Chapter 3 Notes

Chapter 3: The Cellular Level of Organization
What is cell theory?
The Cell
-Performs all life functions
*PIC*

Sex Cells
-Sex Cells (germ cells):
-Reproductive Cells
-Male Sperm
-Female Oocytes (eggs)

Somatic Cells
-Somatic Cells (Soma=body):
-All body cells except sex cells

Organelle functions
*PIC*

*PIC*

Functions of Cell Membrane
-Physical Isolation
-Barrier
-Regulates exchange with environment
-ions and nutrients center
-waste and cellular products released
-Monitors the environment
-the extracellular fluid composition
-chemical signals
-Structural support
-anchors cells and tissues

What are the structures and functions of the cell membrane?

The Cell Membrane
-contains lipids, carbohydrates, and functional proteins
*PIC*

Phospholipid Bilayer
-Double layer of phospholipid molecules:
-hydrophilic heads: toward watery environment, both sides
-hydrophobic fatty acid tails-inside membrane
-barrier to ions and water soluble compounds

Membrane Proteins:
-Integral proteins:
-within the membrane
-Peripheral proteins:
-inner or outer surface of the membrane

6 functions of Membrane Proteins
1. Anchoring proteins (stabilizers):
-attach to inside or outside structures
2. Recognition proteins (identifiers):
-label cells normal or abnormal
3. Enzymes:
-catalyze reactions
4. Receptor proteins:
-bind and respond to ligands (ions, hormones)
5. Carrier Proteins
-transport specific solutes through membrane
6. Channels:
-regulate water flow and solutes through membrane

Membrane Carbohydrates
-Proteoglycans, glycoproteins, and glycolipids:
-extend cell membrane
-form sticky "sugar coat" (glycocalyx)

Functions of Membrane Carbohydrates
-Lubrication and protection
-Anchoring and locomotion
-Specificity in binding (receptors)
-Recognition (immune response)

Cytoplasm
-All materials inside the cell and outside the nucleus
-cytosol (fluid):
-dissolved materials:
-nutrients, ions, proteins, and waste proteins
-organelles:
-structures with specific functions

What are cell organelles and their functions?

Types of Organelles
-Nonmembranous organelles:
-no membrane
-direct contact with cytosol
-Membraneous organelles:
-covered with plasma membrane
-isolated from cytosol

Nonmembranous Organelles
-6 types od nonmembranous organelles:
-cytoskeleton
-microvilli
-centrioles
-cilia
-ribosomes
-proteasomes

The Cytoskeleton
-Structural proteins for shape ans strength
*PIC*

Microfilaments
-Thin filaments composed of the protein actin:
-provide additional mechanical strength
-interact with proteins for consistency
-pairs with thick filaments of myosin for muscle movement

Intermediate Filaments
-Mid-sized between microfilaments and thick filaments:
-durable (collagen)
-strengthen cell and maintain shape
-stabilize organelles
-stabilize cell position

Microtubules
-Large, hollow tubes of tubulin protein:
-attach to centrosome
-strengthen cell and anchor organelles
-change cell shape
-move vesicles within cell (kinesin and dynein)
-form spindle apparatus

Microvilli
-Increase surface area absorption
-Attach to cytoskeleton
*PIC*

Centrioles in the Centrosome
-Centrioles form spindle apparatus during cell division
-Centrosome: cytoplasm surrounding centriole
*PIC*

Cilia Power
-Cilia move fluids across the cell surface
*PIC*

Ribosomes
-Build polypeptides in protein synthesis
-Two types:
-free ribosomes in cytoplasm:
-proteins for cell
-fixed ribosomes attached to ER:
-proteins for secretion

Proteasomes
-Contain enzymes (proteases)
-Disassemble damaged proteins for recycling

Membranous Organelles
-5 types of membranous organelles:
-endoplasmic reticulum (ER)
-Golgi apparatus
-lysosomes
-peroxisomes
-mitochondria

Endoplasmic Reticulum (ER)
-endo=within,plasm=cytoplasm,reticulum=network
-cisternae are storage chambers within membranes
*PIC*

Functions of ER
-Synthesis of proteins, carbohydrates, and lipids
-storage of synthesized molecules and materials
-transport of material within the ER
-Detoxification of drugs or toxins

Smooth Endoplasmic Reticulum (SER)
-No ribosomes attached
-Synthesizes lipids and carbohydrates:
-phospholipids and cholesterol (membranes)
-steroid hormones (reproductive systems)
-glycerides (storage in liver and fat cells)
-glycogen (storage in muscles)

Rough Endoplasmic Reticulum (RER)
-Surface covered with ribosomes:
-active in protein and glycoprotein synthesis
-folds polypeptides protein structures
-encloses products in transport vesicles

Golgi Apparatus
-Vesicles enter forming face and exit maturing face
*PIC*

Vesicles of the Golgi Apparatus
-Secretory Vesicles:
-modify and package products for exocytosis
-Membrane renewal vesicles:
-add or remove membrane components
-Lysosomes:
-carry enzymes to cytosol

Transport vesicles
-carry materials to and from the golgi apparatus
*PIC*

Lysosomes
-Power enzymes, containing vesicles:
-lyso=dissolve, soma=body
*PIC*

Lysosome Structures
-Primary lysosome:
-formed by Golgi and inactive enzymes
-Secondary lysosome:
-lysosome fused with damaged organelle
-digestive enzymes activated
-toxic chemicals isolated

Lysosome Functions
-Clean up inside cells:
-break down large molecules
-attack bacteria
-recycle damaged organelles
-ejects wastes by exocytosis

Autolysis
-Self destruction of damaged cells:
-auto=self lysis=breakdown
-lysosome membranes break down
-digestive enzymes released
-cell decomposes
-cellular materials recycle

Peroxisomes
-Are enzyme containing vesicles:
-break down fatty acids, organic compounds
-produce hydrogen peroxide (H2O2)
-replicate by division

Membrane Flow
-A continuous exchange of membrane parts by vesicles:
-all memranous organelles (except mitochondria)
-allows adaption and change

KEY CONCEPT:
-Cells: basic structural and functional units of life
-respond to their environment
-maintain homeostasis at the cellular level
-modify structure and function over time

Mitochondrion Structure
-Have sooth outer membrane and folded inner membrane (cristae)
-Matrix
-fluid around cristae
*PIC*

Mitochondrial Function
-Mitochonrion takes chemical energy from food (glucose):
-produces energy molecule ATP
*PIC*

Aerobic Cellular Respiration
-Aerobic metabolism (cellular respiration):
-miochondria use oxygen to break down food and produce ATP

The Reactions
glucose + oxygen +ADP
carbon dioxide + water + ATP
-Glycolysis:
-glucose to pyruvic acid (in cytosol)
-Tricarboxylic acid cycle (TCA cycle):
-pyruvic acid to CO2 (in matrix)

KEY CONCEPT:
-Mitochondria provide cells with energy for life:
-require oxygen and organic substrates
-generate carbon dioxide and ATP

How does the nucleus control the cell?

The Nucleus
-Is the cell's control center
*PIC*

Structure of the Nucleus
-Nucleus:
-largest organelle
-Nuclear envelope:
-double membrane around the nucleus
-Perinuclear space:
-between 2 layers of nuclear envelope
-Nuclear Pores:
-communication passages

Within the Nucleus
-DNA:
-all the information to build and run organisms
-Nucleoplasm:
-fluid containing ions, enzymes, nucleotides, and some RNA
-Nuclear matrix:
-support filaments

Nucleoli in Nucleus
-Are related to protein production
-Are made of RNA, enzymes, and histones
-Sythesize rRNA and ribosomal subunits

Organization of DNA
-Nucleosomes:
-DNA coiled around histones
-Chromatin:
-loosely coiled DNA (cells not dividing)
-Chromosomes:
-tightly coiled DNA (cells dividing)
*PIC*

What is genetic code?

DNA and Genes
-DNA:
-instructions for every protein in the body
-Gene:
-DNA instructions for 1 protein

Genetic Codes
-The chemical language of DNA instructions:
-sequence of bases (A,T,C,G)
-triplet code:
-3 bases= 1 amino acid

KEY CONCEPT:
-The nucleus contains chromosomes
-Chromosomes contain DNA
-DNA stores genetic instructions for proteins
-Proteins determine cell structure and function

How do DNA instructions become proteins?

Protein Synthesis
-Transcription:
-copies instruction from DNA to mRNA (in nucleus)
-Translation:
-ribosome reads code from mRNA (in cytoplasm)
-assembles amino acids into polypeptide chain
-Processing:
-by RER and Golgi apparatus produces protein

mRNA Transcription
-A gene is transcribed to mRNA in 3 steps:
-gene activation
-DNA to mRNA
- RNA processing

Step 1: Gene Activation
-Uncoils DNA, removes histones
-Start (promoter) and stop codes on DNA mark location of gene:
-coding strand is code for protein
-template strand used by RNA polymerase molecule

Step 2: DNA to mRNA
-Enzyme RNA polymerase transcribes DNA:
-binds to promoter (start) sequence
-reads DNA code for gene
-binds nucleotides to form messenger RNA (mRNA)
-mRNA duplicates DNA coding strand, uracil replaces thymine

Step 3: RNA Processing
-At stop signal, mRNA detaches from DNA molecule:
-code is edited (RNA processing)
-unnecessary codes (introns) removed
-good codes (exons) spliced together
-triplet of 3 nucleotides (codon) represents one amino acid

Codons
*PIC*

Translation
-mRNA moves:
-from the nucleus
-through a nuclear pore
*PIC*

-mRNA moves:
-to a ribosome in cytoplasm
-surrounded by amino acids
*PIC*

-mRNA binds to ribosomal subunits
-tRNA delievers amino acids to mRNA
*PIC*

-tRNA anticodon binds to mRNA codon
-1 mRNA codon translates to 1 amino acid
*PIC*

-Enzymes join amino acids with peptide bonds
-Polypeptide chain has specific sequence of amino acids
*PIC*

-At stop codon, components seperate
*PIC*

Nucleus Controls Cell Structure and Function
-Direct control through synthesis of:
-structural proteins
-secretions (environmental response)
-Indirect control over metabolism through enzymes

KEY CONEPT:
-Genes:
-a functional units of DNA
-contain instructions for 1 or more proteins
-Protein synthesis requires:
-several enzymes
-ribosomes
-3 types of RNA

-Mutation is a change in the nucleotide sequence of a gene:
-can change gene function
-Causes:
-exposure to chemicals
-exposure to radiation
-mistakes during DNA replication

How do things get in and out of cells?

Overcoming the Cell Barrier
-The cell membrane is a barrier but:
-nutrients must get in
-products and wastes must get out

Permeability
-Permeability detemines what moves in and out of a cell:
-A membrane that:
-lets nothing in or out if impermeable
-lets anything pass is freely permeable
-restricts movement is selectively permeable

Selective Permeability
-Cell membrane is selectively permeable:
-allows some materials to move freely
-restricts other materials

Restricted Materials
-Selective permeability restricts materials based on:
-size
-electrical charge
-molecular shape
-lipid solubility

Transport
-Transport through a cell membrane can be:
-active (requiring energy and ATP)
-passive (no energy required)

3 Categories of Transport
-Diffusion (passive)
-Carrier-mediated transport (passive or active)
-Vesicular transport (active)

Solutions
-All molecules are constantly in motion
-Molecules in solution move randomly
-Random motion causes mixing

Concentration Gradient
-Concentration is the amount of solute in a solvent
-Concentration gradient:
-more solute in 1 part of a solvent than another

Function of Concentration Gradient
-Diffusion:
-molecules mix randomly
-solute spreads through solvent
-eliminates concentration gradient

Diffusion
-Solutes move down a concentration gradient

Factors Affecting Diffusion Rates
-Distance the particle has to move
-Molecule size:
-smaller is faster
-Temperature:
-more heat, faster motion
-Gradient SIze:
-the difference between high and low concentration
-Electrical forces:
-opposites attract, like charges repel

Diffusion and the Cell membrane
-Diffusion can be simple or channel- mediated
*PIC*

Simple Diffusion
-Materials which diffuse through cell membrane:
-lipid soluble compounds (alchols, fatty acids, steroids)
-dissolved gases (oxygen and carbon dioxide)

Channel-Mediated Diffusion
-Materials which pass through transmembrane proteins (channels):
-are water soluble compounds
-are ions

Factors in Channel-Mediated Diffusion
-Passage depends on:
-size
-charge
- interaction with the channel

Osmosis
-Osmosis is the diffusion of water across the cell membrane
*PIC*

How Osmosis Works
-More solute molecules, lower concentration of water molecules
-Membrane must be freely permeable to water, selectively permeable to solutes

Osmosis Water Movement
-Water molecules diffuse across membrane toward solution with more solutes
-Volume increases on the side with more solutes

Osmotic Pressure
-Is the force of a concentration gradient of water
-Equals the force (hydrostatic pressure) needed to block osmosis

Tonicity
-The osmotic effect of a solute on a cell:
-2 fluids may have equal osmolarity, but different tonicity

Isotonic Solutions
-A solution that does not cause osomotic flow of water in ot out of a cell
-iso=same, tonos= tension

Hypotonic Solutions
-hypo=below
-Has less solutes
-Loses water through osmosis

Cells and Hypotonic Solutions
-A cell in a hypotonic
solution:
-gains water
-ruptures (hemolysis of red blood cells)

Hypertonic Solutions
-hyper=above
-has more solutes
-gains water by osmosis

Cells and Hypertonic Solutions

A cell in a hypertonic solution:
-loses water
-shrinks (crenation of red blood cells)

KEY CONCEPT:
-concentration gradients tend to even out
-In the absence of membrane, diffusion eliminates concentration gradients
-When different solute concentrations exist on either side of a selectively permeable membrane, osmosis moves water through the membrane to equalize the concentration gradients

What are special transport mechanisms

Carrier-Mediated Transport
-Carrier mediated transport of ions and organic substrates:
-facilitated diffusion
-active transport

Characteristics of Carrier-Mediated Transport
-Specificity:
-1 transport protein 1 set of substrates
-Saturation limits:
-rate depends on transport proteins, not substrate
-Regulation:
-cofactors such as hormones

Cotransport
-2 substances move in the same direction at the same time

Countertransport
-1 substance moves in while another moves out

Facilitated Diffusion
-passive
-carrier mediated
*PIC*

How facilitated Diffusion Works
-Carrier proteins transport molecules too large to fit through channel proteins (glucose, amino acids):
-molecule binds to receptor site on carrier protein
-protein changes shape, molecules pass through
-receptor site is specific to certain molecules

Active Transport
-Active transport proteins:
-move substrates against concentration gradient
-require energy, such as ATP
-ion pumps move ions (Na+, K+, Ca+,Mg2+)
-exchange pump contertransports 2 ions at the same time

Sodium-Potassium Exhcange Pump
-Active Transport, carrier mediated:
-sodium ions (Na+) out, potassium ions (K+) in
-1 ATP moves 3 Na+
*PIC*

Secondary Active Transport
-Na+ concentration gradient drives glucose transport
-ATP energy pumps Na+ back out
*PIC*

Transport Vesicles
-Also called bulk transport
-Vesicles:
-endocytosis (endo=into)
-active transport using ATP:
-receptor-mediated
-pinocytosis
-phagocytosis
-exocytosis (exo= out of)

Receptor-Mediated Endocytosis
-Receptors (glycoproteins) bind target molecules (ligands)
-Coated vesicle (endosome) carries ligands and receptors into the cell
*PIC*

Pinocytosis
-Pinocytosis (cell drinking)
-Endosomes "drink" extracellular fluid
*PIC*

Phagocytosis
-Phagocytosis (cell eating)
-pseudopodia (psuedo=false, podia= feet)
-engulf large objects in phagosomes
*PIC*

Exocytosis
-Is the reverse of endocytosis
*PIC*

Summary
-The 7 methods of transport
*PIC*

What is transmembrane potential?

Electrical Charge
-Inside cell membrane is slightly negative, outside is slighty positive
-Unequal charge across the cell membrane is transmembrane potential
-Resting potential ranges from -10 mV to -100 mV, depending on cell type

How do cells reproduce?


Cell Life Cycle
Most of a cell's is spent in a nondividing state (interphase)
*PIC*

3 Stages of Cell Divison
-Body (somatic) cells divide in 3 stages:
-DNA replication duplicates genetic material exactly
-Mitosis divdes the genetic material equally
-Cytokinesis divides cytoplasm and organelles into 2 daughter cells

Interphase
-The nondividing period:
-G zero phase: specialized cell functions only
-G1 phase: cell growth, organelle duplication, protein synthesis
-S phase: DNA replication and histone synthesis
-G2 phase: finishes protein synthesis and centriole replication

DNA Replication
-DNA strands unwind
-DNA polymerase attaches complementrary nucleotides
*PIC*

Mitosis
-Mitosis divides duplicated DNA into 2 sets of chromosomes:
-DNA coils tightly into chromatids
-chromatids connect at a centromere
-protein complex around centremere is kinetochore

Stage 1: Prophase
*PIC*

Features of Prophase
-Nucleoli disappear
-Centriole pairs move into cell poles
-Microtubules (spindle fibers) extend between centriole pairs
-Nuclear envelope disappears
-Spindle fibers attach to kinetochore

Stage 2: Metaphase
*PIC*

Features of Metaphase:
-Chromosomes align in a central plane (metaphase plate)

Stage 3: Anaphase
*PIC*

Features of Anaphase
-Microtubules pull chromosomes apart
-Daughter chromosmes groups near centrioles

Stage 4: Telophase
*PIC*

Features of Telophase
-Nuclear membranes reform
-Chromosomes uncoil
-Nucleoli reappear
-Cell has 2 complete nuclei

KEY CONCEPT:
-Mitosis duplicates chromosomes in the nucleus for cell division

Stage 4: Cytokinesis
-Division of the cytoplasm
*PIC*

Features of Cytokinesis
- Cleavage furrow around metaphase plate
-Membrane closes, producing daughter cells

What regulates cell division?

Miotic Rate and Energy
-Rate of cell division:
-slower miotic rate means longer cell life
-cell division requires energy (ATP)

Long Life, Short Life
-Muscles cells, neurons rarely divide
- Exposed cells (skin and digestive tract) live only days or hours

Chemicals Controlling Cell Division
*PIC*

Regulating Cell Life
-Normally, cell division calances cell lose

Factors Increase Cell Division
-Increase cell division:
-internal factors (MPF)
-extracelluar chemical factors (growth factors)

Factors Decrease Cell Division
-Decreases cell division:
-repressor genes (faulty repressors cause cancers)
-worn out telomeres (terminal DNA segments)

Cancer
*PIC*

Cancer Stages
-Cancer develops in steps:
-abnormal cell
-primary tumor
-metastasis
-secondary tumor

Cell Division and Tumors
-Tumors (neoplasm):
-enlarged mass of cells
-abnormal cell growth and division

Benign Tumors
-Benign tumor:
-contained
-not life threatening

Malignant Tumors
-Malignant tumor:
-spread into surrounding tissues (invasion)
-start new tumors (metastasis)

Cancer and Cells
-Cancer:
-illness that disrupts cellular controls
-produces malignant cells

Cancer and Genes
-Oncogenes:
-mutated genes that cause cancer

KEY CONCEPT:
-Mutations disrupt normal controls over cell growth and division
-Cancers often begin where stems cell are dividing rapidly
-More chromosome copies mean greater chance of erroe

What makes cells different?

Cell Diversity
-All cells carry complete DNA instructions for all body functions

Cell Differentiation
-Cells specialize or differentiate:
-to form tissues (liver cells, fat cells, and neurons)
-by turning off all genes not needed by that cell

KEY CONCEPT:
-All body cells except sex cels, contain the same 46 chromosomes
-Differntiation depends on which genes are active and whcih are inactive

Summary
-Structures and functions of human cells
-Structures and functions of membranous and nonmenbranous organelles
-ATP, Mitochondria, and the process of aerobic cellular respiration
-Structures and functions of the nucleus:
-control functions of nucleic acids
-structures and replication of DNA
-DNA and RNA in protein synthesis
-Structures and chemical activities of the cell membreane:
-diffusion and osmosis
-active transport proteins
-vesicles in endocytosis and exocytosis
-electrical propertes of plasma membrane
-Stages and processes of cell division:
-DNA replication
-mitosis
-cytokinesis
-Links between cell division, energy use, and cancer