Cohesion/Adhesion: Water, with its polarity, can attach to other molecules as a result of hydrogen bonding. The attachment of water molecules to other water molecules is cohesion, and the attachment of water molecules to other molecules is adhesion. Cohesion and adhesion play vital roles in water transport in plants.
Moderation of temperature: Heat must be absorbed in order to break hydrogen bonds, and heat is released when hydrogen bonds form. Hydrogen bonds are constantly being formed and broken all the time, releasing and absorbing heat, moderating the temperature of water.
Expansion upon freezing/Why ice floats: Water begins to freeze when its molecules are no longer moving vigorously enough to break their hydrogen bonds. As the temperature falls to 0 degrees Celsius, the water becomes locked into a crystalline lattice, each water molecule bonded to four partners. The hydrogen bonds keep the molecules at "arm's length," far enough apart to make ice about 10% less dense than liquid water at 4 degrees Celsius, causing the ice to float.
Solvent of Life: Because of water's polarity, ionic molecules such as sodium chloride have a mutual affinity for water through electrical attraction. The oxygen regions of water cling onto the sodium cations, and the hydrogen regions of water cling onto the chloride anions. As a result, water molecules surround the individual sodium and chloride ions, separating them from one another. A nonpolar molecule can also be dissolved in water when water molecules surround each of the solute molecules, forming a hydration shell.
Polysaccharides: Polysaccharides generally perform one or two tasks. They either store energy or are structural support. Starch and glycogen can be highly compacted together, making them good for energy storage. Cellulose and chitin are linear polymers, making them good for structural support in plants and animals.
Proteins: The structure of the protein greatly influences its function. Proteins contain an amino group, carboxyl group, and a side chain (the R group). Proteins have many different functions, (enzymes, antibodies, insulin, receptors, storage, transport, motor movement, structural support as collagen), and the side chains dictate what function the protein performs. Some proteins contain nonpolar side chains, which makes them hydrophobic. Some proteins contain polar side chains, which makes them hydrophilic. In addition, if the side chain contains a charge, it will either be acidic (negatively charged) or basic (positively charged). The primary structure of a protein is held together by a peptide bond and composed of a carboxyl group, amino group, and R group in a linear sequence. The primary structure of a protein contains its amino acid sequence, which determines the protein's function. If primary structure is screwed up, then the rest of the protein levels will be as well, and the protein will be unable to perform its function. The secondary structure of proteins are the folded and coiled polypeptide chains. There are two secondary structures of proteins, an alpha helix, and a beta pleated sheet. Tertiary structure contains a disulfide bridge, hydrogen bonds, ionic bonds, and hydrophobic interactions. Quaternary structure contains polypeptide chains with peptide and hydrogen bonds, and it's the entire protein structure that results from the polypeptide units.
Nucleic Acids: The DNA must unzip to create a complementary strand out of the set of Nitrogen bases on the strand being synthesized. The purpose of DNA and RNA is to have all of the genetic codes to code for the making of certain types of proteins throughout the body of the organism it inhabits. Ribosomes are produced by the nucleolus (which contains the codes to make it). Nitrogen Bases complete a nucleotide structure and code for how and what things will get created (proteins). They come in triplet sequences to code for certain amino acids.
DNA is simple, consisting of a deoxyribose sugar, four nitrogenous bases (adenine, guanine, cytosine, thymine), and a phosphate group. It can hold many sequences of amino acids, and different combinations of that. DNA can also be condensed into chromosomes, which can fit into cells, and prevent itself from tangling so it's easier to unwind and be read. DNA also has certain proofreading processes, making sure that there are no abnormalities so the exact same information is passed down correctly. During endocytosis, the cell takes in macromolecules and particulate matter by forming new vesicles from the plasma membrane. A small area of the plasma membrane sinks inward to form a pocket, and as it deepens, it pinches in, forming a vesicle containing material that had been outside the cell. There are three types of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis.
Phagocytosis: A cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane-enclosed sac, or vacuole. The particle is digested after the vacuole fuses with a lysosome containing hydrolytic enzymes.
Pinocytosis: The cell "gulps" droplets of extracellular fluid into tiny vesicles.
Receptor-mediated endocytosis: Extracellular substances, or ligands, bind to the receptor proteins clustered in coated pits. When binding occurs, the coated pit forms a vesicle containing the ligand molecules. After this ingested material is freed from the vesicle, the receptors are recycled to the plasma membrane by the same vesicle.
Endoplasmic reticulum: The ER consists of a network of membranous tubules and sacs called cisternae. The ER membrane separates the internal compartment of the ER, called the ER lumen or cisternal space, from the cytosol. The ER membrane is continuous with the nuclear envelope, therefore the space between the two membranes of the envelope is continuous with the lumen of the ER. In addition, the smooth ER and the rough ER are kept separate and have different structures and functions. The rough ER has ribosomes on them, while the smooth ER doesn't. The smooth ER synthesizes lipids, phospholipids, and steroids. The rough ER is involved with the synthesis of proteins.
Mitochondria: The mitochondria is highly compartmentalized with a double membrane and its own DNA. The folds called "cristae" give more surface area for cellular respiration to occur. Enzymes for this process are all over the inner cristae and the inner membrane for maximum efficiency.
Chloroplasts: The compartmentalization of the chloroplast organelle within the plant cell enables chloroplasts to effectively perform photosynthesis. It has a double membrane, DNA, ribosomes, and a lot of membrane surface area. Inside the inner membrane called granum made of stacked thylakoids filled with lumen and surrounded by stroma. There is a lot of membranous surface area within this organelle to increase productivity. Chloroplasts have the green pigment chlorophyll which along with enzymes absorbs light energy and synthesizes energy through a photosynthesis.
Golgi: The Golgi receives proteins and lipids from the rough ER and then "packages" them into vesicles for transport to other parts of the cell. It is generally thought that secretory proteins in the Golgi act as receptors for the proteins/lipids that come from the ER, and then instruct vesicles to bud off from the main Golgi body to transport materials to other parts of the cell.
Nuclear envelope: It is a double lipid bilayer that surrounds the nucleus. It consists of nuclear pores that regulate the passage of proteins and RNA. It has a good amount of control over the information flow of the nucleus. The outer bilayer has a high concentration of proteins. The inner bilayer is covered by the nuclear lamina which is made of intermediate filaments. Within the nuclear membrane is the chromatin which contains DNA. The DNA is transcribed to mRNA and is then transmitted to the rest of the cell for various processes; information from the cytoplasm is transmitted through the envelope to the nucleus. The envelope is also connected to the ER membranes.
The first stage, interphase, consists of three parts. During G1, the cell simply grows and performs its functions. During S phase, the DNA is replicated. During G2, the centrosome replicates and the cell continues to grow. Next is prophase, in which the chromosomes condense, the mitotic spindle begins to form, and the centrosomes begin to move to opposite ends of the cell. Also, the nucleolus disappears, and the nuclear envelope begins to fragment. In metaphase, microtubules attach to the kinetochores of the chromosomes and tug them back and forth into single-file alignment along the middle of the cell (the metaphase plate). During anaphase, the microtubules contract, pulling each sister chromatid to opposite ends of the cell- it's at this moment that each sister chromatid becomes its own chromosome. The microtubules not attached to the chromosomes (nonkinetochore microtubules) lengthen and elongate the cell. During telophase, two daughter nuclei begin to form in the cell, and the middle of the cell pinches inward on both sides, forming a cleavage furrow. The chromosomes begin to decondense. Mitosis (the division of the nucleus) is now complete. Cytokinesis occurs afterwards, when the cell finally splits in two. Cell division is controlled in many ways, one of them being regulation of a growth factor such as PDGF (platelet-derived growth factor). Even if all other conditions are favorable, cells won't divide unless certain growth factors are present. Another way cell division is controlled is via anchorage dependence- cells must be attached to another surface to divide. Cell division is also controlled through density-dependent inhibition (when crowded cells stop dividing once they make contact with another cell of the same type). However, a primary method of controlling cell division involves regulatory cyclins (proteins that get their name from their cyclically fluctuating content in the cell) and protein kinases (enzymes that activate other proteins by phosphorylating them). The concentration of kinases actually remains constant throughout the cycle, it's simply that the the number of ACTIVE kinases fluctuates. Because the kinase needs to be attached to a cyclin to be active, they're known as Cdks (cyclin-dependant kinases). An important Csk complex is called MPF. Synthesis of cyclin begins in late S phase and continues through G2. Because cyclin is protected from degradation during this stage, it accumulates. The accumulated cyclins combine with recycled Cdk molecules, producing enough molecules of MPF to pass the G2 checkpoint and begin mitosis. MPF promotes mitosis by phosphorylating various important proteins, and its activity peaks during metaphase. However, during anaphase, the cyclin component of MPF is degraded, terminating the M phase. The cell reenters G1, during which conditions in the cell favor degradation of cyclin and the Cdk component of MPF is recycled.