BOIL 102 Chapter 3
Cell Doctrine
1. All living things are composed of cells
2. A single cell is the smallest unit that
exhibits all of the characteristics of life
3. All cells come only from preexisting cells
Cells Are Classified According to Their Internal
Organization
Prokaryotic Cells
▪
Plasma membrane
▪
No nucleus
▪
Cytoplasm: fluid within membrane
▪
No true organelles
▪
Bacterial cells are prokaryotic
Eukaryotic Cells
▪
Plasma membrane
▪
Nucleus: membrane bound information
center
▪
Cytoplasm: fluid within membrane
▪
Organelles: membrane bound
structures with specialized functions
▪
All human cells are eukaryotic
Cell Structure Reflects Cell Function
Structure and function have a direct relationship
with each other.
Though eukaryotic cells are remarkably similar,
there are structural differences
Examples
•
Muscle cells
•
Contain numerous organelles providing
energy needed for muscle contraction
Nerve cells
•
Long and thin to carry impulses over
distance
Cells Remain Small to Stay Efficient
Small cells have a higher surface-to-volume ratio
High surface-to-volume ratio promotes
efficiency in
– Acquisition of nutrients
– Disposal of wastes
– The total metabolic activities of
a cell are proportional to its volume of
cytoplasm, which is, in effect, its size.
a) One large cell.
b) Eight small cells.
c) Cell with microvilli on one surface.
Ribosomes Are Responsible for Protein
Synthesis
▪
Site of protein synthesis
▪
Free: floating in cytoplasm
– These ribosomes synthesize
proteins for immediate use in the cell
▪
Bound: attached to outer surface of
endoplasmic reticulum
– These ribosomes synthesize
proteins that will be transported to other
organelles or exported from the cell
Cells Have Structures for Support and
Movement
▪
Cytoskeleton
– Internal scaffolding—helps maintain cell
shape
▪
Cell structures that enable movement
– Cilia
– Flagella
– Centrioles
The Cytoskeleton Supports the Cell
▪
Cytoskeleton
Microtubules: tiny hollow tubes of protein
Microfilaments: thin solid fibers of protein
▪
Microtubules and microfilaments form
framework that supports the cell
▪
Cytoskeleton also supports and anchors
other cellular structures
Cilia and Flagella Are Specialized for Movement
Cilia
•
Short, numerous
•
Found on cells lining airways
Flagella
•
Long, single
•
Enable spermatozoa to swim
Cilia and flagella have similar internal structure
Centrioles
•
Short rod-like microtubule
structures near nucleus
•
Play important role in
cell division
A Plasma Membrane Surrounds the Cell
Separates a cell from its environment
Is selectively permeable
•
Permits movement of some substances
into and out of the cell, but blocks
others
Enables transfer of information between
environment and cell
Plasma membrane is a lipid bilayer
▪
Phospholipids: polar head and nonpolar
tail
▪
Cholesterol: makes membrane a bit
more rigid
▪
Proteins: provide
means of transport
through membrane
▪
Carbohydrates:
recognition
patterns for cells
and organisms
Non-rigid
Fluid mosaic
Wednesday Week 2
9/1/2021
Molecules Cross the Plasma Membrane in
Several Ways
Passive transport: cell does not need to expend
energy
•
Diffusion
•
Osmosis
Active transport: cell must expend energy
Bulk transport:
•
Involves membranous vesicles to move
larger substances
o Endocytosis
o Exocytosis
Passive Transport: Principles of Diffusion and
Osmosis
▪
Passive transport: transports a
substance without having to expend
energy
▪
Passive transport relies on diffusion
▪
Diffusion: movement of molecules from
a region of high concentration to a
region of low concentration
▪
High concentration → low
concentration
Osmosis: Diffusion of Water
▪
Osmosis: the diffusion of water across a
selectively permeable membrane
▪
Water moves from an area of low solute
concentration to an area of high solute
concentration
▪
Osmotic pressure: fluid pressure
required to exactly oppose osmosis
Active Transport Requires Energy
▪
Active transport moves substances from
an area of lower concentration to an
area of higher concentration
– Transported substance moves
against the concentration
gradient
– Requires a membrane protein
(transporter)
– Requires ATP or other energy
source
▪
Example: Na+/K+ pump
Endocytosis and Exocytosis Move Materials
in Bulk
Used to move larger molecules
•
Endocytosis: brings substances into the
cell
o As substance enters, it is
surrounded by a membrane,
forming a membrane-bound
vesicle
•
Exocytosis: expels substances from the
cell, think exit
o Substance is contained within a
membranous vesicle, which
then fuses with the membrane,
releasing the substance to the
external environment
Isotonic Extracellular Fluid Also Maintains Cell
Volume
▪
Tonicity: relative concentration of
solutes in two fluids
▪
Isotonic, means equal inside and
outside of the cell
– Extracellular and intracellular
solute concentrations are equal
– Cells maintain a normal volume
in isotonic extracellular fluids
– Regulatory mechanisms
maintain extracellular fluid that
is isotonic with intracellular
fluid
Variations in tonicity
Hypertonic
▪
Extracellular solute concentration
higher than intracellular solute
concentration
▪
Water will diffuse out of cell
▪
Cell may shrink and die
Hypotonic
▪
Extracellular solute concentration lower
than intracellular solute concentration
▪
Water will diffuse into cell
▪
Cell may swell and burst
Remember the 5 most important cells
Glucose Provides the Cell with Energy
▪
Cellular respiration: the breakdown of
glucose in the presence of oxygen to
yield ATP
▪
Four stages of cellular respiration
1. Glycolysis
3. Citric acid cycle
4. Electron transport system
Summary of Energy Production from Glucose
▪
Over 20 different enzyme-catalyzed
reactions
▪
Approximately 36 ATP (net) produced
from each molecule
of glucose
▪
Oxygen (O2) consumed,
carbon dioxide (CO2) produced
▪
Cellular respiration: cellular process
that uses O2 and
produces CO2 in the process
of making ATP
Anaerobic Pathways Make Energy Available
without Oxygen
▪
Cellular respiration cannot continue in
the absence of O2
▪
Glycolysis will continue, pyruvate will
build up converted to lactic acid
▪
Lactic acid buildup in muscles will cause
a burning sensation
▪
Two ATP produced per molecule of
glucose
▪
When O2 is available, lactic acid will be
metabolized aerobically
2. Preparatory step
