Biology Unit 2: Molecules and Membranes

The primary building blocks of cells, capable of replicating and performing specialized tasks in multicellular organisms.

Water, inorganic ions, and organic molecules (containing carbon).

A molecule with a slightly positive charge on the hydrogen atoms and a slightly negative charge on the oxygen atom, allowing it to form hydrogen bonds.

Inorganic ions represent less than 1% of the cell's mass. They are essential for various metabolic processes and play a critical role in cellular functions.

Macromolecules that make up over 90% of the dry weight of cells. They consist of carbohydrates, lipids, proteins, and nucleic acids.

Simple sugars (monosaccharides) are the primary energy source for cells. Their breakdown provides energy and starting material for the synthesis of other cellular compounds.

Polysaccharides are complex carbohydrates made up of long chains of simple sugars. They serve as energy storage and structural components of the cell.

A long chain of repeating units of amino acids. Proteins have various functions including structural support, enzymatic activity, transport, defense, and communication.

The basic building block of carbohydrates. It has the general formula (CH2O)n, where n is the number of carbon atoms. Glucose, the main source of energy in cells, is a common example.

A cyclic form of a monosaccharide with 5 or more carbons. It exists in two forms: alpha (α) and beta (β), depending on the configuration of the first carbon atom (C1).

A covalent bond that links two monosaccharides by removing a water molecule. It forms between two carbon atoms.

A short chain of monosaccharides linked by glycosidic bonds. It can have a few to several sugar units.

A long chain of monosaccharides linked by glycosidic bonds. They can have hundreds or thousands of sugar units.

The main storage form of carbohydrates in animals. It is composed of glucose units linked by α(1→4) glycosidic bonds. It has branches with α(1→6) bonds.

The main storage form of carbohydrates in plants. It is composed of amylose and amylopectin. Amylose is a linear chain of glucose units linked by α(1→4) bonds. Amylopectin also has branches with α(1→6) bonds.

The primary structural component of plant cell walls. It is composed of glucose units linked by β(1→4) glycosidic bonds. Its linear chains are packed together to form strong fibers.

Simple lipids with a long hydrocarbon chain and a carboxyl group at one end. They are hydrophobic due to their nonpolar C-H bonds which makes them insoluble in water.

Stored form of fatty acids, composed of three fatty acid molecules linked to a glycerol molecule. Primarily used as an energy reserve for cells, providing more than twice the energy per weight compared to carbohydrates.

Amphipathic molecules, containing both hydrophobic (nonpolar) tails and hydrophilic (polar) heads, crucial components of cell membranes.

A type of phospholipid where two fatty acid chains are attached to a glycerol molecule. The third carbon of glycerol is linked to a phosphate group, which in turn can bind to various other polar molecules. They are essential for cell membrane structure and function.

A non-glyceric phospholipid found in cell membranes, where two fatty acid chains are linked to a polar head group containing serine instead of glycerol. It plays a crucial role in cell signaling and membrane stability.

Lipid molecules that are present in cell membranes alongside phospholipids. They are involved in maintaining membrane fluidity and regulate the permeability of cell membranes.

Lipids that have a sugar molecule attached to their structure. They are located primarily in the outer leaflet of cell membranes and play roles in cell recognition and communication.

Lipids are essential molecules in cells. They serve as energy sources, building blocks for membranes, and play vital roles in cell signaling.

Large organic molecules that carry genetic information. They are composed of nucleotides, which are made up of a sugar, a phosphate group, and a nitrogenous base.

A type of nucleic acid that carries genetic information in the form of a double helix. It's made up of two strands of nucleotides held together by hydrogen bonds between complementary bases.

A type of nucleic acid that plays a crucial role in protein synthesis. It carries genetic information from DNA to ribosomes, where it serves as a template for protein production.

The process by which nucleotides are joined together to form a nucleic acid chain. It involves the formation of a phosphodiester bond between the 5'-phosphate of one nucleotide and the 3'-OH of the next.

The direction in which nucleotides are added during the synthesis of nucleic acids. New nucleotides are always added to the 3'-OH group of the growing chain.

The sequence of bases in a polynucleotide chain that determines the genetic code. It dictates the order of amino acids in a protein, ultimately influencing its structure and function.

The main energy currency used by cells, providing energy for various metabolic processes.

Cyclic adenosine monophosphate (cAMP) is a crucial second messenger in signaling pathways, relaying signals from the cell surface to intracellular targets.

Proteins are the workhorses of the cell, responsible for diverse functions such as structural support, transport, defense against infections, enzymatic activity, and communication.

Amino acids are the building blocks of proteins. Each amino acid consists of a central carbon atom linked to an amino group, a carboxyl group, a hydrogen atom, and a unique side chain (R group).

The side chain (R group) of an amino acid determines its chemical properties, dictating its interaction with other molecules and its role in protein structure and function.

A peptide bond is a covalent bond that connects two amino acids. It is formed between the carboxyl group of one amino acid and the amino group of the next amino acid.

A polypeptide chain is a linear sequence of amino acids linked by peptide bonds. Proteins are made up of one or more polypeptide chains.

Proteins fold into intricate three-dimensional structures that are crucial for their function. These structures are determined by the sequence of amino acids and interactions between them.

The linear sequence of amino acids in a polypeptide chain, forming the building block for all protein structures.

The local spatial arrangements of amino acids within a polypeptide chain, stabilized by hydrogen bonds. Most commonly observed structures include the α helix and the β sheet.

The three-dimensional folding of a single polypeptide chain, determined by interactions between amino acid side chains. These interactions include hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges.

The arrangement of multiple polypeptide chains (subunits) within a protein, stabilized by interactions similar to those found in tertiary structure. These subunits can be identical or different.

The basic structural unit of all biological membranes, composed of two layers of phospholipid molecules. The hydrophobic tails of the phospholipids point inwards, while the hydrophilic heads face outwards.

Proteins embedded within the phospholipid bilayer, performing various functions. Examples include transporters, receptors, and enzymes.

The ability of membrane lipids and proteins to move laterally within the bilayer, contributing to its fluidity and functionality.

The property of a membrane that allows certain molecules to pass through it, while blocking others. This selective permeability is crucial for maintaining cellular homeostasis.