Cell Biology PDF

Generalized Cell A phospholipid molecule has a polar Cell structure head region that is hydrophilic and a Organelles nonpolar tail region that is hydroph...

Generalized Cell A phospholipid molecule has a polar Cell structure head region that is hydrophilic and a Organelles nonpolar tail region that is hydrophobic. Cytoplasm Cell membrane The polar region is exposed to water Cell Membrane The cell membrane , or plasma around the membrane. membrane, is the The nonpolar region is facing the outermost component of a cell. interior of the membrane. It forms a boundary between General Cell Structure material inside the cell and the outside. The interior of a cell is composed of the Materials inside the cell are cytoplasm , which is a jelly-like fluid that intracellular and those surrounds the organelles. outside are extracellular. Organelles are specialized structures It acts as a selective barrier. that perform certain functions. Cell Membrane Structure Organelles include the nucleus, The fluid-mosaic model is the model ribosomes, endoplasmic reticulum, used to describe the cell membrane Golgi apparatus, lysosomes, structure. peroxisomes, mitochondria, The membrane contains cytoskeleton, centrioles, cilia, flagella, phospholipids, cholesterol, proteins, and microvilli. and carbohydrates. Cell Nucleus 1 Phospholipids form a bilayer. The nucleus is a large organelle usually Phospholipids contain 2 regions: polar located near the center of the cell. and nonpolar. The nucleus is bounded by a nuclear envelope, which consists of outer and inner membranes with a narrow space between them. Phospholipid Structure  The nuclear membrane contains nuclear Cell Nucleus 4 pores, through which materials can pass into or out of the nucleus. Cell Nucleus 2 The nuclei of human cells contain 23 pairs of chromosomes which consist of DNA and proteins. During most of a cell ’s life, the Chromosome Structure chromosomes are loosely coiled and collectively called chromatin. When a cell prepares to divide, the chromosomes become tightly coiled and are visible when viewed with a microscope. Cell Nucleus 3 Within the nucleus are Nucleoli, which Ribosomes are diffuse bodies with no surrounding Ribosome components are produced in membrane. that are found within the the nucleolus. nucleus Ribosomes are the organelles where There are usually one to several nucleoli proteins are produced. within the nucleus. Ribosomes may be attached to other The subunits of ribosomes, a type of organelles, such as the endoplasmic cytoplasmic organelle, are formed reticulum. within a nucleolus. Ribosomes that are not attached to any These ribosomal components exit the other organelle are called free nucleus through nuclear pores. ribosomes. Ribosome Production Golgi Apparatus 1 The Golgi apparatus, also called the Golgi complex, consists of closely packed stacks of curved, membrane- bound sacs. It collects, modifies, packages, and distributes proteins and lipids manufactured by the ER. Endoplasmic Reticulum 1 The Golgi apparatus forms vesicles, The endoplasmic reticulum (ER) is a some of which are secretory vesicles, series of membranes forming sacs and lysosomes, and other vesicles. tubules that extends from the outer Golgi Apparatus 2 nuclear membrane into the cytoplasm. The rough ER is involved in protein synthesis and is rough due to attached ribosomes. The smooth ER has no attached ribosomes and is a site for lipid synthesis, cellular detoxification, and it Lysosomes stores calcium ions in skeletal muscle Lysosomes are membrane-bound cells. vesicles formed from the Golgi Endoplasmic Reticulum 2 apparatus. They contain a variety of enzymes that function as intracellular digestive systems. Vesicles formed by endocytosis may fuse with lysosomes in order to break down materials in the endocytotic vesicles.  One example is white blood cells The outer membranes have a smooth phagocytizing bacteria. contour, but the inner membranes have Lysosome Action numerous folds, called cristae, which project into the interior of the mitochondria. Mitochondria 2 The material within the inner membrane is the mitochondrial matrix and contains enzymes and mitochondrial DNA (mtDNA). Peroxisomes Cells with a large energy requirement Peroxisomes are small, have more mitochondria than cells that membrane-bound vesicles containing require less energy. enzymes that break down fatty acids, A Mitochondrion amino acids, and hydrogen peroxide (H 2 O 2 ). Hydrogen peroxide is a by-product of fatty acid and amino acid breakdown and can be toxic to a cell. The Cytoskeleton 2 The enzymes in peroxisomes break The cytoskeleton gives an internal down hydrogen. framework to the cell. Mitochondria 1 It consists of protein structures that Mitochondria (singular mitochondrion) support the cell, hold organelles in are small organelles responsible for place, and enable the cell to change producing considerable amounts of ATP shape. by aerobic (with O 2 ) metabolism. These protein structures are They have inner and outer membranes microtubules, microfilaments , and separated by a space. intermediate filaments. Microtubules A specific type of intermediate filament Microtubules are hollow structures is keratin, a protein associated with skin formed from protein subunits. cells The microtubules perform a variety of The Cytoskeleton 1 roles, including helping to support the cytoplasm of cells, assisting in cell division, and forming essential components of certain organelles, such as cilia and flagella. Microfilaments Centrioles Microfilaments are small fibrils formed The centrosome is a specialized area of from protein subunits that structurally cytoplasm close to the nucleus where support the cytoplasm, determining cell microtubule formation occurs. shape. It contains two centrioles, which are Some microfilaments are involved with normally oriented perpendicular to each cell movement. Microfilaments in other. muscle cells enable the cells to shorten, Each centriole is a small, cylindrical or contract. organelle composed of microtubules. Intermediate Filaments The centriole is involved in the process Intermediate filaments are fibrils of mitosis. formed from protein subunits that are Centriole smaller in diameter than microtubules but larger in diameter than microfilaments. They provide mechanical support to the Cilia cell. Cilia project from the surface of certain cells.  They are responsible for the movement During growth and development, cell of materials over the top of cells, such as division occurs to increase the number mucus. of cells or replace damaged or dying Cilia are cylindrical structures that ones. extend from the cell and are composed This cell division involves a cell cycle. of microtubules. The cell cycle includes two major Flagella phases: a non dividing phase, called interphase , and a cell dividing phase, Flagella have a structure similar to that termed mitosis. of cilia but are much longer, and they usually occur only one per cell. The Cell Cycle 2 Sperm cells each have one flagellum, A cell spends most of its life cycle in which propels the sperm cell. interphase which is divided into three Microvilli phases: G 1 phase, during which the cell carries Microvilli are specialized extensions of out normal metabolic activity the cell membrane that are supported by S phase, during which the DNA is microfilaments. replicated; and They do not actively move as cilia and G 2 phase, during which the cell flagella do. prepares to divide. At the end of Microvilli are numerous on cells that interphase, a cell has two complete sets have them and they increase the surface of genetic material area of those cells. They are abundant on the surface of The Cell Cycle 3 cells that line the intestine, kidney, and other areas in which absorption is an important function. The Cell Cycle 1 Cell Genetic Content During metaphase, the chromosomes Each human cell (except sperm and egg) align near the center of the cell. contains 23 pairs of chromosomes, a The movement of the chromosomes is total of 46. regulated by the attached spindle fibers. The sperm and egg contain 23 Anaphase chromosomes total. At the beginning of anaphase, the One pair of chromosomes are the sex chromatids separate and each chromatid chromosomes, which consist of two X is called a chromosome. chromosomes if the person is a female Each of the two sets of 46 chromosomes or an X and Y chromosome if the person is moved by the spindle fibers toward is a male. the centriole at one of the poles of the Mitosis cell. Mitosis involves formation of 2 daughter At the end of anaphase, each set of cells from a single parent cell. chromosomes has reached an opposite Mitosis is divided into four phases: pole of the cell, and the cytoplasm prophase, metaphase, anaphase, and begins to divide. telophase. Telophase Prophase During telophase, the chromosomes in During prophase the chromatin each of the daughter cells become condenses to form visible chromosomes. organized to form two separate nuclei, Microtubules, termed spindle fibers, one in each newly formed daughter cell. form to assist in breaking the The chromosomes begin to unravel and centromere between the chromatids and resemble the genetic material during move the chromosomes to opposite interphase. sides of the cell. Following telophase, cytoplasm division The nuclear membrane dissolves. is completed, and two separate daughter Metaphase cells are produced.