Download Chapter 7: Structure and Function - Summary

Chapter 7: Structure and Function - Summary
"Seeing is believing" - microscopes weren't used until the 1600s
Robert Hooke: Used a microscope to look at cork and coined the term "cells"
One of the First Microscopes: Anton von Leewenhoek. FIRST person to OBSERVE and
DESCRIBE MICROSCOPIC ORGANISMS and LIVING CELLS.
1665, the English Scientist Robert Hooke used a microscope to examine a thin slice of cork and
described it as consisting of "a great many little boxes". It was after his observation that Hook
called what he saw "Cells". They looked like "little boxes" and reminded him of the small rooms
in which monks lived, so he called the "Cells".
1838, German Botanist Matthias Schleiden studied a variety
of PLANTS and concluded that all PLANTS "ARE
COMPOSED OF CELLS".
The next year, German Zoologist Theodor Schwann reported
that ANIMALS are also made of CELLS and proposed a
cellular basis for all life.
1855, German Physician Rudolf Virchow induced the cell
theory:
1. All living things are composed of cells
2. Cells are the basic unit of structure and function
3. new cells come from preexisting cells
CELL DIVERSITY Not all cells are alike. Even cells within the same organism show
Enormous Diversity in Size, Shape, and Internal Organization. Your Body contains at least 200
Different Cell Types.
CELL SIZE A few types of cells are large enough to be seen by the unaided eye. The Female
Egg is the largest cell in the body, and can be seen without the aid of a microscope.
MOST CELLS ARE SMALL FOR TWO REASONS:
A. Cells are limited in size by the RATIO between their Outer Surface Area and Their
Volume. A SMALL CELL HAS MORE SURFACE AREA THAN A LARGE CELL FOR A
GIVEN VOLUME OF CYTOPLASM. This is important because the nutrients, oxygen, and
other materials a cell requires must enter through it surface. As a cell grows larger at some point
its surface area becomes too Small to allow these materials to enter the cell quickly enough to
meet the cell's need.
B. THE CELL'S NUCLEUS (THE BRAIN) CAN ONLY CONTROL A CERTAIN
AMOUNT OF LIVING, ACTIVE CYTOPLASM.
CELL SHAPE
Cells come in a variety of Shapes. the shape is determined by its function
INTERNAL ORGANIZATION
Cells contain a variety of Internal Structures
called ORGANELLES. (PERFORMS
SPECIFIC FUNCTIONS FOR THE CELL.)
The entire cell is Surrounded by A THIN
MEMBRANE, called the CELL
MEMBRANE.
NUCLEUS. IT CONTAINS THE CELL'S
AND CONTROLS THE ACTIVITIES OF THE
A Large Organelle near the
Center of the Cell is the
GENETIC INFORMATION
CELL.
The PRESENCE OR
ABSENCE of a NUCLEUS
is important for Classifying
Cells.
ORGANISMS WHOSE
CELL CONTAIN A
NUCLEUS AND OTHER
MEMBRANE-BOUND
ORGANELLES ARE
CALLED
EUKARYOTES.
ORGANISMS WHOSE CELLS NEVER CONTAIN (OR LACK) A NUCLEUS AND OTHER
MEMBRANE-BOUND ORGANELLES ARE CALLED PROKARYOTES.
UNICELLULAR ORGANISMS such as bacteria and their relatives are Prokaryotes.
All other organisms are Eukaryotes; plants, fish, mammals, insects and humans.
PARTS OF THE EUKARYOTIC CELL
Eukaryotic Cells generally have THREE Main Components: A Cell Membrane, A Nucleus, and
other Organelles.
THE NUCLEUS (plural, Nuclei)
The Nucleus is the CONTROL CENTER (BRAIN) of the
Cell. Most Cells have a Single Nucleus some cells have more
than one. The nucleus is surrounded by a Double Layer
Membrane called the NUCLEAR ENVELOPE. The
Nucleus contains DNA, the HEREDITARY MATERIAL OF
CELLS.
The DNA is in the form of a long Strand called
CHROMATIN. During Cell Division, Chromatin strands
COIL and CONDENSES into thick structures called
CHROMOSOMES.
RIBOSOMES (RIE-buh-SOHMZ)
Ribosomes Are Not Surrounded by a membrane. They are the site of PROTEIN SYNTHESIS
(Production or Construction) in a cell.
ENDOPLASMIC RETICULUM (ER) (EN-doh-PLAZ-mik ri-TIK-yuh-luhm)
The ER is a system of membranous tubules and sacs which act as
an Intracellular Highway, which transports materials through the
cell.
It Can be ROUGH OR SMOOTH.
A. ROUGH ER is studded with RIBOSOMES and processes
PROTEINS to be exported from the cell.
B. SMOOTH ER IS NOT Covered with RIBOSOMES and
processes LIPIDS and CARBOHYDRATES. The Smooth ER is involved in the synthesis of
steroids in gland cells, the regulation of calcium levels in muscle cells, and the breakdown of
toxic substances by liver cells.
CYTOPLASM (SIET-oh-PLAZ-uhm)
EVERYTHING BETWEEN THE CELL MEMBRANE AND THE NUCLEUS IS THE
CELL'S CYTOPLASM.
GOLGI APPARATUS (GOHL-jee)
The Golgi Apparatus is the Processing, Packaging and Secreting
Organelle of the Cell that is made of flattened SAC
.
LYSOSOMES (LIE-suh-sohmez)
Lysosomes are small spherical organellesthat are filled with enzymes. It's function is digestion,
or breakdown of lipids, carbs, and proteins.
VACUOLES The SECOND prominent structure in Plant Cells is the large VACUOLE. The
VACUOLE is a large membrane-bound sac that takes up a large amount of space in most Plant
Cells.
MITOCHONDRIA (MET-oh-KAHN-dree-uh)
Mitochondria are the sites of Chemical Reactions that transfer Energy from
Organic Compounds to ATP (Cellular Respiration). Energy contain in food is
released. Converted to ATP. ATP is the molecule that most Cells use as their
main Energy Currency. THE "POWERHOUSE" OF THE CELL.
PLASTIDS
A common kind of PLASTID is the CHLOROPLAST,
(figure 4-17) an organelle that converts SUNLIGHT,
CARBON DIOXIDE, AND WATER INTO SUGARS. This
process is called PHOTOSYNTHESIS.
CYTOSKELETON In Animal Cells, an internal framework
called CYTOSKELETON maintains the Shape of the Cell
and helps it to move.The CYTOSKELETON consists of
TWO Types of structures: MICROFILAMENTS AND
MICROTUBULES.
CILIA AND FLAGELLA Cilia and Flagella are Hairlike Organelles that extend from the
surface of the cell, where they assist in movement. CILIA ARE SHORT HAIRLIKE
PROJECTIONS. FLAGELLA ARE LONG WHIPLIKE PROJECTIONS.
PLANT CELLS
1. Most of the Organelles and other parts of the cell are common in ALL Eukaryotic Cells. Cell
from different organisms have even greater difference in structure.
2. Plant Cells have Three Additional Structures Not found in animals cells - CELL
WALLS, VACUOLES, AND PLASTIDS that are extremely important to Plant Function.
3. In addition to their unique structures, Plant Cells have: MITOCHONDRIA, RIBOSOMES,
AND the other organelles.
THE CELL MEMBRANE
The Cell Membrane is a complex barrier separating the cell from it's external environment. The
"Selectively Permeable" Membrane regulates what passes into and out of the cell.
All cells, from all organisms, are
surrounded by a CELL MEMBRANE.
Cell Membranes are made mostly of
PHOSPHOLIPID MOLECULES.
(Figure 4-5) Phosphate + Lipid.
Phospholipids are a kind of Lipid that
consists of TWO FATTY ACIDS
(TAILS), and PHOSPHATE GROUP
(HEADS).
The
Phosphate Head is HYDROPHILIC meaning
"WATER LOVING". Because of its hydrophilic
nature, the head of a Phospholipid will orient itself so
is as close as possible to water molecules.
The Lipid Tails are HYDROPHOBIC meaning
"WATER-FEARING", the Hydrophobic tails will tend
orient themselves away from water.
that it
to
Cell Membranes CONSIST of TWO
Phospholipid LAYERS Called a
LIPID BILAYER. (Figure 4-5)
MEMBRANE PROTEINS (Refer
to Figure 4-5)
Some Proteins are Attached to the surface of
the cell membrane, these are called
PERIPHERAL PROTEINS, and are located
on both the Internal and External Surface.
The Proteins that are Embedded in the Lipid
Bilayer are called INTEGRAL PROTEINS.
Carbhydrates act as "ID" tags for the cells
CELL WALL
One of the most important differences between Plant and Animal CELLS is the Presence of a
CELL WALL IN PLANT CELLS. A Cell Wall DOES NOT REPLACE the Cell Membrane;
Cells with WALLS also have a CELL MEMBRANE. Plant Cells are covered by a Rigid Cell
Wall that lies Outside the Cell Membrane.
PASSIVE TRANSPORT
Cell membranes help organisms maintain Homeostasis by controlling what substances may enter
or leave cells. Some substances can cross the cell membrane without any input of Energy by the
cell. The movement of such substances across the membrane is known as PASSIVE
TRANSPORT.
To stay alive, a CELL MUST EXCHANGE Materials such as Food and Waste With Its
ENVIRONMENT. These materials must cross the Cell Membrane.
DIFFUSION The Simplest type of PASSIVE TRANSPORT, Does Not require the cell to use
Energy, is DIFFUSION. THE MOVEMENT OF MOLECULES FROM AN AREA OF
HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATIONS. This
difference in the Concentration of Molecules across a space is called a CONCENTRATION
GRADIENT.
DIFFUSION ALWAYS
OCCURS DOWN A
CONCENTRATION
GRADIENT, FROM THE
AREA OF GREATER or
HIGHER CONCENTRATION TO THE AREA OF LESS OR LOWER
CONCENTRATION. When the Concentration of the molecules of a Substance is the Same
Throughout a Space, a State of EQUILIBRIUM EXISTS.
OSMOSIS THE PROCESS BY WHICH WATER MOLECULES DIFFUSE ACROSS A
CELL MEMBRANE FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF
LOWER CONCENTRATION IS CALLED OSMOSIS. OSMOSIS OCCURS IN
RESPONSE TO THE CONCENTRATION OF SOLUTES DISSOLVED IN WATER.
Water Moves from AREAS of LOW Solute Concentration to
AREAS of HIGH Solute Concentration. Water will cross the
Membrane toward the Higher Solute Concentration until the
Concentration Gradients of BOTH WATER and SOLUTES
EVEN OUT.
11. The Net Direction of Osmosis DEPENDS on the Relative
IN A HYPERTONIC SOLUTION, THE CONCENTRATION OF
SOLUTE MOLECULES OUTSIDE THE CELL IS HIGHER THAN
THE CONCENTRATION OF SOLUTES INSIDE THE CELL
CYTOSOL. WATER DIFFUSES OUT OF THE CELL until
Equilibrium is established. If the cell loses too much water, the cell will
shrivel and shrink. PLASMOLYSIS
16. IN A HYPOTONIC SOLUTION, THE CONCENTRATION OF
SOLUTE MOLECULES OUTSIDE THE CELL IS LOWER THAN
THE CONCENTRATION OF SOLUTES INSIDE THE CELL
CYTOSOL. WATER DIFFUSES INTO THE CELL until Equilibrium
is established. The Flow of water into a cell causes it to
swell.CYTOLYSIS
Plant Cells do not burst because of their Rigid Cell Wall. The pressure
that Water molecules exert against the cell wall is called TURGOR PRESSURE.
IN AN ISOTONIC SOLUTION, THE CONCENTRATION OF
SOLUTES OUTSIDE AND INSIDE THE CELL ARE EQUAL.
FACILITATED DIFFUSION is PASSIVE TRANSPORT across a Membrane requires NO
ENERGY and ALWAYS occurs DOWN A CONCENTRATION GRADIENT.
Some Molecules are CARRIED
across by CARRIER PROTEINS
EMBEDDED IN the Cell
Membrane that CHANGE SHAPE
when Molecules ATTACH to them.
Ex: Glucose into the Cell.
ACTIVE TRANSPORT (USE OF
ENERGY)
In many cases, cells must move materials up their concentrated gradient, from and area of lower
concentration to an area of higher concentration. Such movement of materials is known as
ACTIVE TRANSPORT. Unlike Passive Transport, Active Transport REQUIRES A CELL
TO EXPEND ENERGY (ATP).
CELL MEMBRANE PUMPS Cells often move molecules across the membrane AGAINST a
Concentration Gradient. From an area of LOW Concentration to areas of HIGH Concentration.
Active Transport often involves CARRIER PROTEINS like those in Facilitated Diffusion. The
CARRIER PROTEINS act as PUMPS that USE ENERGY to move IONS and Molecules
across the membrane.
SODIUM-POTASSIUM PUMPS ARE IMPORTANT FOR MUSCLE CONTRACTIONS,
THE TRANSMISSION OF NERVE IMPULSES, AND THE ABSORPTION OF NUTRIENTS.
SODIUM-POTASSIUM PUMPS IN ANIMAL CELLS PUMP SODIUM IONS OUT, AND
POTASSIUM IN, UP THEIR CONCENTRATION GRADIENT.
TYPES OF BULK TRANSPORT, INCLUDING ENDOCYTOSIS,EXOCYTOSIS,
PINOCYTOSIS, AND PHAGOCYTOSIS.
During ENDOCYTOSIS the Cell Membrane (figure 5-7) Folds
into a POUCH that Encloses the Particles that pinches off
INSIDE the Cell to form a VESICLE (membrane-wrapped
bubbles).
PINOCYTOSIS IS SOMETIMES CALLED "CELL DRINKING".
PHAGOCYTOSIS IS LIKE PINOCYTOSIS, EXCEPT THE CELL ENGULFS A FOOD
PARTICLE OR OTHER CELLS INSTEAD OF A DROP OF LIQUID. "CELL EATING"
DURING EXOCYTOSIS, WASTE AND CELL PRODUCTS
LEAVE THE CELL.
Unicellular organisms vs. multicellular organisms
Cell take on specific tasks - cell specialization
Levels of organization
In most Multicellular Organisms, we find the following organization:
Cellular Level: The smallest unit of life capable of carrying out all the functions of living
things.
Tissue Level: A group of cells that performs a specific function in an organism form the
TISSUE.
Organ Level: Several different types of tissue that function together for a specific purpose
form an ORGAN.
Organ System Level: Several organs working together to perform a function make up an
ORGAN SYSTEM. The different organ systems in a multicellular organism interact to carry out
the processes of life
Organismal Level: all organ systems working together to form an organism