HISTOLOGY CELLS AND NUCLEUS

HISTOLOGY

Is the study of tissues, their functions and their arrangement to constitute an organ.

TISSUES

Group of cells with interrelated functions

Blastomeres

first zygotic cellular differentiation

Differentiation

specialization process of stem cells

Muscle and other contractile cells

Movement

Epithelial cells

Form adhesive and tight junctions between cells

Fibroblasts, cells of bone and cartilage

Synthesize and secrete components of the extracellular matrix

Neurons and sensory cells

Convert physical and chemical stimuli into action potentials

Cells of digestive glands

Synthesis and secretion of degradative enzymes

Cells of mucous glands

Synthesis and secretion of glycoproteins

Certain cells of the adrenal gland, testis, and ovary

Synthesis and secretion of steroids

Cells of the kidney and salivary gland ducts

Ion transport

Macrophages and neutrophils

Intracellular digestion

Fat cells

Lipid storage

Cells lining the intestine

Metabolite absorption

Cells and extracellular material

together comprise the tissues that make up animal organs.
In all tissues, ____are the basic structural and functional units, the smallest living parts of the body.

Cell membrane

border of the cell

Nucleus

Largest organelle; situated in the center; circular in shape, DNA rich

Nucleolus

another circular shape in the cell, RNA rich

Cell membrane, Nucleus, Cytoplasm

3 basic parts of the cell

Solid portion

organelle

Fluid portion

cytosol

Cytoplasm

organelles + cytosol + inclusion bodies

CYTOSKELETON

Maintains intracellular structural support and organization of cells; participates in cell division; facilitates movement

microtubules, actin filaments, intermediate filaments

cytoskeleton three types of polymers

microtubules

25 nm in diameter

actin filaments or microfilaments

(5-7 nm)

intermediate filaments

(8-10 nm)

RIBOSOME

are macromolecular machines that assemble polypeptides from amino acids on molecules of transfer RNA (tRNA) in a sequence specified by mRNA

Smooth Endoplasmic Reticulum (SER)

*Biosynthesis of Lipids
*Regions of ER that lack bound polyribosomes make up the_, which is continuous with RER but frequently less abundant
*Also create proteins (enzymes) that perform synthesis of phospholipids and steroids, allows detoxification, and sequestration an controlled release of Calcium

Rough Endoplasmic Reticulum
(RER)

Biosynthesis of Proteins, Studded with Ribosomes

GOLGI APPARATUS (golgi complex)

Completes posttranslational modifications of proteins produced in the RER and then packages and addresses these proteins to their proper destinations

SECRETORY GRANULES

Originating as condensing vesicles in the Golgi apparatus, secretory granules are found in cells that store a product until its release by exocytosis.

PEROXISOMES

are small spherical organelles containing enzymes for various metabolic reactions, notably for oxidation and detoxification, and catalase that breaks down the H2O2 resulting from those reactions.

Vesicles/granules

contains protein to be secreted via exocytosis

Lysosomes

Contains enzymes. Binds with endocytosed vesicles for digestion.

Proteosome

Degrade improperly folded proteins

MITOCHONDRIA

Powerhouse of the cell, Are the major sites of ATP synthesis and are abundant in cells or cytoplasmic regions where large amounts of energy are expended.

CENTROSOME

Amorphous region adjacent to nucleus; contains a pair of centrioles; Organizes microtubules

Organizes microtubules

participates in mitotic spindle formation during cell division

INCLUSION BODIES

*Contain accumulated metabolites or other substances
*Little to no metabolic activity
*Most are stored units or cell product
*May or may not be present in the cell
*Examples: Lipid droplets, Glycogen granules, Melanin, Lipofucsin, Hemosiderin

Lipofucsin granules

represent an accumulating by-product of lysosomal digestion in long-lived cells

Melanin

protect the cell nuclei from damage to DNA caused by light

Hemosiderin granules

pigment deposits that contain the protein ferritin (form a large complex with iron)

protein ferritin

(form a large complex with iron)

PLASMA MEMBRANE

*Other names: Cell membrane of plasmalemma
*Consists of phospholipids, cholesterol, and proteins, with oligosaccharide chains
*Forms a selective barrier regulating the passage of materials into and out of the cell
*Keep constant the ion content of the cytoplasm
*Membrane phospholipids are amphipathic
*2 nonpolar (hydrophobic) long-chain fatty acids
*Phosphate head/group

amphipathic

Membrane phospholipids are ____,
which means a molecule has both a hydrophili part, and a hydrophobic part

Phospholipids

are organized in a lipid bilayer

Hydrophobic fatty acid chains

located in a middle region, away from water.

phosphate cell

head

fatty acid chain

tail

Cholesterol

insert at varying densities restricting their movement and modulating fluidity

glycolipids

Outer layer contains

Glycocalyx

a carbohydrate-rich layer on the cell's surface, composed of glycoproteins, glycolipids, and other polysaccharides

glycolipids and glycoproteins

Act as receptors and for transport of solutes

Integral proteins,
Transmembrane proteins,
Peripheral proteins,
Multipass proteins

Act as receptors and for transport of solutes

Integral proteins

are firmly embedded in the lipid layers

Transmembrane proteins

subset of integral proteins that completely span the bilayer are called

Peripheral proteins

bound only to one of the two membrane surfaces

Monotopic

(a-helix bound to one side of the membrane)

Biotopic

(a single-pass transmembrane a-helix)

Polytopic

(a multi-pass transmembrane a-helix)

Cholesterol molecules

fit between fatty acid chains in a lipid bilayer.

-Cholesterol

has hydrophobic ring and Hydrophilic hydroxyl group

Phospholipids

have the ability to move around the cell membrane together with the membrane proteins.

Plasma membrane

site where materials are exchanged between the cell and its environment.

Diffusion,
Channels,
Carriers

Most small molecules cross the membrane by the general mechanisms as follows:

Operate passively

allows movement of substances across membranes down a concentration gradient

Diffusion

transports small, nonpolar molecules directly through the lipid bilayer.
fat-soluble molecules diffuse through membranes readily

Channels

Multipass proteins forming transmembrane pores through which ions (Na, K, Ca, etc.) or small molecules pass selectively.

Aquaporins

type of channel that allows passage of water molecules

Carriers

Transmembrane proteins that bind small molecules and translocate them across the membrane via conformational changes.

Membrane pumps

are enzymes/proteins engage in active transport utilizes energy from ATP against concentration gradients .They consume ATP hence they are called ATPase

PASSIVE PROCESSES

Movement of substances down a concentration gradient due to the kinetic energy of the substance; no expenditure of cellular energy is required; continues until equilibrium is reached (if unopposed)

Simple diffusion

Unassisted net movement of small, nonpolar substances down their concentration gradient across a selectively permeable membrane
Exchange of oxygen and carbon dioxide between blood and body tissues

Facilitated diffusion

Movement of ions and small, polar molecules down their concentration gradient; assisted across a selectively permeable membrane by a transport protein

Channel-mediated

Movement of ion down its concentration gradient through a protein channel
Na⁺ moves through Na⁺ channel into cell

Carrier-mediated

Movement of small, polar molecule down its concentration gradient by a carrier protein
Transport of glucose into cells by glucose carrier

Osmosis

Diffusion of water across a selectively permeable membrane; direction is determined by relative solute concentrations; continues until equilibrium is reached
Solutes in blood in systemic capillaries "pulls" fluid from interstitial space back into the blood

ACTIVE PROCESSES

Movement of substances requires expenditure of cellular energy

Active transport

Transport of ions or small molecules across the membrane against a concentration gradient by transmembrane protein pumps

Primary

Movement of substance up its concentration gradient; powered directly by ATP
Ca2+ pumps transport Ca2+ out of the cell
Na+/K+ pump moves Na+ out of the cell and K+ into the cell

Secondary

Movement of a substance up its concentration gradient is powered by harnessing the movement of a second substance (e.g., Na+) down its concentration gradient

Symport

Movement of substance up its concentration gradient in the same direction as Na+
Na+/glucose transport

Antiport

Movement of substance up its concentration gradient in the opposite direction from Na+
Na+/H+ transport

Passive Transport

Movement of molecules from higher to lower concentration
No energy consumption required

Simple Diffusion

Movement occurs without the use of channel or carrier proteins

Facilitated Diffusion

Movement occurs with the aid of channel or carrier proteins

Active Transport

Requires energy consumption,
Pumps transport molecules from lower to higher concentration (against concentration gradient)

Vesicular Transport

Movement of substances into or out of the cell via vesicles

Exocytosis

– Vesicle formed or lost as material is released from the cell
– Bulk movement of substances out of the cell by fusion of secretory vesicles with the plasma membrane
– Example: Release of neurotransmitter by nerve cells

Endocytosis

– Vesicle formed or lost as material is brought into the cell
– Bulk movement of substances into the cell by vesicles forming at the plasma membrane

Phagocytosis

– Vesicles are formed as particulate materials are engulfed by pseudopodia
 – Example: White blood cell engulfing a bacterium

phagosome

Phagocytosis is where the cell extends folds or pseudopodia to surround and engulf particles like bacteria, forming a cytoplasmic vacuole called a

Pinocytosis

the cell membrane forms folds or dimples to trap extracellular fluid, which then pinches off inside the cell as a vesicle containing the fluid.
 – Example: Formation of small vesicles in capillary wall to move substances

Receptor-Mediated Endocytosis

uses membrane receptors to bind specific molecules (ligands). When receptors bind ligands, they cluster together, and the membrane folds inward to form a vesicle containing the receptors and ligands.
 – Example: Uptake of cholesterol into cells

G-coupled protein

composed of 7 transmembrane proteins and alpha, beta and gamma protein subunits

Ligands

bind to the G coupled receptor which later cause the activation of the alpha, beta and gamma subunits

ANKYRIN, ACTIN

peripheral proteins

SPECTRIN

a peripheral protein that will make the ankyrin and actin interact with each other, major membrane skeleton protein.