The Cellular Level of Organization

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The Cellular Level of Organization
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The cell theory states

• Cells are the building blocks of all plants and
  animals
• Cells are produced by the division of preexisting
  cells. Whats wrong with this sentence?
• Cells are the smallest units that perform all
  vital physiological functions
• Each cell maintains homeostasis at the cellular
  level
• Homeostasis at higher levels reflects combined,
  coordinated action of many cells

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Figure 3.1 The Diversity of Cells in the Human
Body
Figure 3.1
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The Anatomy of a Representative Cell

• Label
• Cilia
• Centriole
• Mitochondrion
• Rough ER
• Smooth ER
• Cytosol
• Ribosomes
• Golgi
• Chromatin
• Lysosome

Figure 3.2
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Inside and Outside are not the same

• A cell is surrounded by extracellular fluid.
  This fluid is called interstitial fluid.
• A cell contains intracellular fluid. This fluid
  is called cytosol (not cytoplasm cytoplasm
  cytosol organelles).
• The solute contents and concentrations of
  interstitial fluids differ from those of cytosol.
• The concentration differences are due primarily
  to the cell membrane, which acts as a barrier and
  transporter.
• Name three molecules or atoms that you think
  would differ between the cytosol and interstitial
  fluid. In which solution do you think they would
  be more concentrated? Why?

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Introduction to Cell Division
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cell division

• Define
• Cell division-
• Apoptosis-
• Mitosis-
• Meiosis-
• Typically the cell cycle is composed of two
  separate periods ___________ and __________.
  Most cells spend more time in ___________
  _________ is a relatively short period when the
  nucleus divides.

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Interphase
The cell cycle comprises cell division
(__________ and_________) and interphase.

• Most somatic cells spend the majority of their
  lives in this phase
• Interphase includes
• G1 means? ______________
• S means? ______________
• G2 means? ______________

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The Cell Life Cycle
Write one sentence that describes the
relationship between cancer and the cell cycle.
Figure 3.27
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S phase - DNA Replication
Figure 3.28
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Mitosis, or nuclear division, has four phases
During cytokinesis, the cytoplasm divides and
cell division ends
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Figure 3.29 Interphase, Mitosis, and Cytokinesis
Figure 3.29a-d
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Figure 3.29 Interphase, Mitosis, and Cytokinesis
Figure 3.29e, f
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Mitotic rate and cancer

• Generally, the longer the life expectancy of the
  cell, the slower the mitotic rate
• Stem cells undergo frequent mitoses
• Growth factors can stimulate cell division
• Abnormal cell division produces tumors or
  neoplasms
• Benign
• Malignant (invasive, and cancerous)
• Spread via metastasis
• Oncogenes

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The Cell Membrane
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Cell membrane functions include

• Functions
• Physical isolation
• Regulation of exchange with the environment
• Structural support

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Figure 3.3 The Cell Membrane

• The cell membrane is a phospholipid bilayer with
  proteins, lipids and carbohydrates.

Figure 3.3
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Membrane proteins include

• Integral proteins
• Peripheral proteins
• Anchoring proteins
• Recognition proteins
• Receptor proteins
• Carrier proteins
• Channels

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Figure 3.4 Membrane proteins
Figure 3.4
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Membrane carbohydrates form the glycocalyx

• Proteoglycans
• Glycolipids
• Glycoproteins

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The transmembrane potential

• Difference in electrical potential between inside
  and outside a cell
• Undisturbed cell has a resting potential
• What is a typical value for the resting membrane
  potential? What ions are responsible for
  establishing the resting membrane potential?

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Cell Membranes continued

• Movement Across the Membrane

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Permeability

• The ease with which substances can cross the cell
  membrane
• Nothing passes through an impermeable barrier
• Anything can pass through a freely permeable
  barrier
• Cell membranes are selectively permeable

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Diffusion

• Definition?
• Does it require energy?
• What determines the rate of diffusion?

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Figure 3.18 Diffusion
Figure 3.18
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Figure 3.19 Diffusion across the Cell Membrane
Figure 3.19
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Osmosis

• Diffusion of water across a semipermeable
  membrane in response to solute differences
• Osmotic pressure force of water movement into a
  solution
• Hydrostatic pressure opposes osmotic pressure
• Water molecules undergo bulk flow

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Figure 3.20 Osmosis
Figure 3.20
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Tonicity

• The effects of osmotic solutions on cells
• Isotonic no net gain or loss of water
• Hypotonic net gain of water into cell
• Hemolysis
• Hypertonic net water flow out of cell
• Crenation

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Figure 3.21 Osmotic flow across a cell membrane
Figure 3.21
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Figure 3.22 Facilitated Diffusion
Figure 3.22
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Active transport

• Active transport
• Consumes ATP
• Independent of concentration gradients
• Types of active transport include
• Ion pumps
• Secondary active transport

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Figure 3.23 The Sodium Potassium Exchange Pump
Figure 3.23
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Figure 3.24 Secondary Active Transport
Figure 3.24
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Vesicular transport material moves into or out
of cells in membranous vesicles

• Endocytosis is movement into the cell
• Receptor mediated endocytosis (coated vesicles)
• Pinocytosis
• Phagocytosis (pseudopodia)
• Exocytosis is ejection of materials from the cell

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Figure 3.25 Receptor-Mediated Endocytosis
Figure 3.25
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Figure 3.26 Pinocytosis and Phagocytosis
Figure 3.26
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The cytoplasm contains

• The fluid (cytosol)
• The organelles the cytosol surrounds

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Organelles

• Nonmembranous organelles are not enclosed by a
  membrane and always in touch with the cytosol
• Cytoskeleton, microvilli, centrioles, cilia,
  ribosomes, proteasomes
• Membranous organelles are surrounded by lipid
  membranes
• Endoplasmic reticulum, Golgi apparatus,
  lysosomes, peroxisomes, mitochondria

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• Slide that lists compounds and asks how they
  would be transported

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Figure 3.2 The Anatomy of a Representative Cell
Figure 3.2
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Cytoskeleton provides strength and flexibility

• Microfilaments
• Intermediate filaments
• Microtubules
• Thick filaments
• Microvilli increase surface area

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Figure 3.5 The Cytoskeleton
Figure 3.5
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Centrioles

• Direct the movement of chromosomes during cell
  division
• Organize the cytoskeleton
• Cytoplasm surrounding the centrioles is the
  centrosome

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Cilia

• Is anchored by a basal body
• Beats rhythmically to move fluids across cell
  surface

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Figure 3.6 Centrioles and Cilia
Figure 3.6
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Figure 3.7 Ribosomes
Figure 3.7
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Ribosomes

• Are responsible for manufacturing proteins
• Are composed of a large and a small ribosomal
  subunit
• Contain ribosomal RNA (rRNA)
• Can be free or fixed ribosomes

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Proteasomes

• Remove and break down damaged or abnormal
  proteins
• Require targeted proteins to be tagged with
  ubiquitin

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Figure 3.8 The Endoplasmic Reticulum
Figure 3.8
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Endoplasmic reticulum

• Intracellular membranes involved in synthesis,
  storage, transportation and detoxification
• Forms cisternae
• Rough ER (RER) contains ribosomes
• Forms transport vesicles
• Smooth ER (SER)
• Involved in lipid synthesis

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Figure 3.9 The Golgi Apparatus
Figure 3.9
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Golgi Apparatus

• Forms secretory vesicles
• Discharged by exocytosis
• Forms new membrane components
• Packages lysosomes

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Figure 3.10 Functions of the Golgi Apparatus
Figure 3.10
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Lysosomes and Peroxisomes

• Lysosomes are
• Filled with digestive enzymes
• Responsible for autolysis of injured cells
• Peroxisomes
• Carry enzymes that neutralize toxins

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Figure 3.11 Lysosome Functions
Figure 3.11
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Membrane flow

• Continuous movement and recycling of membranes
• ER
• Vesicles
• Golgi apparatus
• Cell membrane

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Mitochondria

• Responsible for ATP production through aerobic
  respiration
• Matrix fluid contents of mitochondria
• Cristae folds in inner membrane

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Figure 3.13 The Nucleus
Figure 3.13
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The nucleus is the center of cellular operations

• Surrounded by a nuclear envelope
• Perinuclear space
• Communicates with cytoplasm through nuclear pores

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Contents of the nucleus

• A supportive nuclear matrix
• One or more nucleoli
• Chromosomes
• DNA bound to histones
• Chromatin

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Figure 3.14 Chromosome Structure
Figure 3.14
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The genetic code

• The cells information storage system
• Triplet code
• A gene contains all the triplets needed to code
  for a specific polypeptide

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Gene activation and protein synthesis

• Gene activation initiates with RNA polymerase
  binding to the gene
• Transcription is the formation of mRNA from DNA
• mRNA carries instructions from the nucleus to the
  cytoplasm

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Figure 3.16 An overview of Protein Synthesis
Figure 3.16
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Translation is the formation of a protein

• A functional polypeptide is constructed using
  mRNA codons
• Sequence of codons determines the sequence of
  amino acids
• Complementary base pairing of anticodons (tRNA)
  provides the amino acids in sequence

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Figure 3.17 The Process of Translation
Figure 3.17
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Figure 3.17 The Process of Translation
Figure 3.17