Chapter 3 Cells and Tissues Be Able To

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Chapter 3 Cells and Tissues

Be Able To

•Name the four elements that make up the bulk of living matter and list several trace elements.

•Define cell, organelle, and inclusion.

•Identify on a diagram of the cell the three major cell regions.

•List the structures of the nucleus and explain the function of chromatin and nucleoli.

•Identify the organelles on a cell diagram and explain the major function of each.

Key terms: electrolytes, nucleus, nuclear envelope, nucleoplasm, nucleoli, chromatin, chromosomes, plasma membrane, microvilli,

membrane junctions, cytoplasm, cytosol, organelles, inclusions, mitochondria, ribosomes, endoplasmic reticulum, golgi apparatus, lysosomes, peroxisomes, free radicals, cytoskeleton, microfilaments, microtubules, centrioles, flagella, and cilia.

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Cells

• How did the word cell come to be used as the name of the most

basic biological unit of life?

• Although CHON make up most of the cell other trace elements are needed in small quantities.

• Cells are composed of 60% water and are bathed in a dilute

saltwater solution known as interstitial fluid.

• Cells range in size and shape, which often determines function.

• Cells vary dramatically in their functions.

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Anatomy of a Generalized Cell

• A generalized cell is a model which displays many cell features.

• A cell has 3 main regions.

1) Nucleus 2) Cytoplasm

3) plasma membrane

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Anatomy of a Generalized Cell

• The nucleus is the control center of the cell.

• DNA serves as the

blueprints that contains instructions needed for building new cells.

• The nucleus has 3 distinct regions:

1) The nuclear envelope 2) Nucleolus

3) Chromatin

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The Plasma Membrane

• The plasma membrane is a lipid

bilayer with interacting hydrophobic and hydrophilic regions.

• Proteins in the plasma membrane have a wide variety of functions.

• Microvilli are tiny fingerlike projections that increase cell surface area.

• Tight junctions bind cells together into leak-proof sheets.

• Desmosomes anchor cells together through interconnected fine protein filaments.

• Gap junctions connect cells through hollow protein cylinders called

connexons.

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What is in the Cytoplasm?

• Cytoplasm is the cellular material outside the

nucleus and inside the plasma membrane

comprised of cytosol,

organelles, and inclusions.

• Organelles are

specialized cellular parts that perform essential

roles to the maintenance of cellular life.

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Cytoplasmic Organelles

• Mitochondria are bilayered cell organelles that are

responsible for ATP production.

• Cristae house enzymes that carry out reactions that break down food molecules to

release energy for ATP production.

• The nickname of mitochondria is the “powerhouse of the cell”.

• Muscle and liver cells use huge amounts of ATP.

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Cytoplasmic Organelles

• Ribosomes either free floating or attached to ER are directly involved in protein synthesis.

• Endoplasmic reticulum or ER is a fluid-filled tubule

system that provides a network of channels for carrying

substances.

• Rough ER is studded with ribosomes and enzymes that catalyze the synthesis of

membrane lipids.

• Smooth ER (no ribosomes) function in cholesterol

synthesis and breakdown, fat metabolism, and drug

detoxification.

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Cytoplasmic Organelles

• The golgi apparatus is comprised of a stack of flattened membranous sacs that modify and package proteins.

• The golgi packages proteins in secretory vesicles for transport to the plasma

membrane.

• Also packages

hydrolytic enzymes such as lysosomes.

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Cytoplasmic Organelles

• Lysosomes are membrane bound sacs containing digestive enzymes.

• Lysosomes function as the cell’s demolition sites.

• Peroxisomes are membranous sacs that contain oxidase enzymes that detoxify harmful substances, such as free radicals.

• Free radicals are reactive chemicals that damage the structure of proteins and nucleic acids with their unpaired electrons.

• Peroxisomes are abundant in liver and kidney cells.

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Cytoplasmic Organelles

• The cytoskeleton is a

network of protein filaments and tubules that supports other organelles,

determines cell shape, and is involved in intracellular support.

• Intermediate filaments

help form desmosomes and help resist pulling forces.

• Microfilaments are involved in cell motility.

• Microtubules help

determine the overall shape of the cell and are involved in cell division.

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Cytoplasmic Organelles

• Centrioles are rod-shaped bodies made of

microtubules that direct the formation of the mitotic

spindle.

• Cilia are finger-like extensions of the cell surface that move

substances along the surface.

• Flagella are long

projections of microtubules from the cell surface, e.g.

tail of sperm.

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Cell Diversity

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Cell Physiology

• A solution is a homogenous mixture of two or more components.

• A solvent is the dissolving medium.

• A solute is the dissolved substance in a solution.

• Intracellular and interstitial fluids are solutions containing small

amounts of gases, nutrients, and salts.

• The selectively permeable plasma membrane acts as a barrier to certain substances.

• Substances move through the plasma membrane through either passive or active transport processes.

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Passive Transport Processes

• Diffusion is the process by which molecules and ions tend to scatter themselves in available space.

• Generally molecules diffuse down a concentration gradient.

• Solutes that are small and lipid soluble pass through the plasma membrane through simple diffusion.

• Osmosis is the movement of water molecules down a concentration gradient.

• Movement of large lipid-insoluble molecules through carrier proteins is facilitated diffusion.

• Filtration is the process by which water and solutes are forced through a

membrane by fluid or hydrostatic pressure that creates a pressure gradient (ie kidneys).

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Active Transport Processes

• Active transport processes require the use of ATP to move large lipid-insoluble substances often against the concentration gradient.

• Solute pumps use ATP to energize protein carriers to move substances against the concentration gradient (ie NA-K pump).

• Bulk transport processes include:

1) Exocytosis moves substances out of cells packaged in a small membrane vesicle (ie hormones).

2) Endocytosis take up or engulf extracellular substances by enclosing them in a small membrane vesicle (ie phagocytosis).

3) Pinocytosis the membrane folds inward taking extracellular fluids and packaging the contents in a membranous vesicle (ie

absorption in cells of small intestine).

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Cell Division

Be Able To:

• Describe briefly the process of DNA replication and mitosis.

• Explain the importance of mitotic cell division.

Key Terms: cell life cycle, interphase, cell division, template, mitosis, cytokinesis,

prophase, chromatid, centromere, mitotic

spindle, metaphase, anaphase, telophase,

and cleavage furrow.

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DNA Replication

• The cell life cycle is the series of changes a cell

goes through from the time it is formed until it divides.

• This life cycle can be divided into interphase and cell division.

• Interphase is the longest phase of the cell cycle

during which time the cell prepares for cell division.

• The function of cell division is to produce more cells for growth and repair

processes.

The cell spends a majority of its life in which stage?

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DNA Replication

• After the first growth phase (G1), the cell enter the synthesis phase (S), during which time the genetic material of the cell is duplicated.

• DNA replication begins with the uncoiling of the DNA molecule and separation of the two strands.

• Each strand of nucleotides serves as a template to build a

complementary strand.

• The end result is two identical DNA molecules that are exact replicas of the original DNA helix.

• After the S phase, the cell enters the second growth phase (G2)

during which time the cells prepare for cell division.

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Events of Cell Division

• Cell division consists of two events:

1) Mitosis is the division of the nucleus 2) Cytokinesis is division of the cytoplasm.

• Mitosis results in the formation of two identical daughter cells.

• When the nucleus divides each daughter cell receives the same genetic material thanks to DNA replication.

• The stages of mitosis can be divided into 4 separate stages:

1) Prophase 2) Metaphase 3) Anaphase 4) Telophase.

• A cleavage furrow pinches the original cytoplasmic mass into two new cells during cytokinesis.

• In some cells cytoplasm is not distributed equally which creates binucleate or

multinucleate cells.

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Mitosis and Cytokinesis Divide Cells

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Mitosis and Cytokinesis Divide Cells

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FLOW OF GENETIC INFORMATION

• RNA or Ribonucleic acid is responsible for the

movement of genetic

information from the DNA in the nucleus to the site of

protein synthesis in the cytosol.

• The sugar molecule of every RNA molecule is ribose.

• Uracil, a nitrogen containing pyrimidine base replaces

thymine in RNA.

• As a result, uracil pairs with adenine.

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RNA STRUCTURE AND FUNCTION

• Messenger RNA (mRNA): RNA nucleotides in a single uncoiled chain.

• Function: Carry genetic information from DNA in nucleus to cytosol.

• Transfer RNA (tRNA): Single

chain of nucleotides folded into a hairpin shape.

• Function: Bind to specific amino acids

• Ribosomal RNA (rRNA): RNA nucleotide in globular form.

• Function: Along with proteins, rRNA makes up the ribosomes where proteins are made.

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TRANSCRIPTION

• RNA polymerase initiates RNA transcription by binding to specific regions of DNA called promoters.

• When RNA polymerase

binds to a promoter, the DNA molecule separates.

• One of the separated chains, called the template, is used in transcription.

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TRANSCRIPTION

• RNA polymerase adds free RNA nucleotides to the growing

complementary strand.

• Base pairing rules are identical to those in DNA replication

except uracil pairs with adenine.

• Transcription continues until the

RNA polymerase reaches the

termination signal.

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THE GENETIC CODE

• Genetic code, the

correlation between a

nucleotide sequence and an amino acid sequence, is

used to translate mRNA into proteins.

• A codon is a combination of three mRNA nucleotides.

• Start codon (AUG) signals a ribosome to start translating an mRNA molecule

• Stop codon (UAA, UAG,

UGA) signal the ribosome to stop translating mRNA.

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TRANSLATION

• Translation is the

process of assembling polypeptides from

information encoded in mRNA.

• mRNA leaves the

nucleus and migrates

to a ribosome in the

cytosol (fluid).

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TRANSLATION

• tRNA transports the amino acids to the ribosomes.

• One region of tRNA

molecule has a region

that bonds to specific

amino acid called the

anticodon.

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Ribosomes

• Ribosomes are

composed of rRNA and proteins.

• Ribosomes are free in the cytosol and attached to the endoplasmic

reticulum

• Ribosomes have three binding sites.

– One site holds the mRNA transcript – 2 sites hold tRNA

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Protein Assembly

• Polypeptide assembly begins when a ribosome attaches to a start codon (AUG).

• Start codon pairs with the anticodon UAC on a tRNA.

• Each mRNA codon is paired with its tRNA anticodon.

• Pairing of a codon and

anticodon causes a specific amino acid to attach to a

previously attached amino acid.

• When the ribosome reaches a stop codon, translation ends.

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