Y1 Biology 131 Syllabus - Academic Year 2015-2016 (1st Semester)

Day Date Topic PageNo.

Tuesday 20September2016 CellandCellOrganelles CMB47- 53

Wednesday 21September2016 BiologicalMembranes CMB9- 17Sunday 25September2016 TutorialMonday 26September2016 Cytoskeleton CMB17- 32

Tuesday 27September2016 ExtracellularMatrix CMB35- 40

Wednesday 28September2016 CellAdhesion CMB41- 45Sunday 02October2016 AlHijriNewYear- راس السنة الھجریةMonday 03October2016 StemCellsandTheirDifferentiation CMB2- 8

Tuesday 04October2016 MembraneTransportMechanisms LB131- 137

Wednesday 05October2016 ActiveTransport&GlucoseTransport LB140-150Sunday 09October2016 TutorialMonday 10October2016 PurinesandPyrimidinesI LB131- 137Tuesday 11October2016 AshooraWednesday -عطلة عاشورا 12October2016Sunday 16October2016 TutorialMonday 17October2016 PurinesandPyrimidinesII LB140- 150Tuesday 18October2016 ReviewoftheCellStructureSection -

CMB- CellandMolecularBiology

LB- Lippincott- Biochemistry

CELL AND ORGANELLES

Cell Structure and Function• All living organisms are made of

cells.

• A cell (Latin cella meaning “small room”) is the basic structural, functional and biological unit of all living organisms.

• Cells are the smallest unit of life that can replicate independently, called the "building blocks of life".

• Cells are of different size and shape which is related to its specific function.

Cell Size

• On an average, prokaryotic cells range from 1-10 µm and eukaryotic cells are 10-100 µm typically about 10X the size of prokaryotic cells.

Organelles• Organelle is defined as a specialized subunit within a cell that

has a specific function, and is separately enclosed within its own membrane.

• The term organelle comes from the idea that these structures are to cells, what an organ is to the body.

• The nucleus is like the "brain of the cell" and all it's instructions, the chromosomes.

• The mitochondria is the "stomach" of the cell, giving it energy and supplying it with nutrients.

• Together with the cytosol (liquid portion of cell), the organelles help to form the cytoplasm.

• Organelles do not float freely within the cytosol but are interconnected and joined by a framework called as cytoskeleton.

Prokaryotic and Eukaryotic CellsProkaryoticCells EukaryoticCells

SmallCells(<5μm) LargerCells(>10μm)

AlwaysUnicellular Oftenmulticellular

Nonucleusoranymembrane- boundorganelles,suchasmitochondria

Alwayshavenucleusandothermembrane-boundorganelles

DNAiscircular,withoutproteins DNAislinearandassociatedwithproteinstoformchromatin

Ribosomesaresmall(70S) Ribosomesarelarge(80S)

Nocytoskeleton Alwayshasacytoskeleton

Celldivisionisbybinaryfission Celldivisionisbymitosisormeiosis

Prokaryotic and Eukaryotic Cells

NucleusStructure

• Nucleus is the largest organelle in mammalian cells.

• It occupies about 10% of the total cell volume.

• It appears as a dense, roughly spherical organelle.

• Viscous liquid within it is called nucleoplasm.

• The outer most structure of the nucleus is the nuclear envelope which is a double-layered membrane with nuclear pores to permit transfer of materials between the nucleus and the cytosol.

Nucleus

Structure• The space between the

membranes of the envelope is called the perinuclear space.

• DNA in the form of chromosomes are present in the nucleoplasm.

• The nuclear lamina which is the protein foldings of thenucleoplasm forms an association between the DNA and the inner nuclear membrane.

NucleusStructure

• The chromatin which is the DNA-protein complex is of two forms:

• Euchromatin which is the less compact DNA form, and contain genes that are frequently expressed by the cell. The other type, heterochromatin, is the more compact form, and contains DNA that is infrequently transcribed.

• Nucleolus is a densely stained structure found in the nucleus not surrounded by a membrane. •It surrounds the DNA coding for ribosomal RNA. •The main role of the nucleolus is to synthesize rRNA and assemble ribosomes.

Function• Nucleus provides a site for genetic processing that is separated

from the location of protein synthesis in the cytoplasm. This is important for controlling processes on either side of the nuclear membrane.

• Main function of the nucleus is to control gene expression and help the replication of DNA during the cell cycle.

• Newly synthesized mRNA formed from DNA in the nucleus get exported to the cytoplasm.

Nucleus

RibosomesStructure

• Ribosome is a large complex molecular machine, found within all living cells, that serves as the primary site of protein synthesis.

• It is made up of dozens of distinct proteins as well as a few specialized RNA molecules known as ribosomal RNA (rRNA).

• Both are arranged into two distinct parts of different size, known as the large subunit and small subunit of the ribosome.

•Prokaryotes have 70S ribosomes, each consisting of a small (30S) and a large (50S) subunit whereas eukaryotes have 80S ribosomes, each consisting of a small (40S) and large (60S) subunit.

Function• Ribosomes can bind to an mRNA chain and use it as a template for

determining the correct sequence of amino acids in a particular protein.

• The attached amino acids are then linked together to form polypeptide which fold to produce a specific functional three-dimensional structure.

Ribosomes

• Free ribosomes: They can move about anywhere in the cytosol, but are excluded from the nucleus and other organelles. Proteins that are formed from free ribosomes are released into the cytosol and used within the cell.

• Membrane-bound ribosomes: When a ribosome begins to synthesize proteins that are needed in some organelles, that ribosome can become "membrane-bound". In eukaryotic cells this happens in a region of the endoplasmic reticulum (ER).

• Bound ribosomes usually produce proteins that are used within the plasma membrane or are expelled from the cell.

Ribosomes

Endoplasmic ReticulumStructure

• Endoplasmic reticulum (ER) are like a series of interconnected flattened tubes.

• The membranes of the ER are continuous with the outer membrane of the nuclear envelope.

• The ER forms a network of membrane enclosed, interconnected spaces that constitute the ER lumen, which expandes in sacs known as cisternae.

• Endoplasmic reticulum occurs all types of eukaryotic cells, except in red blood cells and spermatozoa.

Function• There are two types of endoplasmic reticulum, rough endoplasmic

reticulum (RER) and smooth endoplasmic reticulum (SER).

• The outer face of the RER is studded with ribosomes that are the sites of protein synthesis. RER prominent in cells such as hepatocytes where active protein synthesis occurs.

• The SER lacks ribosomes and functions in lipid and carbohydrate metabolism, and detoxification. They are especially abundant in mammalian liver and gonad cells.

Endoplasmic Reticulum

Golgi ComplexStructure

• Working outward from nucleus and the ER, the next organelle is Golgi complex.

• Also known as the Golgi Apparatus, Golgi body, or simply the Golgi.

• Golgi is composed of stacks of membrane-bound structures known as cisternae.

• Four and eight cisternae are usually present in a stack.

• Each cisterna comprises a flat, membrane enclosed disc that includes special enzymes which modify or help to modify cargo proteins that travel through it.

Golgi ComplexFunction

• Golgi complex has three regions; the cis which is closest to the ER; the medial; and the trans which is near the plasma menbrane.

• Each region is responsible for performing distinct modifications, such as addition of carbohydrates, phosphate or proteolysis, to the newly synthesized proteins.

• The trans region sorts and packages the newly modified proteins in transport vesicleswhich buds off from the main golgi complex and travel to their final

destination according to the tag placed on them.

Mitochondria

Structure• Mitochondrion (plural

mitochondria).• Mitochondria contains outer and

inner membrane.• Because of this double-

membraned organization, there are five distinct parts to a mitochondrion:

• the outer mitochondrial membrane

• the intermembrane space (the space between the outer and inner membranes)

• the inner mitochondrial membrane, • the cristae (formed by infoldings of the inner membrane) • the matrix (space within the inner membrane).

MitochondriaStructure

• The matrix contains DNA in circular arrangement, ribosomes, fat deposits and enzymes for different metabolic processes.

• Their unique membranes help them to generate ATP.Due to this it is also called as “the powerhouse” of the cell.

• The DNA is inherited from mothers.

MitochondriaFunction

• Inner membrane: It contains components of a system to produce energy which brings about synthesis of ATP by process called as oxidative phosphorylation.

• Outer membrane: It allows most ions and molecules to move from cytosol of cell to intermembranous space and act as supply to the inner impermeable mitochondrial membrane.

Mitochondria

Function

• Matrix: Along with DNA and ribosomes it contains enzymes for oxidation of carbohydrates, fatty acids and amino acids.

• Kearns-Sayre syndrome: caused by a large defect in mitochondrial DNA resulting defective mitochondria in turn resulting in paralysis of eye muscles and degeneration of the retina.

LysosomesStructure

• Lysosome (derived from the Greek words lysis, meaning "to loosen", and soma, "body") is a membrane bound organelle, with an internal acidic pH 5.

• Formed by pinching of proteins from golgi complex.

• They are frequently nicknamed "suicide bags" or "suicide sacs" due to their autolysis.

• Contain potent enzymes collectivelly called as acid hydrolases.

LysosomesFunction

• Lysosomes are the recycling units of a cell.

• Lysosomes are interlinked with three intracellular processes namely phagocytosis, endocytosis and autophagy.

• Extracellular materials such as microorganisms taken up by phagocytosis, macromolecules by endocytosis and unwanted cell organelles are fused with lysosomes in which they are broken down to their basic molecules, autophagy.

Lysosomes

• Any defect or absence of acid hydrolases present in lysosomes results in improper recycling and hydrolysis of macromolecules.

• As a result compounds accumulate in the lysosomes, building up to toxic levels causing a class of diseases known as lysosomal storage diseases.

• Tay-Sachs disease occurs when the lysosome is missing the enzyme needed to digest a ganglioside found in nerve cells.

PeroxisomesStructure

• Called peroxisomes because of their ability to produce or utilize hydrogen peroxide..

• They are small, oval or spherical in shape.

• About 50 enzymes have been identified, which are synthesized on free ribosomes.

PeroxisomesFunction

• Fatty acids and purines are broken down.

• Hydrogen peroxide, a toxic by-product of many metabolic reactions is detoxified in peroxisomes.

• Within hepatocytes, peroxisomes participate in cholesterol and bile acid synthesis.

• Zellweger syndrome: occurs due to defect in transporting of enzymes to peroxisomes in liver, kidney and brain, resulting in improper fatty acid metabolism and defective detoxification. Individuals do not survive beyond 6 months of age.

Summary• A cell is the basic structural,

functional and biological unit of all living organisms.

• Prokaryotic cell are small, unicellular and lack a membrane-bound nucleus.

• Eukaryotic cell can be uni-and multicellular and have a well defined membrane bound nucleus and organelles.

• Organelle is defined as a specialized subunit within a cell that has a specific function

Peroxisome

• Eukaryotic cell contain cellular organelles such as: Nucleus, Ribosomes, Endoplasmic reticulum, Golgi apparatus, Mitochondria, Lysosomes, Peroxisomes.