Chapter 7:
Section 1:
Cell Discovery and Theory
MAINIDEA
RECALL
History of the Cell Theory
•A cell is the basic structural and functional unit of all living organisms.
The cell theory
•Cell theory is one of the fundamental ideas of modern biology, and includes the following three principles:
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.
All living organisms are composed of one of more cells.
Cells are the basic unit of structure and organization of all living organisms.
Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cells.
Give a brief description for each idea of the cell theory:
One cell can make up organisms such as bacteria and many cells can make up another organism like a human.
The cell is the smallest unit of life.
Microscope Technology
Compound light microscopes:
•Use a series of glass lenses and visible light to magnify images
•Magnify images to ~1000x actual size
Electron microscopes:
•Create an image by illuminating a sample with a beam of electrons and collecting the electrons that are reflected back from the sample
Basic Cell Types
•All cells have at least one physical trait in common: a plasma
membrane.
•A plasma membrane is a special boundary that helps control what enters and leaves the cell.
•Most cells contain genetic material in some form.
•Most cells break down molecules to generate energy.
Eukaryotic cells:
•Eukaryotic cells contain a nucleus and other organelles.
•Organelles are specialized structures that perform specific cell
functions.
•The nucleus is the distinct central organelle that contains the cell’s genetic material.
•Eukaryotic cells are generally much larger and more complex than prokaryotic cells.
Prokaryotic cell:
•Prokaryotic cells are cells without a nucleus or other membrane-bound organelles.
•Smaller and simpler than eukaryotes
Compare and contrast eukaryotic and prokaryotic cells by putting the phrases in the Venn diagram:
•bacteria
•contain organelles
•have a nucleus
•have membrane bound organelles
•do not have
membrane-bound organelles
•multicellular organisms
•unicellular organisms
Eukaryotic Cells Prokaryotic Cells Both
bacteria contain organelles
have a nucleus
have membrane
bound organelles do not have membrane-bound organelles
multicellular organisms
Origin of cell diversity:
•Eukaryotic cells may have evolved from prokaryotic cells. •The endosymbiont theory proposes that a symbiotic
relationship formed between two prokaryotic cells, one of which lived inside the other.
•Eventually the symbiotic relationship led to the two cells becoming one.
•Because eukaryotic cells are larger and more complex, they developed specific functions.
•These specific functions led to cell diversity, and thus organismal
Section 2:
The Plasma Membrane
MAINIDEA
RECALL
Phospholipid bilayer Transport protein Selective permeability Fluid mosaic model
Protein that moves needed substances or waste materials through the plasma membrane into or
out of the cell
Large molecules with a glycerol backbone, two fatty acid chains, and a phosphate group, arranged
tail to tail in two layers Structural model of the plasma membrane where phospholipids and proteins
float within the surface of the membrane
A key property of the plasma membrane that allows some molecules to pass through while keeping
others out
Plasma Membrane
•Thin, flexible boundary between the cell and its environment
•Allows nutrients into the cell
•The plasma membrane controls the movement of substances into and out of the cell, therefore it is selectively permeable.
•Controls the amount of a substance entering the cell
Analyzed what would happen if the plasma membrane were not selectively permeable:
•The plasma membrane is composed of the phospholipid
bilayer.
-A phospholipid molecule is composed of a glycerol
•The phospholipid bilayer allows other molecules to “float” in the membrane
•Other components -Proteins
-Cholesterol
Proteins
•Transmit signals inside the cell
•Act as a support structure
Cholesterol
Describe the benefits of the bilayer structure of the plasma membrane:
Section 3:
Cell Structure and Function
MAINIDEA
RECALL
Both animal and plant cells contain membrane bound organelles that each have a specific function:
Animal Cell
Centriole:
Cytoplasm:
•Semifluid material inside the organelles or plasma membrane
in which cell processes take place directly
•Acts as the base of a cell, where all activities and movement takes place
Cytoskeleton:
•Supporting network of long, thin protein fibers forming a
framework for the cell and providing an anchor for organelles
Endoplasmic reticulum (ER):
•Membrane system of folded sacs and interconnected channels that serves as the site for protein and lipid synthesis
•Transports these molecules throughout the cell
•Pleats and folds provide a large amount of surface area where cellular functions take place
•Can be compared to the conveyor belt in a factory because it yields products and transports them to their next destination
•Rough ER: ribosomes attached
Golgi apparatus:
•Flattened sack of membranes that modifies, sorts, and
packages proteins into sacs called vesicles
Lysosome:
•Vesicles that contain substances that digest excess or worn-out organelles and food particles
•Digest bacteria and viruses that have entered the cell
Mitochondria:
•Converts fuel particles (sugar) into useable energy
•Has a highly folded inner membrane that provides a large surface
area for breaking the bonds in sugar molecules
•Often referred to as “powerhouses” of the cell
Nucleus:
•Directs cell processes, contains cell’s DNA, stores information for
cell growth, function, and reproduction
•Surrounded by a double membrane called the nuclear envelope with nuclear pores to allow large molecules in the nucleus
•Site of ribosome production in the nucleolus
Ribosome:
•Helps manufacture proteins
•Produce a variety of proteins that are used by the cell or are moved out and used by other cells
•Some float freely in the cytoplasm, while others are bound to the endoplasmic reticulum (ER)
Vacuole:
•Membrane storage area within the cell
•Can store food, enzymes, and other materials needed by the cell
Only In Plants
Cell Wall:
•Thick, rigid, mesh of fibers that surround the outside of the plasma membrane of a plant cell
Chloroplasts:
•A double-membrane organelle with thylakoids containing clorophyll; where photosynthesis take place
Large central vacuole:
Movement in the Cell
Cilia and Flagella:
•Project outside the plasma membrane
•Cilia are short, numerous projections that look like hairs
Section 4:
Cellular Transport
MAINIDEA
RECALL
Passive Transport
•Movement of particles across the cell membrane without using
energy
•Three modes of passive transport:
•Diffusion
•Facilitated diffusion
Diffusion:
Dynamic Equilibrium:
•Reached when diffusion of material into the cell equals diffusion of material out of the cell
•Molecules continue to move, but the overall concentration remains the same.
Facilitated Diffusion:
Movement of materials across the plasma membrane using
proteins
Osmosis:
• Diffusion of water across a selectively permeable membrane
• Three types of solutions:
– Isotonic : equal amount of water in and out of cell
– Hypotonic : more water in the cell than out of the cell
Active Transport
•Movement of particles across the cell membrane using energy
•Particles move against the concentration gradient form a low to
Types of Active Transport Pumps: Na+/K+ ATPase pump
•Moves three Na+ ions out of the cell and two K+ ions into the cell
Endocytosis:
•Process by which the cell surrounds and takes
particles into the cell
•“Cellular eating”
Exocytosis:
•Secretion of material out of the plasma membrane
