3 Cells: The Living Units: Part A
Cell Theory
• The _________________ is the smallest structural and functional living unit
• Organismal functions depend on _________________ and
_________________ cell functions
• Biochemical activities of cells are dictated by their specific subcellular
_________________
• Continuity of life has a cellular basis
Cell Diversity
• Over _________________ different types of human cells
• Types differ in size, shape, subcellular components, and functions
Generalized Cell
• All cells have some common structures and functions
• Human cells have three basic parts:
• _______________________________—flexible outer boundary
• _________________—intracellular fluid containing organelles
• _________________—control center
Plasma Membrane
• Bimolecular layer of _________________ and _________________ in a
constantly changing fluid mosaic
• Plays a dynamic role in cellular activity
• _________________ intracellular fluid from extracellular fluid (also called the
interstitial fluid)
Membrane Lipids
• _________________ phospholipids (lipid bilayer)
• Phosphate heads: polar and hydrophilic
• Fatty acid tails: nonpolar and hydrophobic (Review Fig. 2.16b)
• _________________ glycolipids
• Lipids with polar sugar groups on outer membrane surface
• _________________ cholesterol
• Increases membrane stability and fluidity
Lipid Rafts
• _________________of the outer membrane surface
• Contain phospholipids, sphingolipids, and cholesterol
• May function as ________________________for cell-signaling molecules
Membrane Proteins
• Integral proteins
• __________________________________ into the membrane (most are
transmembrane)
• Functions:
• __________________________________ (channels and carriers)
• __________________________________
• __________________________________
Membrane Proteins
• Peripheral proteins
• _________________attached to integral proteins
• Include _________________ on intracellular surface and
_________________ on extracellular surface
• Functions:
• Enzymes,
• motor proteins,
• cell-to-cell links,
• provide support on intracellular surface
• form part of glycocalyx
Functions of Membrane Proteins
a. Transport
1 ______________________________
2 ______________________________
b. __________________________________ for signal transduction
c. __________________________________ to cytoskeleton and
extracellular matrix
d. __________________________________ activity
e. __________________________________ joining
f. ______________________________ recognition
Membrane Transport
• Plasma membranes are _________________permeable
• Some molecules easily pass through the membrane; others do not
Types of Membrane Transport
• _________________ processes
• No __________________________________ (__________) required
• Substance moves _________________ its concentration gradient
• _________________ processes
• _________________ (_________) required
• Occurs only in _________________ cell membranes
Summary of Passive Processes
Process
Energy
Movement Process
Kinetic
energy
Moves along the substances
Kinetic
energy
Uses _________________ or
Kinetic
energy
Simple diffusion of water either
Example
Oxygen
_______________________________
Glucose
___________________
Water
through the _________________ or
using channels called
_________________.
Summary of Active Processes
Process
Energy
ATP
Movement Process
Substances move against the
_________________ using
Example
Ions (Na+, K+, Ca2+, and
more)
membrane _________________
powered by ATP
ATP
The secretion or
secretion of
_________________ of
neurotransmitters,
substances from cell using
_________________.
hormones, mucus, etc.;
ejection of cell wastes
Summary of Active Processes (continued)
ATP
Substances from
_________________ the cell are
surrounded by
_________________
_________________and brought
proteins, bacteria, dead cell
debris (phagocytosis ), fluid
(pinocytosis), hormones,
cholesterol, iron, other
macromolecules (receptormediated endocytosis)
into the cell
ATP
Coatomer-coated vesicles pinch
off from organelles and travel to
other organelles to deliver
substances.
Accounts for nearly all
intracellular trafficking
between organelles
except for vesicles
budding from the trans
face of the Golgi
apparatus, which are
clathrin-coated
Cytoplasm
• Located between _________________________________and
_________________
• _________________
• Water with solutes (protein, salts, sugars, etc.)
• Cytoplasmic _________________
• Metabolic machinery of cell
• _________________
• Granules of glycogen or pigments, lipid droplets, vacuoles, and crystals
Mitochondria
• _________________________________ structure with shelflike cristae
• Provide most of cell’s ____________ via aerobic
_________________________________
• Contain their own _________________ and _________________
Ribosomes
• Granules containing _________________ and _________________
• Site of _________________ synthesis
• _________________ ribosomes synthesize soluble proteins
• _________________________________ ribosomes (on rough ER)
synthesize proteins to be incorporated into membranes or exported from the
cell
Endoplasmic Reticulum (ER)
• _________________ tubes and _________________ membranes
enclosing cisternae
• Continuous with _________________________________
• Two varieties:
• _________________ ER
• _________________ ER
Rough ER
• External surface studded with _________________
• Manufactures all secreted _________________________________
• Synthesizes membrane _________________ proteins and
_________________________________
Smooth ER
• _________________ arranged in a looping network
• _________________ (integral protein) functions:
• In the _________________—lipid and cholesterol metabolism, breakdown of
glycogen, and, along with kidneys, detoxification of drugs, pesticides, and
carcinogens
• Synthesis of steroid-based _________________
• In _________________ cells—absorption, synthesis, and transport of fats
• In _________________________________ muscle—storage and release of
calcium
Golgi Apparatus
• _________________ and _________________membranous sacs
• Modifies, concentrates, and packages _________________ and
_________________
Lysosomes
• _________________ membranous bags containing digestive enzymes (acid
hydrolases)
• _________________ ingested bacteria, viruses, and toxins
• Degrade _________________ organelles
• Break down and release _________________
• Break down _________________ to release Ca2+
• Destroy cells in injured or nonuseful tissue (_________________)
Endomembrane System
• Overall function
• Produce, store, and export _________________ molecules
• Degrade potentially _________________ substances
Peroxisomes
• Membranous sacs containing powerful _________________ and
_________________
• _________________ harmful or toxic substances
• _________________ dangerous free radicals (highly reactive chemicals with
unpaired electrons)
Cytoskeleton
• Elaborate series of rods throughout cytosol
• _________________________________
• _________________________________
• _________________________________
Motor Molecules
• Protein complexes that function in motility (e.g., movement of organelles and
contraction)
• Powered by _________________
Centrosome
• “_________________________________” near nucleus
• Generates _________________________________; organizes mitotic
spindle
• Contains _________________: Small tube formed by microtubules
Cellular Extensions
• Cilia and flagella
• Whiplike, motile extensions on _________________ of certain cells
• Contain _________________________________ and motor molecules
• Cilia move substances across cell _________________
• Longer flagella _________________ whole cells (tail of sperm)
• Microvilli
• Fingerlike extensions of _________________________________
• Increase _________________________________ for absorption
• Core of actin filaments for stiffening
Nucleus
• Genetic library with blueprints for nearly all
_________________________________
• Responds to signals and dictates kinds and amounts of proteins to be
synthesized
• Most cells are uninucleate (_________________________________)
• Red blood cells are anucleate (_________________________________)
• Skeletal muscle cells, bone destruction cells, and some liver cells are
multinucleate (_________________________________)
Nuclear Envelope
• _________________________________ barrier containing pores
• Outer layer is _________________________________ with rough ER and
bears ribosomes
• Inner lining (nuclear lamina) maintains _________________ of nucleus
• Pore complex regulates transport of large molecules into and out of nucleus
Nucleoli
• Dark-staining spherical bodies within nucleus
• Involved in _________________ synthesis and ribosome subunit assembly
Chromatin
• Threadlike strands of _________________ (30%), _________________
proteins (60%), and _________________ (10%)
• Condense into barlike bodies called _________________ when the cell starts
to divide
Cell Cycle
• Defines changes from formation of the cell until it reproduces
• Includes:
• _________________________________
• _________________________________ (mitotic phase)
Interphase
• Period from cell _________________ to cell _________________
• Four subphases:
• G1 (_________________)—vigorous _________________ and metabolism
• G0—gap phase in cells that permanently
_________________________________
• S (_________________)—_________________ replication
• G2 (_________________)—_________________ for division
Interphase Checkpoints
 G1 Checkpoint – Restriction point
DNA Replication
• DNA helices unwind from the nucleosomes
• Each nucleotide strand serves as a template for building a new complementary
strand
• DNA polymerase and ligase copy and splice together new strands of DNA
• End result: _________________________________ molecules formed from
the original
• This process is called _________________________________ replication
DNA Replication
Cell Division
• _________________ (M) phase of the cell cycle
• Essential for body growth and tissue repair
• Does not occur in most mature cells of
• _________________________________
• _________________________________
• _________________________________
• Includes two distinct events:
1. Mitosis—four stages of nuclear division:
• Prophase
• Metaphase
• Anaphase
• Telophase
2. Cytokinesis—division of cytoplasm by cleavage furrow
Mitosis Checkpoint
 _________________________________Checkpoint
o Ensures that all of the _________________ are attached to the
_________________________________ by a kinetochore
Checkpoint Failure
 Cancer
o Cells do not respond normally to the body's control mechanism.
o They _________________ excessively and _________________ other tissues
o If left unchecked, they can kill the organism
 Cancer cells do not exhibit contact inhibition
o If cultured, they continue to grow on top of each other when the total
area of the petri dish has been covered
o They may produce required external growth factor (or override
factors) themselves or possess abnormal signal transduction
sequences which falsely convey growth signals thereby bypassing
normal growth _________________
 Cancer cells exhibit irregular growth sequences
o If growth of cancer cells does cease, it does so at random points of
the cell cycle
o Cancer cells can go on dividing _________________ if they are given a
continual supply of nutrients
 Normal mammalian cells growing in culture only divide
_________________ times before they stop dividing
Protein Synthesis
• DNA is the master blueprint for protein synthesis
• _________________e: Segment of DNA with blueprint for one polypeptide
• Triplets of nucleotide bases form genetic library
• Each triplet specifies coding for an _________________
Roles of the Three Main Types of RNA
• _________________ RNA (mRNA)
• Carries instructions for building a _________________, from gene in DNA to
ribosomes in ________________________________
• _________________ RNA (rRNA)
• A structural component of ribosomes that, along with tRNA, helps
_________________message from mRNA
Roles of the Three Main Types of RNA
• _________________ RNAs (tRNAs)
• Bind to amino acids and pair with bases of codons of mRNA at ribosome to
begin process of protein synthesis
Transcription
• Transfers _________________ gene base sequence to a complementary
base sequence of an _________________
Translation
• Converts base sequence of nucleic acids into the amino acid sequence of
proteins
• Involves _________________, _________________, and
_________________
Genetic Code
• Each three-base sequence on DNA is represented by a codon
• _________________—complementary three-base sequence on mRNA
Developmental Aspects of Cells
• All cells of the body contain the same _________________but are not
_________________
• Chemical signals in the embryo channel cells into specific developmental
pathways by turning some genes off
• Development of specific and distinctive features in cells is called cell
_________________
• Elimination of excess, injured, or aged cells occurs through programmed rapid
cell death (_________________) followed by phagocytosis
Theories of Cell Aging
• ________________________________: Little chemical insults and free
radicals have cumulative effects
• _________________________________: Autoimmune responses and
progressive weakening of the immune response
• _________________________________: Cessation of mitosis and cell
aging are programmed into genes. Telomeres (strings of nucleotides on the
ends of chromosomes) may determine the number of times a cell can divide.