Download Biology Chapter 7: Cell Structure and Function

Biology Chapter 7: Cell Structure and Function
I.
7-1 Life Is Cellular
a. The Discovery of the Cell
i. Because there were no instruments to make cells visible, the existence of
cells was unknown for most of human history.
ii. This changed with the invention of the microscope
b. Early Microscopes
i. In 1665, Robert Hooke used an early compound microscope to look at a
thin slice of cork, a plant material.
ii. Cork looked like thousands of tiny, empty chambers.
iii. Hooke called these chambers “cells.”
iv. Cells are the basic units of life.
v. At the same time, Anton van Leeuwenhoek used a single-lens microscope
to observe pond water and other things.
vi. The microscope revealed a world of tiny living organisms
c. What is the cell theory?
Hooke’s Drawing of Cork Cells
i. The Cell Theory:
1. In 1838 Matthias Schleiden
concluded that all plants were
made of cells.
2. In 1839, Theodor Schwann
stated that all animals were
made of cells
3. In 1855, Rudolph Virchow
concluded that new cells were
created only from division of
existing cells.
4. These discoveries led to the
cell theory.
ii. The cell theory states:
1. All living things are composed
of cells.
2. Cells are the basic units of structure and function in living things
3. New cells are produced from existing cells.
d. Exploring the cell
i. New technologies allow researchers to study the structure and movement
of living cells in great detail.
ii. Electron Microscopes
1. Electron microscopes reveal details 1000 times smaller than those
visible in light microscopes.
2. Electron microscopy can be used to visualize only nonliving,
preserved cells and tissues.
iii. Transmission electron microscopes (TEMs)
1. Used to study cell structures and large protein molecules
2. Specimens must be cut into ultra-thin slices
1.
iv. Scanning electron microscopes (SEMs)
1. Produce three-dimensional images of
cells
2. Specimens do not have to be cut into
thin slices
v. Confocal Light microscopes
1. Confocal light microscopes scan
cells with a laser beam.
2. This makes it possible to build threedimensional images of cells and their
parts
vi. Scanning Probe Microscopes
1. Scanning probe microscopes allow us to observe single atoms
2. Images are produced by tracing surfaces of samples with a fine
probe
e. Prokaryotes and Eukaryotes
i. Cells come in a variety of shapes and sizes
ii. All Cells:
1. are surrounded by a barrier called a cell membrane
2. at some point contain DNA
iii. Cells are classified into two categories, depending on whether they contain
a nucleus
iv. The nucleus is a large membrane-enclosed structure that contains the
cell’s genetic material in the form of DNA
v. The nucleus controls many of the cell’s activities
vi. Eukaryotes are cells that contain nuclei
vii. Prokaryotes are cells that do not contain nuclei
f. What are the characteristics of prokaryotes and Eukaryotes?
i. Prokaryotes
1. Prokaryotic cells have genetic material that is not contained in a
nucleus
2. Prokaryotes do not have membrane-bound organelles
3. Prokaryotic cells are generally smaller and simpler than eukaryotic
cells.
4. Bacteria are prokaryotes.
ii. Eukaryotes
1. Eukaryotic cells contain a nucleus in which their genetic material
is separated from the rest of the cell
2. Eukaryotic cells are generally larger and more complex than
prokaryotic cells.
3. Eukaryotic cells generally contain dozens of structures and internal
membranes
4. Many eukaryotic cells are highly specialized
5. Plants, animals, fungi, and protists are eukaryotes
2.
3.
4.
5.
Biology
II.
7-2 Eukaryotic Cell Structure: Comparing the Cell to a Factory
a. Eukaryotic Cell Structures
i. Structures within a eukaryotic cell that perform important cellular
functions are known as organelles
ii. Cell biologists divide the eukaryotic cell into two major parts: the nucleus
and the cytoplasm
iii. The cytoplasm is the portion of the cell outside the nucleus
iv. Plant Cell
1. nucleolus
2. nucleus
3. smooth endoplasmic reticulum
4. rough endoplasmic reticulum
5. cell wall
6. cell membrane
7. chloroplast
8. vacuole
9. mitrochondrion
10. golgi apparatus
11. ribosome (attached)
12. ribosome (free)
13. nuclear envelope
v. Animal cell
1. nucleolus
2. nucleus
3. nuclear envelope
4. rough endoplasmic reticulum
5. centrioles
6. mitrochondrion
7. golgi apparatus
8. ribosome (attached)
9. cell membrane
10. ribosome (free)
11. smooth endoplasmic reticulum
b. What is the function of the nucleus?
i. The nucleus is the control center of the cell
ii. The nucleus contains nearly all the cell’s DNA and with it the coded
instructions for making proteins and other important molecules
iii. The nucleus is surrounded by a nuclear envelope composed of two
membranes
iv. The envelope is dotted with nuclear pores, which allow material to move
in and out of the nucleus
v. The granular material in the nucleus is called chromatin
vi. Chromatin consists of DNA bound to protein
vii. When a cell divides, chromatic condenses to form chromosomes
c.
d.
e.
f.
viii. Chromosomes contain the genetic information that is passed on from one
generation of cells to the next.
ix. Most nuclei also contain a nucleolus
1. The nucleolus is where the assembly of ribosomes begins
What is the function of the ribosomes?
i. Ribosomes
1. One of the most important jobs carried out in the cell is making
proteins
2. Proteins are assembled on ribosomes
3. Ribsomes are small particles of RNA and protein found
throughout the cytoplasm
4. Ribosomes produce proteins by following coded instructions that
come from the nucleus
5. Cells that are active in protein synthesis are often packed with
ribosomes
What is the function of then endoplasmic reticulum?
i. Endoplasmic Reticulum
1. Eukaryotic cells contain an internal membrane system called the
endoplasmic reticulum, or ER
2. The endoplasmic reticulum is where lipid components of the cell
membrane are assembled, along with proteins and other materials
that are exported from the cell.
3. There are two types of ER – rough and smooth
4. The portion of the ER involved in protein synthesis is called rough
endoplasmic reticulum, or rough ER
5. Ribosomes are found on the surface of rough ER
6. Rough ER is abundant in cells that produce large amounts of
protein for export.
7. Smooth ER does not have ribosomes on its surface
8. Smooth ER contains collections of enzymes that perform
specialized tasks, such as synthesis of membrane lipids and
detoxification of drugs
What is the function of the Golgi apparatus?
i. Golgi Apparatus
1. Proteins produced in the rough ER move into the Golgi apparatus
2. The Golgi apparatus appears as a stack of closely apposed
membranes
3. The Golgi apparatus modifies, sorts and packages proteins and
other materials from the endoplasmic reticulum for storage in the
cell or secretion outside the cell
4. From the Golgi apparatus, proteins are then “shipped” to their final
destinations throughout the cell or outside of the cell
What is the function of Lysosomes?
i. Lysosomes
1. Lysosomes are small organelles filled with enzymes
g.
h.
i.
j.
2. Lysosomes break down lipids, carbohydrates, and proteins into
small molecules that can be used by the rest of the cell
3. Lysosomes also break down organelles that have outlived their
usefulness
What is the function of vacuoles:?
i. Vacuoles
1. Some cells contain saclike structures called vacuoles that store
materials such as water, salts, proteins, and carbohydrates
2. In many plant cells there is a single, large central vacuole filled
with liquid
3. The pressure of the central vacuole allows plants to support heavy
structures such as leaves and flowers
4. Vacuoles are also found in some unicellular organisms and in some
animals
5. The paramecium contains a contractile vacuole that pumps excess
water out of the cell
What is the function of the mitochondria?
i. Nearly all eukaryotic cells contain mitochondria
ii. Mitochondria convert the chemical energy stored in food into compounds
that are more convenient for the cell to use.
iii. Mitochondria are enclosed by two membranes – an outer membrane and
an inner membrane
iv. The inner membrane is folded up inside the organelle
What is the function of chloroplasts?
i. Plants and some other organisms contain chloroplasts
ii. Chloroplasts capture energy from sunlight and convert it into chemical
energy in a process called photosynthesis.
iii. Chloroplasts are surrounded by two membranes
iv. Chloroplasts contain the green pigment chlorophyll
What are the functions of the cytoskeleton?
i. Cytoskeleton
1. Eukaryotic cells are given their shape and internal organization by
the cytoskeleton.
2. The cytoskeleton is a network of protein filaments that helps the
cell to maintain its shape. The cytoskeleton is also involved in
movement.
3. The cytoskeleton is make up of:
a. Microfilaments
i. Are threadlike structures made up of the protein
actin
ii. Form extensive networks in some cells
iii. Produce a tough, flexible framework that supports
the cell
iv. Help some cells move
b. Microtubules
1.
2.
i. Microtubules are hollow structures made up of
proteins known as tubulins. Microtubules:
ii. Maintain cell shape
iii. Are important in cell division
iv. Build projections from the cell surface-cilia and
flagella-that enable some cells to swim rapidly
through liquids
4. In animals cells, structures known as centrioles are formed from
tubulin.
5. Centrioles are located near the nucleus and help to organize cell
division
3.
4.
5.
In the nucleus of a cell, the DNA is usually visible as
• a dense region called the nucleolus.
• the nuclear envelope.
• granular material called chromatin.
• condensed bodies called chloroplasts.
Two functions of vacuoles are storing materials and helping to
• break down organelles.
• assemble proteins.
• maintain homeostasis.
• make new organelles.
Chloroplasts are found in the cells of
• plants only.
• plants and some other organisms.
• all eukaryotes.
• most prokaryotes.
Which of the following is NOT a function of the Golgi apparatus?
• synthesize proteins
• modify proteins
• sort proteins
• package proteins
Which of the following is a function of the cytoskeleton?
• manufactures new cell organelles
• assists in movement of some cells from one place to another
• releases energy in cells
• modifies, sorts, and packages proteins