Histology: The Cell Intro and Nucleus

Organism

Living being

Protoplasm

Living substance of all organisms is known as ….

Cell

Smallest unit of protoplasm capable of independent existence

Cell

Basic structural and functional unit of life

Bacteria and archaea

Simplest organisms

Prokaryotic cell

No nucleus or organelles

Human cell

Small mass of protoplasm

Karyoplasm

Protoplasm inside the nucleus is called…

Cytoplasm

The remaining part minus the karyoplasm is …..

200

How many different types of cells are in the human body?

WBC and ova

Free cell examples

5 to 50 micrometer

Diameter of human cells

120 micrometer

Mature ovum diameter

Upto 150 micrometer

Diameter of large neurons

Plasma membrane

Cell membrane is also called ….

Plasmalemma

Cell membrane is also called ….

Cell membrane

Envelops the cell completely and acts as a selective structural barrier between the contents of the cell and contents of the extracellular space

7\.5nm

Thickness of the cell membrane under the electron microscope

Trilaminar

Cell membrane is …..

7\.5 nm to 10 nm

The variable range of the thickness of the cell membrane

Phospholipids, proteins, cholesterol

Cell membrane is composed of ……,…..,….

Bimolecular

Cell membrane consists of a …. Layer of phospholipids

Embedded proteins and cholesterol

The lipid bilayer has …..

Fluid

Lipid bilayer is …. In nature

Polar head and nonpolar tail

Each phospholipid molecule consists of a …and ….

Head of a phospholipid molecule

Composed of glycerol conjugated to a nitrogenous compound by a phosphate bridge

Choline, serine, or ethanolamine

The nitrogenous compound may be …,…,…

Two long chains of fatty acids

Non polar chain of each phospholipid molecule is made up of …..

Covalently

The two long fatty acid chains are … linked to the glycerol component of the polar head

Between the long fatty acid chains

Where does cholesterol lie?

Cholesterol

Stiffens the cell membrane

50%

Protein molecules make up approx…. Of the total membrane mass

Integral and peripheral

Membrane proteins can be divided into …and …

Integral protein

These proteins are either embedded within the lipid bilayer or pass through the bilayer completely

Peripheral proteins

These proteins are not embedded in the lipid bilayer, they stay loosely associated with the integral proteins

Weak electrostatic forces

What binds the peripheral proteins to the integral proteins

Integral proteins

Most of the membrane proteins are ….

Transmembrane protein

These proteins pass through the lipid bilayer from side to the other

Oligosaccharides

….are attached on the surface of the plasma membrane which faces away from the cytosol

Glycocalyx

Dense meshwork of glycoproteins and glycolipids

Epithelial cells

Glycocalyx is mostly found in …..

Fuzzy layer

Glycocalyx appears as a … under the EM

Cell coat

Glycocalyx is also called…

Help cell recognize other cells, help in cell association and adhesion, serve as receptor sites for hormones

Moleucles of the glycocalyx enable the cell to….

Luminal surface of the small intestine and endothelial cells of blood vessels

Examples of glycocalyx

Passive transport

No input of energy is involved

Passive diffusion and facilitated diffusion

Two types of passive transport

Passize diffusion

Substances easily pass through the lipid bilayer of cell membrane down their concentration gradient

Fats, fat soluble molecules, small uncharged hydrophobic molecules and dissolved gases

Substances that cross the cm by passive transport

Facilitated diffusion

Substances which require channel proteins

Water and water-soluble molecules like glucose, amino acids and various ions

Substances which use facilitated

Hydrophilic channels

Channel proteins form …..

Active transport

Transporting ions and small molecules against their concentration gradients

Carrier proteins

Active transport requires…..

Continuous extrusion of Na+ out of the cell by sodium pumps

Best example of active transport

Vesicular transport

Mechanism by which large molecules and small particles enter, leave or move within the cell is …

Vesicles

…are membrane bound spherical structures which are formed either by budding off from the cell membrane or other organelles

Endocytosis

Processes of vesicular transport by which substances enter the cells

Pinocytosis, receptor-mediated endocytosis and phagocytosis

3 mechanisms of endocytosis

Pinocytosis

Process by which the fluids and small molecules enter the cell

50-100 nm

Diameter of a pinocytotic vesicle

Receptor mediated endocytosis

Mechanism by which specific macromolecules are allowed to enter the cell

Cargo receptors

Receptor mediated endocytosis depends on the presence of Receptor proteins called…

Cargo receptors

Recognize and bind to specific macromolecules

Clathrin

Cargo receptors become associated with a special protein called…

Phagocytosis

Process by which large particles are engulfed by the phagocytic cells

Ligands

Cell surface receptors respond to ….

Integral glycoproteins

The cell surface receptors are generally the …

Ion channel-linked receptors, enzyme-linked receptors and G protein-linked receptors

3 main types of cell surface receptors

Ion channel linked receptor

Gated channel proteins which require the binding of a ligand to open their gate

Enzyme linked receptors

One pass transmembrane proteins whose outer surfaces serve as receptors for specific ligands

G protein-linked receptors

Multipass transmembrane proteins whose extracellular surfaces function as receptor site for ligands

Adenylate cyclase pathway or phospholipase-c pathway

G Protein linked receptors activate a chain of intracellular events either through ….or ….

Nucleus

Contains the genetic material of the cell, functions as the command center of the cell, controls metabolic activities

Mature erythrocytes

Whigh cell does not contain a nucleus

3 to 10 micrometer

Diameter of a nucleus in a human cell

6 micrometer

Average diameter of a human nucleus

Spherical, oval,fusiform, lobulated, irregular

Different shapes of a nucleus

Center of the cell

Position of nucleus in spherical and polygonal cells

Central position

Position of nucleus in cuboidal, fusiform and squamous cells

Basal region of the cell

Position of nucleus in columnar and pyramidal cells

Binucleate

Liver cells are ….

Nuclear envelope

Nucleus of a resting cell is surrounded by a ….

Two parallel unit membranes

Nuclear membrane is composed of ...

Chromatin

Granules and particles of a basophilic material

Chromatin

….. occupies most of the space in the nuclear envelope

Nucleolus

Round, non membrane bound, dark staining body

Nuclear sap or nuclear ground substance

Semifluid material in the nucleus….

Dark blue or purple line

Nuclear envelope appears as …..under the LM

40 nm thick

EM reveals that the nuclear envelope is ….thick

Perinuclear cisternal space

The space between the 2 parallel unit membranes of the nuclear envelope

Nuclear lamina

Network of protein filaments in the inner nuclear membrane

Supports and stabilises the nuclear envelope

Nuclear lamina function

Ribosomes

The outer membrane of the nuclear envelope is studded with …

Cisternae of RER

Perinuclear cisternal space is connected to ….

Nuclear pores

Small circular openings in the nuclear envelope

70 nm

Diameter of the nuclear pores

Fusion of the outer and inner membranes of the nuclear envelope

How are nuclear pores formed

Function of nuclear pores

Serve as channels through which exchange of materials between the nucleus and cytoplasm occurs

mRNA from nucleus to cytoplasm and histones from cytoplasm to nucleus

Example of substances moving through nuclear pores