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Marieb’s HumanAnatomy and Physiology

Ninth Edition

Chapter 3Cells: The Living Units

Lecture 6

Marieb Hoehn

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• Mitochondria

• Intro to Cellular Respiration

• The cell nucleus

• The cell cycle

• Mitosis & Meiosis

• Cell Death

• Stem & Progenitor Cells

Lecture Overview

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Cytoplasmic Organelles (cont’d) - Mitochondria

Mitochondria• membranous sacs with inner partitions• contain their own DNA• generate energy

Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson

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Overview of Cellular Metabolism

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Metabolism – All the chemical reactions that occur in an organism

ETS

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Overview of Glucose Breakdown

Figure from: Hole’s Human A&P, 12th edition, 2010

NAD+

NAD+

NAD+FAD

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Overview of Cellular RespirationFigure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Cellular respiration

(aerobic)

AnaerobicATP

*Most ATP from here

ATP

• Structural – Functional Relationship - Inner membrane:• Contains Matrix where TCA cycle takes place• Has enzymes and molecules that allow Electron Transport System to be carried out

e-

+ e-

ETS

e-

e-

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Anaerobic Glycolysis & Lactic Acid

During glycolysis, if O2 is not present in sufficient quantity, lactic acid is generated to keep glycolysis going so it continues to generate ATP (even without mitochondria)

NOTE what happens with and without O2 being available…

Figure from: Hole’s Human A&P, 12th edition, 2010

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Cell Nucleus• control center of cell

• nuclear envelope (membrane)

• porous double membrane• separates nucleoplasm from cytoplasm (*eukaryotes only)

• nucleolus• dense collection of RNA and proteins• site of ribosome production

• chromatin• fibers of DNA and proteins• stores information for synthesis of proteins Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson

The Cell Cycle

• series of changes a cell undergoes from the time it forms until the time it divides

• stages • interphase• mitosis• cytoplasmic division• differentiation

Differentiated cells may spend all their time in ‘G0’ (neurons, skeletal muscle, red blood cells). Stem cells may never enter G0

Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson

Why the Cell Cycle Must Have Controls

1. DNA/Cell replication must not proceed unless a ‘signal to proceed’ is received

2. DNA must be completely and correctly replicate before mitosis takes place otherwise it should not occur.

3. Chromosomes must be correctly positioned during mitosis so they are separated correctly

What are the Controls of the Cell Cycle?

• cell division capacities vary greatly among cell types• skin and bone marrow cells divide often• liver cells divide a specific number of times then cease

• chromosome tips (telomeres) that shorten with each mitosis provide a mitotic clock (cell senescence)

• cells divide to provide a more favorable surface area to volume relationship

• growth factors and hormones stimulate cell division• hormones stimulate mitosis of smooth muscle cells in uterus• epidermal growth factor stimulates growth of new skin

• tumors are the consequence of a loss of cell cycle control

• contact inhibition

• Cyclins and Cyclin-dependent kinases provide central control

The Cell Cycle and Mitosis

• INNKEEPER (INTERPHASE)

• POUR (PROPHASE)

• ME (METAPHASE)

• ANOTHER (ANAPHASE)

• TEQUILA (TELOPHASE/CYTOKINESIS)

Interphase and Mitosis (IPMAT)

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Interphase Early Prophase Late Prophase

Metaphase Anaphase Telophase/Cytokinesis

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Mitosis and MeiosisFigures from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Mitosis – production of two identical diploid daughter cells

Meiosis – production of four genetically varied, haploid gametes

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Chromosome Crossing Over• mixes up traits

• different colors represent the fact that one homologous chromosome comes from the individual’s father (paternal) and one from the mother (maternal)

• the genetic information in sperm cells and egg cells varies from cell to cell

TetradFigure from: Hole’s Human A&P, 12th edition, 2010

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Cell Death• Two mechanisms of cell death

– Necrosis– Programmed cell death (PCD or apoptosis)

• Necrosis– Tissue degeneration following cellular injury or

destruction– Cellular contents released into the environment

causing an inflammatory response

• Programmed Cell Death (Apoptosis)– Orderly, contained cell disintegration– Cellular contents are contained and cell is

immediately phagocytosed

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Necrosis vs. Apoptosis

Necrosis

ApoptosisFigure from: Alberts et al., Essential Cell Biology, Garland Press, 1998

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Stem and Progenitor Cells

Stem cell • can divide to form two new stem cells• can divide to form a stem cell and a progenitor cell• totipotent – can give rise to any cell type (Embryonic stem cells)• pluripotent – can give rise to a restricted number of cell types

Progenitor cell • committed cell further along differentiation pathway• can divide to become any of a restricted number of cells • pluripotent• *not self-renewing, like stem cells

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Figure from: Hole’s Human A&P, 12th edition, 2010

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GLYCOLYSIS TCA ETC

Where it takes place

Cytoplasm Mitochondria Mitochondria

Products Produced ATPNADH

Pyruvate

ATPNADH,FADH2

CO2

ATPNAD+,FAD

H2O

Purpose Breakdown of glucose (6 carbons) to 2

molecules of pyruvate (3 carbons)

Generation of energy intermediates (NADH, FADH2, ATP) and CO2

Generation of ATP and reduction of O2 to H2O (Recall that reduction is the addition of

electrons)What goes on 1. Glucose is

converted to pyruvate, which is converted to acetyl CoA when there is sufficient O2 present.2. Acetyl CoA enters the TCA cycle.3. If O2 is not present, pyruvate is converted to lactic acid to replenish the supply of NAD+ so glycolysis can continue to make ATP

1. The energy in acetyl CoA is trapped in activated carriers of electrons (NADH, FADH2) and activated carriers of phosphate groups (ATP). 2. The carries of electrons that trap the energy from acetyl CoA bring their high energy electrons to the electron transport chain.

1. Chemiosmosis (oxidative phosphorylation) uses the electrons donated by NADH and FADH2 to eject H+ from the matrix of the mitochondria to the intermembrane space. 2. These H+ then flow down their concentration gradient through a protein (ATP synthase) that makes ATP from ADP and phosphate.3. During this process, the H+

that come through the channel in ATP synthase are combined with O2 to make H2O.

Summary Table of Cell Respiration

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Review

• Cellular respiration– The metabolic processes by which ATP is produced

– Major cellular steps:• Glycolysis

– Cytoplasm

– Anaerobic

• TCA (Krebs, Citric Acid) cycle– Mitochondria

– Aerobic

• Electron Transport Chain– Mitochondria

– Aerobic

– Most ATP produced here

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Review• The goal of metabolism

– provide the cell with energy (via catabolism; breakdown) and

– materials for the manufacture of cellular components (via anabolism; synthesis, building up)

• Cell Nucleus– Nuclear envelope (membrane)• porous double membrane

• separates nucleoplasm from cytoplasm (*eukaryotes only)

• Nucleoli – RNA organizing centers

• Chromatin – combination of DNA and RNA

Review• The Cell Cycle

– series of changes a cell undergoes from the time it forms until the time it divides

– stages can include

• interphase (G1, S, G2)

• mitosis (PMAT)

• cytoplasmic division (cytokinesis)

• differentiation (G0; exit from cell cycle)

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Review

• Cell Death occurs by two processes– Necrosis

• Sudden insult to cell causing rapid death

• Causes inflammation in surrounding tissues

– Programmed Cell Death (apoptosis)• Planned, orderly shutdown of cell

• Ubiquitous in normal cellular processes

• Does not cause inflammation of surrounding tissues

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Review• Mitosis

– Identical daughter cells

– Diploid number of chomosomes

• Meiosis– Used by sex cells

– Genetically varied daughter cells

– Haploid number of chomosomes

• Stem cells – can produce many, if not all, other cell types

• Progenitor cells – can produce only a limited number of cell types

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