Download Chapter 4 Section 2 Cell Structure and Function

Chapter 4
Section 2 Cell Structure and
Function
Review
Who am I? What did I do?
Robert Hooke
Robert Hooke
• He was an English scientist who cut a thin slice of
cork and looked at it with a homemade microscope in
1665.
• Hooke compared what he observed to the cells, or
box-like rooms, in which monks slept.
• Therefore he named the structures that make up cork
“cells.”
Review: Who am I?
Anton van Leeuwenhoek
was a Dutch lens maker, who was
the first person to observe living
cells.
Anton van Leeuwenhoek
• used a simple microscope he had made to
observe such things as blood, rainwater, and teeth
scrapings.
• In 1675, he observed single-celled organisms in a
drop of pond water, which he called these tiny
living things “animalcules.”
Review: Cell
Theory
• Key players in the Cell
Theory:
– Matthias Schleiden
– Theodor Schwann
– Rudolph Virchow
Cell structure and Function
• In the cell theory, cells are described as the
basic unit of structure and function in living
things.
• Do you know why the cell is described this
way?
– Example: brick house
Cell structure and Function (cont.)
• Many different kind of cells make up your body.
• In fact, every cell in your body is adapted to its
function.
• Most cells are very small.
• Plant and animal cells usually are between 10 and
50 micrometers in size.
• The smallest cell may be 0.2 micrometers in
diameter.
Cell structure and Function (cont.)
• Some cells may be very large.
• Several nerve-cell axons in your legs are about 1
meter long.
• A large cell that is found in many animals is an
egg.
– Ex: a single cell that you probably see everyday is a
chicken egg.
• How many cells do you think make up and ostrich
egg?
Main Cell Parts
• What are the 3 main cell structures that control
most of the activities in the cell?
– Cell membrane
– Nucleus
– Cytoplasm
Cell Membrane
• Cells are enclosed by a thin structure called the
cell membrane.
– It is a living part of the cell made mostly of lipids and
proteins.
– It is sometimes called the plasma membrane.
Cell Membrane (cont.)
• The cell membrane has 3 important jobs:
– Protect the inside of the cell by separating the cell
from its surroundings.
– Support the cell and give it shape.
– Controls the passage of substances into and out of the
cell.
Cell Wall
• Some cells, such as plant cells, have a structure
surrounding the cell membrane called the cell
wall.
– Unlike the cell membrane, the cell wall is not a living
part of the cell.
• Cell wall is made mostly of cellulose.
– It is a carbohydrate made up of many sugar molecules
linked together.
– The cell wall also contains pectin, which is a starch
used to thicken jams and jellies.
Cell Wall (cont.)
• The cell wall has several functions:
– It protects the cell and give it shape.
– Provides cell with support.
– Because of the support provided by the cell wall,
large plants do not need a skeleton.
Nucleus
• The nucleus is the “control center” of the cell.
– It controls most of the activities that take place in the
cell.
– It controls cell reproduction.
• What would happen to a cell if the nucleus were
removed?
– The cell would not be able to carry on its activities or
reproduce. It would die.
Nucleus (cont.)
• The nucleus is separated from the rest of the cell
by the nuclear membrane.
• Like the cell membrane, the nuclear membrane
has 3 jobs. What do you think the 3 jobs are?
– Protects the inside of the nucleus.
– Support the nucleus and give it shape.
– Controls the passage of substances into and out of the
nucleus.
Nucleus (cont.)
• Within the nucleus there are nucleoli, which
makes rRNA.
– These molecules are involved in making
proteins.
• Chromosomes are also located in the
nucleus.
– They control heredity.
• Heredity is the passing of traits from parent to
offspring.
Cytoplasm
• Cytoplasm is all the living substance in a cell
except the nucleus.
• Most of the life processes take place within the
cytoplasm of the cell.