Histo (1-5)

Cytoplasm

• has organelles suspended in fluid (cytosol)

Cytoskeleton

• supporting network of tubules and filaments

Plasma membrane

• basic structural feature of eukaryotic cells

• interface with the environment

Plasma membrane: Phospholipid Bilayer

• fluid mosaic model

  • spontaneously form bilayer in aqueous solution

  • intrinsic, extrinsic, and transmembrane proteins

Plasma membrane: Glycocalyx

composed of polysaccharides on outer surface

Phospholipids

• amphipathic

Head of phospholipid

polar (hydrophilic)

Tail of phospholipid

non-polar (hydrophobic)

Cholesterol

• amphipathic

  • kinked in conformation

Why is cholesterol kinked?

prevent packing of hydrophobic ends

Nucleus

• basic structural feature of eukaryotic cells

• contains genetic material of the cell and is limited by a lipid membrane

Nucleus: Two major types of proteins

• histone

• non-histone

Nucleus: Histone proteins

DNA associated protein controlling DNA coiling and gene expression

Nucleus: Non-histone proteins

mainly enzymes for synthesis of DNA and RNA, regulatory proteins (gene regulation)

Nuclear RNA

• mRNA

• tRNA

• rRNA

  • not in cytoplasm!

Heterechromatin

• inactive

• tightly coiled DNA (not transcribing)

• electron dense

Euchromatin

• uncoiled RNA

• actively transcribing RNA

• occurs in the nucleoplasm

Nucleoli

• site of ribosomal RNA synthesis

• assembly of subunits of ribosomes

Nuclear envelope

• two membranes with intermembranous space

Nuclear pores

inner and outer membranes are continuous

DNA codes for?

proteins

Protein synthesis

• Transcription (nucleus)

• Translation (Ribosomes)

Transcription

• DNA to mRNA

Translation

mRNA → specific amino acid sequence

• will eventually fold into a protein

Ribosomes are responsible for?

• translation of mRNA to amino acid sequences/proteins

  • can function free in cytosol or attached to the rER

ER (rough)

interconnected network of membranous tubules and flattened sacs

• studded w ribosomes

  • proteins destined for export or incorporation into lysosomes

ER (smooth)

interconnected network of membranous tubules and flattened sacs

• no ribosomes

• cholesterol and phospholipid synthesis

Passive diffusion

• dependent on concentration gradient across PM

Facilitated Diffusion

• concentration dependent

• no energy, but requires reversible binding to protein carrier molecules

• pores/molecules

Active transport

• concentration independent

  • requires energy (ATPase)

Bulk transport

• membrane bound vacuoles containing large molecules or particles

Exocytosis

• bulk transport out of cytoplasm (protein secreting cells)

Endocytosis

• bulk transport into cytoplasm (phagocytosis, receptor mediated endocytosis)

Principle organelle involved in cellular energy production (ATP)?

mitochondria

Golgi apparatus

• major organelle in cellular secretions

• exocytosis of proteins/large molecular weight secretory products

• associated with RER

Example of a cell with a good golgi apparatus?

• plasma cells have an abundant rough ER and GA due to excretion of antibodies

Phagocytosis

• monocyte, lymphocyte, neutrophil

• ingest and kill pathogenic organisms

  • can form phagolysosomes by fusing w lysosomes

RM endocytosis

uptake of specific molecules (ligands) that bind to the cell surface

• receptors bound with ligand are concentrated in clathrin

  • vesicles will lose clathrin and fuse with sorting endosomes

Where does aerobic respiration take place in mitochondria?

matrix and inner membrane

Components of cytoskeleton

• microfilaments

• intermediate filaments

• microtubules

Microfilaments

• actin

  • forms supporting meshwork called the cell cortex

Intermediate filaments

• larger than microfil

  • bind structures to one another and to membrane proteins (cytokeratin)

Microtubules

• globular proteins

• allow for alterations in cell shape and position of organelles

  • important w cilia and cell division

Cilia: where to find?

• respiratory tract of epithelium

• ependymal cells lining ventricles in CNS

• reproductive tract

Cilia

• motile specialized structures

• found on apical surface of simple epithelia

• actions result from energy release from ATP mediated by dynein

How do cilia move things along?

• wave like synchronous rhythm propelling surface material in a consistent direction

Microvili: Where to find?

• surface epithelium of the intestinal tract

• choroid plexus cells in CNS

• proximal renal tubules

Microvilli

• epithelial cell surface modification

• finger like projections of PM supported by actin microfilaments

• absorptive function

Goblet cell

• modified columnar cell that secretes mucous

• common in resp. and gastro tracts

Centrosome

• pair of centrioles together with the centrosome matrix

Centrioles will associte with tubulin ring complexes which will form?

center for polymerization of microtubules

Function of organizing center for microtubules of cytoskeleton

• control centromere during cell division/mitosis

  • centrioles attach to microtubules at base of cilia

Mitosis

• yields 2 diploid daughter cells with full complement chromosomes

Meiosis

• yields 4 haploid gametes that each contain half the complement chromosomes

What type of cells undergo meiosis?

germ cells

• produce gametes only

Chiasma formation

• crossing over

• mixes up maternal and paternal alleles and contributes to genetic diversity

  • ONLY in meiosis

Two components of connective tissue

• cells

• extracellular matrix (dominant component)

Classifications of connective tissue

• cartilage

• bone

• blood

• adipose tissue

• lymphatic tissue

Most abundant fiber in the body?

collagen

Properties of collagen

• flexible with high tensile strength

• eosinophilic

Type 1 collagen

fibrous CT (dermis), tendon, ligaments, bone, arranged in high tensile-strength bundles of fibrils

Type 2 collagen

fine fibrils found in hyaline cartilage

Type 3 collagen

• reticulin

  • forms fine networks of fibers supporting highly cellular tissues (liver, bone marrow, lymphoid organs)

  • earliest type of collagen produced during development

Type IV collagen

• does not form fibrils

  • forms a meshwork that is found only in basement membranes

Type VII

forms anchoring fibrils that link to basement membranes

Elastin location

• skin

• lung

• blood

• vessels

Elastin

• short branching fibers

• high capacity for stretch and recoil

• contains cells, fibers, and ground substance

Ground substance

• amorphous transparent extracellular material forming semi-fluid gel that fills the space between cells and fibers

  • allows for exchange of molecules with the circulation

Ground substance: glycosaminoglycans (GAG’s)

• long unbranched polysaccharide chains

• repeating disaccharide units

• negatively charged (acidic)

Predominant GAG in loose CT

Hyaluronic acid

• extremely hydrophilic acid

Basement membranes

• act as an interface between epithelial and parenchymal tissue and the connective tissue

• act as a limiting membrane

What are basement membranes composed of?

collagen IV

Cells of connective tissue are derived from?

mesenchyme

Fibroblast

• most common connective tissue cell

• synthesizes tropocollagen

  • repairs connective tissue (recycling old collagen) and can produce excess collagen in response to stimuli

Supporting CT

cartilage and bone

Proper CT

lies beneath epithelia and parenchyma

Special CT

• adipose

• blood

• lymphatic tissue

• embryonic

Variations of collagenous tissue is based on?

• density

• regularity of packing of collagen bundles

Loose collagenous tissue

• areolar (alot of space)

• highly cellular

  • reticulin or collagen

Dense irregular collagenous tissue

• more fibers than cells

• random weave of fiber bundles (dermis)

• organ capsules

• sheaths of nerve

Dense regular collagenous tissue

• few cells

  • parallel arrays of fibers (ligaments and tendons)

Granulation collagenous tissue

• wound healing by fibroblasts from mesenchymal cells in CT and neocapillaries

• replaces CT after macrophages remove debris

• myofibroblasts provide wound contraction

Adipose tissue types

• white and brown

  • adapted for the storage and processing of fat

  • have receptors for insulin

White adipose tissue

• throughout body (particularly in deep layers)

• important in energy storage (rich blood supply)

• serves as thermal insulator under the skin

  • cushion against mechanical shock

Brown adipose tissue

• specialized

• found mostly in newborns and hibernating mammals

• important in body temp regulation

• highly metabollicaly active

• UCP1 (thermogenin)

Cartilage: Cells

• chondrocytes

• chondroblasts

Chondrocytes

• mature cells of cartilage

• maintains cartilage matrix

• located in lacunae

Chondroblasts

• cartilage forming cells

  • produces ground substance, capable of mitosis, participates in growth of cartilage

Perichondrium

• surrounding layer of collagen fibers and spindle shaped fibroblastic cells

  • can transform into chondroblasts

Cartilage is

avascular

3 types of cartilage

• hyaline

• elastic

• fibrocartilage

hyaline cartilage

• most common

• growth plates of bones and joints

• matrix: type 2 collagen w proteoglycan ground substance

• small nuceli and reside in lacunae

elastic cartilage

• matrix contains elastin and elastic fibers

• also present in perichondrium and disposed between elastic fibers

  • found in ear pinna, epiglottis, and larynx

Fibrocartilage

• intermediate between cartilage and dense fibrous connective tissue

• alternating layers of hyaline cartilage matrix and dense collagen

• tough, high tensile, and compressive strength

Where is fibrocartilage?

intervertebral discs

• menisci pads of joints

• pubic symphysis

Bone

• composed of cells in a mineralized organic matrix

• rigid structural support lattice and calcium reservoir

  • organice matrix is approx. 90% type 1 collagen

Cells of the bone

• osteoblasts

• osteocyte

• osteoclasts

Osteoblasts

• bone formation; synthesizes osteoid

  • located along edge of bony trabeculae

Osteocyte

• resting stage of the osteoblast trapped in matrix