VanPutte_Seeleys_Essentials_11e_Chap03_PPT_Accessible-compressed.pdf

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Chapter 3
Cell Structures and Their
Functions
Lecture Outline
Seeley’s ESSENTIALS OF
ANATOMY & PHYSIOLOGY
Eleventh Edition
Cinnamon VanPutte
Jennifer Regan
Andrew Russo
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Cell Structure
Organelles:
•specialized structures in cells that perform
•specific functions
•Example: nucleus, mitochondria, ribosomes
Cytoplasm:
•jelly-like substance that holds organelles
Cell membrane:
•also termed the plasma membrane
•a structure that encloses the cytoplasm
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Generalized Cell
Figure 3.1
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Functions of the Cell
•Smallest units of life
•Cell metabolism and energy use
•Synthesis of molecules
•Communication
•Reproduction and inheritance
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Cell Membrane
•The cell membrane, or plasma membrane, is the
outermost component of a cell.
•It forms a boundary between material in inside the cell and
the outside.
•Materials inside the cell are intracellular and those
outside are extracellular.
•It acts as a selective barrier.
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Cell Membrane Structure
•The fluid-mosaic model is the model used to describe
the cell membrane structure.
•The membrane contains phospholipids, cholesterol,
proteins, and carbohydrates.
•Phospholipids form a bilayer.
•Phospholipids contain 2 regions: polar and nonpolar.
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Phospholipid Structure
•A phospholipid molecule has a polar head region that is
hydrophilic and a nonpolar tail region that is hydrophobic.
•The polar region is exposed to water around the
membrane.
•The nonpolar region is facing the interior of the
membrane.
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The Cell Membrane
Figure 3.2a
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Movement through the Cell Membrane
•The cell membrane has selective permeability, which
allows only certain substances to pass in and out of the
cell.
•Substances such as enzymes, glycogen, and potassium
are found in higher concentrations inside the cell.
•Substances such as sodium, calcium, and chloride are
found in higher concentrations outside the cell.
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Cell Membrane Passage 1
•Some substances, like O
2 and CO
2, can pass directly
through the cell membrane’s phospholipid bilayer.
•Some substances must pass through transmembrane
protein channels, such as Na
+
through its channels.
•The route of transport through the membrane depends on
the size, shape, and charge of the substance.
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Cell Membrane Passage 2
•Some substances require carrier molecules to transport
them across the cell membrane, such as glucose.
•Some substances require a vesicular transport across the
membrane.
•The vesicle must fuse with the cell membrane for
transport.
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Active Transport and Passive Transport 1
•Passive membrane transport does not require the cell to
expend energy.
•Active membrane transport does require the cell to
expend energy, usually in the form of ATP.
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Active Transport and Passive Transport 2
•Passive membrane transport mechanisms include
diffusion, osmosis, and facilitated diffusion.
•Active membrane transport mechanisms include active
transport, secondary active transport, endocytosis,
and exocytosis.
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Diffusion 1
•Diffusion generally involves movement of substances in a
solution down a concentration gradient.
•A solution is generally composed of two major parts,
solutes and the solvent.
•Solutes are substances dissolved in a predominant liquid
or gas, which is called the solvent.
•Solutes, such as ions or molecules, tend to move from an
area of higher concentration of a solute to an area of lower
concentration of that same solute in solution.
•This movement from high concentration to a low
concentration is diffusion.
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Concentration Gradient
•A concentration gradient is the difference in the
concentration of a solute in a solvent between two points
divided by the distance between the two points.
•The concentration gradient is said to be steeper when the
concentration difference is large and/or the distance is
small.
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Diffusion 2
Figure 3.3
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Osmosis 1
•Osmosis is the diffusion of water (a solvent) across a
selectively permeable membrane from a region of higher
water concentration to one of lower water concentration.
•Osmosis exerts a pressure, termed osmotic pressure,
which is the force required to prevent movement of water
across cell membrane
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Osmosis 2
Figure 3.4
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Osmotic Pressure and the Cell
•Osmotic pressure depends on the difference of solution
concentrations inside a cell relative to outside the cell.
•A cell may be placed in solutions that are either
hypotonic, isotonic, or hypertonic compared to the cell
cytoplasm.
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Hypotonic
•A hypotonic solution has a lower concentration of solutes
and a higher concentration of water relative to the
cytoplasm of the cell.
•The solution has less tone, or osmotic pressure, than the
cell.
•Water moves by osmosis into the cell, causing it to swell.
•If the cell swells enough, it can rupture, a process called
lysis.
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Isotonic
•A cell immersed in an isotonic solution has the same
solute concentrations inside and outside the cell.
•The cell will neither shrink nor swell.
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Hypertonic
•The cytoplasm of a cell in a hypertonic solution has a
lower solute concentration and higher water concentration
than the surrounding solution.
•Water moves by osmosis from the cell into the hypertonic
solution, resulting in cell shrinkage, or crenation.
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Red Blood Cell Changes in Differing Solutions
Figure 3.5
David M. Phillips/Science Source
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Facilitated Diffusion 1
•Lipid soluble substances such as oxygen, carbon dioxide,
and steroids can diffuse directly through the phospholipid
bilayer.
•Water-soluble substances, such as ions, can diffuse
across the cell membrane only by passing through cell
membrane channels or through carrier molecules.
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Facilitated Diffusion 2
•Facilitated diffusion is a carrier-mediated transport
process that moves substances across the cell membrane
from an area of higher concentration to an area of lower
concentration of that substance.
•Because movement is with the concentration gradient,
metabolic energy in the form of ATP is not required.
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Diffusion through the Cell Membrane
Figure 3.6
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Leak and Gated Channels 1
•Two classes of cell membrane channels include leak
channels and gated channels.
•Leak channels constantly allow ions to pass through.
•Gated channels limit the movement of ions across the
membrane by opening and closing.
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Leak and Gated Channels 2
Figure 3.7
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Carrier Molecules 1
•Carrier molecules are proteins within the cell membrane
involved in facilitated diffusion.
•Move water soluble molecules or ions across the
membrane.
•They exhibit specificity; only specific molecules are
transported by the carriers.
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Carrier Molecules 2
Figure 3.8
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Active Transport
•Active transport is a carrier-mediated process, requiring
ATP, that moves substances across the cell membrane
from regions of lower concentration to those of higher
concentration against a concentration gradient.
•Active transport processes accumulate necessary
substances on one side of the cell membrane at
concentrations many times greater than those on the other
side.
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Sodium-Potassium Pump 1
•A major example of active transport is the action of the
sodium-potassium pump present in cell membranes.
•The sodium-potassium pump moves Na
+
out of cells and
K
+
into cells.
•The result is a higher concentration of Na
+
outside cells
and a higher concentration of K
+
inside cells.
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Sodium-Potassium Pump 2
Figure 3.9
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Secondary Active Transport 1
•Secondary active transport uses the energy provided by a
concentration gradient established by the active transport
of one substance, such as Na
+
to transport other
substances.
•No additional energy is required above the energy
provided by the initial active transport pump.
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Secondary Active Transport 2
•In cotransport, the diffusing substance moves in the same
direction as the initial active transported substance.
•In countertransport, the diffusing substance moves in a
direction opposite to that of the initial active transported
substance.
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Secondary Active Transport 3
Figure 3.10
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Endocytosis
•Endocytosis is a process that that brings materials into cell
using vesicles.
• Receptor-mediated endocytosis occurs when a specific
substance binds to the receptor molecule and is
transported into the cell.
•Phagocytosis is often used for endocytosis when solid
particles are ingested.
•Pinocytosis has much smaller vesicles formed, and they
contain liquid rather than solid particles.
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Receptor-Mediated Endocytosis
Figure 3.11
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Exocytosis 1
•Exocytosis involves the use of membrane-bound sacs
called secretory vesicles that accumulate materials for
release from the cell.
•The vesicles move to the cell membrane and fuse,
ultimately releasing the material by exocytosis.
•Examples of exocytosis are the secretion of digestive
enzymes.
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Exocytosis 2
Figure 3.12
(b) ©Dr. Birgit H. Satir
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General Cell Structure
•The interior of a cell is composed of the cytoplasm, which
a jelly-like fluid that surrounds the organelles.
•Organelles are specialized structures that perform certain
functions.
•Organelles include the nucleus, ribosomes, endoplasmic
reticulum, Golgi apparatus, lysosomes, peroxisomes,
mitochondria, cytoskeleton, centrioles, cilia, flagella, and
microvilli.
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Generalized Cell 2
Figure 3.1
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Cell Nucleus 1
•The nucleus is a large organelle usually located near the
center of the cell.
•The nucleus is bounded by a nuclear envelope, which
consists of outer and inner membranes with a narrow
space between them.
•The nuclear membrane contains nuclear pores, through
which materials can pass into or out of the nucleus.
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Cell Nucleus 2
•The nuclei of human cells contain 23 pairs of
chromosomes which consist of DNA and proteins.
•During most of a cell’s life, the chromosomes are loosely
coiled and collectively called chromatin.
•When a cell prepares to divide, the chromosomes become
tightly coiled and are visible when viewed with a
microscope.
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Cell Nucleus 3
•Within the nucleus are Nucleoli, which are diffuse bodies
with no surrounding membrane. that are found within the
nucleus
•There are usually one to several nucleoli within the
nucleus.
•The subunits of ribosomes, a type of cytoplasmic
organelle, are formed within a nucleolus.
•These ribosomal components exit the nucleus through
nuclear pores.
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Cell Nucleus 4
Figure 3.13
(b,c) Don W. Fawcett/Science Source
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Chromosome Structure
Figure 3.14
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Ribosomes
•Ribosome components are produced in the nucleolus.
•Ribosomes are the organelles where proteins are
produced.
•Ribosomes may be attached to other organelles, such as
the endoplasmic reticulum.
•Ribosomes that are not attached to any other organelle
are called free ribosomes.
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Ribosome Production
Figure 3.15
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Endoplasmic Reticulum 1
•The endoplasmic reticulum (ER) is a series of membranes
forming sacs and tubules that extends from the outer
nuclear membrane into the cytoplasm.
•The rough ER is involved in protein synthesis and is
rough due to attached ribosomes.
•The smooth ER has no attached ribosomes and is a site
for lipid synthesis, cellular detoxification, and it stores
calcium ions in skeletal muscle cells.
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Endoplasmic Reticulum 2
Figure 3.16a
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Golgi Apparatus 1
•The Golgi apparatus, also called the Golgi complex,
consists of closely packed stacks of curved, membrane-
bound sacs.
•It collects, modifies, packages, and distributes proteins
and lipids manufactured by the ER.
•The Golgi apparatus forms vesicles, some of which are
secretory vesicles, lysosomes, and other vesicles.
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Golgi Apparatus 2
Figure 3.17
(b) BiophotoAssociates/Science Source
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Lysosomes
•Lysosomes are membrane-bound vesicles formed from the
Golgi apparatus.
•They contain a variety of enzymes that function as
intracellular digestive systems.
•Vesicles formed by endocytosis may fuse with lysosomes
in order to breakdown materials in the endocytotic vesicles.
•One example is white blood cells phagocytizing bacteria.
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Lysosome Action
Figure 3.18
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Peroxisomes
•Peroxisomes are small, membrane-bound vesicles
containing enzymes that break down fatty acids, amino
acids, and hydrogen peroxide (H
2O
2).
•Hydrogen peroxide is a by-product of fatty acid and amino
acid breakdown and can be toxic to a cell.
•The enzymes in peroxisomes break down hydrogen.
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Mitochondria 1
•Mitochondria (singular mitochondrion) are small organelles
responsible for producing considerable amounts of ATP by
aerobic (with O
2) metabolism.
•They have inner and outer membranes separated by a
space.
•The outer membranes have a smooth contour, but the
inner membranes have numerous folds, called cristae,
which project into the interior of the mitochondria.
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Mitochondria 2
•The material within the inner membrane is the
mitochondrial matrix and contains enzymes and
mitochondrial DNA (mtDNA).
•Cells with a large energy requirement have more
mitochondria than cells that require less energy.
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A Mitochondrion
Figure 3.19
(b) EM Research Services, Newcastle University
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The Cytoskeleton 2
•The cytoskeleton gives internal framework to the cell.
•It consists of protein structures that support the cell, hold
organelles in place, and enable the cell to change shape.
•These protein structures are microtubules,
microfilaments, and intermediate filaments.
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Microtubules
•Microtubules are hollow structures formed from protein
subunits.
•The microtubules perform a variety of roles, including
helping to support the cytoplasm of cells, assisting in cell
division, and forming essential components of certain
organelles, such as cilia and flagella.
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Microfilaments
•Microfilaments are small fibrils formed from protein
subunits that structurally support the cytoplasm,
determining cell shape.
•Some microfilaments are involved with cell movement.
•Microfilaments in muscle cells enable the cells to shorten,
or contract.
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Intermediate Filaments
•Intermediate filaments are fibrils formed from protein
subunits that are smaller in diameter than microtubules but
larger in diameter than microfilaments.
•They provide mechanical support to the cell.
•A specific type of intermediate filament is keratin, a protein
associated with skin cells.
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The Cytoskeleton 1
Figure 3.20
(b) ©Don W. Fawcett/Science Source
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Centrioles
•The centrosome is a specialized area of cytoplasm close
to the nucleus where microtubule formation occurs.
•It contains two centrioles, which are normally oriented
perpendicular to each other.
•Each centriole is a small, cylindrical organelle composed
of microtubules.
•The centriole is involved in the process of mitosis.
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Centriole
Figure 3.21
(b) Biology Media/Science Source
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Cilia
•Cilia project from the surface of certain cells.
•They are responsible for the movement of materials over
the top of cells, such as mucus.
•Cilia are cylindrical structures that extend from the cell and
are composed of microtubules.
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Flagella
•Flagella have a structure similar to that of cilia but are
much longer, and they usually occur only one per cell.
•Sperm cells each have one flagellum, which propels the
sperm cell.
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Microvilli
•Microvilli are specialized extensions of the cell membrane
that are supported by microfilaments.
•They do not actively move as cilia and flagella do.
•Microvilli are numerous on cells that have them and they
increase the surface area of those cells.
•They are abundant on the surface of cells that line the
intestine, kidney, and other areas in which absorption is an
important function.
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Whole Cell Activity
•A cell’s characteristics are determine by the type of
proteins produced.
•The proteins produced are in turn determined by the
genetic information in the nucleus.
•Information in DNA provides the cell with a code for its
cellular processes.
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DNA 1
•DNA contains the information that directs protein
synthesis; a process called gene expression.
•A DNA molecule consists of nucleotides joined together
to form two nucleotide strands.
•The two strands are connected and resemble a ladder that
is twisted around its long axis.
•Each nucleotide consists of a 5-carbon sugar, a phosphate
group, and a nitrogenous base.
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DNA 2
•Each nucleotide on one DNA strand has a specific
bonding pattern to another nucleotide on the opposite
strand.
•A gene is a sequence of nucleotides that provides a
chemical set of instructions for making a specific protein.
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Gene Expression
•Gene expression, which is protein synthesis, involves
transcription and translation.
•Transcription involves copying DNA into messenger
RNA.
•Translation involves messenger RNA being used to
produce a protein.
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Overview of Gene Expression
Figure 3.22
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Transcription 1
•Transcription takes place in the nucleus of the cell.
•DNA determines the structure of mRNA through
transcription.
•During transcription, the double strands of a DNA segment
separate, and DNA nucleotides of the gene pair with RNA
nucleotides that form the mRNA.
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Transcription 2
•DNA contains one of the following organic bases: thymine,
adenine, cytosine, or guanine.
•Messenger RNA (mRNA) contains uracil, adenine,
cytosine, or guanine.
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Transcription 3
•DNA nucleotides pair only with specific RNA nucleotides.
•DNA’s thymine pairs with RNA’s adenine.
•DNA’s adenine pairs with RNA’s uracil.
•DNA’s cytosine pairs with RNA’s guanine
•DNA’s guanine pairs with RNA’s cytosine.
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Transcription 4
Figure 3.23
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Translation 1
•Translation occurs in the cell cytoplasm after mRNA has
exited the nucleus through the nuclear pores.
•The mRNA attaches to a ribosome.
•Codons (3 nucleotide bases) on the mRNA are read by
anticodons (3 nucleotide bases) on transfer RNA
(tRNA).
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Translation 2
•Transfer RNA transports specific amino acids from the
cytoplasm to the ribosome-mRNA complex and initiates
formation of the polypeptide chain.
•The process continues until the entire polypeptide is
completely formed.
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The Cell Cycle 1
•During growth and development, cell division occurs to
increase the number of cells or replace damaged or dying
ones.
•This cell division involves a cell cycle.
•The cell cycle includes two major phases: a nondividing
phase, called interphase, and a cell dividing phase,
termed mitosis.
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The Cell Cycle 2
A cell spends most of its life cycle in interphase which is
divided into three phases:
•G
1 phase, during which the cell carries out normal
metabolic activity
•S phase, during which the DNA is replicated; and
•G
2 phase, during which the cell prepares to divide.
At the end of interphase, a cell has two complete sets of
genetic material
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The Cell Cycle 3
Figure 3.24
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Cell Genetic Content
•Each human cell (except sperm and egg) contains 23
pairs of chromosomes, a total of 46.
•The sperm and egg contain 23 chromosomes total.
•One pair of chromosomes are the sex chromosomes,
which consist of two X chromosomes if the person is a
female or an X and Y chromosome if the person is a male.
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Mitosis
•Mitosis involves formation of 2 daughter cells from a single
parent cell.
•Mitosis is divided into four phases: prophase, metaphase,
anaphase, and telophase.
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Prophase
•During prophase the chromatin condenses to form visible
chromosomes.
•Microtubules, termed spindle fibers, form to assist in
breaking the centromere between the chromatids and
move the chromosomes to opposite sides of the cell.
•The nuclear membrane dissolves.
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Metaphase
•During metaphase, the chromosomes align near the
center of the cell.
•The movement of the chromosomes is regulated by the
attached spindle fibers.
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Anaphase
•At the beginning of anaphase, the chromatids separate
and each chromatid is called a chromosome.
•Each of the two sets of 46 chromosomes is moved by the
spindle fibers toward the centriole at one of the poles of
the cell.
•At the end of anaphase, each set of chromosomes has
reached an opposite pole of the cell, and the cytoplasm
begins to divide.
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Telophase
•During telophase, the chromosomes in each of the
daughter cells become organized to form two separate
nuclei, one in each newly formed daughter cell.
•The chromosomes begin to unravel and resemble the
genetic material during interphase.
•Following telophase, cytoplasm division is completed, and
two separate daughter cells are produced.
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The Cell Cycle
Figure 3.25
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Tumors
•Tumors are abnormal proliferations of cells.
•They are due to problems occurring in the cell cycle.
•Some tumors are benign and some are malignant
(cancer).
•Malignant tumors can spread by a process, termed
metastasis.
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Differentiation
•A sperm cell and an oocyte unite to form a single cell, then
a great number of mitotic divisions occur to give the
trillions of cells of the body.
•The process by which cells develop with specialized
structures and functions is called differentiation.
•During differentiation of a cell, some portions of DNA are
active, but others are inactive.
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Diversity of Cell Types
Figure 3.26
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Apoptosis
•Apoptosis, termed programmed cell death, is a normal
process by which cell numbers within various tissues are
adjusted and controlled.
•In the developing fetus, apoptosis removes extra tissue,
such as cells between the developing fingers and toes.
•In some adult tissues, apoptosis eliminates excess cells to
maintain a constant number of cells within the tissue.
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Cellular Aspects of Aging
There are various causes for cellular aging.
•Existence of a cellular clock
•Presence of death genes
•DNA damage
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