Cell Organelles and Biomolecules - Our Lady of Fatima University PDF

BIOCHEMISTRY h Cell Organelles and Biomolecules y CELL THEORY  CELL THEORY ▪ The microscopes we use today are far more complex than those used in the 1600s by Antony van Leeuwenhoek, a Dutch shopkeeper who had great skill in crafting lenses. Des...

BIOCHEMISTRY h Cell Organelles and Biomolecules y CELL THEORY  CELL THEORY ▪ The microscopes we use today are far more complex than those used in the 1600s by Antony van Leeuwenhoek, a Dutch shopkeeper who had great skill in crafting lenses. Despite the limitations of his now-ancient lenses, van Leeuwenhoek observed the movements of protista (a type of single-celled organism) and sperm, which he collectively termed “animalcules. ”  CELL THEORY ▪ In a 1665 publication called Micrographia, experimental scientist Robert Hooke coined the term “cell” for the box-like structures he observed when viewing cork tissue through a lens. In the 1670s, van Leeuwenhoek discovered bacteria and protozoa. Later advances in lenses, microscope construction, and staining techniques enabled other scientists to see some components inside cells. STRUCTURE OF AN ANIMAL CELL  CELL THEORY ▪ By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells. Rudolf Virchow later made important contributions to this theory. CELL THEORY ▪ Schleiden and Schwann proposed spontaneous generation as the method for cell origination, but spontaneous generation (also called abiogenesis) was later disproven. Rudolf Virchow famously stated “Omnis cellula e cellula”… “All cells only arise from pre-existing cells. “The parts of the theory that did not have to do with the origin of cells, however, held up to scientific scrutiny and are widely agreed upon by the scientific community today. ▪ The generally accepted portions of the modern Cell Theory are as follows: ▪ The cell is the fundamental unit of structure and function in living things. ▪ All organisms are made up of one or more cells. ▪ Cells arise from other cells through cellular division. ▪ The expanded version of the cell theory can also include: ▪ Cells carry genetic material passed to daughter cells during cellular division ▪ All cells are essentially the same in chemical composition ▪ Energy flow (metabolism and biochemistry) occurs within cells  CELL DEFINITION ▪ Cells are the basic unit of life. In the modern world, they are the smallest known world that performs all of life’s functions. All living organisms are either single cells, or are multicellular organisms composed of many cells working together. ▪ Cells are the smallest known unit that can accomplish all of these functions. Defining characteristics that allow a cell to perform these functions include: ▪ A cell membrane that keeps the chemical reactions of life together. ▪ At least one chromosome, composed of genetic material that contain the cell’s “blueprints” and “software.” ▪ Cytoplasm – the fluid inside the cell, in which the chemical processes of life occur.  FUNCTION OF CELLS ▪ Scientists define seven functions that must be fulfilled by a living organism. These are: ▪ A living thing must respond to changes in its environment. ▪ A living thing must grow and develop across its lifespan. ▪ A living thing must be able to reproduce, or make copies of itself. ▪ A living thing must have metabolism. ▪ A living thing must maintain homeostasis, or keep its internal environment the same regardless of outside changes. ▪ A living thing must be made of cells. ▪ A living thing must pass on traits to its offspring. CELL TYPES ORGANELLES ORGANELLES ▪ Very small (Microscopic) ▪ Perform various functions for a cell ▪ Found in the cytoplasm ▪ May or may not be membrane-bound  CELL OR PLASMA MEMBRANE ▪ Composed of double layer of phospholipids and proteins ▪ Surrounds outside of ALL cells ▪ Controls what enters or leaves the cell ▪ Living layer Outside of cell Carbohydrate chains Proteins Cell membrane Inside of cell Protein (cytoplasm) channel Lipid bilayer PHOSPHOLIPIDS ▪ Heads contain glycerol & phosphate and are hydrophilic (attract water) ▪ Tails are made of fatty acids and are hydrophobic (repel water) ▪ Make up a bilayer where tails point inward toward each other ▪ Can move laterally to allow small molecules (O2, CO2, & H2O to enter) THE CELL MEMBRANE IS FLUID Molecules in cell membranes are constantly moving and changing CELL MEMBRANE PROTEINS ▪ Proteins help move large molecules or aid in cell recognition ▪ Peripheral proteins are attached on the surface (inner or outer) ▪ Integral proteins are embedded completely through the membrane 21 CELL MEMBRANE Cell membrane IN PLANTS Lies immediately against the cell wall in plant cells Pushes out against the cell wall to maintain cell shape  Cell wall CELL WALL Found outside of the cell membrane Nonliving layer Supports and protects cell Found in plants, fungi, & bacteria CYTOPLASM OF A CELL cytoplasm Jelly-like substance enclosed by cell membrane Provides a medium for chemical reactions to take place  cytoplasm MORE ON CYTOPLASM Contains organelles to carry out specific jobs THE CONTROL ORGANELLE - NUCLEUS Controls the normal activities of the cell Contains the DNA in chromosomes Bounded by a nuclear envelope (membrane) with pores Usually the largest organelle  MORE ON THE NUCLEUS Nucleus Each cell has fixed number of chromosomes that carry genes Genes control cell characteristics NUCLEAR ENVELOPE ▪ Double membrane surrounding nucleus ▪ Also called nuclear membrane ▪ Contains nuclear pores for materials to enter & leave nucleus Nuclear pores  INSIDE THE NUCLEUS The genetic material (DNA) is found DNA is spread out DNA is condensed & And appears as wrapped around proteins CHROMATIN forming in non-dividing cells as CHROMOSOMES in dividing cells WHAT DOES DNA DO? DNA is the hereditary material of the cell Genes that make up the DNA molecule code for different proteins NUCLEOLUS ▪ Inside nucleus ▪ Disappears when cell divides ▪ Makes ribosomes that make proteins  CYTOSKELETON ▪ Helps cell maintain cell shape ▪ Also help move organelles around ▪ Made of proteins ▪ Microfilaments are threadlike & made of ACTIN ▪ Microtubules are tubelike & made of TUBULIN  CYTOSKELETON MICROTUBULES MICROFILAMENTS CENTRIOLES ▪ Found only in animal cells ▪ Paired structures near nucleus ▪ Made of bundle of microtubules ▪ Appear during cell division forming mitotic spindle ▪ Help to pull chromosome pairs apart to opposite ends of the cell MITOCHONDRION (PLURAL = MITOCHONDRIA) ▪ “Powerhouse” of the cell ▪ Generate cellular energy (ATP) ▪ More active cells like muscle cells have MORE mitochondria ▪ Both plants & animal cells have mitochondria ▪ Site of CELLULAR RESPIRATION (burning glucose) MITOCHONDRIA Surrounded by a DOUBLE membrane Has its own DNA Folded inner membrane called CRISTAE (increases surface area for more chemical Reactions) Interior called MATRIX INTERESTING FACT --- ▪ Mitochondria Come from cytoplasm in the EGG cell during fertilization Therefore … ▪ You inherit your mitochondria from your mother! ENDOPLASMIC RETICULUM - ER ▪ Network of hollow membrane tubules ▪ Connects to nuclear envelope & cell membrane ▪ Functions in Synthesis of cell products & Transport Two kinds of ER ---ROUGH & SMOOTH ROUGH ENDOPLASMIC RETICULUM (ROUGH ER) ▪ Has ribosomes on its surface ▪ Makes membrane proteins and proteins for export out of cell ROUGH ENDOPLASMIC RETICULUM (ROUGH ER) ▪ Proteins are made by ribosomes on ER surface ▪ They are then threaded into the interior of the Rough ER to be modified and transported FUNCTIONS OF THE SMOOTH ER ▪ Makes membrane lipids (steroids) ▪ Regulates calcium (muscle cells) ▪ Destroys toxic substances (Liver) ENDOMEMBRANE SYSTEM Includes nuclear membrane connected to ER connected to cell membrane (transport) RIBOSOMES ▪ Made of PROTEINS and rRNA ▪ “Protein factories” for cell ▪ Join amino acids to make proteins through protein synthesis 🡪 RIBOSOMES Can be attached to Rough ER OR Be free (unattached) in the cytoplasm  GOLGI BODIES ▪ Stacks of flattened sacs CIS ▪ Have a shipping side (cis face) & a receiving side (trans face) ▪ Receive proteins made by ER TRANS ▪ Transport vesicles with modified proteins pinch off the ends Transport vesicle GOLGI BODIES Look like a stack of pancakes Modify, sort, & package molecules from ER for storage OR transport out of cell Golgi Animation Materials are transported from Rough ER to Golgi to the cell membrane by VESICLES LYSOSOMES ▪ Contain digestive enzymes ▪ Break down food, bacteria, and worn out cell parts for cells ▪ Programmed for cell death (APOPTOSIS) ▪ Lyse & release enzymes to break down & recycle cell parts)  Lysosome Digestion Cells take in food by phagocytosis Lysosomes digest the food & get rid of wastes CILIA & FLAGELLA ▪ Function in moving cells, in moving fluids, or in small particles across the cell surface CILIA & FLAGELLA ▪ Cilia are shorter and more numerous on cells ▪ Flagella are longer and fewer (usually 1-3) on cells CELL MOVEMENT WITH CILIA & FLAGELLA CILIA MOVING AWAY DUST PARTICLES FROM THE LUNGS VACUOLES ▪ Fluid filled sacks for storage ▪ Small or absent in animal cells ▪ Plant cells have a large Central Vacuole VACUOLES ▪ In plants, they store Cell Sap ▪ Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes  CHLOROPLASTS ▪ Found only in producers (organisms containing chlorophyll) ▪ Use energy from sunlight to make own food (glucose) ▪ Energy from sun stored in the Chemical Bonds of Sugars CHLOROPLASTS ▪ Surrounded by DOUBLE membrane ▪ Outer membrane smooth ▪ Inner membrane modified into sacs called Thylakoids ▪ Thylakoids in stacks called Grana & interconnected ▪ Stroma – gel like material surrounding thylakoids 57  CARBOHYDRATES ▪ Carbohydrates are chemically defined as polyhydroxy aldehydes or ketones or compounds which produce them on hydrolysis. In layman’s terms, we acknowledge carbohydrates as sugars or substances that taste sweet. ▪ They are collectively called as saccharides (Greek: sakcharon = sugar). Depending on the number of constituting sugar units obtained upon hydrolysis, they are classified as monosaccharides (1 unit), oligosaccharides (2-10 units) and polysaccharides (more than 10 units). ▪ They have multiple functions’ viz. they’re the most abundant dietary source of energy; they are structurally very important for many living organisms as they form a major structural component, e.g. cellulose is an important structural fibre for plants.  PROTEINS ▪ Proteins are another class of indispensable biomolecules, which make up around 50 per cent of the cellular dry weight. ▪ Proteins are polymers of amino acids arranged in the form of polypeptide chains. ▪ The structure of proteins is classified as primary, secondary, tertiary and quaternary in some cases. These structures are based on the level of complexity of the folding of a polypeptide chain. ▪ Proteins play both structural and dynamic roles. Myosin is the protein that allows movement by contraction of muscles. Most enzymes are proteinaceous in nature.  NUCLEIC ACIDS ▪ Nucleic acids refer to the genetic material found in the cell that carries all the hereditary information from parents to progeny. There are two types of nucleic acids namely, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). ▪ The main function of nucleic acid is the transfer of genetic information and synthesis of proteins by processes known as translation and transcription. ▪ The monomeric unit of nucleic acids is known as nucleotide and is composed of a nitrogenous base, pentose sugar, and phosphate. The nucleotides are linked by a 3’ and 5’ phosphodiester bond. ▪ The nitrogen base attached to the pentose sugar makes the nucleotide distinct. There are 4 major nitrogenous bases found in DNA: adenine, guanine, cytosine, and thymine. In RNA, thymine is replaced by uracil. ▪ The DNA structure is described as a double-helix or double-helical structure which is formed by hydrogen bonding between the bases of two antiparallel polynucleotide chains. Overall, the DNA structure looks similar to a twisted ladder.  LIPIDS ▪ Lipids are organic substances that are insoluble in water, soluble in organic solvents, are related to fatty acids and are utilized by the living cell. ▪ They include fats, waxes, sterols, fat-soluble vitamins, mono-, di- or triglycerides, phospholipids, etc. ▪ Unlike carbohydrates, proteins, and nucleic acids, lipids are not polymeric molecules. Lipids play a great role in the cellular structure and are the chief source of energy.