copyright © 2010 pearson education, inc. generalized cell human cells have three basic parts:...

Copyright © 2010 Pearson Education, Inc.

Generalized Cell

• Human cells have three basic parts:

• Plasma membrane—flexible outer boundary

• Cytoplasm—intracellular fluid containing organelles

• Nucleus—control center

Copyright © 2010 Pearson Education, Inc. Figure 3.2

Secretion beingreleased from cellby exocytosis

Peroxisome

Ribosomes

Roughendoplasmicreticulum

Nucleus

Nuclear envelopeChromatin

Golgi apparatus

Nucleolus

Smooth endoplasmicreticulum

Cytosol

Lysosome

Mitochondrion

CentriolesCentrosomematrix

Cytoskeletalelements• Microtubule• Intermediate filaments

Plasmamembrane


Plasma Membrane

• The plasma membrane separates the intracellular fluid (ICF) from extracellular fluid (ECF)

• The plasma membrane is semi-permeable which means that some things can cross the membrane and some things cannot


Extracellular fluid

Intracellular fluid


Types of Membrane Transport

• A concentration gradient is:

• Passive Transport

• No cellular energy (ATP) required

• Substance moves down its concentration gradient

• Active Transport

• Energy (ATP) required

• Substances are moved or“pumped” against their gradient


Passive Transport

•Two main factors determine whether or not a substance can passively cross the plasma membrane.

1. Is the substance a lipid (Lipid solubility of substance)

2. Size of substance passing


Three Types of Passive Transport Across Cellular Membranes

• Simple diffusion- Small, nonpolar, hydrophobic substances diffuse directly through plasma membrane (O2, CO2)

• Facilitated diffusion-Larger, hydrophilic molecules (glucose, amino acids)

• Use membrane proteins to cross

• Osmosis-Movement of solvent (water) across a selectively permeable membrane from where it is most concentrated to where it is less concentrated

• Water mainly diffuses through channels (AQP) in the plasma membrane

Copyright © 2010 Pearson Education, Inc. Figure 3.7a

Extracellular fluid

Lipid-solublesolutes

Cytoplasm

Copyright © 2010 Pearson Education, Inc. Figure 3.7b

Hydrophilic moleculesA Carrier Protein

Copyright © 2010 Pearson Education, Inc. Figure 3.7d

Watermolecules

Lipidbillayer

Aquaporin

A Channel Protein


Importance of Osmosis

• When osmosis occurs, water enters or leaves a cell

• A change in cell volume disrupts cell function

• Tonicity is the ability of a solution to change a cell’s volume

• Hypertonic, Hypotonic and Isotonic solutions


(a) Membrane permeable to both solutes and water

Solute and water molecules move down their concentration gradientsin opposite directions.

Membrane

H2O

Solute

Solute(sugar)

Both solutions have thesame osmolarity: volumeunchanged

Copyright © 2010 Pearson Education, Inc. Figure 3.8b

(b) Membrane permeable to water, impermeable to solutes

Both solutions have identicalosmolarity, increases on the right

because only water is free to move

Solute molecules are prevented from moving but water moves by osmosis.Volume increases in the compartment with the higher osmolarity.

Leftcompartment

Rightcompartment

Membrane

Solute(sugar)

H2O


(a) Isotonic solutions (b) Hypertonic solutions (c) Hypotonic solutions


Other Cellular Organelles

• Membranous structures

• Nucleus with chromatin-

• Mitochondria –

• Endoplasmic Reticulum (ER) (rough and smooth) –

• Golgi Apparatus-

• Lysosomes-


Golgiapparatus

Transportvesicle

Plasmamembrane

Vesicle

Smooth ER

Rough ER

Nuclear envelope

Lysosome

Nucleus


Nuclearenvelope

Ribosomes

Rough ER

Smooth ER


Other Organelles

• Non-Membranous structures

• Cytoskeleton- protein filaments that help maintain cell shape, cell movement and in cell division (microtubules)


Extensions of the plasma membrane

• Cilia are: short, hairlike structures; move substances across cell surfaces

• Flagella are: Whiplike, tails that move the entire cell


THE CELL CYCLE


The Cell Cycle• Includes:

• Interphase

• Period from cell formation to cell division

• Three sub phases of Interphase:

• G1, S, G2

• Cell division (mitotic phase or mitosis)

• Consists of four sub phases of mitosis (PMAT) and cytokinesis


G1

Growth

SGrowth and DNA

synthesis G2

Growth and finalpreparations for

divisionM

Mitosis (Cell Division)

• Mitosis increases the # of cells for growth/tissue repair


During the S-phase of Interphase DNA is Replicated

• Helicase untwists the double helix and exposes complementary chains

• Each nucleotide strand serves as a template for building a new complementary strand

• DNA polymerase forms new DNA strand


DNA Replication

• End result: two DNA molecules formed from the original in a process called semiconservative replication

• After DNA has been replicated the cell progresses into mitosis and cytokinesis


Mitosis and Cytokinesis

• Mitosis—four stages of nuclear division:

•Prophase-

•Metaphase-

•Anaphase-

•Telophase-

•Cytokinesis—division of cytoplasm by cleavage furrow


G1

Growth

SGrowth and DNA

synthesis G2

Growth

M


Early mitoticspindle

Early Prophase

Centromere

Aster

Chromosomeconsisting of twosister chromatids

Early Prophase


Microtubule

Microtubule

Late Prophase

Fragmentsof nuclearenvelope

Late Prophase


Spindle

MetaphaseplateMetaphase

Metaphase


Anaphase

Daughterchromosomes

Anaphase


Cytokinesis

• Begins during late anaphase

• Ring of actin microfilaments contracts to form a cleavage furrow

• Two daughter cells are pinched apart, each containing a nucleus identical to the original


Contractilering atcleavagefurrow

Nuclearenvelopeforming

Nucleolusforming

Telophase

Telophase and Cytokinesis

copyright © 2010 pearson education, inc. generalized cell human cells have three basic parts:...

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