HA Cells and Tissues

HA lesson 1

Cell

• smallest living unit

• basic functional unit of complex organisms

level of organization

Atom > Molecule > Cell > Tissue > organ > organ system > Organism

Robert Hooke

Discovered cell

Observed the silver of cork
Saw “row of empty box”

Theodor Schwann and Matthias Schleiden (1839)

“all living things are made of cells”

Rudolf Virchow (1855)

“all cells come from cells”

Principles of Cell Theory

• All living things are made of cells

• Smallest living unit of structure and function of all organisms is the cell

• All cells arise from preexisting cells (this principle discarded the idea of spontaneous generation)

Characteristics of All Cells

• A surrounding membrane

• Protoplasm – cell contents in thick fluid

• Organelles – structures for cell function

• Control center with DNA

Protoplasm

cell contents in thick fluid

Organelles

structures for cell function

Prokaryotic

No nucleus

No membrane enclosed organelles

single chromosome

no streaming in the cytoplasm

cell division without mitosis

Simple flagella

Smaller ribosomes

simple cytoskeleton

no cellulose in cell walls

no histone proteins

Eukaryotic

nucleus

membrane enclosed organelle

chromosome in pairs

streaming in the cytoplasm

cell division by mitosis

complex flagella

larger ribosomes

complex cytoskeleton

cellulose in cell walls

DNA bound to histone proteins

Prokaryotes

DNA:

DNA is naked

DNA is circular

Usually no introns

Organelles:

No nucleus

No membrane-bound

70S ribosomes

Reproduction:

Binary fission

Single chromosome (haploid)

Average size: Smaller (1-5 μm)

Eukaryotes

DNA:

DNA bound to protein

DNA is linear

Usually has introns

Organelles:

Has a nucleus

Membrane-bound

80S ribosomes

Reproduction:

Mitosis and meiosis

Chromosomes paired (diploid or more)

Average size: Larger (10-100 μm)

ORGANELLES

Cell components that perform specific functions for the cell

Cell Membrane

a.k.a Plasmalemma

Selective permeable barrier between cytoplasm and external milieu

Functions:

Maintaining structural integrity of the cell

Controlling movement of substances

Regulating cell to cell interactions

Establishing transport system

Transducing extracellular physical and chemical signals into inter intracellular events

CELL MEMBRANE

A phospholipid bilayer with integral membrane protein and peripheral membrane protein

Polar Head and Nonpolar tail

For cell membrane, each phospholipid molecule comprised of a __________________

Glycocalyx

• Composed of carbohydrate chain

that coats the cell surface

• Function:

⚬ Protection of the cell from

interaction with inappropriate

proteins from chemical and

physical injury

⚬ Cell-cell recognition

⚬ Adhesion

Membrane transport proteins

• Facilitate movement of aqueous molecules and ions across the plasmalemma

• Channel Proteins:

- May be gated or ungated; they are incapable of transporting substance against a concentration gradient

- Voltage-gated channels

- Ligand-gated channels

- Mechanically gated channels

- G-protein-gated ion channels

- Ungated channels (Potassium Leak Channels)

- Aquaporins

MEMBRANE TRANSPORT PROTEINS

• Facilitate movement of aqueous molecules and

ions across the plasmalemma

• CARRIER PROTEINS:

⚬ Can utilize ATP-driven transport mechanisms to ferry specific substances across the plasmalemma against a

concentration gradient

⚬ Primary Active Transport

⚬ Secondary Active Transport

Protein synthetic and package machinery of the cell

Ribosomes

Smooth Endoplasmic Reticulum

Rough Endoplasmic Reticulum

Golgi apparatus

RIBOSOMES

Small particles, composed of proteins and Ribosomal RNA (rRNA)

Function: Surface for Synthesis of Proteins

Composed of a large subunit and small subunit

P-site:

for binding of peptidyl tRNA

A-site

for binding of aminoacyl tRNA

E-site

site for exit of amino acids

Endoplasmic Reticulum

• Largest membranous system of the cell

• Interconnected tubules and vesicles

whose lumen is referred as CISTERNS

⚬ Smooth Endoplasmic Reticulum

(SER)

⚬ Rough Endoplasmic Reticulum (RER)

■ participates in protein synthesis

CISTERNS

Interconnected tubules and vesicles whose lumen is referred as _______

SMOOTH ENDOPLASMIC RETICULUM

Anastomosing tubules and

occasional flattened membrane-bound vesicles

Present in cells active of

steroids, cholesterol and

triglycerides, and cells that

function in detoxification of

toxic materials

Sarcoplasmic reticulum

Sequestering calcium ions from cytosol

Sarcoplasmic reticulum

Sequestering calcium ions from cytosol

Structure of a Smooth Endoplasmic Reticulum

A system of membranous tubules and sacs

Function(s) of a Smooth Endoplasmic Reticulum

Helps move lipids, steroids, and fatty acids within the cell (intracellular highway); regulates calcium levels; breaks down toxic substances

Smooth Endoplasmic Reticulum found in

found in Animal and Plant Cells

Rough Endoplasmic Reticulum

Increased number in cells functioned for Protein Synthesis

Possessed integral proteins recognizing and binding ribosomes

ROUGH ENDOPLASMIC RETICULUM

• Network of continuous sacs, studded with ribosome’s

• Manufactures, processes, and transports proteins for export from cell

• Continuous with nuclear envelope

Golgi Apparatus

• Composed of one or more series of flattened, slightly curved membrane-bounded cisternae, the Golgi stack.

• Functions in the synthesis of carbohydrates and in the

modifications and sorting of proteins manufactured in the RER

Lysosomes

• Round polymorphous shape

• Posses proton pumps that active transports H+ ions

• Have acidic pH 5

• Contains hydrolytic enzymes

• Aid in digesting macromolecules, phagocytosed

microorganisms, cell debris and senescent organelles

Lysosomal Storage Disorder

• Certain individuals with hereditary enzyme deficiencies are

incapable of completely degrading various macromolecules

into soluble by-products.

Tay-Sachs Diseases

⚬ Deficient: Hexosaminidase

⚬ Accumulate GM2 ganglioside

Peroxisomes

• Microbodies or small spherical to ovoid membrane bound organelles

• Contains 40 oxidative enzymes

• Function : catabolism of long chain fatty acids forming Acetyl co enzyme A and Hydrogen peroxide (H2O2)

LYSOSOMES

Membrane bound sacs performing a digestive function

Contains enzymes to digest food, wastes, invading bacteria and breaks down old organelles

Present in animal cells only

Golgi apparatus produces lysosomes

Tay-Sachs disease

PEROXISOMES

Membrane bound sacs performing a digestive function

Enzymes in peroxisomes are oxidases that catalyze redox reactions

Liver contains many peroxisomes to breakdown alcohol

Form by budding off from ER

Present in animal cells only

Mitochondria

• Possess their own DNA and perform oxidative phosphorylation and lipid synthesis

• Flexible, rod-shaped

• Produce ATP, stable storage form of energy that can be used by the cell for its various energy-requiring activities

Cytoskeleton Thin Filaments

actin filament that interact with myosin

Cytoskeleton Intermediate Filaments

establishment and maintenance of the three dimensional framework of the cell

Cytoskeleton Microtubules

long straight rigid tubular appearing structure that act as intracellular pathways

Nucleus

Largest organelle of the cell

Contains nearly DNA or RNA

Nucleolus: Location for the assembly of ribosomal subunits

Nucleolus

Location for the assembly of ribosomal subunits

Nucleus

Bounded by two lipid membranes, has 3 major components:
Chromatin

Nucleolus

Nucleoplasm

CHROMATIN

genetic material

NUCLEOLUS

genetic material

NUCLEUS

• Control center of the cell,

regulates all cell activities

• Stores hereditary information

(DNA)

• Makes RNA and protein

• Makes ribosomes (nucleolus)

Simple Diffusion

is the only form of transport that is not carrier-mediated.

occurs down an electrochemical gradient (“downhill”).

does not require metabolic energy and therefore is passive.

Factors that increase permeability

⚬ ↑ Oil/water partition coefficient of

the solute increases solubility in

the lipid of the membrane.

⚬ ↓ Radius (size) of the solute

increases the diffusion coefficient

and speed of diffusion.

⚬ ↓ Membrane thickness decreases

the diffusion distance.

SIMPLE DIFFUSION

• Small hydrophobic solutes (e.g., O2) have the highest

permeabilities in lipid membranes.

• Hydrophilic solutes (e.g., Na+) must cross cell membranes

through water-filled channels, or pores. If the solute is an ion

(is charged), then its flux will depend on both the concentration

difference and the potential difference across the membrane.

carrier mediated transport

Includes facilitated diffusion and primary and secondary active

Characteristics of carrier-mediated transport

• Stereospecificity

• Saturation

• Competition

Facilitated diffusion

• occurs down an electrochemical gradient (“downhill”), similar to simple diffusion

• does not require metabolic energy and therefore is passive

• is more rapid than simple diffusion

• is carrier-mediated and therefore exhibits stereospecificity, saturation, and competition

FACILITATED DIFFUSION

1. A solute particle enters the channel of a membrane protein (carrier)

2. The solute binds to a receptor site on the carrier and the carrier changes conformation

3. The carrier releases the solute on the other side of the membrane

Process of Facilitated Transport

• Protein binds with molecule

• Shape of protein changes

• Molecule moves across membrane

PRIMARY ACTIVE TRANSPORT

occurs against an electrochemical gradient (“uphill”).

requires direct input of metabolic energy in the form

of adenosine triphosphate (ATP) and therefore is

active.

is carrier-mediated and therefore exhibits

stereospecificity, saturation, and competition.

SECONDARY ACTIVE TRANSPORT

• The transport of two or more solutes is coupled.

• One of the solutes (usually Na+) is transported “downhill” and provides energy for the “uphill” transport of the other solute(s).

• Metabolic energy is not provided directly

OSMOSIS

is the flow of water across a semipermeable membrane from a

solution with low solute concentration to a solution with high solute concentration.

Simple diffusion

Electrochemical Gradient: Downhill

Carrier-Mediated: No

Metabolic Energy: No

Na* Gradient: No

Inhibition of Na*-K* Pump: —

Facilitated Diffusion

Electrochemical Gradient: Downhill

Carrier-Mediated: Yes

Metabolic Energy: No

Na* Gradient: No

Inhibition of Na*-K* Pump: —

Primary active transport

Electrochemical Gradient: Uphill

Carrier-Mediated: Yes

Metabolic Energy: Yes

Na* Gradient: —-

Inhibition of Na*-K* Pump: Inhibits (if Na^+ K^+ pump)

Cotransport

Electrochemical Gradient: Uphill*

Carrier-Mediated: Yes

Metabolic Energy: Indirect

Na* Gradient: Yes, same direction

Inhibition of Na*-K* Pump: Inhibits

Countertransport

Electrochemical Gradient: Uphill*

Carrier-Mediated: Yes

Metabolic Energy: Indirect

Na* Gradient: Yes, opposite direction

Inhibition of Na*-K* Pump: Inhibits

Endocytosis

• Movement of largematerial

⚬ Particles

⚬ Organisms

⚬ Large molecules

• Movement is into cells

• Types of endocytosis

⚬ bulk-phase (nonspecific)

⚬ receptor-mediated (specific)

Process of Endocytosis

Plasma membrane surrounds material

Edges of membrane meet

Membranes fuse to form vesicle

Forms of Endocytosis

Phagocytosis

Pinocytosis

Phagocytosis

Cell eating

Pinocytosis

Cell drinking

Exocytosis

• Reverse of endocytosis

• Cell discharges material

Process of EXOCYTOSIS

• Vesicle moves to cell surface

• Membrane of vesicle fuses

• Materials expelled