaller cell.
• Small cells have a surface-area to volume
ratio that is HIGHER than large cells.
• This is why it is better for us to have so
many tiny cells instead of a few large
ones.
Take two minutes to summarize what you have
learned about cell theory, and the reasons why
SMALL SIZE such an important feature of cells.
Discuss with your shoulder partner• What do you understand well?
• What is a little confusing?
Types of Cells
– Cells fall into two broad categories,
depending on whether they contain a
nucleus.
– The nucleus is a large membraneenclosed structure that contains the
cell’s genetic material in the form of
DNA.
• Function- the nucleus controls many of the
cell’s activities.
Prokaryotes and Eukaryotes
– Eukaryotes are cells that enclose their DNA
in nuclei. * Plural for nucleus
– Prokaryotes are cells that do not enclose
DNA in nuclei.
Prokaryotic Cells
– Prokaryotic cells are
generally smaller and
simpler than
eukaryotic cells.
– Because they are
such simple cells,
they cannot carry out
many specialized
functions.
Prokaryotes were the first life form on earth.
• They lived at least 3.5 billion years ago.
• For nearly 2 billion years, prokaryotes were the
only organisms on Earth!
– Single celled organisms. The organisms we
call bacteria are modern day prokaryotes
Eukaryotes
– Eukaryotic cells are generally larger and more
complex than prokaryotic cells.
– Most eukaryotic cells contain dozens of
structures and internal membranes. Many
eukaryotes are highly specialized.
– There are many types of eukaryotes: plants,
animals, fungi, and organisms commonly
called “protists.”
Take two minutes to summarize what you have
learned about the two categories of cells as well
as their characteristics.
Discuss with your shoulder partner• What do you understand well?
• What is a little confusing?
Unit 2: Cell Structure & Function
Lecture #2 5 Common features of ALL Cells
1. Cell Membrane
(plasma membrane)
What is it?
A semipermeable barrier that encloses the cell
and separates the cell interior from its
surroundings.
• It also regulates what enters and leaves a cell
( gases, nutrients, wastes, etc)
2. Cytoplasm
What is it?
Semitransparent fluid (mostly water) that
provides a liquid environment for cell activities.
• Many structures necessary for cell function
are found suspended in the cells cytoplasm.
3. Cytoskeleton
What is it?
A system ( web) of microscopic protein fibers
found inside cytoplasm.
• This is what suspends the structures of the cell
found within the cytoplasm.
• This holds the cell together and prevents it from
collapsing or folding.
Two types of fibers make up the
cytoskeleton
1. Microtubules - long hollow tubes that
extend throughout the cytoplasm,
supporting the cell.
2. Microfilaments - extremely thin protein
strands that also support cell shape and
structure.
• They may also help in moving organelles
around the cell.
4. Ribosomes
What is it?
Cellular structures on which proteins are made.
AKA the ‘protein factory’
Tying it all together…….
Remember from Unit 1
• DNA is like a cookbook, with 30,000 recipes.
• Each recipe is a gene.
• Each gene codes for the production of a
particular protein.
• The recipe is delivered to the ribosome by
DNA’s helper, RNA.
• The proteins is then built on the ribosome.
5. DNA
All cells have DNA. Remember, this is one of the
8 characteristics of life that we learned about
last unit.
DNA serves three important functions
1. It provides instructions for making proteins
2. Regulates cellular activities
3. Enables cells to reproduce