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Cytology
Studying Cells
Cell Theory: Four Basic Concepts
1. Basic building blocks of all animals and plants
2. Smallest functional units of life
3. Products of cell division
4. Basic homeostatic units
Studying Cells
The Diversity of Cells in the Human Body
Figure 3-1
Studying Cells
Overview of Cell Anatomy
•Extracellular (interstitial )fluid - outside cell
•Cell Membrane
•Cytoplasm - stuff inside (not including the
membrane & nucleus)
a. Cytosol = intracellular fluid
b. Organelles = “little organs” structures that
perform special functions for cell
•Nucleus
Studying Cells
Anatomy of a
Representative
Cell
Figure 3-2
The Cell Membrane
Functions of the cell membrane
• Physical isolation
• Regulation exchange of materials
• Sensitivity - receptors allow cell to
recognize & respond to specific
molecules in environment
• Support
The Cell Membrane
The Cell Membrane
Figure 3-3
The Cell Membrane
Table 3-2
The Cell Membrane
Membrane is Selectively
permeable = chooses what
can pass through based on
• Size
• Electrical charge
• Shape
• Lipid solubility
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Membrane Transport Processes
• Passive transport - no energy needed
• Diffusion (including Osmosis)
• Facilitated diffusion - diffusion with help
of a protein channel
• Active Transport - uses ATP energy
• Sodium-potassium exchange pump
• Phagocytosis - cell eating
• Exocytosis - sending materials out
The Cell Membrane
Membrane Transport Definitions
• Diffusion
Movement of materials from higher to
lower concentration (tries to even out)
•Osmosis
Diffusion of water across a membrane to
where there is more solute (less water)
The Cell Membrane
Diffusion
Figure 3-4
The Cell Membrane
Diffusion Across Cell Membranes
Figure 3-5
Osmosis & Solutions That Affect It
Isotonic = cell
maintains balance
Hypotonic = water
moves in to where
there is more
solute - cell swells
& bursts
(hemolysis in
RBC’s)
Hypertonic =
water moves out
of cell to where
there is more
solute - cell
shrivels
The Cell Membrane
Facilitated Diffusion
Figure 3-8
The Cell Membrane
The SodiumPotassium
Exchange Pump
Figure 3-9
Phagocytosis
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
This fusion activates digestive
enzymes.
CYTOPLASM
EXTRACELLULAR FLUID
Undissolved
residue
The enzymes break down the
structure of the phagocytized
material.
Residue is then ejected from the
cell by exocytosis.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
1 of 8
Exocytosis
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Lysosomes
Cell
membrane
Secretory
vesicles
Transport
vesicle
Golgi apparatus
(a)
Membrane renewal
vesicles
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
(b) Exocytosis
Vesicle
Incorporation in
cell membrane
Figure 3-14
1 of 7
Cell Structures - Organelles
Anatomy of a
Cell
Figure 3-2
The Cytoplasm
Organelles
• Microvilli - Surface projections increase
surface area for absorption
•Cilia - Move fluids across cell surface
•Flagella - Moves cell through fluid
•Ribosome - proteins factories
•Lysosomes - “janitors” - hold digestive
enzymes to get rid of wastes & bacteria
•Mitochondria - “power plant” - make ATP energy
The Cytoplasm
Key Note
Mitochondria provide most of the
energy needed to keep your cells
(and you) alive. They use oxygen
and organic compounds, such as
glucose, and make carbon dioxide
and ATP.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Nucleus = Control Center
Nuclear envelope surrounds nucleus
Nuclear pores Allows movement of materials
in & out (but NOT DNA)
The Nucleus
Chromosome
Structure
DNA makes up 23
pairs of chromosomes
contained in nucleus
Figure 3-17
The Nucleus
Key Note
The nucleus contains DNA, the genetic
instructions within chromosomes. The
instructions tell how to synthesize the
proteins that determine cell structure
and function. THEREFORE - the
nucleus controls everything else by
regulating (controlling) protein
synthesis!
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Nucleus
The Genetic Code
• Triplet code
= Sequence of 3 nitrogen bases
(codon) which code for a certain
amino acid
•A Gene
= All the amino acids needed to make 1 protein
Protein Synthesis
Problem: DNA can’t leave nucleus & protein
factories (ribosomes) are in the cytoplasm
Solution: Make a copy of DNA & send it out
Protein Synthesis:
1. Transcription = DNA is copied to make mRNA
2. Translation = Info from mRNA is used to make a protein
with help of tRNA
Transcription
DNA
Translation
RNA
In Nucleus
Protein
In Cytoplasm
http://www.lewport.wnyric.org/jwanamaker/animations/protein%20synthesis%20-%20long.html
The Cell Life Cycle
Interphase - Most of a cell’s life performing
normal function - time between cell division
• Includes DNA replication
Mitosis - When copied chromosomes split
apart & the 2 nuclei divide
Cytokinesis - the last part of mitosis when the
cytoplasm divides to create 2 new cells
The Cell Life Cycle
Occurs in Somatic Cells
= all cells in body aside
from sex cells (sperm &
eggs)
Involves: Interphase,
Mitosis & Cytokinesis
Note: some cells never divide apoptosis = genetically
programmed cell death
The Cell Life Cycle
DNA ReplicationThe Cell Life Cycle
Figure 3-21
Interphase
Nucleus
Early prophase
Mitosis
begins
Spindle
fibers
Centrioles
(two pairs)
Metaphase
Late prophase
Centromeres
Anaphase
Chromosome
with two
sister chromatids
Telophase
Separation
Daughter
chromosomes
Cytokinesis
Metaphase
plate
Cleavage
furrow
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Daughter
cells
Figure 3-22
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The Cell Life Cycle
Cell Division and Cancer
• Tumor (neoplasm) - a mass or swelling made
by abnormal cell growth & division
• Malignant Tumor = when it no longer responds to normal
control mechanisms & spreads into surrounding tissues
• Cancer = illness from effects of malignant cells
The Cell Life Cycle
Key Note
Cancer results from mutations that
disrupt the control mechanism that
regulates cell growth and division.
Cancers most often begin where
cells are dividing rapidly, because
the more chromosomes are copied,
the greater the chances of error.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Cell Diversity and Differentiation
Somatic Cells
• All have same genes
• Some genes inactivate during
development
• Cells thus become functionally
specialized
• Specialized cells form distinct tissues
• Tissue cells become differentiated
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings