The Cell 2017 Dr. Amjad Shatarat Dr. Maha ELBeltagy Department of Anatomy and Histology Faculty of Medicine University of Jordan 2017

Parts of cell Plasma Membrane Cytoplasm Nucleus Cytosol Organelles (Fluid Party) Organelles

A- Cytosol B- Organelles 1. The plasma membrane forms the cell’s outer surface, separating the cell’s internal environment (everything inside the cell) from the external environment (everything outside the cell). 2. The cytoplasm consists of all the cellular contents between the plasma membrane and the nucleus. This compartment has two components: A- Cytosol B- Organelles Cytosol the fluid portion of cytoplasm, contains water, dissolved solutes, and suspended particles. Within the cytosol are several different types of organelles. the cytoskeleton, ribosomes, endoplasmic reticulum, Golgi complex, lysosomes, and mitochondria. 3. The nucleus is a large organelle that houses most of a cell’s DNA.

Structure of the Plasma Membrane The basic structural framework of the plasma membrane is the lipid bilayer Two back-to-back layers made up of three types of lipid molecules: A-Phospholipids about 75% of the membrane lipids are Phospholipids B-Cholesterol C-Glycolipids

Why the PLASMA membrane occurs in bilayer arrangement? The bilayer arrangement occurs because the phospholipids are Amphipathic molecules It means that phospholipid have both polar and nonpolar parts. The polar part is the phosphate-containing “head,” which is hydrophilic (hydro- water; -philic loving). The nonpolar parts are the two long fatty acid “tails,” which are hydrophobic (phobic -fearing). In this way, the heads face a watery fluid on either side cytosol on the inside and extracellular fluid on the outside. The hydrophobic fatty acid tails in each half of the bilayer point toward one another, forming a nonpolar,hydrophobic region in the membrane’s interior.

1-Integral 2-Peripheral Arrangement of Membrane Proteins Membrane proteins are classified according to whether they are firmly embedded in the membrane or not into: 1-Integral 2-Peripheral 1-Integral proteins extend into or through the lipid bilayer which means that they span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid 2-Peripheral proteins are not firmly embedded in the membrane. They are attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane.

Functions of integral proteins 1-Form ion channels, pores or holes such as potassium ions (K), can flow through to get into or out of the cell. 2-Act as carriers, selectively moving a polar substance or ion from one side of the membrane to the other. Carriers are also known as transporters. 3-Receptors serve as cellular recognition sites. Each type of receptor recognizes and binds a specific type of molecule. For instance, insulin receptors bind the hormoneinsulin.

4-Act as enzymes that catalyze specific chemical reactions 5- serve as linkers that anchor proteins in the plasma membranes of neighboring cells to one another or to protein filaments inside and outside the cell.

2-CYTOPLASM The cytosol (intracellular fluid) is the fluid portion of the cytoplasm that surrounds organelles A-Cytosol B-Organelles The cytoskeleton is a network of protein filaments Three types of filamentous proteins contribute to the cytoskeleton’s structure 1-Microfilament Are the thinnest elements of the cytoskeleton. They are composed of the proteins ACTIN AND MYOSIN . 2- Intermediate 3-Microtubules Largest of the cytoskeletal components. are hollow tubes composed mainly of the protein Tubulin. Microtubules help determine cell shape. They also function in the movement of organelles such as secretory vesicles.

B-Organelles 1-Centrosome Specialized structures with characteristic shapes. Each organelle has specific functions. 1-Centrosome Pair of centrioles plus pericentriolar material. The pericentriolar material contains Tubulins

FUNCTIONS OF RIBOSOMES are the sites of protein synthesis. The name of these tiny structures reflects their high content of one type of ribonucleic acid, ribosomal RNA (rRNA), FUNCTIONS OF RIBOSOMES 1. Ribosomes associated with endoplasmic reticulum synthesize proteins. 2. Free ribosomes synthesize proteins used in the cytosol

3-Endoplasmic Reticulum (ER) 1-Rough ER is continuous with the nuclear membrane and usually is folded into a series of flattened sacs. The outer surface of rough ER is studded with ribosomes, Functions: synthesizes glycoproteins and phospholipids detoxify certain drugs. 2-Smooth ER extends from the rough ER to form a network of membrane tubules Unlike rough ER,smooth ER does not have ribosomes on the outer surfaces of its membrane Function: synthesizes fatty acids and steroids, such as estrogens and testosterone

1- An entry face is a cisterna (faces the rough ER). 4-Golgi Complex Most of the proteins synthesized by ribosomes attached to rough ER are ultimately transported to other regions of the cell through Golgi complex It consists of cisternae small, flattened membranous sacs with bulging edges that Consists of 1- An entry face is a cisterna (faces the rough ER). 2-The exit face (faces the plasma Membrane). Sacs between the entry and exit faces are called medial cisternae. FUNCTIONS OF GOLGI COMPLEX 1. Modifies, sorts, packages, and transports proteins received from the rough ER. 2. Forms secretory vesicles.

5-Lysosomes are vesicle formed from Golgi complex that contain several types of powerful digestive enzymes. FUNCTIONS OF LYSOSOMES 1. Digest substances that enter a cell via endocytosis. 2. the digestion of worn-out organelles. 3. Implement autolysis, the digestion of an entire cell.

Genes are arranged along chromosomes Nucleus The nucleus is a spherical or oval-shaped Most cells have a single nucleus, some, such as mature red blood cells, have no nucleus a few other types of cells have multiple nuclei for example, skeletal muscle cells. Within the nucleus are most of the cell’s hereditary units, called genes, which control cellular structure and direct cellular activities. Genes are arranged along chromosomes

Human somatic (body) cells have 46 chromosomes, 23 inherited from each parent.. Each chromosome is a long molecule of DNA that is coiled together with several proteins This complex of DNA, proteins, and some RNA is called chromatin. The DNA replicates (duplicates) and the loops condense even more, forming a pair of chromatids. a pair of chromatids constitutes a chromosome

SUMMARY

Plasma Membrane lipid bilayer Protein Integral Peripheral A-Phospholipids about 75% B-Cholesterol C-Glycolipids Integral Peripheral Function 1-Ion channels (K,Na) 2-Receptors (Insulin) 3-Act as enzymes

Organelles 1-Centrosome :Pair of centrioles ,it contains Tubulins 2-Ribosomes : sites of protein synthesis 3-Endoplasmic Reticulum : A- Rough Endoplasmic Reticulum : ( is studded with ribosomes,) 1- Synthesizes glycoproteins and phospholipids. 2-Detoxify certain drugs. B- Smooth Endoplasmic Reticulum : (does not have ribosomes ) synthesizes fatty acids and steroids, such as estrogens and testosterone 4-Golgi Complex : 1. Modifies, sorts and transports proteins. 2. Forms secretory vesicles. 5-Lysosomes 1. Digest substances that enter a cell via endocytosis. 2. Digestion of worn-out organelles.

Nucleus Single nucleus NO nucleus Multiple nuclei As mature red blood cells Multiple nuclei As skeletal muscle cells Within the nucleus cell’s hereditary units, called genes. Genes are arranged along chromosomes. Human somatic (body) cells have 46 chromosomes, 23 inherited from each parent. Each chromosome is a long molecule of DNA that is coiled together with several proteins. Function of Nucleus : Control Cellular structure Direct Cellular activities Produce Ribosomes