Download Biology Chapter 7 Cellular Structure and Function

Biology Chapter 7
Cellular Structure and Function
Section 1 Cell Discovery & Theory
History of the Cell Theory
• In 1665, English scientist Robert Hooke made a
simple microscope and looked at a piece of cork,
which are dead cells of oak bark.
• He observed boxed like structures which he
coined cells.
• A cell is the basic structural and functional unit of
all living organisms.
• During the late 1600s, Dutch scientist Anton van
Leeuwenhoek observed living organisms in
pond water and other substances.
The Cell Theory
• In 1838, German scientist Matthias Schleiden
studied plant tissue and concluded that all plants
are composed of cells.
• A year later another German scientist, Theodor
Schwann reported that animal tissue also
consisted of cells.
• In 1855, Prussian physician Rudolph Virchow
proposed that all cells are produced from the
division of existing cells.
The Cell Theory
• The ideas and observations of these scientists
are summarized in the cell theory.
1. All living organisms are composed of one or
more cells.
2. Cells are the basic unit of structure and
organization of all living organisms.
3. Cells arise only from previously existing cells,
with cells passing copies of their genetic material
on to their daughter cells.
Microscope Technology
• REVIEW NOTES ON MICROSCOPES
FROM CHAPTER 1.
Basic Cell Types
• Scientists have grouped cells into two
broad categories.
• These categories are prokaryotic and
eukaryotic cells.
Basic Cell Types
• Scientists place them into 2 board
categories based on internal structures.
• Prokaryotic cells are defined as cells
without specialized internal structures.
• Most prokaryotic cells are unicellular like
bacteria.
• The eukaryotic cell is larger and more
complex than a prokaryotic cell.
Basic Cell Types cont.
• Eukaryotic cells contain a structure
called a nucleus and other organelles.
• Organelles are specialized structures that carry out
specific cell functions.
• The nucleus is a distinct central organelle that
contains the cell’s genetic information in the form of
DNA.
• Organelles enable cell functions to take place in
different parts of the cell at the same time.
• Most organisms are made up of eukaryotic cells and
even some unicellular organisms like algae and
yeast are made of eukaryotic cells.
Biology Chapter 7
Cellular Structure & Function
Section 2 The Plasma Membrane
Function of the Plasma Membrane
• The plasma membrane is a thin, flexible
boundary between a cell and its environment
that allows nutrients into the cell an allows waste
and other products to leave the cell.
• A key property of cell membranes is selective
permeability, by which a membrane allows
some substances to pass through while keeping
others out.
• Control of how, when, and how much of these
substances enter and leave a cell relies on the
structure of the plasma membrane.
Structure of the Plasma Membrane
• Most of the molecules in the plasma membrane
are lipids, which are composed of glycerol and 3
fatty acids.
• If a phosphate replaces one of the fatty acids, a
phospholipid is formed.
• The plasma membrane is composed of a
phospholipid bilayer, in which 2 layers of the
phospholipids are arranged tail-to-tail.
• In the plasma membrane, phospholipids arrange
themselves in a way that allows the plasma
membrane to exist in a watery environment.
Structure of the Plasma Membrane
Phospholipid Bilayer
Structural
Formula of a
Phospholipid
Phospholipid
Bilayer
Tail
Region(Nonpolar)
Head
Region(Polar)
Structure of the Plasma MembraneOther Components of Membrane
• Moving with and among the phospholipids in the plasma
membrane are cholesterol, proteins, and
carbohydrates.
• Proteins found on the outer surface of the plasma
membrane called receptors transmit signals to the
inside of the cells.
• Proteins on the inner surface anchor the plasma
membrane to the cell’s internal support structure, giving
the cell its shape.
• Other proteins span the entire membrane and create
tunnels through which certain substances enter
and leave the
cell.
Structure of the Plasma MembraneOther components of membrane
• Cholesterol helps to prevent the fatty acid tails
of the phospholipid bilayer from sticking
together, which contributes to the fluidity of the
plasma membrane.
• Carbohydrates attached to proteins, stick out
from the plasma membrane to define the cell’s
characteristics and help cells identify chemical
signals.
Structure of the Plasma Membrane
Chapter 7 Cellular Structure
and Function
Section 3
Structures and Organelles
Cytoplasm and Cytoskeleton
• The environment inside the plasma membrane is a semifluid material called cytoplasm.
• In prokaryotes all the chemical processes take place
within the cytoplasm.
• Eukaryotic cells perform these processes within
organelles in their cytoplasm.
• The cytoskeleton is a supporting network of long, thin
protein fibers that form a framework for the cell and
provide an anchor for the organelles inside.
• The cytoskeleton is made of substructures called
microtubules and microfilaments.
Cell Structures-Nucleus
• The nucleus is the cell’s managing structure.
• It contains most of the cell’s DNA, which stores
information used to make proteins for cell growth,
function, and reproduction.
• The nucleus is surrounded by a double membrane called
the nuclear envelope.
• The nuclear envelope is similar to the plasma
membrane, except the nuclear
membrane has nuclear pores
that allow larger-sized substances
to move in and out of the nucleus.
Cell Structures-Ribosomes
• The organelles that help manufacture proteins
are called ribosomes.
• Ribosomes are made of two components; RNA
and protein, and are not bound to a membrane
like other organelles.
• Within the nucleus is the site of ribosome
production called the nucleolus.
• Cells have many ribosomes that produce a
variety of proteins that are used by the cell or
are moved out and used by other cells.
Cell Structures-Endoplasmic
Reticulum
• The endoplasmic reticulum is a membrane system of
folded sacs and interconnected channels that serves as
the site for ribosome attachment.
• The area of the ER where ribosomes are attached is
called rough ER.
• The area of ER where no ribosomes are attached is
called the smooth ER.
• The smooth ER provides a membrane surface where a
variety of complex carbohydrates and lipids are
synthesized. Smooth ER in the liver detoxifies harmful
substances.
Cell Structures-Golgi Apparatus
• The golgi apparatus is a flattened sac of
membranes that modifies, sorts, and packages
proteins into sacs called vesicles.
• Vesicles then can fuse with the cell’s plasma
membrane to release proteins to the
environment outside the cell.
Cell Structures-Vacuoles
• A vacuole is a sac used to store food, enzymes, and
other materials needed in the cell.
• Some vacuoles store waste products.
• Animal cells usually do
not contain vacuoles,
but if they do they are
usually smaller than
those in plant cells.
Cell Structures-Lysosomes
• In the cell, the lysosomes contain substances
that digest excess or worn-out organelles and
food particles.
• Lysosomes also digest bacteria and viruses that
have entered the cells.
• The membrane surrounding a lysosome
prevents the digestive enzymes inside from
destroying the cell.
• Lysosomes can fuse with vacuoles and dispense
their enzymes into the vacuole, digesting the
wastes inside.
Cell Structures-Centrioles
• Centrioles are organelles made of
microtubules that function during cell
division.
• Centrioles are located in the cytoplasm of
animal cells and most protists and are
usually near the nucleus.
Cell Structures-Mitochondria
• Cells have energy generators called mitochondria, that
convert fuel particles (mainly sugars), into usable
energy.
• The mitochondria have an outer membrane and a highly
folded inner membrane that provides a surface area for
breaking the bonds in sugar molecules.
• The energy produced
from that breakage is stored in
bonds of other molecules
and later used by the cell.
Cell Structures-Chloroplasts
• Chloroplasts are organelles that capture light energy
and convert chemical energy through a process called
photosynthesis.
• Chloroplasts belong to a group of plant organelles called
plastids, some of which are used for storage.
• Some plastids store starches or lipids.
Cell Structures-Cell Walls
• The cell wall is a thick, rigid, mesh of fibers that
surrounds the outside plasma membrane, protecting the
cell and giving it support.
• Rigid cell walls allow
plants to stand at
various heights.
• Plant cell walls are
made of a carbohydrate
called cellulose.
Cell Structure-Cilia & Flagella
• Some cell surfaces have structures called cilia and
flagella that project outside the plasma membrane.
• Cilia are short, numerous projections that look like hairs.
• Flagella are longer and less numerous than cilia.
• Cilia and flagella are composed of microtubules.
• Both cilia and flagella often are used to move cells
through watery environments.