Cell and macromolecules

Simplified and explained according to the syllabus

1. Cell and macromolecules 1.Cellular classification 2.Subcellular organelles 3.Macromolecules and Macromolecular Assemblies B. REVATHI VIPS

2. 1. Cellular classification THE DYNAMIC CELL The cell comes from the Latin cellula , meaning “a small room”. The cell is the structural and functional unit of all living organisms . The cell was discovered by Robert Hooke in 1665. Human contains about 10 trillion cells. Most plant and animal cells are between 1 and 100µm and therefore are visible only under the microscope.

3. Types of cells There are two types of cell. Prokaryotic and eukaryotic . Prokaryotic ( Prokaryotic word derived from Greek meaning- before nuclei) -lack a nucleus or membrane-bound structures. Ex- Bacteria, Cyanobacteria. Eukaryotic ( Greek- eu means good and karyon means nut or kernel) - have a nucleus and membrane-bound organelles . Ex- Fungi, Plants, Animals.

4. Prokaryotic cell

5. Prokaryotic cell The bacterial cells are very small (about 1-2 µm diameter and 10 µm long). These cells have 3 shapes- rod, spherical and spiral. The cell division is by binary fission. The structural components of prokaryotic cells: The nuclear material of prokaryotic cell consists of a single chromosome.

6. The flagella and pili are projected from the cell surface. These consist of proteins. They facilitate the movement and communication between the cells. The cells enclosed by cell envelop . This consists of plasma membrane and cell wall. Some bacteria also have another layer- capsule . This envelop gives the rigidity to the cell. Inside the cell is the cytoplasm is present that contains the cell genome (DNA), ribosomes and various cell inclusions . The DNA is condensed to a nucleoid . There are circular structures called plasmids, which carry extra chromosomal DNA.

7. Eukaryotic cells These cells contain complex structures enclosed within the membranes. The membrane bound nucleus is present in these cells. Most of these cells also contain other membrane bound organelles such as mitochondria, chloroplast and the Golgi apparatus . All species of large complex organisms are eukaryotes, including animals, plants and fungi .

8. Animal cell

9. Comparison between animal and plant

10. 2. Subcellular organelles (eukaryotes) A cell consists of a plasma membrane inside which there are a number of organelles floating in a watery fluid called cytosol . Organelles are small structures with highly specialised functions, many of which are contained within a membrane . They include: the nucleus , mitochondria, ribosomes, endoplasmic reticulum,Golgi apparatus, centrioles, lysosomes , microfilaments and microtubules.

11. Cell structure and organelles

12. Plasma membrane It consist of two layers of phospholipids (fatty substances) with some protein molecules embedded in them. The phospholipid molecules have a head which is hydrophilic and a tail which has no charge and is hydrophobic . The phospholipid bilayer is arranged like a sandwich These differences influence the transfer of substances across the membrane.

13. Plasma membrane Functions of membrane proteins in plasma membrane: These provide channels for passage of electrolytes and non-lipid-soluble substances. Acts as receptors Some are enzymes Some provide immunological identity

14. Nucleus The Nucleus-Brain of Cell Bordered by a porous membrane - nuclear envelope . Contains thin fibers of DNA bind with histone protein called Chromatin . During cell division thread like structures condensed to form Rod Shaped Chromosomes (contains genes). Contains a small round nucleolus – produces ribosomal RNA which makes ribosomes. 

15. Nucleoli The nuclei of most cells contain one or more highly staining structures called nucleoli. • it is simply an accumulation of large amounts of RNA and proteins of the types found in ribosomes. • The nucleolus becomes considerably enlarged when the cell is actively synthesizing proteins . Functions of nucleus: It contains the body's genetic material, which directs the activities of the cell and synthesis all the proteins required.

16. Mitochondria • Power house of the cell Double Membranous, sausage shaped • It’s the size of a bacterium • Contains its own DNA- mitochondrial DNA • Produces high energy compound ATP  Cristae –cell respiration (aerobic) occurs.

17. Ribosomes Small non-membrane bound organelles. • Contain two sub units (60s+40s ( 80s) eukaryotes) • Site of protein synthesis . • Protein factory of the cell • Either free floating or attached to the Endoplasmic Reticulum.

18. Endoplasmic Reticulum • Series of interconnecting membranous canals • Two types: 1. Smooth ER - ribosome free and functions synthesis of lipids and steroids and also in poison detoxification . 2. Rough ER - contains ribosomes and releases newly synthesised protein from the cell.

19. Golgi apparatus Flattened membranous sacs . M odifies , packages, stores, and transports materials out of the cell. • Works with the ribosomes and Endoplasmic Reticulum . These are packaged ' into membrane-bound vesicles called secretory granules . The vesicles are stored and transported, through which the proteins are exported

20. L ysosomes  Recycling Center – Recycle cellular debris Formed from secretary vesicles of golgi apparatus. • Membrane bound organelle containing a variety of hydrolytic enzymes . • Internal pH is 5 . Functions: • Help in digest food particles inside or out side the cell. Autophage (engulfing aged cells) Autolysis (suicidal bags)

21. Cytoskeleton structures Microfilaments -tiny strands of protein-shape and structure of cell. Intermediate filaments Microtubules - contractile protein structures in the cytoplasm- movement of cell organelles and cilia.

22. Centrioles • Found only in animal cells • Paired centrioles found together near the nucleus, at right angles to each other. • Role in building cilia and flagella • Play a role in cellular division, mitosis

23. Vacuoles • Sacs that help in food digestion or helping the cell maintain its water balance. • Found mostly in plants and protists . • Smaller one in animal cell

24. Plant and animal cell organelles and functions

25. 3. Macromolecules and macromolecular assemblies The FOUR Classes of Large Biomolecules or macromolecules present in all cells. • Carbohydrates • Lipids • Protein • Nucleic Acids • Macromolecules are large molecules composed of thousands of covalently bonded atoms. (carbon and hydrogen bonds) • Have different Molecular structure and functions.

26. C ell substances

27. Macromolecles and their importance

28. Carbohydrates These are the sugars and polymers of sugars composed of carbon, oxygen and hydrogen where the carbon atoms are normally arranged in a ring . Two sugar molecules join by condensation and the resulting bond called a glycosidic linkage.

29. Functions of carbohydrates F unction mainly as a source of chemical energy for generating ATP needed to drive metabolic reactions in living cells. P rovides a form of energy storage , e.g. glycogen • F orms an integral part of the structure of DNA ( deoxyribose ) and RNA ( ribose ) C an act as receptors on the cell surface, allowing the cell to recognise other molecules and cells

30. Classification of carbohydrates Monosaccharides –glucose, fructose Disaccharides - sucrose, maltose, lactose. Polysaccharides -starch, glycogen, cellulose, chitin Polysaccharides consists of many sugar molecules forms the macromolecules of the carbohydrates .

31. Starch and glycogen These are polysaccharides that function to store energy. They are composed of glucose monomers bonded together producing long chains. Animals store extra carbohydrates as glycogen in the liver and muscles. Between meals, the liver breaks down glycogen to glucose in order to keep the concentration of glucoses in the blood . Amylopectin is a form of starch that is very similar to glycogen. It is branched but glycogen has more branches.

32. Cellulose and chitin These are polysaccharides that function to support and protect the organism. The cell walls of the plant composed of cellulose . The cell walls of fungi are composed of chitin . Cellulose is composed of beta-glucose monomers S tarch and glycogen are composed of alpha-glucose. Cellulose is the glucose monomers of chitin (N-acetyl glucosamine) have a side chain containing nitrogen. Cotton and wood are composed mostly of cellulose. Humans and most animals do not have necessary enzymes to break the linkages of cellulose or chitin.

33. Lipids Lipids are made up of carbon, hydrogen and oxygen atoms are insoluble in water but soluble in nonpolar solvents . Lipids make 18-25% of body mass in lean adults.  Triglycerides (fat): A molecule of fat consists of three fatty acids, each linked to a molecule of glycerol . They are used in the body for : insulation, protection of body parts (cell membrane) and energy storage.

34. Types of lipids Triglycerides (fats and oils) Phospholipids Steroids E icosanoids (Prostaglandins) A variety of other lipids including fat-soluble vitamins (A,D,E and K ) and lipoproteins.

35. Fats and oils (Triglycerides) These consist of two moeities , a single glycerol molecule and three fatty acid molecules. Fatty acids have a long hydrocarbon chain with a carboxyl (acid) group. Hydrohobic molecules The chains usually contain 16 to 18 carbons . Glycerol contains 3 carbons and 3 hydroxyl groups .

36. Types of fats 1. Saturated fat - Palmitic acid (C15H31 COOH), stearic acid (C15H35COOH), butter, cocoa butter, coconut oil, meats, etc . 2. Unsaturated fats Monounsaturated fats- Eg- olive oil, peanut oil. These fats are decrease the risk of heart disease. Poly unsaturated fats- Eg- corn oil, sunflower oil, soybean oil and fatty fish.

37. Phospholipids They have a structure like triglycerides, but contain a phosphate group in place of the third fatty acid. The phosphate group is polar and therefore capable of interacting with water molecule. These are amphipathic in nature, as they have both polar and nonpolar groups . Phospholipids form a bilayer in a watery environment.eg Cell membrane.

38. Steroids Steroids differs from triglycerides. They have four rings of carbon atoms. Body cells synthesize other steroids from cholesterol. Cholesterol has a large nonpolar region consisting of the four rings and a hydrocarbon tail. The steroids of the body are cholesterol, estrogens, testosterone, cortisol, bile salts, and vitamin D.

39. Important functions of the steroids 1.Cholesterol is needed for cell membrane structure . 2.Estrogen and testosterone are required for regulating sexual functions . 3.Cortisol is needed for maintaining the stress of body. 4.Bile salts are needed for lipid digestion and absorption . 5.Vitamin D is related to bone growth.

40. Proteins Proteins are large molecules that contain hydrogen, oxygen and nitrogen . Some proteins also contain sulfur. Proteins have complex structure. The proteins make up 12-18% of body mass in a lean adult. Proteins have many roles in the body and are largely responsible for the structure of the body tissues and functioning of body eg . Enzymes, hormones (insulin), antibodies and carrier molecules (haemoglobin) etc.,

41. Amino acids These are building blocks of proteins. It consist of a carboxylic group (COOH) and an amino group (NH2 ) . 20 amino acids are used as the principal building blocks of protein Amino acid structures: A. Common structure, R = variable side chain. B. Glycine, the simplest amino acid. C. Alanine. D. Phenylalanine

42. Classification of amino acids

43. Peptide bond A peptide bond is formed between two amino acids (NH2 and –COOH), a water molecule is removed. This reaction is dehydration . Dipeptide Tripeptide Polypeptides(10-2000 amino acids)

44. Larger proteins (macromolecules of protein) The large number of charged atoms in a polypeptide chain facilitates hydrogen bonding within the molecule, causing it to fold into a specific 3-dimensional shape is important activity of a protein . Primary structure proteins

45. Types of large protein structure Based on the structure, large proteins are classified as follows Primary structure: Polypeptide chain linked with peptide bonds Secondary structure :  P oly peptide chains linked peptide and hydrogen bonds. Eg . keratin protein present hairs, nails and skin. Secondary structure protein

46. Tertiary structure : Poly peptide chains are linked peptide, hydrogen bonds and sulfhydryl bonds. Tertiary structure protein

47. Quaternary structure 2 or more polypeptide chains, macromolecular assemblies of subunits associate to form a single protein linked with hydrogen bonds, sulfhydryl bonds and ionic bonds. Eg. hemoglobin contains four polypeptide chains.

48. Conjugated proteins Simple proteins contains only proteins Conjugated proteins contain proteins combined with other macromolecules. For example- glycoproteins contain glucose nucleoproteins contain nucleic acids, lipoprotein contains lipids.

49. Nucleotides Nucleotides are defined as phosphoric acid esters of nucleosides. A nucleotide is made up of 3 components, namely a nitrogen base, a pentose sugar and a phosphoric acid. The nucleotides are named according to purines and pyrimidines . Purine : Adenine [A], Guanine [G] Pyrimidine: Thymine [T], Cytosine[C], Uracil. Adenosine monophosphate Guanosine monophosphate Cytidine monophosphate Thymidine monophosphate Uridine monophosphate In addition many nucleotides occur freely in the tissues. They are ADP and ATP. 

50. Bonds linking nucleotides Many nucleotides are linked together to form a polynucleotide chain. Two nucleotides are joined by a phosphodiesterase bond. It is formed between sugar of one nucleotide and phosphate component of another nucleotide. The linking between purines and pyrimidines is brought about by hydrogen bonds . There are two hydrogen bonds between A and T (A=T), and 3 hydrogen bonds between G and C (G= C). The amount of adenine is equivalent to the amount of thymine and the amount of guanine is equivalent to the amount of cytosine.

51. N ucleic acids Nucleic acids are the largest macromolecule in the body and are built from components called nucleotides, which consist of three subunits: • a sugar unit • a base • one or more phosphate groups linked together. Nucleic acids are found in all organisms such as plants, animals, bacteria and viruses . Deoxyribonucleic acid (DNA ) Ribonucleic acid (RNA )

52. DNA D ouble strand of poly nucleotide chains arranged in a spiral (helix) The nucleotides contain the sugar deoxyribose, phosphate groups and one of nitrogenous bases. The DNA contains four different types of nucleotides. Deoxy Adenosine monophosphate Deoxy Guanosine monophosphate Deoxy Cytidine monophosphate and Deoxy Thymidine monophosphate.

53. Structure of DNA The two chains of a DNA are complimentary to each other. At one end of the polynucleotide chain, the 3rd carbon atom of the sugar is free and it is not linked to any nucleotide. This end is called 3 prime (3’) end . At the other end of the 5th carbon of the sugar is free and this end is called 5prime (5’) end.

54. Types of DNA Circular DNA / plasmid DNA (prokaryotes) Double stranded DNA (Eukaryotes)

55. Functions of DNA DNA acts as the template for protein synthesis and is stored safely in the nucleus . It acts as the carrier of genetic information from generation to generation. It plays an important role in all biosynthetic and hereditary functions of all living organisms. It controls all developmental processes of an organisms and all life activities. DNA synthesizes RNA s

56. RNA It is a nucleic acid containing ribose sugar with single strand of nucleotides (nitrogenous base, sugar and phosphate). It contains no thymine, instead contains uracil [U ] ( uridine monophosphate). Present in cytoplasm and nucleus. Function: Synthesised in the nucleus from the DNA template, and carries the message instructing synthesis of a new protein from the DNA (which cannot leave the nucleus) to the protein-synthesis (ribosomes) in the cell cytoplasm.

57. Types of RNA Messenger RNA (mRNA ) :  Its sequence is copied from genetic DNA  and travels to cytoplasm during proteins synthesis. Ribosomal RNA ( rRNA ) : Ribosomes are a complex of proteins and rRNA . The rRNA provides both structure and catalysis. Transfer RNA ( tRNA ) : Transports amino acids to the ribosomes where they are joined together to make proteins 

58. ATP ( energy currency of the body) ATP is a nucleotide which contains ribose (the sugar unit ), adenine (the base) and three phosphate groups attached to the ribose. Number of reactions release energy , e.g. the breakdown of sugars in the presence of Oxygen. . The body captures the energy released by these reactions, using it to make ATP from adenosine diphosphate (ADP).

59. Functions of ATP D rive synthetic reactions (i.e. building biological molecules ) F uel movement T ransport substances across membranes

60. Functions of Nucleotides and Nucleic Acids Nucleotide Functions : – Energy for metabolism (ATP ) – Enzyme cofactors (NAD + Nicotinamide adenine dinucleotide ) – Signal transduction ( cAMP ) Nucleic Acid Functions (Macromolecular nucleotides) : – Storage of genetic info (DNA) – Transmission of genetic info (mRNA) – Processing of genetic information ( ribosomes) – Protein synthesis ( tRNA and rRNA )

61. Macromolecular assembly (MA) • The term macromolecular assembly (MA) refers to massive chemical structures such as viruses and non-biological nanoparticles cellular organelles and membranes and ribosomes, They are complex mixtures of polypeptide, polynucleotide, polysaccharide or other polymeric molecules.

62. Examples for macromolecular complexes Protein complexes RNA-protein complexes:  ribosome. Such complexes in cell nucleus are called  ribonucleoproteins  (RNPs). DNA-protein complexes:  nucleosome . Protein-lipid complexes:  lipoprotein

63. They are generally the mixtures of macromolecules are defined spatially (i.e., with regard to their chemical shape), and with regard to their underlying chemical composition and structure [1]. Eg :Each subunits of Ribosomes is assembly –poly peptide chains and rRNA