Download Structure and Function

Cells
Structure and Function
Week 5
Ukiah Adult School, Vocational Nursing
Objectives
At the end of this module, the student will be
able to:
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Understand the vocabulary related to cell
structure and function
Name the organic molecules that make up cell
membranes and state their functions
Describe the functions of each of the cell of the
types of epithelial cells organelles
Describe what happens in mitosis and meiosis
Label diagrams of cells and their parts
Objectives
Explain cellular transport mechanisms and
where each type of transport occurs
Define isotonic, hypertonic and hypotonic
solutions and their effects on cells
Explain the purposes of: DNA, RNA, tRNA,
mRNA, codons and anticodons
Cells
smallest structural unit of an organism that
is capable of independent function.
Cell Structure
Many different kinds of human cells
All have several similar features
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Nucleus
Cell membrane
Cytoplasm
Cell organelles
Cell Membrane
AKA: plasma membrane
Consists of
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Phospholipids
Cholesterol
proteins
Quick quiz
Which of these is NOT true of the cell
membrane?
 A) It selectively allows materials to enter
the cell.
 B) It forms the outer boundary of the cell.
 C) It enables cells to respond to hormones.
 D) It is made of protein, glucose, and
cholesterol.
Cell nucleus
Cytoplasm
Watery solution containing:
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Minerals
Gases
Organic molecules
Cell organelles
Cytosol
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The watery portion of cytoplasm
Medium for chemical reactions
Organelles
Ribosomes
Endoplasmic Reticulum (ER)
Golgi apparatus
Proteasome
Lysosomes
Mitochondria
Centrioles
Cilia
Flagella
Microvilli
Quick quiz
What is the function of the cell’s antigens?
Which structure may also be called a
transporter?
What is the purpose of cholesterol in the cell
membrane?
What is the function of the cell’s antigens?
 Antigens are markers of “self”
Which structure may also be called a transporter?
 The protein channels, which are specific for certain
molecules, are called transporters
What is the purpose of cholesterol in the cell membrane ?
 It decreases its fluidity and stabilizes it.
Cellular Transport Mechanisms
Diffusion
Osmosis
Facilitated diffusion
Active Transport Filtration
Phagocytosis
Pinocytosis
Passive Transport
Passive transport is the movement of
molecules across the cell membrane and does
not require energy.
It is dependent on the permeability of the cell
membrane.
There are three main kinds of passive
transport - Diffusion, Osmosis and
Facilitated Diffusion.
Diffusion
Movement of molecules
from an area of greater
concentration to an
area of lesser
concentration
Concentration gradient
Osmosis
The movement of water
across a semi permeable
membrane.
Osmosis is the
movement of water (red
dots) through a semipermeable membrane to
a higher concentration
of solutes (blue dots).
Facilitated Diffusion
This process does not
require ATP but does
require cell membrane
proteins which are
called carrier proteins
to carry the molecules
across the cell
membrane from an
area of higher
concentration to an
area of lower
concentration.
Active Transport
Active Transport requires the cell to use
energy, usually in the form of ATP.
Active Transport creates a charge gradient in
the cell membrane. For example, in the
mitochondrion hydrogen ion pumps pump
hydrogen ions into the inter-membrane space
of the organelle as part of making ATP. Active Transport keeps unwanted ions or
other molecules out of the cell that are able to
diffuse through the cell membrane. Active
transport uses energy to send substances
against the direction they would travel by
simple diffusion: that is from a region of low
concentration to a region of high
concentration.
Active Transport
Filtration
Requires energy
Not directly from ATP
Mechanical pressure
H2O and solutes forced
Blood pressure
Phagocytosis
Cell flows around
Then engulfs
Finally digests
Aided by opsonins
Pinocytosis
Pinocytosis is the ingestion
of dissolved materials by
endocytosis. The cytoplasmic
membrane invaginates and
pinches off placing small
droplets of fluid in a
pinocytic vesicle. The liquid
contents of the vesicle is then
slowly transferred to the
cytosol.
Solutions
Isotonic
Hypotonic
Hypertonic
Isotonic Solutions
A solution that has the
same salt concentration as
the normal cells of the body
and the blood.
When a cell is placed in an
isotonic solution, the water
diffuses into and out of the
cell at the same rate. The
fluid that surrounds the
body cells is isotonic.
Hypertonic solutions
A Hypertonic solution
contain a high
concentration of solute in
relation to the solution
within the cell (e.g. the
cell's cytoplasm). When a
cell is placed in a
hypertonic solution, the
water diffuses out of the
cell, causing the cell to
shrivel up.
Hyp0tonic Solutions
A solution with a
lower salt
concentration than
in normal cells
When a cell is
placed in a
hypotonic solution,
the water diffuses
into the cell,
causing the cell to
swell and possibly
explode.
DNA and the Genetic Code
DNA
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Double helix—like a spiral
ladder
Uprights are alternating
phosphate groups and
deoxyribose sugar
molecules
Rungs are made of 4
nitrogenous bases in
complementary pairs:
Adenine- Thymine
Guanine- Cytosine
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Humans have 46
chromosomes
Genes
A gene is the basic unit of heredity in a living
organism. All living things depend on genes.
Genes hold the information to build and maintain
their cells and pass genetic traits to offspring. A
modern working definition of a gene is " a locatable
region of genomic sequence, corresponding to a
unit of inheritance, which is associated with
regulatory regions, transcribed regions, and or
other functional sequence regions ". A gene is the
basic instruction, a sequence of DNA; an allele is
one variant of that instruction.
RNA
Possibly involved in DNA repair
Involved in gene expression
Translation and transcription of DNA into
proteins
Protein Synthesis
mRNA—
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a single strand of nucleotides formed as a
complementary copy of a DNA gene
Leaves DNA in the nucleus, enters cytoplasm
Attaches to ribosome
Ribosomes
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Organelles that are the site of protein synthesis
Contain enzymes to form peptide bonds between amino
acids
tRNA
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Picks up amino acids for transportation to proper site
Has anticodons to match mRNA codon
RNA-Transcription
Let’s imagine DNA as a reference book. When you need
information about something you make a copy of the pages
(genes) you're interested in, returning the book to the
library. This way you don't have to risk losing or
destroying the book.
DNA never leaves the nucleus, instead the genetic code (the
genes) is copied into RNA which then in turn is decoded
(translated) into proteins in the cytoplasm. Why? One
important reason is security. The cytoplasm is a dangerous
environment for the DNA and the daily transcription of
genes to proteins would be very harmful to the DNA, which
has to stay intact in order to maintain life. Therefore, RNA
works as a sort of throw-away version of DNA (like the
copies from the reference book) - good for limited work but
not for long-term storage. Another reason is to regulate the
rate of protein synthesis
Codon
Anti-codon
Transfer RNA
Protein synthesis
Cell Division
Mitosis
Meiosis
Mitosis
Start with one cell with the diploid number
End with two cells with diploid number
Daughter cells are identical to original cell
Mitosis is nuclear division plus cytokinesis, and produces
two identical daughter cells during prophase, prometaphase,
metaphase, anaphase, and telophase. Interphase is often
included in discussions of mitosis, but interphase is
technically not part of mitosis, but rather encompasses
stages G1, S, and G2 of the cell cycle
Phases of cell Division
Interphase: DNA replication takes place.
• Prophase: The chromosomes coil up and
become visible; each is a pair of chromatids;
spindle fibers form between the centrioles.
• Metaphase: The pairs of chromatids line up
on the equator of the cell; the centromeres
divide, making two full sets of
chromosomes.
• Anaphase: Spindle fibers pull the
chromosomes, one set to each pole of
the cell.
• Telophase: The sets of chromosomes uncoil;
nuclear membrane reforms around each set.
• Cytokinesis: The cytoplasm divides as
new
cell membrane is formed.
Interphase
Interphase refers to all
stages of the cell cycle
other than mitosis.
During interphase,
cellular organelles double
in number, the DNA
replicates, and protein
synthesis occurs. The
chromosomes are not
visible and the DNA
appears as uncoiled
chromatin.
Prophase
During the first stage
of mitosis, prophase,
the chromatin
condenses and the
chromosomes become
visible. Also the
nucleolus disappears,
the nuclear
membrane
fragments, and
spindle fibers are
assembled.
Metaphase
During metaphase,
the nuclear membrane
fragmentation is
complete and the
duplicated
chromosomes line up
along the cell's
equator
Anaphase
During anaphase,
diploid sets of
daughter chromosomes
move toward opposite
poles of the cell and
cytokinesis
(cytoplasmic cleavage)
begins
Telophase
During telophase, the
nuclear membrane and
nucleoli reform,
cytokinesis is nearly
complete, and the
chromosomes
eventually uncoil to
chromatin.
Cytokinesis
Cytokinesis results when a fiber ring
composed of a protein called actin around the
center of the cell contracts pinching the cell
into two daughter cells, each with one
nucleus.
When a human cell undergoes mitosis,
how many chromosomes does each new
cell have?
When a human cell undergoes mitosis,
how many chromosomes does each new
cell have?
46
Meiosis
More complex than mitosis
Results in the formation of haploid gametes
One diploid cell divides twice to form 4
haploid cells
In women: oogenesis
In men: spermatogenesis
Abnormal Cell Functioning
Cancer
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200+ types
Malignant
Benign
Mutation
Carcinogens
Metastasis
Chemotherapy
The Aging Process on a Cellular Level
Cells may be limited in the number of times
they can divide before dying
Telomeres
Cellular aging
All aging us ultimately at the cellular level