General Biology 1 (Reviewer) PDF

**GENERAL BIOLOGY 1 (REVIEWER)** **STEM 12 -- CURIE** - **BIOLOGY** - is the scientific study of living organisms and their interactions with each other and their environment. - a diverse and multifaceted field that encompasses a wide range of topics, from the smallest molecules withi...

**GENERAL BIOLOGY 1 (REVIEWER)** **STEM 12 -- CURIE** - **BIOLOGY** - is the scientific study of living organisms and their interactions with each other and their environment. - a diverse and multifaceted field that encompasses a wide range of topics, from the smallest molecules within cells to entire ecosystems. - seeks to understand the fundamental principles that govern life, including its origin, growth, reproduction, evolution, and interactions. **BRANCHES OF BIOLOGY** **BOTANY -** the study of plants, including their structure, growth, reproduction, physiology, classification, and ecology. **ZOOLOGY** - deals with the study of animals, including their anatomy, physiology, behavior, classification, evolution, and ecology. **GENETICS** - is the study of heredity and variation in living organisms. - explores how traits are passed from one generation to the next, the mechanisms of inheritance, and the role of genes in shaping organisms. **EVOLUTIONARY BIOLOGY** - the study of the interactions between organisms and their environment. - examines how organisms interact with each other and their surroundings, including topics like ecosystems, biodiversity, and conservation. **ANATOMY AND PHYSIOLOGY** - These branches deal with the structure and function of organisms. - Anatomy examines the physical structures of organisms, while physiology explores how these structures function and interact to maintain life processes. **CELL BIOLOGY** - **studies the basic unit of life, the cell**. - It delves into cell structure, function, and the molecular processes that occur within cells. **MOLECULAR BIOLOGY** - **the study of biological molecules and their interactions**. INCLUDES: DNA, RNA, proteins, and enzymes. - It provides insights into the molecular mechanisms underlying various biological processes. **BIOCHEMISTRY** - **combines principles from biology and chemistry**. - to study the chemical processes and compounds that occur within living organisms. **BIOTECHNOLOGY** - involves the **application of biological principles to develop and create products and processes that benefit society**. - This can include areas like genetic engineering, pharmaceuticals, and agricultural improvements. **NEUROSCIENCE** - **explores the structure and function of the nervous system**. INCLUDES: the brain and nerves, to understand processes related to behavior, cognition, and sensory perception. **CELLS** - the basic building blocks of all living things. - They provide structure for the body, take in nutrients from food, convert those nutrients into energy. - carry out specialized functions. - "The basic unit of life" **ROBERT HOOKE (1665)** - **English physicist** used of the **first light microscopes** to look at thin slices of plant tissue. One of these, **a slice of cork,** caught his eyes. - **Cork** was made of **thousands of tiny chambers**. Hooke called this chambers **"CELLS"** because they reminded him of a **monastery's tiny rooms,** which were also known as **cells.** **ANTON VAN LEEUWENHOEK (1676)** - published his observations on **tiny living organisms** which he named **animalcules.** - It was believed that Leeuwenhoek was the **first to observe under his microscope** the **structure of a** **red blood cell of different animals** as well as a **sperm cell.** **ROBERT BROWN (1831)** - One of the **leading botanist**. - was **able to compare diverse kinds of plant specimens** under the microscope. - He markedly indicated that there is a common thing about them-they are all composed of cells, and inside the cell is a **dark dense spot** which he termed as the **nucleus.** **RUDOLF VIRCHOW (1858)** - Concluded that all cells come from pre-existing cells. **MATTHIAS SCHLEIDEN (1838)** - **German botanist** - concluded that **all plant parts are made of cells.** **THEODOR SCHWANN (1839)** - A **botanist** and a **close friend of Schleiden** - stated that all **animal tissues are composed of cells,** too. **2 TYPES OF CELLS** 1. **PROKARYOTIC** -- Achaea and Bacteria 2. **EUKARYOTIC** -- Plants, Animals, Protist and Fungi **CELL THEORY** **Cell structures** can only **be observed under a high magnification microscope** and are separated internally into numerous membranous compartments called **organelles (little organs).** **POSTULATE OF CELL THEORY** 1. All living organisms are made up of one or many cells. 2. The Cells are the building block of life just as atoms are the basic building blocks of all matter. 3. Each cell contains materials that carry out basic life processes. **CELL FUNCTIONS** 1. **NUTRITION** -- the process by which cells obtain food molecules to support their activities. 2. **DIGESTION**- the process by which food particles are broken down with the help of enzymes into smaller, soluble units suitable for cell use. 3. **ABSORPTION** - the process by which cells absorb from their environment water, minerals and other materials essential to life. 4. **BIOSYNTHESIS** - the process by which all cells organize complex chemical from simple building units or substances. 5. **EXCRETION** - the process by which cell by-products that are not needed for further cell functioning are eliminated; 6. **EGESTION** - the process by which insoluble, undigested particles are eliminated by the cell. 7. **SECRETION** - the process by which substance that are synthesized by the cells are expelled from the elimination process. 8. **MOVEMENT** - a process that consists of the locomotion of cells by means of special structures like cilia or flagella. 9. **IRRITABILITY** - the process by which cells respond or react to external factors or conditions around them. 10. **METABOLISM** - the process of breaking down and building up of chemical energy that cells need to function. 11. **CELLULAR REPRODUCTION** - a process by which a cell copies or replicates its DNA and increases in number by cell division. **PROKARYOTIC VS. EUKARYOTIC CELLS** - **LYSOSOMES** - Suicide bags of the cells - **MITOCHONDRIA** - Powerhouse of the cells. - **VACUOLES** -- Storage Tanks of the cell. - **ENDOPLASMIC RETICULUM** - Manufacturer and Shipper of the cells. - **GOLGI BODIES** - Packing Counters of the cells. - **PEROXISOMES** - Oxidizes and breaks down fatty acids and amino acids and detoxifies toxins. - **CELL WALL** - Protection, structural support, and maintenance of the cell shape. - **CHLOROPLAST** - Site of photosynthesis. - **CYTOPLASM** - Provide structure to cell, site of many metabolic reaction. - **CENTROSOME AND CENTRIOLES** - Helper in cell division - **CYTOSKELETON** -- Framework of the cells - **CILIA** -- Serves as cellular locomotion, movement of particles along extracellular surface of plasma membrane and filtration. - **NUCLEUS** -- Control Ce nter of the cell. - **NUCLEOLUS** -- A structure involved in the production of ribosomal RNA that translate messenger RNA to proteins.  **ORGANELLES PECULIAR TO PLANT CELLS** 1. **Cell wall** - the cells of the plants, fungi, and some single-celled organisms are protected and supported by a rigid cell wall, which lies outside the plasma membrane. 2. **Plastids** - large membrane-bound organelles and found in the cytoplasm of most plant cells. 1. **Chromoplast** - **yellow or orange pigments called carotenoids.** It gives many flowers ripen fruits; autumn leaves their characteristic yellow or orang color. - **Chloroplast** - are the chromoplast containing the **green coloring** pigment called **CHLOROPHYLL** which is essential in photosynthesis. - **Rheodoplast** - Chloroplast in tomatoes. 2. **Leukoplast -** serve as **food storehouses in many plant cells.** They contain oil, starch grain, and proteins, as well as enzymes necessary to link glucose molecules together and form starch molecules. **TWO BASIC TYPES OF CELLS** - **Prokaryotic Cells** - The term "prokaryote" is derived from the Greek word "pro", (meaning:before) and "karyon" (meaning: kernel). It translates to "before nuclei." - are one of the most ancient groups of living organisms on earth, with fossil records dating back to almost 3.5 billion years ago. These prokaryotes thrived in the earth's ancient environment, some using up chemical energy and others using the sun's energy. - **Eukaryotic Cells** - The term "Eukaryotes" is derived from the Greek word "eu", (meaning: good) and "karyon" (meaning: kernel), therefore, translating to "good or true nuclei." - Eukaryotes are more complex and much larger than the prokaryotes. They include almost all the major kingdoms except the kingdom monera. **STEROLS** - they are lipids and regulates biological processes and sustain the structure of cell membranes and considered as MEMBRANE REINFORCERS  **STRUCTURES AND FUNCTIONS OF ANIMAL AND PLANT CELLS** *HIERARCHY OF BIOLOGICAL ORGANIZATION* - In complex multicellular organisms like animals, cells come in different structures and functions---they differ in terms of shapes and sizes, and they also have specialized functions.  - ATOM - The basic unit of life. - MOLECULES - Combination of group of atoms. - ORGANELLE - atoms and molecules that make up the basic unit of life. Four types of biomolecules or molecules associated with life: - carbohydrates - proteins - lipids or fats - nucleic acids - distinct and specialized subcellular structures that contribute to the cell's maintenance and reproduction; membrane-bound structures in eukaryotic cells. - CELLS - The smallest, basic, functional unit of life is formed when different atoms and molecules combine and function together. EXAMPLES: skin cells, blood cells, muscle cells or fibers, neurons - TISSUES - groups of cells that work together to perform a specialized function. Four types of animal tissue: - epithelial tissue - connective tissue - muscle tissue - nervous tissue - ORGANS - groups of tissues that work together to perform a specialized function. EXAMPLES: skin, lungs, heart muscle, brain - ORGAN SYSTEMS - groups of organs that work together to perform a certain process in the body. EXAMPLES Integumentary system, respiratory system, circulatory system. - ORGANISMS - formed by different organ systems that create complex interactions with one another to maintain balance or *homeostasis* and sustain life.  EXAMPLES: Humans, grasses, dogs, cats, mushroom - POPULATION - COMMUNITY - different populations living in the same area. Examples: Humans, cats, and dogs living in the same house; koalas, kangaroos, and various tree species in an area of the forest. - ECOSYSTEM - includes all the communities interacting with one another and with their environment. EXAMPLES: Humans, cats, dogs, and grasses getting resources from nonliving things like soil, water, and sunlight. - BIOME - BIOSPHERE - includes all the different kinds of ecosystem. EXAMPLES: The entire surface of Earth where life thrives. **SPECIALIZED CELLS AND CELL STRUCTURES IN ANIMALS** 1. MICROVILLI - Found in the small intestine, kidneys, egg cells and white blood cells. - These **increase the surface area** for the absorption of nutrients and other essential substances from the gut cavity into the underlying tissues and blood vessels. 2. CILIA AND STEREOCILIA **Structure of Cilia** - A **cilium's structural core** is made of **nine pairs of microtubules** on the [outside ring with 2 microtubules] on the central portion. - **Stereocilia** in a frog's inner ear allow it **to detect sounds from its environment**. Frogs have mechanism to detect and escape from potential threats. 3. FLAGELLA - This are **tail-like structures** that **provide motility to cells.** - HOW DOES THE LOCATION OF SPECIALIZED STRUCTURES IN CELLS RELATE TO THEIR FUNCTIONS? - The placement and organization of specialized structures within cells are highly evolved to optimize their functions and contribute to the overall efficiency and survival of the cell and the organism as a whole. The spatial arrangement of these organelles allows for the coordination of various cellular processes, enabling the cell to carry out its functions effectively. 4. BASAL INFOLDINGS AND HEMIDESMOSOMES - Both found at [the basement of membrane of epithelial cells.] - **Hemidesmosomes** helps the epithelial tissue provide protection and structural support to the underlying cells. - **Basal Infoldings** are responsible for increasing surface area and for ion and fluid transport. 5. CELL JUNCTIONS - Are found in epithelial cells and are mainly responsible for connecting adjacent cells. TYPES OF CELL JUNCTIONS: - Tight Junction -- prevent leakage of substances. - Adherens Junction - connect adjacent cells. - Gap Junctions -- serves as channels of ions, water, and other essential substances. - Desmosomes -- connect adjacent cells. 6. BLOOD CELLS AND SEX CELLS Red Blood Cells (RBC) -- are biconcave to aid in the diffusion of gases from the air sacs of the lungs and into the oxygen-deprived tissues of the rest of the body. - The lack of nucleus in red blood cells gives more space for hemoglobin. Thus, more oxygen molecules can be transported. - RBC also lack mitochondria. They generate their energy through anaerobic respiration. **BLOOD CELLS -- ERYTHOCYTES** - For adult males: 4.5 to 6.0 million cells per microliter (mcL) or micrometer (µL). - For adult females: 4.0 to 5.5 million cells per mcL or µL. - **LIFE SPAN: 120 DAYS** WHITE BLOOD CELLS - Responsible for the body's defenses. - They can either be granulocytes or agranulocytes. **WHITE BLOOD CELLS- LEUKOCYTES** - are a critical component of the immune system, defending the body against infections and diseases. DIFFERENT TYPES OF WHITE BLOOD CELLS: - **Neutrophils:** are the most abundant type of white blood cell and are often the first to arrive at the site of an infection. They have a short lifespan of only a few hours to a few days, and their primary function is to engulf and destroy bacteria and other pathogens. - **Lymphocytes:** including T cells and B cells, play a central role in the adaptive immune response. Some lymphocytes can have a relatively long lifespan, ranging from a few months to years, while others, like activated T cells, may have shorter lifespans as they are actively involved in fighting infections. - **Monocytes:** are white blood cells that can differentiate into macrophages, which are involved in phagocytosis (engulfing and digesting pathogens). Monocytes typically circulate in the bloodstream for about one to three days before entering tissues, where they may live for weeks to months. - **Eosinophils and Basophils** are involved in the response to allergies and parasitic infections. They have a relatively short lifespan in the bloodstream, typically lasting a few days to a week. - It\'s important to note that white blood cells are continually produced in the bone marrow to replace those that have completed their function or have reached the end of their lifespan. **DIFFERENCES BETWEEN TRICHOMES AND ROOT HAIRS:** - Trichomes and root hairs **are both structures found in plants,** but they serve different functions and are in different parts of the plant. **STRUCTURE AND FUNCTION OF TRICHOMES\ **These are epidermal outgrowths responsible for - preventing insect attacks, - shading leaves, and - trapping insects. **LOCATION** - Trichomes are small hair-like structures that can be found on various parts of a plant, including leaves, stems, and even flowers. **FUNCTION** - Trichomes have diverse functions depending on their type. They can serve as a defense mechanism against herbivores by producing toxic chemicals or causing physical irritation. - Some trichomes also help reduce water loss by forming a barrier that reduces transpiration. Additionally, trichomes can trap and deter insects that may want to feed on the plant. **ROOT HAIR** - **Location:** Root hairs are specialized structures found on the root system of a plant, specifically on the tiny, root-hair-bearing roots. **FUNCTION** - They are involved in the process of water and mineral uptake through osmosis and active transport. Root hairs are essential for the plant\'s ability to take up essential resources from the soil and support its growth and development. **OSMOSIS** - is a fundamental biological process that involves the movement of water molecules across a selectively permeable membrane, such as a cell membrane, from an area of lower solute concentration to an area of higher solute concentration. It is a type of passive transport, meaning it does not require energy input from the cell. **ACTIVE TRANSPORT** - is a biological process that moves molecules or ions against their concentration gradient, meaning it moves them from an area of lower concentration to an area of higher concentration. **TRANSPIRATION** - is a fundamental biological process that occurs in plants. It involves the loss of water vapor from the aerial parts of a plant, primarily through tiny openings called stomata in the leaves, but also through the cuticle and the lenticels in stems and other plant parts. **ROOT HAIRS** Structure and Function of Root Hairs: - Root hairs are tiny hair-like structures that originated from the epidermis of plants. Root hairs facilitate the absorption of water from the substrate.  - Mesophyll layer is primarily responsible for photosynthesis.  - It is made up of palisade cells and spongy cells. **THE ARRANGEMENT OF CELLS IN THE MESOPHYLL LAYER** - The arrangement of cells in the mesophyll layer of leaves is highly specialized and adapted to facilitate photosynthesis, the process by which plants convert light energy into chemical energy (glucose) using carbon dioxide and water. **The mesophyll layer contains two main types of cells:** 1. Palisade mesophyll cells 2. Spongy mesophyll cells, **ADVANTAGES FOR PHOTOSYNTHESIS:** 1. Maximizing Light Absorption 2. Gas Exchange 3. Surface Area 4. Water Transport 5. Temperature Regulation 6. Adaptation to Environmental Conditions - **Function of Xylem and Phloem** - Xylem and phloem tissues consist of specialized cells that are responsible for transporting essential substances, such as water, minerals, and food needed by the plants.  **MICROSCOPE** - Used to magnify objects that are too small to be seen by the naked eye. **ZACHARIAS JANSSEN** along with his father **Hans Janssen**, is often [credited with creating one of the earliest compound microscopes] around [1590 in the Netherlands.] This early microscope **consisted of two convex lenses** that could **magnify objects.** **ANTON VAN LEEUWENHOEK** a [Dutch scientist], is renowned for his [contributions to microscopy]. He designed and built [single-lens microscopes] with [remarkable precision, achieving high magnification. ] - He used these microscopes **to observe a wide range of microscopic organisms**, such as bacteria, protozoa, and sperm cells. Van Leeuwenhoek\'s pioneering work in microscopy laid the foundation for the field of microbiology. **2 BASIC PRINCIPLES IN USING A MICROSCOPE** 1. **MAGNIFICATION** - is the **ability to make small objects seem larger,** such as making a microscopic organism visible. 2. **RESOLUTION** - is the **ability to distinguish two objects from each other.** **PARTS OF A COMPOUND MICROSCOPE** - **MAGNIFYING PARTS** - Used to enlarge the specimen 1. **OCULAR OR EYEPIECE** **-** this is where **one look through to view the specimen.** It also [magnifies the image of the object that has been magnified by the objectives.] It **usually ranges from 5x to 15x.** **2. OBJECTIVES** **-** metal cylinders **attached below the nosepiece and contain lenses.** a\. **Low power objectives (LPO)** - gives the lowest magnification usually [10x.] b\. **High Power objective (HPO)** - gives higher magnification, usually [40x or 43x.] - **MECHANICAL PARTS** - Used to adjust and support the parts. 1. **DRAW TUBE** **-** it **holds the ocular.** 2. **BODY TUBE** **- connects the eyepiece to the revolving nosepiece** with the objectives. 3. **REVOLVING NOSEPIECE** - facilitates the changing of objectives. 4. **COARSE ADJUSTMENT KNOB** - **raises or lowers the body tube to bring the object in focus.** It is used when **focusing under LPO.** 5. **FINE ADJUSTMENT KNOB** - used **to focus the image further**. It is used when **focusing under the HPO**. 6. **ARM** - **supports the body tube** and it is where the microscope is held. 7. **BASE** - bottom part of that supports the entire microscope. 8. **STAGE** - platform where an object to be examined is placed. 9. **STAGE CLIPS** - **secures the specimen to the stage** while viewing under the microscope. 10. **INCLINATION JOINT** - allows tilting of the microscope for the convenience of the user. 11. **PILLAR** - part above the base that supports the other parts of the microscope. - **ILLUMINATING PARTS** - Used to provide the light. 1. **MIRROR** - **used to gather and direct light** in order to illuminate the object. 2. **DIAPHRAGM** - **regulates the amount of light reflected** into the specimen. - the bigger the opening, the greater is the amount of light reflected. **LABORATORY TOOLS AND EQUIPMENT** **LABORATORY EQUIPMENT -** refers to the **various tools and equipment used by scientists working in a laboratory.** - It is generally **used to either perform an experiment or to take measurements and gather data.** **DIFFERENT TOOLS AND EQUIPMENT IN THE LABORATORY:** - **GLASSWARE** - Watch Glass - Crystalizer - Magnifying Glass - Stirring Rod - Slide with coverslip - Petri dish - Pipettes - RoundBottomed flask  - Boiling Tube Glass Boiling Tube, Round, Capacity: 50ml - **HEATING** - These objects are all used in the process of heating, but each one has a different function. - Bunsen Burner - Tripod stand - Boiling Tube - Wire gauze = - **MEASURING** - We use these materials to measure different measurements such as mass, volume, time and temperature. - Stopwatch - Thermometer - Balance Scales - Pipettes - **OBSERVING** - The observing equipment allows you to have a look at substances and different materials. - Microscope - Slide with coverslip  - Petri Dish - Magnifying Glass - Watch Glass - **HOLDING AND GRABBING** - The items in this group keep things in the right position, to be used. - Test Tube Rack - Retort stand with clamps - Wire gauze - Tripod - Tongs - Tweezers - Spatula - **CUTTING** - These two objects have a sharp edge which can penetrate or divide things. - Dissecting Scissors - Scalpel - **FILTERING** - Through these materials, a fluid is passed to separate out matter in suspension. - Filter Paper - Funnel **USES OF LABORATORY TOOLS:** - **GRADUATED CYLINDER** \- Used to measure the volume of liquids - **BEAKER** \- Used as a container when measuring approximate volume of liquids - **FLORENCE FLASK** \- Graduated flask used in volumetric analysis - **ERLENMEYER FLASK** \- Erlenmeyer flasks are suitable for heating liquids, e.g. with a Bunsen burner. - **TEST TUBE** - These are widely used by chemists to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays. - **FUNNEL** - Used in filtration and in transferring liquid. - **WATCH GLASS** \- Used as a container when observing the reaction of a substance when exposed to air. - **STIRRING ROD** - Used in mixing solutions; directs the flow of liquids. - **GLASS TUBE** \- Used in glass connections, preparation of medicine dropper, glass jets, etc. - **MEDICINE DROPPER** - Used to transfer and measure small amounts of liquid. - **EVAPORATING DISH** \- Container for evaporation. - **MORTAR AND PESTLE** \- Used for grinding solids. - **CRUCIBLE AND COVER** \- Container for hightemperature heating - **SPOT PLATE** \- Container for observing small amount of solids - **THERMOMETER** **-** Used in determining the temperature of a substance. **METAL EQUIPMENT AND ACCESSORIES:** - **IRON STAND** - Used to hold iron ring, utility clamp, etc. - **IRON CLAMP** - Used to hold apparatus in a set-up. - **WIRE GAUZE** - Placed over the iron ring to prevent direct heating. - **IRON RING** - Used as support to the wire gauze. - **TRIPOD** **-** Used as a stand during heating. - **BUNSEN BURNER/ ALCOHOL LAMP** - Sources of heat - **TEST TUBE RACK** - Used as a stand for test tubes. - **RUBBER STOPPER** - Cover for test tubes and flasks; used in glass connections. - **CLAY TRIANGLE** - Holds crucible and cover during heating process. - **TEST TUBE HOLDER** - Used to hold the test tube during heating process. - **CRUCIBLE TONGS** - Used to hold hot objects, especially crucible and cover. **CELL CYCLE** The cell cycle is the time of growth and division of a cell. A cell's life cycle is divided into two periods. 1. Interphase- Growth Period 2. Mitosis- period of nuclear division - The cell cycle was discovered by **Prevost and Dumas (1824)** while studying the **cleavage of the zygote of Frog**. - In frogs and many other animals, the **cleavage of the zygote is an important early developmental process that leads to the formation of a multicellular embryo.** **CLEAVAGE** - is a series of rapid cell divisions without significant growth in the size of the embryo. It results in the formation of smaller and smaller cells, called blastomeres, from the original zygote. **DNA MOLECULE** - **DNA is the genetic material in living cells.** - Almost every cell in our bodies has genetic material in the form of deoxyribonucleic acid (DNA). - Most biological traits such as eye color, hair color, and height are coded by DNA. - Also called as "**Molecule of life**\" because it [carries the genetic information needed for the inheritance of traits from one generation to the next.] **KEY FEATURES OF DNA** **Structure:** DNA is a long, double-stranded molecule that resembles a twisted ladder, known as **a double helix**. Each strand consists of a **chain of nucleotides**, which are the **building blocks of DNA.** **NUCLEOTIDES** - The building blocks of DNA. **Nucleotides: consists of three components:** 1. **a phosphate group** 2. **a deoxyribose sugar molecule** 3. **a nitrogenous base.** **There are four types of nitrogenous bases in DNA:** 1. **adenine (A)** 2. **thymine (T)** 3. **cytosine (C)** 4. **guanine (G).**  - **These base pairs (A-T and C-G) are crucial for maintaining the double-stranded structure of DNA.** The specificity of base pairing is a fundamental feature of DNA and is essential for its functions, such as accurate replication and the encoding of genetic information. - This specific base pairing ensures that the genetic code is faithfully preserved during processes like DNA replication and transcription. **FUNCTION:** - DNA serves as a b**lueprint for the synthesis of RNA** *(ribonucleic acid),* which, in turn, is used to make proteins. Proteins carry out a wide range of functions in cells and are essential for life. RNA -- used to make proteins. **DNA Packing** - In eukaryotic cells, DNA is organized into a highly compact and structured form known as **chromatin**. Chromatin is a complex of DNA and proteins. The primary proteins involved in this packaging are **histone proteins**. - **Positively charged histone proteins aid in DNA packaging.** **DNA-HISTONE Interaction** The electrostatic attraction between the positively charged histones and the negatively charged DNA causes the DNA to wrap around the histone octamers. These wrapping forms a structure known as a **nucleosome**, **which is the basic repeating unit of chromatin.**  Interphase DNA is **found in the form of chromatin**, a complex of DNA and proteins. Chromatin in dispersed inside the intact cell nucleus during interphase. A close-up of a cell Description automatically generated **CHROMOSOMES** **Chromatin** will sometimes need to further condense into a highly coiled and compact structure. **This highly condensed form of DNA** is known as a **chromosome.**  A screenshot of a computer Description automatically generated **AUTOSOME** - In humans and many other organisms, autosomes are the chromosomes that determine an individual\'s traits and characteristics unrelated to their sex. **Humans typically have 22 pairs of autosomes and one pair of sex chromosomes, for a total of 46 chromosomes in each diploid cell.**  **HOMOLOGOUS CHROMOSOMES:** **-** Within each autosomal pair, the two chromosomes are **homologous,** meaning they carry genes for the same traits in the same locations. **DIPLOID CELLS** **-** In diploid organisms like humans, autosomes are found in pairs in **most somatic (body) cells.** In contrast, sex chromosomes (X and Y in humans) determine an individual\'s sex and are not autosomes. **HAPLOID CELLS** refers to the presence of a single set of chromosomes in an organism's cells. Sexually reproducing organisms are diploid (having two sets of chromosomes, one from each parent). In humans, only **the egg and sperm cells are haploid.** **DIFFERENT PHASES OF CELL CYCLE** 3 Stages of Cell Cycle  - INTERPHASE - Also known as the resting phase of the cell cycle; interphase is the time during which the cell prepares for division by undergoing both cell growth and DNA replication. A diagram of events during the g1 phase Description automatically generated - INTERPHASE - During interphase, a cell grows in size, carries on metabolism, duplicates chromosomes, and prepares for division. Interphase is the busiest phase of the cell cycle. It occupies around 95% time of the overall cycle. The interphase is divided into three phases: **1. G1 Phase** **2. S Phase (Synthesis)** **3. G2 Phase** **G1 Phase (GAP 1)** **Description:** The G1 phase is the first phase of interphase. During this phase, the cell grows in size and carries out its normal functions, such as protein synthesis and metabolic activities. It is also a period when the cell checks for DNA damage and the readiness for cell division. **Purpose:** G1 phase serves as a preparatory phase for cell division. The cell accumulates the necessary resources and energy needed for DNA replication in the S phase and subsequent cell division. **Key Events:** 1. Cell growth 2. Protein synthesis 3. Monitoring for DNA damage 4. Preparation for DNA replication. **S Phase (Synthesis)** **Description:** The S phase is the second phase of interphase. During this phase, DNA replication takes place. This means that the cell\'s DNA is duplicated, resulting in the formation of two identical copies of each chromosome (sister chromatids) attached at the centromere. **Purpose:** The primary purpose of the S phase is: 1. To ensure that each daughter cell can go through the cell division 2. To receives a complete and identical set of genetic information. DNA replication is a crucial step in the cell cycle to maintain genetic integrity. **Key Events:** 1. DNA synthesis 2. The replication of the entire genome occur in this phase. **GENOME** - A genome is the **complete set of an organism\'s genetic material,** including all of its genes and non-coding sequences of DNA. The genome contains **all the information needed for the growth, development, and functioning of an organism.** **GENES** **Genes** are the **functional units of a genome that encode instructions for building and maintaining the organism.** **G2 Phase (GAP 2)** **Description:** The G2 phase is the third and final phase of interphase. During this phase, **the cell continues to grow and prepares for mitosis (or meiosis in the case of germ cells).** It completes the synthesis of various proteins, including those required for cell division. **Purpose:** 1. **acts as a checkpoint to ensure that the cell is ready for cell division.** 2. **It checks for DNA damage, verifies that DNA replication in the S phase was successful.** 3. **It ensures that the cell has sufficient resources and energy for mitosis.** **Key Events:** 1. **Cell growth** 2. **Protein synthesis (including those required for mitosis)** 3. **Final check for DNA damage and cell readiness.** **M Phase** The M phase in eukaryotic organisms involves either one of two processes, namely, **mitosis and meiosis.** **○** Sex cells or gametes **undergo meiosis, whereas somatic cells or non-sex cells undergo mitosis.** **CYTOKINESIS**  - **is the final stage of the cell cycle, following the completion of either mitosis (in somatic cells) or meiosis (in germ cells). It is the process by which the cytoplasm of a eukaryotic cell is divided into two daughter cells, each containing a nucleus and a full set of organelles.** \- Cytokinesis **ensures that the newly replicated genetic material is distributed to the daughter cells, resulting in the formation of two separate, genetically identical cells.** **STAGES OF MITOSIS** **Mitosis** refers to how a cell divides to produce new cells. Only **somatic cells** (also known as body cells) undergo mitosis. A cell will only begin mitosis if the conditions are correct and favorable for cell division. THE ROLE OF MITOSIS IN THE CELL CYCLE M Phase - The cell undergoes mitosis if it is a somatic cell or meiosis if it is a sex cell. - It allows the cell to divide and produce new cells. Preparing for Mitosis: Cell cycle checkpoints check for errors.  **Preparing for Mitosis:** The synthesis phase involves the duplication of the cell's DNA. CHANGES IN CHROMOSOME NUMBER DURING MITOSIS **The Chromosome** - DNA in interphase is found in the form of chromatin which condenses during mitosis. - Each chromosome is made up of two sister chromatids. **Haploid and Diploid Cells** The human genome has 23 pairs of chromosomes for a total of 46 chromosomes in each cell. 23 is the haploid number whereas 46 is the diploid number. - Haploid is often represented as n while diploid is 2n. - The number of sets of chromosomes that a cell or an organism has is known as ploidy. **Haploid and Diploid Cells**  All human body cells are diploid except gametes which are haploid. DIPLOID (2n) Two sets of chromosomes. HAPLOID (n) One set of chromosomes. Mitosis is also divided into multiple phases. **THE PHASES OF MITOSIS** - PROPHASE The chromatin condenses into chromosomes. The nucleolus disintegrates. The mitotic spindle starts to form.  **PROMETOPHASE** - It begins after the nuclear envelope breaks down. - The centrosomes move to opposite poles. - The kinetochores found at the centromeres become apparent. - METAPHASE - The microtubules of the mitotic spindle attach and interact with the kinetochores of the chromosomes. - The chromosomes align at the center of the cell, in the metaphase plate.  - ANAPHASE - The mitotic spindle pulls and separates the sister chromatids apart. - The chromatids, now called daughter chromatids, are then pulled toward the opposite poles.  - TELOPHASE - Daughter chromatids decondense. - In animals, the boundary of the new cells is known as the cleavage furrow. - In plants, it is known as the cell plate.  When trying to differentiate between the appearance of cells in the different phases of mitosis, remember that the first letter of the phase shares the first letter of what the cell looks like in that phase. - In **P**rophase, the cell's genetic material resembles Polka dots or strings. - In **M**etaphase, the chromosomes Migrate to the Middle of the cell. - In **A**naphase, the chromosomes move Away from each other. - In **T**elophase, the parent cell starts to form Two new cells. AFTER M PHASE **Cytokinesis** - After telophase, cytokinesis will divide the cell into two. - Cytokinesis is not a phase of mitosis but is closely related to it. Recall from the previous lesson that each of the two daughter cells will inherit a nucleus, similar genetic material, organelles, and more. **PLOIDY IN MITOSIS** The number of chromosomes before and after mitosis. **DNA** is in the form of **chromatin** in interphase, and it condenses into **chromosomes** during mitosis. These phases are **prophase, prometaphase, metaphase, anaphase, and telophase.** Each phase performs a crucial role that contributes to the process of cell division. - Chromosome condensation happens in prophase. Spindle formation also begins. - Prometaphase begins after the completion of the breakdown of the nuclear envelope. - Metaphase involves the alignment of the chromosomes in the metaphase plate. - The sister chromatids move to the opposite poles of the cell in anaphase. - Telophase ends when two nuclei are formed in the cell.  **STAGES OF MITOSIS** **MITOSIS** - refers to how a cell divides to produce new cells. **SOMATIC CELLS** \- Also known as BODY CELLS undergo mitosis. **M Phase (Mitotic Phase)** 1. The cell undergoes mitosis if it is a somatic cell or meiosis if it is a sex cell. 2. It allows the cell to divide and produce new cells. **CELL CYCLE\ ** 1. **INTERPHASE** 2. **SYNTHESIS PHASE** 3. **G2** **CHROMATIN** - It condensed during mitosis and called as CHROMOSOMES. - can be seen in interphase. **CHROMATID** - one of the two identical copies of a chromosome that are joined at the centromere. **TELOMERE** - are protective structures found at the ends of linear chromosomes in eukaryotic cells.  - Their primary function is to protect the ends of chromosomes from degradation and fusion with neighboring chromosomes. Without telomeres, genetic information could be lost during DNA replication. **CENTROMERE** - are specific regions of a chromosome that play a critical role in cell division, particularly during mitosis and meiosis. - Their primary function is to ensure the accurate segregation of chromosomes into daughter cells. During cell division, spindle fibers attach to the centromere, allowing chromosomes to be pulled apart and distributed correctly. **KINETOCHORE** - is a specialized protein structure found on the centromere of each chromatid (or sister chromatid) of a replicated chromosome. - serves as the attachment site for spindle fibers (microtubules) during cell division, specifically during mitosis and meiosis. **HAPLOID** - refers to a cell or organism that has a single set of chromosomes. - is often represented as "n" - are typically involved in sexual reproduction. **DIPLOID** - refers to a cell or organism that has two complete sets of chromosomes in its nucleus. - often represented as "2n" **PLOIDY** - is a term used in genetics and biology to describe the number of complete sets of chromosomes in a cell or organism. **PHASE OF MITOSIS** 1. **PROPHASE** - chromatin condense into chromosome. - The nucleolus disintegrates. - the mitotic spindle fiber starts to form. **PROMETAPHASE** - It begins after the nuclear envelope breaks down. - The centrosomes move to opposite poles. - The kinetochores found at the centromeres become apparent. 2. **METAPHASE** - The microtubules of the mitotic spindle attach and interact with the kinetochores of the chromosomes. - The chromosomes align at the center of the cell, in the metaphase plate. 3. **ANAPHASE** - The mitotic spindle pulls and separates the sister chromatids apart. - The chromatids, now called daughter chromatids, are then pulled toward the opposite poles. 4. **TELOPHASE** - Daughter chromatids decondense. - In animals, the boundary of the new cells is known as the cleavage furrow. - In plants, it is known as the cell plate. **CYTOKINESIS** After telophase, cytokinesis will divide the cell into two. Cytokinesis is not a phase of mitosis but is closely related to it. It is the final step in the cell cycle and involves the physical separation of the parent cell into two daughter cells. ensures that each daughter cell receives a complete set of organelles and a portion of the cytoplasm and cellular contents. **MEIOSIS** - a specialized type of cell division that occurs in sexually reproducing organisms, resulting in the formation of haploid gametes (sperm and egg cells). - also refers to how cells divide to produce new cells. - Sex cells or gametes are produced from meiotic division. 1. PRODUCTION OF FUNCTIONAL SEX CELLS OR GAMETES. 2. REDUCTION IN THE CHROMOSOME NUMBER 3. REDUCTION IN THE CHROMOSOME NUMBER 4. ALLOWS RESTORATION OF ORIGINAL CHROMOSOME NUMBER DURING FERTILIZATION **PROPHASE I**  **SYNAPSIS** - involves the pairing of the members of homologous chromosomes so as to allow them to undergo crossing over and to segregate them. **CROSSING OVER** - involves the pairing of the members of homologous chromosomes so as to allow them to undergo crossing over and to segregate them. - also known as genetic recombination, is a crucial process in meiosis with several significant biological and evolutionary implications. Its importance lies in its role in enhancing genetic diversity, increasing adaptability, and promoting the evolution of species. **METAPHASE I** - Alignment of Tetrads - Spindle Fiber Attachment - Checkpoint Control: - The cell checks for proper attachment of spindle fibers to the kinetochores of each chromosome. **ANAPHASE** - Separation of homologous pairs - Maternal and paternal members move to either pole. **TELOPHASE** - Chromosome Separation - Formation of Haploid Nuclei - As the separated chromosomes reach their respective poles, they begin to de-condense and unwind. - The nuclear envelope, which had broken down during earlier stages of meiosis, starts to reform around each set of chromosomes. **CYTOKINESIS** - the process of physically dividing the cell into two daughter cells, occurs simultaneously with Telophase I. - In animal cells, a cleavage furrow forms at the cell\'s equator and gradually pinches the cell\'s membrane to separate the two nuclei, resulting in two distinct daughter cells. - In plant cells, a cell plate consisting of vesicles containing cell wall material and membrane components forms at the equator. As it enlarges and fuses, it divides the cell into two daughter cells, each enclosed by a cell wall.   A diagram of cell division Description automatically generated