Principles of Cell Biology

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Principles of Cell Biology

• Dr. P. Pokorski
• University of MichiganDearborn
• Department of Biology

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The Characteristics of Life

• Life is diverse yet all living things share
  common characteristics.
• Living things are organized.

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• Living things acquire materials and energy.
• Photosynthetic organisms use carbon dioxide,
  water, and solar energy to make food.
• Animals obtain nutrients and energy from food
  eaten.
• Energy is the capacity to do work.
• Many living things can convert energy to
  motion.

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• Living things reproduce.
• Genes (DNA) contain information needed for
  heredity and metabolism.
• Metabolism is all the chemical reactions in
  the cell.
• Reproduction may be asexual or sexual.

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• Living things respond to stimuli.
• Living things may respond to external stimuli
  by movement toward or away from a stimulus.
• Movement constitutes part of the behavior of
  an organism.

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• Living things are homeostatic.
• Homeostasis is the ability of an organism to
  maintain relatively constant internal conditions.
• An example is temperature regulation in the
  human body.
• All organ systems contribute to homeostasis.

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• Living things are adapted.
• Adaptations come about through evolution.
• Evolution is the process by which a species
  changes through time.
• Evolution explains both the unity and
  diversity of life.

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The Classification of Living Things

• Taxomony is the science of identifying and
  classifying organisms according to specific
  criteria using these categories
• Kingdom
• Phylum (Division)
• Class
• Order
• Family
  
  
• 
  Genus
  
• 
  Species

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There are three domains

• Archaea and Bacteria unicellular prokaryotes
  that lack a membrane-bound nucleus.
• Eukarya showing cellular complexity and having
  a nucleus and other organelles.

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• Archaea live in harsh environments and may
  represent the first cells to have evolved.
• Bacteria, some of which cause human diseases, are
  present in almost all habitats on earth.
• Many bacteria are important environmentally and
  commercially.

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• The Domain Eukarya is divided into 4 kingdoms
  
• Protists (kingdom Protista)
• Fungi (kingdom Fungi)
• Plants (kingdom Plantae)
• Animals (kingdom Animalia)

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• Scientific names are binomial names, using
  genus and species.
• Modern humans are Homo sapiens.
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The Organization of the Biosphere

• The biosphere is the zone of life in the air,
  water, and land that surrounds the planet.
• Groups of individuals of a species are called
  populations.
• Populations of different species that interact
  make up communities.
• Communities plus the physical habitat form
  ecosystems.

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The Process of Science

• Biology, the study of life, uses the scientific
  method.
• The scientific method has these steps
• Observation
• Hypothesis
• Experiments/Further Observations
• Conclusion
• Theory

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• An experimental design contains a control group
  that goes through all the steps of the experiment
  but is not exposed to the factor being tested.
• Results of an experiment are called data.
• Data undergo statistical evaluation.

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The Cellular Level of Organization

• Living things are constructed of cells.
• Living things may be unicellular or
  multicellular.
• Cell structure is diverse but all cells share
  common characteristics.

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• The cell theory states
• All organisms are composed of one or more cells.
• Cells are the basic unit of structure and
  function in organisms.
• All cells come only from other cells.

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• Cells are small so they can exchange materials
  with their surroundings.

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Sizes of living things
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Eukaryotic Cells

• Eukaryotic cells have a nucleus that controls the
  workings of the cell.
• All cells are surrounded by a plasma membrane
  made of phospholipids and proteins.

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• The plasma membrane regulates what enters and
  exits the cell.
• Inside the plasma membrane, the nucleus is
  surrounded by cytoplasm.
• Plant cells have a cell wall in addition to the
  plasma membrane.

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• Animal and plant cells have organelles.
• Organelles compartmentalize functions within the
  cell.
• The organelles of animal and plant cells are
  similar to each other except that centrioles are
  present only in animal cells, and chloroplasts
  are present only in plant cells.

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Animal cell anatomy
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Plant cell anatomy
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Structure of the Nucleus

• Chromatin DNA and proteins
• Nucleolus Chromatin and ribosomal subunits
• Nuclear envelope Double membrane with pores
• Nucleoplasm semifluid medium inside the nucleus.

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Nucleic Acids

• Nucleic acids are polymers of nucleotides.
• Examples include Deoxyribonucleic Acid (DNA) and
  Ribonucleic Acid (RNA).

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• DNA is double-stranded, with complementary base
  pairing.

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Nucleus and nuclear envelope
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Ribosomes

• Protein synthesis occurs at tiny organelles
  called ribosomes.
• Ribosomes are composed of a large subunit and a
  small subunit.
• Ribosomes can be found alone in the cytoplasm, in
  groups called polyribosomes, or attached to the
  endoplasmic reticulum.

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The Endomembrane System

• The endomembrane system consists of
• Nuclear envelope
• Endoplasmic reticulum
• Golgi apparatus
• Vesicles

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The endoplasmic reticulum

• The endoplasmic reticulum (ER) is a system of
  membranous channels and saccules.
• Rough ER is studded with ribosomes and is the
  site of protein synthesis and processing.
• Smooth ER lacks ribosomes and is the site of
  synthesis of phospholipids and the packaging of
  proteins into vesicles, among other functions.

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The endoplasmic reticulum
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Proteins

• Proteins perform many functions in cells.
• Proteins
• Serve as structural proteins
• Act as enzymes to speed reactions
• Serve as transport carriers
• Act as antibodies
• Allow materials to cross cell membranes

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• Proteins are polymers of amino acids.

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The Golgi apparatus

• The Golgi apparatus consists of a stack of curved
  saccules.
• The Golgi apparatus receives protein and also
  lipid-filled vesicles from the ER, packages,
  processes, and distributes them within the cell.
• This organelle may also be involved in secretion.

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The Golgi apparatus
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Lysosomes and vacuoles

• Lysosomes are vesicles produced by the Golgi
  apparatus.
• Lysosomes contain hydrolytic enzymes and are
  involved in intracellular digestion.
• Vacuoles (large) and vesicles (small) are
  membranous sacs in the cell that store substances.

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Peroxisomes

• Peroxisomes are vesicles than contain enzymes.
• The enzymes in these organelles use up oxygen and
  produce hydrogen peroxide.
• Peroxisomes are abundant in the liver where they
  produce bile salts and cholesterol and break down
  fats.

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Energy-Related Organelles

• The two energy-related organelles of eukaryotes
  are chloroplasts and mitochondria.
• Both organelles house energy in the form of ATP.

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Chloroplasts

• A chloroplast is bounded by two membranes
  enclosing a fluid-filled stroma that contains
  enzymes.
• Membranes inside the stroma are organized into
  thylakoids that house chlorophyll.
• Chlorophyll absorbs solar energy and
  carbohydrates are made in the stroma.

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Chloroplast structure
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Mitochondria

• Mitochondria are found in plant and animal cells.
• Mitochondria are bounded by a double membrane
  surrounding fluid-filled matrix.

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The inner membranes of mitochondria are
cristae. The matrix contains enzymes that break
down carbohydrates and the cristae house protein
complexes that produce ATP.
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Mitochondrion structure
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The Cytoskeleton

• The eukaryotic cytoskeleton is a network of
  filaments and tubules that extends from the
  nucleus to the plasma membrane.
• The cytoskeleton contains three types of elements
  responsible for cell shape, movement within the
  cell, and movement of the cell
• Actin filaments
• Microtubules
• Intermediate filaments

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• Actin filaments occur in bundles or mesh-like
  networks.
• Actin filaments play a structural role in
  intestinal microvilli and also interact with
  motor molecules, such as myosin.

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Actin filaments
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• Microtubles are small hollow cylinders made of
  the globular protein tubulin.
• Microtubule assembly is controlled by the
  microtubule organizing center, called the
  centrosome.
• Microtubules help maintain the shape of the cell
  and act as tracks along which organelles can move.

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Microtubule structure
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• Intermediate filaments are ropelike assemblies of
  fibrous polypeptides that support the plasma
  membrane and nuclear envelope.

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Structure of intermediate filaments
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Centrioles

• Centrioles are short cylinders with a 9 0
  pattern of microtubule triplets.
• Centrioles may be involved in microtubule
  formation and disassembly during cell division
  and in the organization of cilia and flagella.

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Centriole structure
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Cilia and flagella

• Cilia (small and numerous) and flagella (large
  and single) have a 9 2 pattern of microtubules
  and are involved in cell movement.
• Cilia and flagella move when the microtubule
  doublets slide past one another.
• Each cilium and flagellum has a basal body at its
  base.

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Structure of a flagellum or cilium
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Prokaryotic Cells

• Prokaryotic cells include the bacteria and
  archaea.
• Bacterial cells have these constant features
• Outer Boundary Cell wall
• Plasma membrane
• Cytoplasm Ribosomes
• Thylakoids
  (Cyanobacteria)
• Innumerable
  enzymes
• Nucleoid Chromosome (DNA only)

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• Bacterial cells may have plasmids, small
  accessory rings of DNA.
• Some bacteria have a capsule or a slime layer.
• Most bacteria have flagella.
• Some also have fimbriae that help cells attach to
  surfaces.
• Bacteria have a great metabolic diversity.