1. Chapter 3
Cells
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2. Introduction
The basic organizational structure of the human body is the cell.
There are about 75 trillion cells in the human body.
Cell size is measured in micrometers.
Differentiation is when cells specialize.
As a result of differentiation, cells vary in size and shape due to their unique function.

3. A Composite Cell Also called a ‘typical’ cell Major parts include:
Nucleus
Cytoplasm
Cell membrane
Within the cytoplasm are specialized organelles that perform specific functions for the cell.
Phospholipid bilayer
Flagellum
Nucleus
Nuclear envelope
Chromatin
Nucleolus
Ribosomes
Microtubules
Basal body
Cell membrane
Centrioles
Rough
Endoplasmic
reticulum
Mitochondrion
Smooth
Endoplasmic
reticulum
Microvilli
Secretory
vesicles
Cilia
Golgi
apparatus
Microtubule
Microtubules L
ysosomes

4. Cell Membrane (aka Plasma Membrane)
Outer limit of the cell
Controls what moves in and out of the cell, participates in signal transduction,
and helps cells adhere to other cells
Selectively permeable
Phospholipid bilayer
Water-soluble “heads” form surfaces (hydrophilic)
Water-insoluble “tails” form interior (hydrophobic)
Permeable to lipid-soluble substances (gases, steroid hormones)
Cholesterol strengthens and stabilizes the membrane and makes it less permeable
to water-soluble substances
Proteins:
Receptors
Pores, channels and carriers
Enzymes
CAMS (cellular adhesion molecules)
Self-markers

5. Cell Membrane

6. Cell Adhesion Molecules (CAMs)
Guide cells on the move
Selectin – allows white blood cells to “anchor”
White blood cell
Attachment
(rolling)
Selectin
Integrin – guides white blood cells through capillary walls
Carbohydrates
on capillary wall
Adhesion
Adhesion
receptor proteins
Integrin
Important for growth of embryonic tissue
Blood vessel
lining cell
Exit
Splinter
Important for growth of nerve cells

7. Cytoplasm
Cytoplasm - networks of membranes and organelles suspended in the cytosol (clear liquid)
Cytoskeleton forms supportive framework and is made of protein rods and tubules

8. Organelles Endoplasmic Reticulum (ER)
Connected, membrane-bound sacs, canals, and vesicles
Transport system
Rough ER
Studded with ribosomes
Functions in protein synthesis
Smooth ER
Lipid synthesis
Added to proteins arriving from rough ER
Break down of drugs
ER membrane
Ribosomes
(a)
Membranes
Membranes
Ribosomes
Ribosomes
Free floating in cytoplasm or connected to ER
Composed of protein and RNA and provide structural support and enzyme activity to amino acids to form protein
(b)
(c)

9. Organelles Golgi apparatus Stack of flattened, membranous sacs
Modifies, refines, packages and delivers proteins
Vesicles
Vesicles formed on ER travel to the Golgi apparatus which modifies their contents chemically.
The vesicle may then move to the cell membrane and secrete its contents to the outside.
Vesicles form a “delivery service,” carrying chemicals throughout the cell (vesicle trafficking).

10. Organelles Nuclear envelope Nucleus Cytosol Rough endoplasmic
reticulum
Golgi
apparatus
Secretion
Transport
vesicle
Cell membrane
(a)
(b)

11. Organelles Mitochondria
the powerhouses of the cell and contain enzymes needed for aerobic respiration.
The inner membrane of the mitochondrion is folded into cristae which hold the enzymes needed in energy transformations to make ATP.
Very active cells contain thousands of mitochondria.

12. Organelles
Inner membrane
Cristae
Outer membrane
(a)
(b)

13. Organelles Lysosomes Centrosome Enzyme-containing sacs
Digest worn out cell parts or unwanted substances
“garbage disposals”
Centrosome
Two rod-like centrioles
Used to produce cilia and flagella
Distributes chromosomes during cell division
Peroxisomes
Enzyme-containing sacs that function in the synthesis of bile acids
Break down organic molecules

14. Organelles
Cilia
Short hair-like projections abundant on the free surfaces of certain epithelial cells
Propel substances on cell surface
Flagellum
Long tail-like projection
Provides motility to sperm

15. Organelles Microfilaments and microtubules Thin rods and tubules
Support cytoplasm
Allows for movement of organelles
Microfilaments: made of actin, cause various cellular movements.
Microtubules: made of the globular protein tubulin, are attached in a spiral to form a long tube.
Mitochondrion
Nucleus
Vesicle
Rough
endoplasmic
reticulum
Cell membrane
(a)
Microfilaments
Ribosome
Microtubules
(b)

16. Cell Nucleus Control center of the cell Nuclear envelope
Porous double membrane
Separates nucleoplasm from cytoplasm
Nucleolus
Dense collection of RNA and proteins
Site of ribosome production
Nucleus
Nuclear
envelope
Chromatin
Consists of all the cell’s chromosomes, each containing DNA wound around proteins
Fibers of DNA and proteins
Stores information for synthesis of proteins
Nucleolus
Chromatin
Nuclear
pores
(a)