Cell Division: Biology GRD101 PDF

Cell division results in daughter cells – The ability of organisms to produce more of their own kind is the one characteristic that best distinguishes living things from nonliving matter. – This unique capacity to procreate, like all biological functions, has a cellular basis. – The continu...

Cell division results in daughter cells – The ability of organisms to produce more of their own kind is the one characteristic that best distinguishes living things from nonliving matter. – This unique capacity to procreate, like all biological functions, has a cellular basis. – The continuity of life is based on the reproduction of cells or cell division. 10/14/2024 GRD101 Biology - Cell Growth and Division 5 (p; 285) What are the functions of cell division? 1. Asexual reproduction: When a prokaryotic cell divides, it is reproducing, because the process gives rise to a new organism (another cell) 2. Growth and development: As for multicellular eukaryotes, cell division enables each of these organisms to develop from a single cell— the fertilized egg. A two- celled embryo, the first stage in this process 3. Tissue renewal: Cell division continues to function in renewal and repair in fully grown multicellular eukaryotes, replacing cells that die from accidents or normal wear and tear 10/14/2024 GRD101 Biology - Cell Growth and Division 6 Cellular Organization of the Genetic Material – A cell’s DNA, its genetic information, is called its genome. 1. A prokaryotic genome is often a single DNA molecule 2. Eukaryotic genomes usually consist of several DNA molecules. Prokaryotes: Eukaryotes: Single DNA molecule Several Number of DNA molecules 10/14/2024 GRD101 Biology - Cell Growth and Division 7 Cellular Organization of the Genetic Material – The DNA molecules are packaged into structures called chromosomes. – The entire complex of DNA and proteins that are the building materials of chromosomes is referred to as chromatin. Chromatin = DNA + Histone Protein Chromosome = Supercoiled chromatin 10/14/2024 GRD101 Biology - Cell Growth and Division 8 Number of chromosomes vary in each species : Organism Number of – Every eukaryotic species has a chromosomes characteristic number of chromosomes in (2n) each cell’s nucleus; Human 46 1. The nuclei of human somatic cells (all body cells) each contain 46 Dog 78 chromosomes, made up of two sets of 23 (2n), one set inherited from each parent. Cat 38 2. Reproductive cells, or gametes (such as Pea plant 14 sperm and eggs) have one set of 23 (1n) chromosomes. Camel 70 10/14/2024 GRD101 Biology - Cell Growth and Division 9 (p; 285) Karyotypes –Chromosomes can be visualized using a karyotype. –Karyotypes are prepared from dividing (mitotic) cells that have been arrested during cell division (metaphase stage). –Why do scientists use Karyotyping? 1. To detect the abnormal number of chromosomes: congenital disorders 2. Defective chromosomes 10/14/2024 GRD101 Biology - Cell Growth and Division 10 Distribution of Chromosomes During Eukaryotic Cell Division Chromosomal Chromosomes DNA molecules Sister chroma&ds During cell division, the 1 Centromere two sister chromatids of each duplicated Chromosome chromosome separate arm and move into two Chromosome duplica&on nuclei 2 Centromere Once separate, the Sister chromatids are called chroma&ds chromosomes Separa&on of sister chroma&ds 3 10/14/2024 11 Types of Cell Division Mitosis Meiosis Take place in somatic cells Take place in reproductive cells to form gametes (sperm and egg cells) Two daughter cells are formed with identical genetic Four daughter cells are formed with non-identical genetic background background Number of chromosome sets remains diploid (2n) in Number of chromosome becomes haploid (1n) in daughter cells daughter cells Necessary for growth and repair Necessary for sexual reproduction 10/14/2024 GRD101 Biology - Cell Growth and Division 12 The Cell Cycle –Somatic cells divide by mitosis to grow, repair and regenerate. – A cell cycle is a series of events that takes place (MM ) PIT in a cell as it grows and divides. HOASTEIC The cell cycle in a dividing cell has two main steps: 1. Interphase (90%): where the DNA replicates 2. M- phase: Which DNA is distributed into two nuclei and two cells are separated 10/14/2024 GRD101 Biology - Cell Growth and Division 13 Sub-phases of Interphase a) G1 phase: a) The longest phase of the cell cycle b) Cells grow, and metabolic activities occur. b) S phase: a) DNA Synthesis occurs b) Chromosomes duplicated c) G2 phase: a) Growth b) Preparation for cell division 10/14/2024 GRD101 Biology - Cell Growth and Division 14 Sub-phases of M-Phase a) Mitosis a) Division of the nucleus b) Duplicated DNA separated. b) Cytokinesis a) Division of cytoplasm b) Formation of two daughters of two cells 10/14/2024 GRD101 Biology - Cell Growth and Division 15 Cell Division Copyright ©2021 John Wiley & Sons, Inc. 16 The Mitotic Phase Alternates with Interphase in the Cell Cycle 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Chromosomes condense The chromosomes The two sister chromatids of Nuclear envelopes (DNA is replicated by still have all arrived at the each pair get separated. is formed at each connected) metaphase plate, a end. plane that is midway The two new daughter Nuclear envelope between the spindle’s chromosomes begin moving The chromosomes disappears two poles. toward opposite ends become less condensed. 10/14/2024 GRD101 Biology - Cell Growth and Division Cytokinesis: A Closer Look − The division of the cytoplasm is cytokinesis. − It usually happens by late telophase, − In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow (made from actin and myosin) − In plant cells, a cell plate forms during cytokinesis (made from coalesce; cell wall material) 10/14/2024 GRD101 Biology - Cell Growth and Division 18  Events of the Somatic Cell Cycle (1 of 2) Phase Ac2vity Interphase Period between cell divisions; chromosomes not visible under light microscope. G1 phase Metabolically active cell duplicates most of its organelles and cytosolic components; replication of chromosomes begins. (Cells that remain in the G1 phase for a very long time and possibly never divide again are said to be in the G0 phase.) S phase Replication of DNA and centrosomes. G2 phase Cell growth, enzyme and protein synthesis continue; replication of centrosomes complete. Copyright ©2021 John Wiley & Sons, Inc. 19  Events of the Somatic Cell Cycle (2 of 2) Phase Ac2vity Mitotic phase Parent cell produces identical cells with identical chromosomes; chromosomes visible under light microscope. Mitosis Nuclear division; distribution of two sets of chromosomes into separate nuclei. Prophase Chromatin fibers condense into paired chromatids; nucleolus and nuclear envelope disappear; each centrosome moves to an opposite pole of the cell. Metaphase Centromeres of chromatid pairs line up at metaphase plate. Anaphase Centromeres split; identical sets of chromosomes move to opposite poles of cell. Telophase Nuclear envelopes and nucleoli reappear; chromosomes resume chromatin form; mitotic spindle disappears. Cytokinesis Cytoplasmic division: A contractile ring forms a cleavage furrow around the center of the cell, dividing cytoplasm into separate and equal portions. Copyright ©2021 John Wiley & Sons, Inc. 20 The Cell Cycle Control System − The cell cycle is a process derived from specific chemical signals present in the cytoplasm − The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is like a clock − Both internal and external controls regulate the cell cycle control system 10/14/2024 GRD101 Biology - Cell Growth and Division 21 The Cell Cycle Checkpoints −The clock has specific checkpoints where the cell cycle stops until a go- ahead signal is received −There are 3 checkpoints: G1, G2, and metaphase 22 −Some cells enter Non-dividing or resting state called as G Phase. Stop and Go Signs: Internal and External factors act as stop-and-go signals for the cell cycle. External signals that influence cell division include; 1. Growth factors 2. Density-dependent inhibition 3. Anchorage dependence 10/14/2024 GRD101 Biology - Cell Growth and Division 23 What happens when cells do not follow the control system ? − When cells do not follow the stop and go signals, they lose control on Unwanted cell division division. − these cells are called as Cancer cells. − Cancer cells do not respond normally to the body’s control mechanisms. 10/14/2024 GRD101 Biology - Cell Growth and Division 24 Cancer Cells − A normal cell is converted to a cancerous cell by a process called transformation. − Cancer cells that are not eliminated by the immune system form tumors, masses of abnormal cells within otherwise normal tissue. − If abnormal cells remain only at the original site, the lump is called a benign tumor. − Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form additional tumors 10/14/2024 GRD101 Biology - Cell Growth and Division 25 What is Cancer ? 10/14/2024 GRD101 Biology - Cell Growth and Division 26  Types of Cancer o Melanoma: cancerous growths of melanocytes, skin epithelial cells that produce the pigment melanin. o Sarcoma: is a general term for any cancer arising from muscle fibers or connective tissues. o Osteogenic sarcoma: (osteo- = bone; -genic = origin), the most frequent type of childhood cancer, destroys normal bone tissue. o Leukemia: (loo-KĒ-mē-a; leuk- = white; -emia = blood) is a cancer of blood- forming organs characterized by rapid growth of abnormal leukocytes (white blood cells). o Lymphoma: (lim-FŌ-ma) is a malignant disease of lymphatic tissue—for example, of lymph nodes. Copyright ©2021 John Wiley & Sons, Inc. 27  Cancer causes  Carcinogens:  A chemical agent or radiation that produces cancer  Carcinogens induce mutations, permanent changes in the DNA base sequence of a gene  Cigarette tar, UV radiations  Oncogenes or cancer-causing genes:  When inappropriately activated, these genes could transform a normal cell into a cancerous cell.  Most oncogenes derive from normal genes called proto-oncogenes that regulate growth and development. Copyright ©2021 John Wiley & Sons, Inc. 28 Cancer Treatment Methods Radiation therapy: use of high-energy particles to destroy cancer cells Damages their DNA so they can’t continue to divide or grow Usually used on localized tumors and cancers close to the surface Typically performed after surgical removal of tumor. Chemotherapy: To treat metastatic cancers, drugs that selectively target the dividing cells are used Often, a combination of different drugs (“cocktail”) is used to interrupt cell division in different ways. Helps prevent resistance to the drugs from arising Normal dividing cells are also killed (hair follicles, bone marrow, stomach lining) 10/14/2024 GRD101 Biology - Cell Growth and Division 29 Reproduction- To form new species Asexual reproduction: – Only from one parent cell passes all of its genes to its offspring without the fusion of gametes – Offspring cells are genetically identical (Clones)to the parent cell Sexual reproduction: – Two parents give rise to offspring – Offspring are genetically different from one another and from the parents 10/14/2024 GRD101 Biology - Cell Growth and Division 31 Binary Fission in Bacteria (Asexual Reproduction) –Prokaryotes (bacteria and archaea) Origin of Cell wall reproduce by a type of cell division replica&on Plasma called binary fission (Asexual form of E. coli cell membrane Bacterial reproduction) 1 Chromosome Two copies chromosome replica&on begins. of origin –In binary fission, the chromosome replicates (beginning at the origin of 2 One copy of the Origin Origin replication, Ori), and the two origin is now at daughter chromosomes actively each end of the cell. move apart 3 Replica&on 4nishes. –The plasma membrane pinches inward, dividing the cell into two 4 Two daughter –No mitotic spindle formation cells result. Sexual Reproduction – Two parents give rise to offspring that have unique combinations (variation) of genes inherited from the two parents – This is because of sexual reproduction – DNA is arranged in chromosomes – Different species have different numbers of chromosomes – This needs a special cell called gametes which are haploid 10/14/2024 GRD101 Biology - Cell Growth and Division 33 Haploid and Diploid cells in Human Human somatic cells are diploid cells because have 23 pairs (2n) of chromosomes (a total of 46 chromosomes);  22 + 22 = 44 are autosomal chromosomes  1 + 1 = 2 are sex chromosome; Human females (XX) Human males (XY) Human gamete cells (sperm or egg) are haploid, which means have 23 chromosomes (1n);  22 autosomal chromosomes  1 single-sex chromosome  In an unfertilized egg (ovum), the sex chromosome is X  In a sperm cell, the sex chromosome may be either X or Y 10/14/2024 GRD101 Biology - Cell Growth and Division 34 Sets of Chromosomes in Human Cells During DNA synthesis in a cell, each chromosome is replicated Each replicated chromosome consists of two identical sister chromatids The two chromosomes in each pair are called homologous chromosomes, or homologs Homologs are the same length and shape and carry genes controlling the same inherited characters 10/14/2024 GRD101 Biology - Cell Growth and Division 35 Sexual Life Cycle Figure 13.6 Three types of sexual life cycles. Gametes are the only haploid cells in animals They are produced by meiosis and undergo no further cell division before fertilization Gametes fuse to form a diploid zygote that divides by mitosis to develop into a multicellular organism 10/14/2024 GRD101 Biology - Cell Growth and Division 36  Key Haploid gametes (n = 23) Sexual Life Cycle Haploid (n) Egg (n) Diploid (2n) Fertilization is the union of gametes (the sperm and the egg) Sperm (n) MEIOSIS FERTILIZATION The fertilized egg is called a zygote Ovary Tes&s Zygote has one set of chromosomes from each parent (2n = 46 chromosomes) Diploid zygote (2n = 46) Gametes (sperm and egg) are the only Mitosis and types of human cells produced by development meiosis, while somatic cells are Mul&cellular diploid produced by mitosis adults (2n = 46) 10/14/2024 GRD101 Biology - Cell Growth and Division 37 The Stages of Meiosis (p; 309-311) Figure 13.7 Overview of meiosis Chromosomes duplicate during Interphase interphase Pair of homologous chromosomes in diploid parent cell The chromatids are sorted into four Pair of duplicated Chromosomes duplicate haploid daughter cells, and this is homologous chromosomes carried out through meiosis which Sister Diploid cell with chromatids takes place in two stages: duplicated chromosomes Meiosis I Separating out the Meiosis I 1 homologous pairs into 2 separate Homologous chromosomes cells separate Haploid cells with duplicated chromosomes Meiosis II: Separating out the sister Meiosis II chromatids in each cell to produce 2 Sister chromatids separate 4 haploid cells. 10/14/2024 GRD101 Biology - Cell Growth and Division Haploid cells with unduplicated chromosomes  Figure 13.8 Exploring Meiosis in an Animal Cell 10/14/2024 The Stages of Meiosis (p; 309-311) The Stages of Meiosis – Meiosis I (p; 309-311) The Stages of Meiosis – Meiosis II (p; 309-311) 10/14/2024 41 Crossing Over and Synapsis During Prophase I (p; 312) After interphase, the sister chromatids are held together by proteins called cohesions The non-sister chromatids are broken at precisely corresponding positions A zipper-like structure called the synaptonemal complex holds the homologs together tightly DNA breaks are repaired, joining DNA from one non-sister chromatid to the corresponding segment of another GRD101 Biology - Cell Growth and Division Product of Meiosis Cytokinesis separates the cytoplasm At the end of meiosis, there are four daughter cells, each with a haploid set of unreplicated chromosomes Each daughter cell is genetically distinct from the others and from the parent cell. Note: No chromosome replication occurs between the end of meiosis I and the beginning of meiosis II because the chromosomes are already replicated in Interphase 10/14/2024 GRD101 Biology - Cell Growth and Division 43 A Comparison of Mitosis and Meiosis Mitosis conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell Meiosis reduces the number of chromosomes sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell 10/14/2024 GRD101 Biology - Cell Growth and Division  Comparison Between Mitosis (Left) and Meiosis (Right) Copyright ©2021 John Wiley & Sons, Inc. 45 A Comparison of Mitosis and Meiosis (p; 312) Three events are unique to meiosis, and all three occur in meiosis l; 1. Synapsis and crossing over in prophase I: Homologous chromosomes physically connect and exchange genetic information 2. Homologous pairs at the metaphase plate 3. Separation of homologs during anaphase I 10/14/2024 GRD101 Biology - Cell Growth and Division 46 Origins of Genetic Variation Among Offspring (p; 315) The behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation. Three mechanisms contribute to genetic variation: 1. Independent assortment of chromosomes 2. Crossing over 3. Random fertilization 10/14/2024 GRD101 Biology - Cell Growth and Division 47 1. Independent Assortment of Chromosomes (p; 315) Homologous pairs of chromosomes orient randomly at metaphase I of meiosis In independent assortment, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs The number of combinations possible when chromosomes assort independently into gametes is 2n, where n is the haploid number For humans (n = 23), there are more than 8 million (223) possible combinations of chromosomes 10/14/2024 2. Crossing Over (p; 315-316) Crossing over produces recombinant chromosomes, which combine DNA inherited from each parent Crossing over contributes to genetic variation by combining DNA from two parents into a single chromosome In humans, an average of one to three crossover events occurs per chromosome 10/14/2024 GRD101 Biology - Cell Growth and Division 49 3. Random Fertilization (p; 316) Random fertilization adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg) The fusion of two gametes (each with 8.4 million possible chromosome combinations from independent assortment) produces a zygote with any of about 70 trillion diploid combinations Crossing over adds even more variation Each zygote has a unique genetic identity 10/14/2024 GRD101 Biology - Cell Growth and Division 50 Fundamental Unit of Life and the Cell Theory The cell is the life’s fundamental unit of structure and function. It is the smallest unit of organization that can perform all activities required for life. The Cell Theory states that: – All organisms are made of cells – The cell is the simplest collection of matter that can be alive – All cells are related by their descent from earlier cells (come from pre- existing cells by division) GRD101 Biology_ Eukaryoc Cell Structure & Funcon 4  Types of Cells Cells are the basic structural and functional units of every organism. They are two types: 1. Prokaryotic: Bacteria Archaea 2. Eukaryotic: Protists (unicellular eukaryotes) Fungi Plants Animals and humans GRD101 Biology_ Eukaryoc Cell Structure & Funcon 5  Prokaryotic Cell Lacking a true nucleus and the other membrane-enclosed organelles of the eukaryotic cell. The prokaryotic cell appears much simpler in internal structure. Prokaryotes include bacteria and archaea; the general cell structure of these two domains is quite similar. GRD101 Biology_ Eukaryoc Cell Structure & Funcon 6 Eukaryotic Cell: Animal Cell  Cell Anatomy Link 7  Nuclear NUCLEUS envelope Eukaryotic Cell : Plant Cell Nucleolus Rough ER Chromatin Smooth ER Ribosomes Golgi Central vacuole apparatus Microfilaments CYTOSKELETON Microtubules Mitochondrion Peroxisome Plasma Chloroplast membrane  Cell Anatomy Link Cell wall Plasmodesmata Wall of adjacent cell GRD101 Biology_ Eukaryoc Cell Structure & Funcon 8 Comparing Prokaryotic and Eukaryotic Cells: Recap Prokaryotes Eukaryotes Plasma No nucleus membrane Nucleus DNA in nucleoid Cytoplasm DNA in Nucleus No membrane- Cytosol Membrane-bound bound organelles Chromosomes organelles Ribosomes GRD101 Biology_ Eukaryoc Cell Structure & Funcon 9 Tour into Eukaryotic cells Eukaryotic cells Have internal membranes that partition the cell into organelles (membrane-bound organelles). Plants and animal cells have in common: Nucleus, ribosomes Endomembrane system Mitochondria Peroxisomes, cytoskeleton Plasma membrane  Plant cells have, in addition: Cell wall (only in plants) Chloroplasts (only in photosynthetic eukaryotes) GRD101 Biology_ Eukaryoc Cell Structure & Funcon 10 Cytoplasm The cytoplasm has two components: 1. Cytosol - also known as the intracellular fluid portion of the cytoplasm 2. Organelles - the specialized structures that have specific shapes and perform specific functions  Site of all intracellular activities except those occurring in the nucleus. Copyright ©2021 John Wiley & Sons, Inc. 11  The Nucleus: The information center – It is usually the most visible organelle. – The nuclear envelope encloses the nucleus, separating it from the cytoplasm. The nuclear envelope is a double membrane; each membrane consists of a lipid bilayer. – Nuclear pores regulate the entry and exit of molecules from the nucleus. – The nuclear side of the envelope is lined by the nuclear lamina, which is composed of proteins and maintains the shape of the nucleus (called intermediate filaments proteins). 12 The Endomembrane System The endomembrane system: regulates protein traffic and performs metabolic functions in the cell The endomembrane system consists of; 1. Nuclear envelope 2. Endoplasmic reticulum 3. Golgi apparatus 4. Lysosomes 5. Vacuoles 6. Plasma membrane GRD101 Biology_ Eukaryoc Cell Structure & Funcon 13  Nucleus The nucleus contains the hereditary Genes are arranged along units of the cell, called genes chromosomes Copyright ©2021 John Wiley & Sons, Inc. 14 Ribosomes “Protein Factories”  Ribosomes are complexes made of ribosomal RNA (rRNA) and proteins (1 large subunit and 1 small subunit)  Ribosomes use the information from the DNA to make proteins-translation Copyright ©2021 John Wiley & Sons, Inc. 15 15 The Endoplasmic Reticulum: Biosynthetic Factory – The Endoplasmic Reticulum (ER) is an extensive network of membranes that accounts for more than half of the total membrane in many eukaryotic cells – The ER membrane is continuous with the nuclear envelope – There are two distinct regions of ER  Smooth ER: which lacks ribosomes  Rough ER: whose surface is covered with ribosomes GRD101 Biology_ Eukaryoc Cell Structure & Funcon 16 Functions of Rough ER The Rough Endoplasmic Reticulum (RER): Has bound ribosomes, which secrete proteins into ER lumen ER modifies proteins like glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles which include secretory proteins surrounded by membranes Is a membrane factory for the cell GRD101 Biology_ Eukaryoc Cell Structure & Funcon 17 Functions of Smooth ER The Smooth Endoplasmic Reticulum (SER) assures the following: 1. Synthesizes lipids: including oils, steroids, and phospholipids, to make the new membranes 2. Metabolizes carbohydrates in the liver, which helps regulate sugar in your blood. 3. Detoxifies drugs and poisons: especially in liver cells, add hydroxyl group to make it more soluble. 4. Stores calcium ions: for example, the smooth ER stores calcium in muscle cells. GRD101 Biology_ Eukaryoc Cell Structure & Funcon 18 The Golgi Apparatus (GA): Shipping and Receiving Center –The Golgi apparatus consists of flattened membranous sacs called cisternae. – Functions of the Golgi Apparatus are: 1. Modifies products of the ER 2. Manufactures certain macromolecules (polysaccharides e.g., pectin) 3. Sorts and packages materials into transport vesicles (by adding groups for example phosphate). GRD101 Biology_ Eukaryoc Cell Structure & Funcon 19 Lysosomes: Digestive Compartments –Lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules inside its acidic environment. Some types of cells can engulf another cell by phagocytosis; this forms a food vacuole. A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell’s organelles and macromolecules, a process called autophagy GRD101 Biology_ Eukaryoc Cell Structure & Funcon Macrophage engulng bacteria 20 Vacuoles Vacuoles are single membrane vesicles. Animal cells have small vacuoles and Plant cells have large central vacuoles. Vacuoles perform a variety of functions in different kinds of cells: Animal cell 1. Storage compartment: stores food or waste material 2. Contractile vacuoles: found in many freshwater protists, pump excess water out of cells and help them to live in freshwater. 3. Large Central vacuoles: found in many mature plant cells, hold organic compounds and water. GRD101 Biology_ Eukaryoc Cell Structure & Funcon 21 Peroxisomes: Oxidation Peroxisomes are specialized metabolic compartments bounded by a single membrane. Contain enzymes that use oxygen to oxidize (break down) organic substances Peroxisomes perform reactions with many different functions: Take part in lipid metabolism (breakdown of fatty acids). During lipid metabolism hydrogen peroxide (H2O2) is produced, and peroxisomes convert it to water. In the liver, they detoxify alcohol. GRD101 Biology_ Eukaryoc Cell Structure & Funcon 22 Mitochondria: Chemical Energy Conversion − Mitochondria are the powerhouse of cells. They are present in nearly all eukaryotic cells. − They are sites for cellular respiration and the formation of ATP. − They have a smooth outer membrane and an inner membrane folded into cristae. − Cristae have a large surface area for enzymes that synthesize ATP. − The matrix contains ribosomes for the protein synthesis 23  Chloroplasts: The Site of Photosynthesis The chloroplast is present in plant cells and Algae Chloroplast structure includes: 1. an outer and inner membrane; in between is an intermembrane space. 2. Thylakoids, membranous sacs, stacked to form a granum 3. Stroma, the internal fluid 4. Ribosomes are present 5. Chloroplast is the site for photosynthesis GRD101 Biology_ Eukaryoc Cell Structure & Funcon 24  Mitochondria and chloroplasts change energy from one form to another Chloroplasts - capture sunlight energy and then convert it to chemical energy (glucose) by photosynthesis. Carbon dioxide + Water + Sunlight energy → Glucose + Oxygen + Water Oxygenic photosynthesis: 6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O Mitochondria - Conversion of chemical energy (glucose) to ATP by cellular respiration. Glucose + Oxygen → ATP (Energy) + Carbon dioxide + Heat + Water Cellular respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (38 ATP) + Heat GRD101 Biology_ Eukaryoc Cell Structure & Funcon 25 Cell Wall of Plants – The cell wall is an extracellular structure that distinguishes plant cells from animal cells – Prokaryotes, fungi, and some unicellular eukaryotes also have cell walls – The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water – Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein – The cell wall are connected by cytoplasmic bridges called plasmodesmata GRD101 Biology_ Eukaryoc Cell Structure & Funcon 26 Roles of Cytoskeleton The cytoskeleton is a network of fibers that organizes structures and activities in the cytosol of the cell and thus can function in ; 1. Anchoring many organelles 2. It gives mechanical support to the cell and maintains its shape 3. It interacts with motor proteins to produce motility 4. Inside the cell, vesicles can travel along tracks provided by the cytoskeleton GRD101 Biology_ Eukaryoc Cell Structure & Funcon 27  Roles of Cytoskeleton Three main types of fibers make up the cytoskeleton: Microtubules (tubulin protein units): Help in cell division- spindle fibers Cell Movement- cilia and flagella Intracellular movement of organelles and vesicles Microtubules Microfilaments (actin filaments): Change in cell shape and muscle movement Intermediate filaments (e.g., keratin): Fixing the organelles in place GRD101 Biology_ Eukaryoc Cell Structure & Funcon 28  The Extracellular Matrix (ECM) of Animal Cells Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) The ECM comprises glycoproteins such as collagen, proteoglycans, and fibronectin. ECM proteins bind to receptor proteins in the plasma membrane called integrins Extracellular environment can affect the cell’s behavior by changes in ECM GRD101 Biology_ Eukaryoc Cell Structure & Funcon 29 Cell Juncons Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through three types of cell junctions (direct physical contact). Three types of cell junctions are present in animal cells e.g., in epithelial tissues. 1. Tight junctions 2. Desmosomes 3. Gap junctions  Intercellular Junctions - Animation GRD101 Biology_ Eukaryoc Cell Structure & Funcon 30 Life at the Edge – The plasma membrane is the boundary that separates the living cell from its surroundings – The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others. GRD101 Biology_ Eukaryoc Cell Structure & Funcon 33 Cellular membranes are fluid mosaics of lipids and proteins The fluid mosaic model states that the cell membrane is a mosaic of different protein molecules embedded in a fluid bilayer of phospholipids. ― Fluid – because individual phospholipids can move freely within the layer like a liquid and cholesterol maintain the membrane's fluidity. – Mosaic – because the scattered proteins produce a pattern like a mosaic. – Phospholipids – form the main fabric of the membrane and are the most abundant molecules (structural role) – But proteins determine most of the membrane’s functions (functional role) Components of Cell Membranes The cell membrane is made of three main components: 1. Phospholipids 2. Proteins 3. Cholesterol GRD101 Biology_ Eukaryoc Cell Structure & Funcon 35 1. Phospholipids – Polar phosphate heads (glycerol) are hydrophilic or ‘water-loving’. Face the water in the exterior and the cytosol in the cell’s interior. – Non-polar lipid tails (fatty acids) are hydrophobic or ‘water fearing’. Form layers sandwiched in the middle of the plasma membrane. – Hydrophobic molecules pass easily through the membrane. – Hydrophilic molecules do not pass easily. – Thus, the membrane is ‘selectively permeable’.  Membrane Anatomy Link 2. Proteins The plasma membrane is comprised of Transmembrane proteins different proteins embedded in the lipid integral proteins that cross the membrane from outside to inside bilayer. Two major types: Integral (also called transmembrane) proteins: penetrate the hydrophobic interior of the lipid bilayer Peripheral proteins: are bound to the surface of the membrane o Proteins determine most of the membrane’s specific functions. 37 3. Cholesterol How does cholesterol affect membrane fluidity? The steroid cholesterol has different effects on membrane fluidity at different temperatures; – At warm/moderate temperatures (such as 37°C), cholesterol leads to less fluidity by reducing the movement of phospholipids (more packing) – At cool/low temperatures, cholesterol leads to more fluidity by preventing solidification through disturbing tight packing of phospholipids  Membrane Anatomy Link 38 Major Functions of Membrane Proteins Six major functions of membrane proteins; 1. Transport of molecules across the membrane 2. Enzymatic activity 3. Signal transduction: transfer of signal from ECM to inside cell 4. Cell-cell recognition 5. Intercellular joining 6. Attachment to the cytoskeleton and extracellular matrix (ECM) 39 The Permeability of the Lipid Bilayer DON’T Need the help from transport protein (or called channel protein) Need the help from transport protein (or called channel protein) 40 Cell membrane transport Two major types High concentration Low concentration 1. Passive transport : Molecules move according to the concentration gradient (high to low) without the need of energy 2. Active transport Low concentration High concentration Using energy, molecules move against the concentration gradient (from low to high) Transport Processes Interactions Animation:  Transport Across The Plasma Membrane 41  1. Passive transport Di$usion Three types: 1.Diffusion Hydrophobic molecules (O2 /CO2) move across lipid bilayer according to conc gradient. 2.Facilitated Diffusion Hydrophilic molecules (salt/glucose) move according to concentration gradient using transport proteins. Facilitated Di$usion 3. Osmosis Movement of water across lipid bilayer. GRD101 Biology_ Eukaryoc Cell Structure & Funcon 42 Osmosis The net movement of a solvent (Water) through a selectively permeable membrane from an area of high concentration (solute) to an area of low concentration Copyright ©2021 John Wiley & Sons, Inc. 43  Tonicity - Tonicity of a solution relates to how the solution influences the shape of body cells. Types of solutions across the cell membrane : 1. Isotonic solution: Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane 2. Hypertonic solution: Solute concentration is greater than that inside the cell; the cell loses water 3. Hypotonic solution: Solute concentration is less than that inside the cell; the cell gains water 44 The E$ect of Water Balance on Human Cells Solution type Examples compared to The effect on the cell Human cells Isotonic solution: Normal saline (0.9% NaCl) No change. Hypotonic solution: Water Water enters the cell. Cell bursts or lyse. Hypertonic solution: Sea water Water leaves the cell. Cell shrinks/shrivels or crenate. 45 Active Transport – Active transport moves substances against their concentration gradients (low to high) – Active transport allows cells to maintain concentration gradients that differ from their surroundings – Active transport is performed by membrane proteins called as pumps, e.g. sodium-potassium pump – Sodium potassium pump takes three sodium out of the cell and two potassium into the cell using 1 ATP. sodium-potassium pump GRD101 Biology_ Eukaryoc Cell Structure & Funcon 46 Bulk transport across the plasma membrane Large molecules, such as polysaccharides and proteins, cross the membrane in bulk via vesicles Bulk transport requires energy (Active transport) 1. Exocytosis: cell releasing large molecules outside the cells 2. Endocytosis: cells taking in large molecules GRD101 Biology_ Eukaryoc Cell Structure & Funcon 47 Exocytosis In exocytosis, membrane-enclosed structures called secretory vesicles that form inside the cell fuse with the plasma membrane and release their contents into the extracellular fluid For example, nerve cells use exocytosis to release neurotransmitters that signal other neurons or muscle cells. GRD101 Biology_ Eukaryoc Cell Structure & Funcon 48 Endocytosis  In endocytosis, materials move into a cell in a vesicle formed from the plasma membrane.  There are three types of endocytosis: a) Receptor-mediated endocytosis is cells' selective uptake of large molecules and particles. b) Phagocytosis is the ingestion of solid particles. c) Pinocytosis is the ingestion of extracellular fluid. Also called bulk phase endocytosis Phagocytosis and Pinocytosis a). Phagocytosis b). Pinocytosis Copyright ©2021 John Wiley & Sons, Inc. 50 Copyright ©2021 John Wiley & Sons, Inc. 51  Summary: Types of Cell Transport Types of cell (1) Passive diffusion (2) Active transport transport (small molecules) (2b) Bulk transport (big molecules) (2a) Sodium Sub-types of (1a) (1b) (1c) Facilitated diffusion potassium cell transport Diffusion Osmosis Endocytosis Exocytosis channel (small ions) Movement of High to low High to low High to low Low to high Low to high / High to low molecules Energy No need for No need - No need for energy Need Need energy and transport vesicles requirement energy for energy - Need transport protein energy Example of - Glucose - Gasses - Sucrose Large amounts of molecules like nutrients, proteins transported - Little water Water - Many Water ions and others molecules - Ions  Low to high concentration = Against the concentration gradient  High to low concentration = With the concentration gradient 52 Nucleic Acid  Nucleic acids are polymers of nucleotides  Nucleotides are formed of a phosphate group, a pentose sugar, and a nitrogenous base  There are two types of nucleic acids: 1. DNA (deoxyribonucleic acid) 2. RNA (ribonucleic acid) 10/14/2024 GRD 101-Molecular Genecs 5 Deoxyribonucleic acid (DNA) Purines Pyrimidines DNA is a chain of nucleotides having: (double ring) (single ring) Base NH2 O 1. Phosphate group O – N CH3 H N N O P O CH2 H O 2. Pentose sugar O– N N H N O HH HH Phosphate H ―Deoxyribose H OH H Adenine (A) Thymine (T) 3. Nitrogenous base Deoxyribose O NH2 H ―Purines (double ring)– Adenine (A), H N N H N Guanine(G) N NH2 H O N N H H Guanine (G) Cytosine (C) ―Pyrimidines (single ring) – Cytosine (C), Thymine (T) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10/14/2024 GRD 101-Molecular Genecs 6 Ribonucleic acid (DNA) RNA is a chain of nucleotides having: Base NH2 O O– 1. Phosphate group O P O CH2 N N H N H O H O– N H O 2. Pentose sugar H H HH H N N Phosphate H ― Ribose (ribonucleic Acid) OH OH Adenine (A) Uracil (U) Ribose O NH2 3. Nitrogenous base N H H N N ―Purines (double ring)– H Adenine (A), Guanine (G) N N NH2 H N O H H Guanine (G) Cytosine (C) ―Pyrimidines (single ring) – Cytosine (C), Uracil (U) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10/14/2024 GRD 101-Molecular Genecs 7 Nucleotide numbering system O 4 H CH3 5  Sugar carbons are 1’ to 5’. N 3 Thymine 6 H 2 O O– 1N  Base attached to 1’ carbon on sugar O P O CH2 5′ O O – 1′ 4′ H H H H  Phosphate attached to 5’ carbon on Phosphate 3′ 2′ sugar OH H Deoxyribose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10/14/2024 GRD 101-Molecular Genecs 8 Chain of nucleotides or Strands ― Nucleotides are covalently bonded ― The Backbone has phosphodiester bonds to join phosphate group links to sugar ― Hydrogen bond is formed between two nitrogen bases ― Bases project away from the backbone 10/14/2024 GRD 101-Molecular Genecs 9 DNA is the Genetic Material The Search for the Genetic Material: Scientific Inquiry Early in the 20th century, the identification of the molecules of inheritance was a major challenge to biologists T. H. Morgan’s group showed that genes are located on chromosomes. The two components of chromosomes —DNA and protein—became candidates for the genetic material. Thomas Hunt Morgan 10/14/2024 GRD 101-Molecular Genecs 10 Timeline of the DNA Discovery 10/14/2024 GRD 101-Molecular Genecs 11 Chargaff's Discovery In 1950, Erwin Chargaff reported that DNA composition varies from one species to the next 10/14/2024 GRD 101-Molecular Genecs 12 Chargaff’s rules Chargaff’s rules state the following : 1. The base composition of DNA varies between species 2. In any species the number of A and T bases are equal, and the number of G and C bases are equal. ? ? ? ? 10/14/2024 GRD 101-Molecular Genecs 13 Watson & Crick’s DNA model Watson and Crick combined the studies of Franklin and Chargaff and proposed Watson and Crick DNA Model. The main features of the model are: 1. DNA had two sides or strands with a fixed width, and these strands were twisted together like a twisted ladder - the double helix. 2. The DNA double helix is anti-parallel and elongates in the 5’ to 3’ direction. 3. DNA base pairs (A-T and G-C) on two strands are complementary and are connected via hydrogen bonds. 4. DNA can copy itself by semiconservative mode (which was later proved correct). 10/14/2024 GRD 101-Molecular Genecs 14 DNA double helix C G 5′ end Watson and Crick C G Hydrogen bond 3′ end G C G C T A 3.4 nm T A G C G C C G A T 1 nm C G T A C G G C C G A T A T 3′ end NOTE: New nucleo des can only be A T added at the 3’ end. 0.34 nm Sugar phosphate Backbone T A 5′ end (b) Partial chemical structure DNA is an parallel, so the two strands (a) Key features of Adenine (A) paired only with thymine (T), and elongate in opposite direc ons. DNA structure guanine (G) paired only with cytosine (C)- Justifying Chargaff's rules. 10/14/2024 GRD 101-Molecular Genecs 15 DNA base pairing – Hydrogen bonds! The two strands of DNA are linked and stay in a stable shape because of the many hydrogen bonds linking the base pairs: 2 hydrogen bonds connect A-T 3 hydrogen bonds connect G-C 10/14/2024 GRD 101-Molecular Genecs 16  DNA Replication is Semiconservative The Basic Principle: Base Pairing to a Template Strand The two strands of DNA are The two strands separate and each strand acts as a template for complementary building a new strand in replication 10/14/2024 GRD 101-Molecular Genecs 17 Summary of DNA replication: Overview Leading Origin of strand replication Lagging Leading strand strand 3′ template Leading Single-strand Lagging strand 5′ binding proteins strand Leading Overall directions Helicase strand of replication 5′ DNA pol III 3′ Primer 3′ 5′ 3′ Primase Parenta 5 DNA pol Lagging l 5′ III DNA pol I 4 3′ strand DNA DNA 5′ 3 ligase 3′ 2 1 Lagging strand 5′ template 10/14/2024 GRD 101-Molecular Genecs 18 10/14/2024 GRD 101-Molecular Genecs 19 10/14/2024 GRD 101-Molecular Genecs 20 Central Dogma: The flow of genetic information, named by Francis Crick in 1956 Transcription: is the synthesis of mRNA under the direction of DNA. Translation: is the synthesis of a protein using the information in the mRNA. Ribosomes are the sites of translation/protein synthesis. 10/14/2024 GRD 101-Molecular Genecs 22  Nucleus DNA Protein synthesis: Step 1: Transcription and Transcription RNA Translation Plasma membrane Cytoplasm RNA Step 2: Ribosome Translation Protein 10/14/2024 GRD 101-Molecular Genecs 23 Types of RNA There are three major classes of RNA, each with specific functions in protein synthesis: 1. Messenger RNA (mRNA) – takes a message from DNA in the nucleus to the ribosomes in the cytoplasm 2. Transfer RNA (tRNA) – transfers amino acids to the ribosomes 3. Ribosomal RNA (rRNA) – along with proteins, makes up the ribosomes, where polypeptides are synthesized 10/14/2024 GRD 101-Molecular Genecs 24 Protein Synthesis: Transcription occurs in the nucleus genetic information encoded in DNA is copied onto a strand of RNA to direct protein synthesis. Information in one DNA strand is converted to messenger RNA (mRNA). mRNA is synthesised in a 5’ 3’ direction. mRNA is complementary to that strand of DNA (Template strand). Copyright ©2021 John Wiley & Sons, Inc. 25 Steps of Transcription 1. Initiation It is the start of transcription The enzyme RNA polymerase binds to the 5’ region of a gene called the promoter. 2. Elongation RNA polymerase reads the unwound DNA strand Synthesizes mRNA molecule using complementary base pairs. 3. Termination Occurs when RNA polymerase crosses a stop (termination) sequence in the gene. The mRNA strand is complete, and it detaches from DNA. 10/14/2024 GRD 101-Molecular Genecs 26 Protein Synthesis: Translation  Process of mRNA converting to a protein  Occurs in the cytoplasm on the ribosome  three sequences of bases on mRNA are called codons, and they determine which amino acid is coded for by the RNA (and DNA).  The translators are tRNA molecules, each with a specific anticodon at one end and a corresponding amino acid at the other. Copyright ©2021 John Wiley & Sons, Inc. 27  Synthesis of Protein 1. Initiation Small subunit binds to mRNA start codon is AUG – which means methionine is the first amino acid attached at the P-site 2. Elongation A site recognizes codon and pairs with the correct tRNA peptide bond forms between the carboxyl end of the polypeptide at the P site and the amino acid at the A site The amino acid in the A site translocate to the P site 3. Termination 1. Stop codon is reached at the A site (UAA, UAG, UGA) 2. Release factors free the polypeptide from the ribosome 10/14/2024 GRD 101-Molecular Genecs 28  Protein Synthesis During Translation 1.Ini a on: Ribosomal subunits bind to mRNA. 2.Elonga on: The ribosome moves along the mRNA molecule, linking amino acids and forming a polypepde chain. 3.Termina on: The ribosome reaches a stop codon, which terminates protein synthesis and releases the ribosome. 10/14/2024 GRD 101-Molecular Genecs 29 Triplet Code: Codons Codon Chart 3 Nucleotides = 1 amino acid 10/14/2024 GRD 101-Molecular Genecs 30 10/14/2024 GRD 101-Molecular Genecs 32 10/14/2024 GRD 101-Molecular Genecs 33 10/14/2024 GRD 101-Molecular Genecs 34 Try to find the amino acid sequence DNA Sequence: GTA CCA GAA CGA RNA Sequence: ___ ___ ___ ___ Amino Acid Sequence: ___ ___ ___ ___ Now change one base (e.g. GTA > ATA) and find the amino acid sequence. What is the change? 10/14/2024 GRD 101-Molecular Genecs 35 Level of Organization Each level of complexity builds upon the previous level System of organs Organ Organism Tissue Cell Population Cell Organelles Community Biosphere Biome Ecosystem Molecule Atom h ps://micro.magnet.fsu.edu/primer/java/scienceopcsu/powersof10/index.html Warm Up Quiz Atoms combine (bonds) to form? Biological Macromolecules Macromolecules will be? Micro Macro Food provides building blocks for large biological YOU ARE WHAT YOU EAT!!!!! molecules which your body is made of! The Molecules of Life All living things are made up of four classes of large biological molecules: - Carbohydrates - lipids - proteins - nucleic acids Macromolecules are polymers, built from monomers What is the structure of biological macromolecules? Macromolecules are (1) large molecules, (2) complex, and (3) arise from the orderly arrangement of their atoms. Macromolecules build up in polymer structure, which is a long molecule consisting of many similar building blocks. The repeating units that serve as building blocks are called monomers. Macromolecules Properties The properties of Macromolecules include ; Water (H2O) 1) Large 2) Complex 3) Arise from the orderly arrangement of their atoms One Protein molecule surrounded by water molecules Macromolecules are polymers, built from monomers Three of the four classes of life’s organic molecules are polymers; - Carbohydrates - proteins - nucleic acids Why? ! However, lipids are not considered polymers ! The Synthesis & Breakdown of Polymers Enzymes are needed to make or break down polymers. (a) A dehydration reaction occurs when two monomers bond together through the loss of a water molecule (b) Polymers are disassembled into monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction Carbohydrates Serve as Fuel and Building Material Carbohydrate macromolecule is made up of sugars or (polymers of sugars) Main source of quick energy (fuel molecules) The simplest carbohydrates are the monosaccharides or simple sugars; these are the monomers from which more complex carbohydrates are built When two monosaccharides are linked together by a glycosidic bond, they are called disaccharides Carbohydrate polymers are called polysaccharides, which are composed of many monosaccharides (more than 10) Monosaccharides and Disaccharides Examples of monosaccharides: – Glucose, galactose, and fructose – Ribose and ribulose – Glyceraldehyde and dihydroxyacetone Examples of common disaccharides: 1. Sucrose Glucose+ Fructose The most prevalent disaccharide, Table sugar 2. Maltose Glucose +Glucose Used in Brewing 3. Lactose Glucose + Galactose Found in Milk Carbohydrates: Polysaccharides Polysaccharides, the polymers of sugars, have storage and structural roles. Storage of polysaccharide – Starch a storage polysaccharide of plants consists entirely of glucose monomers – Glycogen a storage polysaccharide in animals Glycogen is stored mainly in liver and muscle cells Hydrolysis of glycogen in these cells releases glucose when the demand for sugar increases Carbohydrates: Storage Polysaccharides Starch: Present in plants - wheat, maize (corn), rice Made of amylose (unbranched) and amylopectin (branched) Most animals have enzymes that can hydrolyze (break) plant starch, making glucose available as a nutrient for cells Glycogen: Present in animals Polymer of glucose (highly branched) Stored in muscle cells and liver cells Carbohydrates: Structural Polysaccharides The polysaccharide cellulose is a major component of the tough wall of plant cells. - Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods Chitin also provides structural support for the cell walls of many fungi Chitin is used to make a strong and flexible surgical thread. Proteins include a diversity of structures, resulting in a wide range of functions After digestion, monomers (amino acids) are absorbed, and new proteins are made within cells. Proteins account for more than 50% of the dry mass of most cells Some proteins (enzymes) speed up chemical reactions Other protein functions include defense, storage, transport, cellular communication, movement, or structural support Amino Acid Monomers Proteins are all constructed from the same set of 20 amino acids (monomers) Amino acid monomers join to form long, unbranched chains called Polypeptides A protein is a biologically functional molecule that consists of one or more polypeptides Amino acids are organic molecules consisting of (1) amino and (2) carboxyl groups Amino acids differ in their properties due to differing side chains, called R groups Polypeptides (Amino Acid Polymers) Linking amino acids to form polypeptides Long linear chains of amino acids linked by peptide bonds are called polypeptide A protein is a biologically functional molecule that consists of one or more polypeptides Each polypeptide has a unique linear sequence of amino acids, with a carboxyl end (C-terminus) and an amino end (N- terminus) Peptide bond is always formed N C Protein Structure and Function The function of a protein usually depends A functional protein consists of one on its ability to recognize and bind to some other molecule or more polypeptides precisely twisted, folded, and coiled into a unique shape The sequence of amino acids determines a protein’s three- dimensional structure A protein’s structure determines how it works Four Level of Protein Structure 1. The primary structure of a protein is its unique sequence of amino acids, like the alphabet in a word 2. Secondary structure, found in most proteins, consists of
helix and  pleated sheets 3. Tertiary structure is determined by interactions among various side chains (R groups) 4. Quaternary structure results when a protein consists of multiple polypeptide chains Primary Structure of Protein The primary structure of a protein is its sequence of amino acids Primary structure is like the order of letters in a long word and is determined by inherited genetic information Primary structure is determined by inherited genetic information Secondary Structure of Protein The coils and folds of the secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone. Tertiary Structure of Protein The overall shape of polypeptide results from interactions between R groups rather than interactions between backbone constituents These interactions include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions Strong covalent bonds called disulfide bridges may reinforce the protein’s structure Quaternary Structure of Protein results when two or more polypeptide chains form one macromolecule 3D structure of proteins composed of multiple subunits. Examples: Collagen and Hemoglobin Collagen (protein) Hemoglobin (protein) Sickle-Cell Disease: A Change in Primary Structure A slight change in primary structure can affect a protein’s structure and ability to function Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution (Glu  Val) in the protein haemoglobin Nucleic Acid Store, Transmit, and help express hereditary information – The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene – Genes consist of Deoxyribonucleic acid (DNA), a nucleic acid made of monomers called nucleotides Types of Nucleic Acids – There are two; 1. Deoxyribonucleic acid (DNA) 2. Ribonucleic acid (RNA)  mRNA Genec material tRNA rRNA The Components of Nucleic Acids – Nucleic acids are polymers of nucleotides. – Each nucleotide consists of the following; 1. nitrogenous base: Purine (double ring), Pyrimidines (single ring) 2. a pentose sugar: DNA (deoxyribose), RNA (ribose) 3. one or more phosphate groups – Adjacent nucleotides are joined by a phosphodiester linkage, which consists of a phosphate group that links the sugars of two nucleotides Lipids are a Diverse Group of Hydrophobic Molecules – Lipids are the one class of large biological molecules that do not include true polymers Lipids – The unifying feature of lipids is that they mix poorly, if at all, with water. Fatty Acids Steroids – Lipids are hydrophobic because they consist primarily of hydrocarbons (C and H), Triacylglycerides Phospholipids Cholesterol – The most biologically important lipids are fats, phospholipids, and steroids  Lipids’ Funcons Stores double energy than carbohydrates (Vital organs such as the heart, and (maintains internal liver are protected temperature-Adipose by visceral fat) ssue) (cell membrane) (Adipose ssue) Nerve Impulse (nerve cell membranes, insulate neurons, and facilitate the signaling of (Reserve fuel) electrical impulses) Fats – Fats are constructed from two types of smaller molecules: 1. glycerol 2. fatty acids – In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol or triglyceride Fats Fatty acids vary in length (number of carbons, 15-18 C) and in the number and locations of double bonds, based on that fats are classified into two categories; 1. Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds 2. Unsaturated fatty acids have one fewer hydrogen atom and one or more double bonds Pay attention to the double bond and kink Fats : Saturated Vs. Unsaturated Fats SATURATED UNSATURATED have the maximum number of hydrogen have 1 or more double bonds atoms possible and NO double bonds Solid at room temperature , so named as Liquid at room temperature so named as fats oils Animal fats are rich in saturated fats and Plant fats and fish fats are usually may contribute to cardiovascular disease unsaturated and are very good for health through plaque deposits Essential Fatty Acids Certain unsaturated fatty acids are not synthesized in the human body and must be supplied in the diet. These essential fatty acids include omega-3 fatty acids (good fats), which are required for normal growth and are thought to provide protection against cardiovascular disease. Humans and other mammals store their long-term food reserves in adipose cells. Adipose tissue also cushions vital organs and insulates the body. Fats Phospholipids In a phospholipid, two fatty acids and a phosphate group are attached to glycerol. The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head- Amphipathic molecules. The structure of phospholipids results in a bilayer arrangement found in cell membranes. The existence of cells depends on phospholipids. Steroids Steroids are lipids characterized by a carbon skeleton consisting of four fused rings. Cholesterol, a type of steroid, is a component in animal cell membranes and a precursor from which other steroids are synthesized. Needed for bile formation, hormone synthesis, cell membrane Steroids: cholesterol Cholesterol is found in foods from animal sources, such as egg yolks, meat, and cheese. Our body needs cholesterol, but a high cholesterol level in the blood may contribute to cardiovascular disease. High cholesterol may be because of Unhealthy eating habits Lack of physical activity Smoking Summary of key concepts Summary of key concepts Summary of key concepts