Download Orientation to the Human Body

Anatomy & Physiology I
Chapter 3
All organisms composed of cells and cell products.
The cell is the smallest structural and functional
unit of life.
An organism’s structure and functions are due to
the activities of its cells.
Cells come only from preexisting cells, not from
nonliving matter.
Cells of all species have many fundamental
similarities in their chemical composition and
metabolic mechanisms.
Over 200 different types of human cells
Types differ in size, shape, subcellular
components, and functions
Squamous - thin and flat with nucleus creating bulge
Polygonal - irregularly angular shapes with 4 or more
sides
Stellate – starlike shape
Cuboidal – squarish and about as tall as they are wide
Columnar - taller than wide
Spheroid to Ovoid – round to oval
Discoid - disc-shaped
Fusiform - thick in middle, tapered toward the ends
Fibrous – threadlike shape
Squamous
Cuboidal
Columnar
Polygonal
Stellate
Spheroid
Discoid
Fusiform (spindle-shaped)
Fibrous
Erythrocytes
Fibroblasts
Epithelial cells
(a) Cells that connect body parts,
form linings, or transport gases
Skeletal
Muscle
cell
Smooth
muscle cells
(b) Cells that move organs and
body parts
Macrophage
Fat cell
(c) Cell that stores
nutrients
(d) Cell that
fights disease
Nerve cell
(e) Cell that gathers information
and control body functions
Sperm
(f) Cell of reproduction
All cells have some common structures
and functions
Human cells have three basic parts:
Plasma membrane—flexible outer boundary
Cytoplasm—intracellular fluid containing
organelles
Nucleus—control center
ZOOMING IN
• What is attached to
the ER to make it look
rough?
• What is the liquid
part of the cytoplasm
called?
Regulates the movement of substance into and
out of the cell
Encloses cell contents
Separates intracellular fluid (ICF) from
extracellular fluid (ECF)
Interstitial fluid (IF) = ECF that surrounds cells
Participates in cellular activities
Bilayer structure
Phospholipids
Cholesterol
Proteins
75% phospholipids (lipid bilayer)
Phosphate heads: polar and hydrophilic
Fatty acid tails: nonpolar and hydrophobic
5% glycolipids
contributes to glycocalyx – carbohydrate coating on
the
cells surface
20% cholesterol
Increases membrane stability and fluidity
ZOOMING IN
• How many
layers make up
the main
substance of the
plasma
membrane?
Chemical
messenger
(a) Receptor
A receptor that
binds to chemical
messengers such
as hormones sent
by other cells
Breakdown
products
(b) Enzyme
An enzyme that
breaks down
a chemical
messenger and
terminates its
effect
Ions
(c) Ion Channel
A channel protein
that is constantly
open and allows
ions to pass
into and out of
the cell
CAM of
another cell
(d) Gated ion channel
A gated channel
that opens and
closes to allow
ions through
only at certain
times
(e) Cell-identity marker
A glycoprotein
acting as a cellidentity marker
distinguishing the
body’s own cells
from foreign cells
(f) Cell-adhesion
molecule (CAM)
A cell-adhesion
molecule (CAM)
that binds one
cell to another
Unique fuzzy coat external to the plasma
membrane
carbohydrate moieties of membrane glycoproteins
and glycolipids
unique in everyone, but identical twins
Functions
protection
- cell adhesion
immunity to infection
- fertilization
defense against cancer - embryonic development
transplant compatibility
Structures projecting from the cell surface used
for motion
Cilia
Flagellum
Cilia
10 m
Motile cilia – respiratory tract, uterine tubes, ventricles
of the brain, efferent ductules of testes
beat in waves
sweep substances across surface in same direction
power strokes followed by recovery strokes
Mucus
Saline layer
Epithelial cells
1 2 3 4
Power stroke
5
6
7
Recovery stroke
Saline layer at cell surface due to chloride pumps move
Cl- out of cell. Na+ ions and H2O follow
Cystic fibrosis – hereditary disease in which cells make
chloride pumps, but fail to install them in the plasma
membrane
chloride pumps fail to create adequate saline layer on cell
surface
thick mucus plugs pancreatic ducts and respiratory tract
inadequate digestion of nutrients and absorption of oxygen
chronic respiratory infections
life expectancy of 30
Mucus
Saline layer
Epithelial cells
tail of the sperm - only functional flagellum
whiplike structure
much longer than cilium
movement is more snakelike
no power stroke or recovery stroke as in cilia
Located between plasma membrane and
nucleus
Cytosol
Water with solutes (protein, salts, sugars, etc.)
Cytoplasmic organelles
Metabolic machinery of cell
Inclusions
Granules of glycogen or pigments, lipid droplets,
vacuoles, and crystals
Nucleus - Contains chromosomes (DNA) and nucleolus
Rough ER - Manufactures all secreted proteins
Smooth ER – Synthesize steroids and other lipids;
manufactures all membranes of the cell
Ribosomes - Site of protein synthesis
Mitochondria – cellular respiration (ATP production)
Golgi apparatus – Storage warehouses of the cell;
carbohydrate synthesis
Lysosomes - contain digestive enzymes; Digest ingested
bacteria, viruses, and toxins
Peroxisomes - Detoxify harmful or toxic substances;
Neutralize dangerous free radicals
Centrioles - play role in cell division
Largest organelle in a cell
Genetic library with blueprints for nearly all
cellular proteins
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 pores
Nuclear envelope
Chromatin (condensed)
Nucleolus
Cisternae of rough ER
Nucleus
DNA and RNA have similar structures
Four nucleotides
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T) or uracil (U)
Sugar
Ribose or deoxyribose
Phosphate
Nitrogen base
DNA – deoxyribonucleic acid -
a long
threadlike molecule with
uniform diameter, but varied
length
Adenine
NH2
N
HC
N
H
46 DNA molecules in the nucleus of most human
cells
DNA and other nucleic acids
are polymers of nucleotides
one sugar - deoxyribose
one phosphate group
one nitrogenous base
A, T, G or C
C
HO
P
O
OH
O
CH2
H H
Phosphate
H H
H
Deoxyribose
N
CH
N
O
OH
Each nucleotide consists of
C
C
A
T
G
C
A
T
A
T
G
C
A
T
C
G
T
A
G
C
T
C
G
T
A
G
Sugar–phosphate
backbone
Molecular shape is a double helix
(resembles a spiral staircase)
each sidepiece is a backbone
composed of phosphate groups
alternating with the sugar
deoxyribose.
C
Sugar–phosphate
backbone
steplike connections between
the backbones are pairs of
nitrogen bases
Nitrogenous bases united by
hydrogen bonds
a purine on one backbone with a
pyrimidine on the other
A – T two hydrogen bonds
C – G three hydrogen bonds
T
T
A–T
C–G
one strand determines base
sequence of other
C
G
DNA base pairing
Law of Complementary Base
Pairing
G
C
A
G
Sugar–phosphate
backbone
C
Sugar–phosphate
backbone
Genes – genetic instructions for synthesis of
proteins
Gene – segment of DNA that codes for a specific
protein
Genome - all the genes of one person
humans have estimated 25,000 to 35,000 genes
2% of total DNA
other 98% is noncoding DNA
plays role in chromosome structure
regulation of gene activity
no function at all – “junk” DNA
chromatin – fine filamentous DNA
material complexed with proteins
occurs as 46 long filaments called
chromosomes
in nondividing cells, chromatin is so
slender it cannot be seen with light
microscope
histones – disc-shaped cluster of eight
proteins
DNA molecule winds around the cluster
appears to be divided into segments nucleosomes
nucleosome consists of :
core particle – histones with DNA
around them
linker DNA – short segment of DNA
connecting core particles
2 nm
1
DNA double
helix
Core particle
Linker DN
A
11 nm 2
Nucleosome
DNA winds
around core
particles to form
nucleosomes
11 nm in
diameter
Nucleosomes
fold accordionlike into zigzag
fiber 30 nm in
diameter
300 nm 4 30 nm fiber is
thrown into
irregular loops
to form a fiber
300 nm thick
In dividing cells only
In dividing
700 nm 5 cells, looped
chromatin coils
further into a
700 nm fiber to
form each
Chromatids Centromere
chromatid
30 nm 3
700 nm 6 Chromosome
at the midpoint
(metaphase) of
cell division
RNA much smaller cousin of DNA (fewer bases)
messenger RNA (mRNA) over 10,000 bases
ribosomal RNA (rRNA)
transfer RNA (tRNA) 70 - 90 bases
DNA averages 100 million base pairs
one nucleotide chain (not a double helix as DNA)
ribose replaces deoxyribose as the sugar
uracil replaces thymine as a nitrogenous base
Essential function
interprets code in DNA
uses those instructions for protein synthesis
leaves nucleus and functions in cytoplasm
A segment of DNA that carries the code for a particular
protein
The segment of DNA first codes for the production of a
molecule of RNA
The molecule of RNA then plays a role in synthesizing
one or more proteins (protein synthesis)
The amino acid sequence of a protein is determined by
the nucleotide sequence in the DNA
Genome – all the DNA in one 23-chromosome set
3.1 billion nucleotide pairs in human genome
46 human chromosomes comes in two sets of 23
chromosomes
one set of 23 chromosomes came form each parent
each pair of chromosomes has same genes but different
versions (alleles) exist
body can make millions of different proteins, all from the same 20
amino acids, and encoded by genes made of just 4 nucleotides
(A,T,C,G)
Genetic code – a system that enables these 4 nucleotides to code
for the amino acid sequence of all proteins
minimum code to symbolize 20 amino acids is 3 nucleotides per
amino acid
Base triplet – a sequence of 3 DNA nucleotides that stands for one
amino acid
codon - the 3 base sequence in mRNA
64 possible codons available to represent the 20 amino acids
61 code for amino acids
Stop Codons – UAG, UGA, and UAA – signal the ‘end of the message’, like a
period at the end of a sentence
Start Codon – AUG codes for methionine , and begins the amino acid sequence
of the protein
process of protein synthesis
DNA
mRNA
protein
transcription – step from DNA to mRNA
occurs in the nucleus where DNA is located
translation – step from mRNA to protein
most occurs in cytoplasm
15-20% of proteins are synthesized in the nucleus
DNA too large to leave nucleus and participate directly in
cytoplasmic protein synthesis
necessary to make a small mRNA copy that can migrate through a nuclear
pore into the cytoplasm
Transcription – copying genetic instructions from DNA to RNA
translation – the process that converts the
language of nucleotides into the language of
amino acids
ribosomes - translate sequence of nucleotides
into the sequence of amino acids
occur mainly in cytosol, on surface of rough ER, and
nuclear envelope
Nuclear
envelope
Transcription
RNA Processing
DNA
Pre-mRNA
mRNA
Translation
Polypeptide
Ribosome
Nuclear
pores
1 DNA double helix
2 Seven base triplets on the
template strand of DNA
3 The corresponding codons of
mRNA transcribed from the
DNA triplets
4 The anticodons of tRNA that
bind to the mRNA codons
5 The amino acids carried by
those six tRNA molecules
6 The amino acids linked into a
peptide chain
Gene (DNA)
1 Transcription
Intron
Pre-mRN A
A
B
C
D
Exon
E
F
2 Splicing
mRNA 1
A
C
mRNA 2
D
B
D
mRNA 3
E
A
E
3 Translation
Protein 1
Protein 2
Protein 3
One gene can code for more than one protein
F
Defines changes from formation of the cell until
it reproduces
Includes:
Interphase
Cell division (mitotic phase)
Period from cell formation to cell division
Nuclear material called chromatin
Subphases:
G1 (gap 1)—vigorous growth and metabolism
S (synthetic)—DNA replication
G2 (gap 2)—preparation for division
S
Growth and DNA
synthesis
G2
G1
Growth
M
Growth and final
preparations for
division
Mitotic (M) phase of the cell cycle
Essential for body growth, tissue repair and
renewal
Does not occur in most mature cells of nervous
tissue, skeletal muscle, and cardiac muscle
Includes two distinct events:
1. Mitosis—four stages of nuclear division:
Prophase - Chromosomes become visible
Metaphase - chromosomes are aligned at the equator
Anaphase - Centromeres of chromosomes split
simultaneously—each chromatid now becomes a
chromosome
Telophase - chromosomes uncoil to form chromatin
2. Cytokinesis—division of cytoplasm by cleavage furrow
The stages of mitosis.
ZOOMING IN
• If the original cell shown
has 46 chromosomes, how
many chromosomes will
each new daughter cell
have?
plasma membrane – a barrier and a
gateway between the cytoplasm and ECF
selectively permeable – allows some things through, and prevents other
things from entering and leaving the cell
Some molecules easily pass through the
membrane; others do not
Travel across the membrane is based on
several factors:
Molecular size
Solubility
Electrical charge
Diffusion through lipid bilayer
Nonpolar, hydrophobic, lipid-soluble substances
diffuse through lipid layer
Diffusion through channel proteins
water and charged, hydrophilic solutes diffuse
through channel proteins in membrane
Cells control permeability by regulating
number of channel proteins or by opening and
closing gates
Passive transport mechanisms
Simple Diffusion
Facilitated Diffusion
Carrier-mediated facilitated diffusion
Channel-mediated facilitated diffusion
Osmosis
Filtration
Passive transport mechanisms require no ATP.
Random molecular motion of particles provides
the necessary energy.
Active transport
Carrier-mediated Active Transport
Vesicular (Bulk) Transport
Endocytosis
Phagocytosis
Pinocytosis
Exocytosis
Active transport mechanisms consume ATP.
Simple Diffusion – the net
movement of particles from
area of high concentration to
area of low concentration
due to their constant,
spontaneous motion
Also known as movement
down the concentration
gradient – concentration of a
substance differs from one point to
another
Down
gradient
Up
gradient
Extracellular fluid
Lipidsoluble
solutes
Simple diffusion of
fat-soluble molecules
directly through the
phospholipid bilayer
Cytoplasm
facilitated diffusion - carrier-mediated transport
of solute through a membrane down its
concentration gradient
does not consume ATP
solute attaches to binding site on carrier, carrier
changes confirmation, then releases solute on
other side of membrane
ECF
ICF
1
A solute particle enters
the channel of a membrane
protein (carrier).
2
The solute binds to a receptor
site on the carrier and the
carrier changes conformation.
3
The carrier releases the
solute on the other side of
the membrane.
Lipid-insoluble
solutes (such as
sugars or amino
acids)
Carrier-mediated
facilitated diffusion
Small lipidinsoluble
solutes
Channel-mediated facilitated
diffusion
mostly ions selected on basis of size and
charge
Filtration - process in which particles are driven through a
selectively permeable membrane by hydrostatic pressure (force
exerted on a membrane by water)
Examples
filtration of nutrients through gaps in blood capillary walls into tissue
fluids
filtration of wastes from the blood in the kidneys while holding back blood
cells and proteins
Solute
Water
Figure - Blood pressure in capillary
forces water and small solutes such as
salts through narrow clefts between
capillary cells.
Capillary wall
Red blood
cell
Clefts hold back
larger particles
such as red blood
cells.
Osmosis - flow of water from one side of a
selectively permeable membrane to the other
from side with higher water concentration to the side with lower water
concentration
Water diffuses through plasma membranes:
Through the lipid bilayer
Through water channels called aquaporins (AQPs)
Water
molecules
Lipid
billayer
Aquaporin
(d) Osmosis, diffusion of a solvent such as
water through a specific channel protein
(aquaporin) or through the lipid bilayer
Water concentration is determined by solute
concentration because solute particles displace
water molecules
Osmolarity: The measure of total concentration
of solute particles
When solutions of different osmolarity are
separated by a membrane, osmosis occurs until
equilibrium is reached
(a)
Membrane permeable to both solutes and water
Solute and water molecules move down their concentration gradients
in opposite directions. Fluid volume remains the same in both compartments.
Left
compartment:
Solution with
lower osmolarity
Right
compartment:
Solution with
greater osmolarity
H2O
Solute
Membrane
Solute
molecules
(sugar)
Both solutions have the
same osmolarity: volume
unchanged
(b)
Membrane permeable to water, impermeable to solutes
Solute molecules are prevented from moving but water moves by osmosis.
Volume increases in the compartment with the higher osmolarity.
Left
compartment
Right
compartment
Both solutions have identical
osmolarity, but volume of the
solution on the right is greater
because only water is
free to move
H 2O
Membrane
Solute
molecules
(sugar)
Figure 3.8b
When osmosis occurs, water enters or leaves a
cell
Change in cell volume disrupts cell function
Tonicity - ability of a solution to affect fluid volume and pressure in
a cell; depends on concentration and permeability of solute
Hypotonic solution
has a lower concentration of nonpermeating solutes than intracellular fluid
(ICF)
high water concentration
cells absorb water, swell and may burst (lyse)
Hypertonic solution
has a higher concentration of nonpermeating solutes
low water concentration
cells lose water + shrivel (crenate)
Isotonic solution
concentrations in cell and ICF are the same
cause no changes in cell volume or cell shape
(a)
Isotonic solutions
Cells retain their normal size and
shape in isotonic solutions (same
solute/water concentration as inside
cells; water moves in and out).
(b)
Hypertonic solutions
Cells lose water by osmosis and
shrink in a hypertonic solution
(contains a higher concentration
of solutes than are present inside
the cells).
(c)
Hypotonic solutions
Cells take on water by osmosis until
they become bloated and burst (lyse)
in a hypotonic solution (contains a
lower concentration of solutes than
are present in cells).
active transport – carrier-mediated transport of solute
through a membrane up (against) its concentration
gradient
ATP energy consumed to change carrier
Examples of uses:
sodium-potassium pump keeps K+ concentration higher inside
the cell
each pump cycle consumes
one ATP and exchanges three
Na+ for two K+
3 Na+ out
keeps the K+ concentration
higher and the Na+
concentration lower with in
the cell than in ECF
Extracellular
fluid
ATP
necessary because Na+ and K+
constantly leak through membrane
half of daily calories utilized for
Na+ - K+ pump
ADP + P i
Intracellular fluid
2 K+ in
Vesicular Transport – processes that move large particles, fluid
droplets, or numerous molecules at once through the membrane
in vesicles – bubblelike enclosures of membrane
Endocytosis –vesicular processes that bring material into the cell
phagocytosis – “cell eating” - engulfing large particles
macrophages
pinocytosis – “cell drinking” taking in droplets of ECF
containing molecules useful in the cell
Exocytosis – discharging material from the cell
Particle
7 The indigestible
residue is voided by
exocytosis.
1 A phagocytic cell encounters a
particle of foreign matter.
Pseudopod
Residue
2 The cell surrounds
the particle with its
pseudopods.
Nucleus
6 The phagolysosome
fuses with the
plasma membrane.
Phagosome
Lysosome
Vesicle fusing
with membrane
3 The particle is phagocytized
and contained in a
phagosome.
Phagolysosome
5 Enzymes from the
lysosome digest the
foreign matter.
4 The phagosome fuses
with a lysosome and
becomes a phagolysosome.
Keeps tissues free of debris and infectious microorganisms.
Taking in droplets of ECF
occurs in all human cells
Membrane caves in, then
pinches off into the
cytoplasm as pinocytotic
vesicle
Certain mutations may cause changes in cells
Uncontrolled reproduction of cells
Cells spread (metastasize), producing cancer
Cancer cells form tumors, crowding out normal
cells
Certain forces increase the chances of developing cancer
Heredity – individuals are more likely to develop certain
types of cancers if they have a family history of cancer.
Chemical carcinogens in cigarettes, foods, drugs, etc.
Ionizing radiation from x-rays, UV rays and radioactive
substances
Continued physical irritation – increased cell division
increases the chance of mutation
Diets high in fats and low in fiber, fruits and vegetables
make individuals more susceptible to digestive cancers
Viruses trigger some cancers: cervical cancer,
lymphomas, leukemias, liver cancer