Chapter 2: Cells and Tissues Lesson 2.1 Molecules of Life
Molecules of Life • An almost countless number of different types of molecules exists in the human body. • Biochemistry is the detailed study of the molecules of life, how they are made, how they interact, and how they are broken down. • Many chemicals important for life are organic molecules. Ex. Glucose (C6H12O6) • Organic molecules always contain carbonand hydrogen. • They usually contain oxygen, as well as nitrogen, phosphorous, sulfur, and other elements CHNOPS
Molecules of Life • Major classes of large organic molecules in the body include: • Carbohydrates • Proteins • Lipids • Nucleic acids • Water*
Carbohydrates • These are also known as saccharides, they are “sugar or starch” molecules • Simple carbohydrates • Glucose – circulates in the body • Complex carbohydrates • Glycogen (stored in animals) • The main functionof carbohydrates in the body is to serve as a source of chemical energy, or fuel. • The body can quickly utilize this fuel to make energy (ATP)
Proteins • Proteins are large biological molecules made of chains of hundreds of amino acids. • There are 20 common amino acids, which are the building blocks of proteins • Amino acids are linked together by peptide bonds • Long chains of amino acids are called polypeptides
Proteins • The structure and shape of a protein is organized into the following levels: • Primary – amino acid chain (polypeptide) • Secondary • Tertiary • Quaternary –2 or more polypeptides = protein
Proteins • Proteins have many functions in the body including acting as: • Structural elements: collagen which gives strength to ligaments and tendons • Enzymes: salivary amylase found in saliva and breaks down carbohydrate molecules into smaller sugar molecules – accelerate biological reactions
Lipids • Lipids are fats, oils and related molecules. • Fatty acids: • Key building blocks of other lipids. Hydrocarbon with carboxylic acid group. • Glycerides • Composed of a glycerol molecule (a simple sugar) with one, two, or three fatty acids attached, to make mono-, di-, and triglycerides • Glycerides are important energy storage molecules in the body.
Lipids • Phospholipids • Are similar to glycerides with a hydrophilic phosphate head and a hydrophobic tail • As a result, phospholipids in a watery environment tend to form bilayers Ex. Cell membranes • Steroids • Have a structure different from other lipids • Have the same four-ring backbone but differ in the attached side groups • Three well-known steroid molecules—cholesterol, testosterone, and estrogen
Nucleic Acids • Nucleic acids are key information-carrying molecules in cells. • They are chains (polymer) of nucleotides (subunits) • The two kinds of nucleic acids found in cells are: • Deoxyribonucleic acid (DNA ) • Ribonucleic acid (RNA) • messenger RNA (mRNA) • transfer RNA (tRNA) • ribosomal RNA (rRNA)
Energy • Adenosine Triphosphate (ATP) • is a nucleotide composed of an adenine base, a sugar, and three phosphate groups. • This is an energy source used in many cellular processes
Water* • Water makes up about two-thirds of the mass of the human body. • Hydrogen bonding • These are relatively weak bonds and are responsible for several biologically important properties of water such as solvent properties • Good solvent • The polar nature of water makes it a good solvent for many compounds. H2O
Water • pH • A small fraction of water molecules in solution dissociate to make hydrogen ion (H+) plus hydroxide ion (OH-).
Review and Assessment True or False? • Proteins are made up of fatty acids. 2. Glucose is a simple carbohydrate. 3. A steroid is a type of lipid. 4. A nucleic acid is a chain of amino acids. 5. Water has one hydrogen atom. FALSE TRUE TRUE FALSE FALSE
Chapter 2: Cells and Tissues Lesson 2.2 Cells
Anatomy and Physiology of Cells • The cells of the human body are surrounded by extracellular fluid, which is mostly water, and an extracellular matrix. • Plasma membrane makes up the shell of the cell • regulates the movement of material in and out of the cell • Cytoplasm • liquid inside the cell which contains the organelles • Nucleus • control center of cell
Plasma Membrane Components • This is a phospholipid bilayer which contains cholesterol and a variety of proteins including channel proteins which allow water or small, charged particles such as sodium, to pass into or out of the cell.
Membrane Transport • Membrane transport is the movement of substances across the plasma membrane which can occur on one of two ways: • Passive transport • Requires no energy • Usually involves diffusion – movement of a substance from an area of high to low concentration. • Active transport • Requires energy expenditure • Involves the movement of a substance from an area of low to high concentration • Sodium-potassium pump found in neuron membranes used to move Na+ out of the cell and K+ into the cell
Cytoskeleton • The cytoskeleton strengthens and gives the cell its shape. • The cytoskeleton contains three types of long fibers: • Microfilaments: • the thinnest of these fibers, especially prominent in muscle cells. • Intermediate filaments: • give the cell strength to resist external pulling forces • Microtubules: • help to separate and organize chromosomes during cell division.
Organelles in the Cytoskeleton • Microvilli • Finger-like extensions that increase the surface area of a cell. • Cilia • Hair-like projections that actively flex back and forth to move mucus or fluids across the outside of the cell • Centrioles • The centrioles help guide the movement and separation of chromosomes during cell division.
Mitochondria and Energy • Mitochondria • Tubular- shaped structures in the cytoplasm of cells responsible for making ATP, the universal carrier of energy within cells • Powerhouses of the cell
Golgi Apparatus • The Golgi is a set of membranous discs in the cytoplasm, usually between the endoplasmic reticulum and the plasma membrane of the cell. • Forms small vesicles used to package or move materials out of the cell.
Ribosomes and Endoplasmic Reticulum • Ribosomes are very large enzymes that make polypeptides. • Endoplasmic reticulum (ER) is a network of membranes in the cytoplasm connected to the nuclear envelope • Rough ER has ribosomes attached to it and is a site for protein production and modification • Smooth ER has no ribosomes, it is a site where “replacement” membrane is made for the cell.
The Nucleus • The nucleus is enclosed by nuclear envelope • Contains the cells genetic information – DNA, some RNA and proteins • The nucleolus is an area in the nucleus where ribosomal RNA is made and packaged
DNA, RNA, and Proteins • The sequence of bases in DNA contains the information essential for making the RNA and Proteins needed for life. • The production of RNA from DNA is called transcription. • The production of Proteins from RNA is called translation.
Life Cycle of a Cell • Most cells do not have a long life span • Intestinal cells have a life span of just 2 to 7 days. • Red blood cells live for about 120 days (4 months). • Many of the nerve cells in your brain, on the other hand, are as old as you are. • Cells must divide to make new cells for our bodies. • Interphase: the cell performs its usual functions and prepares for cell division. • The mitotic phase: cell divides into two identical daughter cells. • Mitosis is the division of the cell nucleus and chromosomes • prophase • metaphase • anaphase • telophase • Cytokinesis is the division of the cell cytoplasm, final step of cell division.
Mitosis • Prophase • chromatin condenses into chromosomes, cell membrane breaks down • Metaphase • chromosomes line up in the center of the cell • Anaphase • centromeres are cut in half, sister chromatids pull toward centrioles • Telophase • chromosomes “decondense,” new nuclear membrane forms
Cancer • Cancer is the uncontrolled division and growth of abnormal cells. • grows too much • grows where it does not belong • does not die when it should • Cancer is caused by damage to a cell’s DNA molecules.