Biology Chapter on Proteins and Nucleic Acids

Proteins have diverse roles like catalysis, structure, storage, transport, hormone regulation, muscle contraction, and defense.

Pepsin and Amylase are examples of proteins that speed up biochemical reactions.

Nucleotides are the building blocks of nucleic acids.

A nucleotide has three parts: a pentose sugar, a nitrogenous base, and a phosphate group.

Purines have two rings (Adenine, Guanine), while Pyrimidines have one ring (Cytosine, Thymine, Uracil).

Deoxyribose sugar has one less oxygen atom than ribose.

A nucleoside is a nucleotide without a phosphate group.

Two main types of nucleic acids are DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).

Cilia and flagella are cellular projections with a 9+2 microtubule arrangement, covered by plasma membrane, and anchored to a basal body (9+0 arrangement).

Cilia and flagella are used for movement (propulsion) and moving fluids over cell surfaces.

Centrioles are cylindrical microtubule structures found in animal cells, arranged in triplets (9+0).

Cell movement is enabled by various cellular components including cilia, flagella, and pseudopodia.

The cytoskeleton helps maintain the shape and structure of the cell, particularly in animal cells.

The cytoskeleton (including filaments) anchors organelles and enzymes within the cytoplasm.

Cytoplasmic streaming is the movement in the cytoplasm enabling distribution of materials, and positioning of organelles within the cell.

The cytoskeleton plays a role in cell division, such as cleavage furrow formation (animal cells).

Lignin cements cellulose fibers together, creating a strong, rigid plant cell wall.

Channels that connect the cytoplasm of adjacent plant cells.

Structures where neighboring animal cell membranes join.

Cell junctions that seal adjacent animal cells tightly.

Cell junctions that mechanically attach animal cell cytoskeletons.

Animal cell junctions that create channels for material exchange.

A complex network of proteins and carbohydrates outside animal cells.

The most abundant glycoprotein in animal ECM, forming strong fibers.

A groove in the cell membrane that forms during cytokinesis in animal cells, pinching off the cytoplasm and creating two daughter cells.

A structure formed in the middle of a dividing plant cell during cytokinesis, eventually developing into a new cell wall.

Mitosis ensures genetic stability, supports growth and development, facilitates cell repair and regeneration, and enables asexual reproduction.

A type of cell division that produces four haploid, genetically diverse daughter cells from a diploid parent cell. This process is essential for sexual reproduction.

The pairing and physical connection of homologous chromosomes during prophase I of meiosis.

A tumor is a mass of abnormal cells that forms when single cells in a tissue undergo transformation and proliferate.

The exchange of genetic material between non-sister chromatids of homologous chromosomes during synapsis in prophase I of meiosis.

The visible points of crossing over between homologous chromosomes, seen after the synaptonemal complex disassembles.

A benign tumor is a non-invasive tumor that remains confined to its original site. Most benign tumors are not harmful and can be removed surgically.

A malignant tumor is a cancerous tumor that invades surrounding tissues and can spread to other parts of the body.

In animal cells, during prophase I of meiosis, centrosomes move towards opposite poles and form spindle fibers that attach to chromosomes.

Metastasis is the process by which cancer cells spread from the original tumor to distant parts of the body.

Galls are abnormal growths on plants caused by an imbalance of plant growth regulators like auxins and cytokinins, often triggered by viruses, fungi, bacteria, insects, or mites.

Metabolism is the sum of all biochemical reactions occurring in a living organism, involving both catabolic and anabolic processes.

Catabolism is the breakdown of complex molecules into simpler ones, releasing energy in the process.

Anabolism is the synthesis of complex molecules from simpler ones, requiring energy input.

International textbooks used for Advanced Level science subjects in Sri Lanka had issues like contradicting facts, content beyond the local curriculum, and difficulty in understanding for teachers and students.

This textbook offers students the opportunity to study relevant subject content in the mother tongue, within the limits of the local curriculum. It also provides reliable information aligned with the curriculum.

The book is written by science subject specialists and university lecturers, ensuring accuracy and quality.

The textbook has been reviewed and approved by the Academic Affairs Board and the Council of the National Institute of Education (NIE).

Dr.(Mrs.)T.A.R.J.Gunasekara is the Director General of the National Institute of Education.

Mr.R.S.J.P.Uduporuwa is the Director of the Science Department at the National Institute of Education.

Miss.P.T.M.K.C.Tennakoon is the Assistant Lecturer in the Science Department and the Subject Leadership for Biology.

Mrs.H.M.Mapagunarathna (Senior Lecturer) and Mrs.D.A.H.U.Sumanasekara (Assistant Lecturer) from the National Institute of Education contributed to this resource.