BIOLOGICAL COMPOUNDS

Flashcards of key vocabulary and definitions.

Atom

The smallest constituent unit of ordinary matter that has the properties of a chemical element.

Element

A substance made up of only one type of atom.

Molecule

Two or more atoms chemically bonded together.

Compound

Two or more elements chemically bonded together.

Organic compound

A compound containing carbon and hydrogen and produced by a living organism.

Inorganic compound

A compound not containing carbon and hydrogen and not produced by living organisms.

Macronutrient

A nutrient that is required by a living organism in small amounts, e.g. iron and calcium.

Micronutrient

A nutrient that is required by a living organism in very small quantities e.g. copper and zinc.

Micronutrients

needed in minute (trace) concentrations. E.g. copper and zinc

Macronutrients

needed in small concentrations. (You need to know these 4).

Magnesium (Mg2+)

A component of chlorophyll molecules. A deficiency causes chlorosis. Plant growth is often stunted due to a lack of glucose (reduced photosynthesis)

Magnesium (Mg2+ in animals)

Needed for teeth and bones

Iron (Fe2+) in plants

Needed as a cofactor in chlorophyll synthesis. A deficiency also leads to chlorosis

Iron (Fe2+) in animals

A component of haemoglobin. Haemoglobin is responsible for the transport of oxygen in the blood. A deficiency in Iron leads to anemia.

Phosphate ions (PO43-)

A component of DNA, RNA and ATP. A component of phospholipids found in plasma membranes

Calcium (Ca2+) in plants

A component of the middle lamella of cell walls. Deficiency leads to stunted growth due to poor cell wall development

Calcium (Ca2+) in animals

A component of bones and teeth. A deficiency could lead to rickets

Anabolic reactions

building up molecules.

Catabolic reactions

breaking down molecules

Monomers

small individual molecules which may be joined together in a repeating fashion to form a larger more complex molecule called a polymer.

Structure of Water

Water (H2O) consists of two hydrogen atoms covalently bonded to one oxygen atom. Each hydrogen shares a pair of electrons with the oxygen. The shared electrons are not shared equally. The oxygen has a greater affinity for electrons than the hydrogens, so it ‘pulls’ the electrons closer.This leaves the water molecule with positive and negative charged ends and is therefore called a polar molecule (molecule with separated charges). Water is a dipole.

Hydrogen bonds

The slightly negative charge on the oxygen atom (𝜕−), makes it attract the slightly positive hydrogen atom (𝜕+), of another water molecule. This slight uneven distribution of charge allows hydrogen bonds to form between a hydrogen atom and the oxygen atom of another water molecule.

Polar molecule (Properties of water)

Makes a good solvent (polar substances dissociate forming solutes). Good for transport (non-viscous). Good reaction medium. Adheres to surfaces (to aid transport in xylem).

Forces of Cohesion and Adhesion

Hydrogen bonding between water molecules (weak bonds) creates a force known as cohesion, (that ‘stick’ the water molecules to each other). Water molecules can also show attraction to other polar molecules called adhesion. The advantage to plants is that forces of cohesion allow water to be held in a continuous column in the transpiration stream. Also, forces of adhesion allow the water molecules to adhere to the inside walls of xylem vessels.

Surface Tension of Water

Cohesion forces are responsible for the high surface tension of water and the formation of a ‘skin’ at the point where the water meets the air. The surface of water can behave like an elastic sheet; this is due to cohesion between water molecules. Those molecules in the surface are not affected by molecules above them, and therefore ‘pull’ together more strongly, effectively resembling a stretched membrane.

High Latent Heat of Vaporisation

Water has a high latent heat of vaporisation/ evaporation (for cooling by sweating).

High Specific Heat Capacity

Water has a very high Specific Heat Capacity (temperature buffer-good for organisms and enzymes)

Water as a solvent

It is known as a universal solvent as it dissolves a wide variety of different solutes and it can therefore be used as a solvent. E.g. NaCl. The positive end of the water molecule attracts the negative ion and the negative end of the water molecule attracts the positive ion. The water molecules surround the ions and they therefore dissolve.

Density of water

Solid water has a lower density than liquid water. This means that ice is less dense than water and will therefore float on top of it.

Transparency – transmission of light

Water is colourless and is therefore transparent to light, so light can get through. This is important for plants and algae, as it means that sunlight can reach the cells of these aquatic plants, so that photosynthesis may occur.

Water as a metabolite

Water is a reactant in many metabolic reactions. It is therefore referred to as a metabolite. Examples:Hydrolysis - water molecules are chemically inserted in order to break bonds in hydrolysis reactions. Photosynthesis

Buoyancy and support

Water supports organisms. Examples: Water supports large animals such as whales.Water supports and helps to disperse reproductive structures such as larvae and coconuts. Water helps to maintain the turgidity of plant cells which is essential for support in plants.

Water as a Transport medium

Water remains liquids over large temperature range and can act as a solvent for many chemicals. This makes it an ideal transport medium in living organisms.

Carbohydrates

Contain the elements C, H, O (chitin also contains N).

Monosaccharides

Single units of carbohydrates. They are classed as sugars because sugars have the following 3 properties: o Sweet o Soluble in water o Form crystals at normal temperatures

Triose

An intermediate in respiration

Deoxyribose

Component of DNA

Ribose

Component of RNA and ATP

Glucose

provides energy via respiration

Fructose

Sweetens fruit

Galactose

A milk sugar

Isomers

molecules that have the same chemical formulae but different structural formulae.

α-glucose β-glucose

In α-glucose the OH group on carbon 1 lies below the plane of the ring. In β-glucose the OH group on carbon 1 lies above the plane of the ring.

As source of energy in respiration

Carbon-hydrogen and carbon-carbon bonds are broken to release energy, which is transferred to make adenosine triphosphate (ATP).

Disaccharides

Monosaccharide + Monosaccharide

Glycosidic Bond

In order for two monosaccharides to bond together they undergo a condenstation reaction. This involves the elimation of a water molecule. A hydroxyl group is lost from one monosaccharide whilst a hydrogen atom is lost from the other. The bond that is formed is known as a glycosidic bond.

Maltose

Used in seed germination.

Sucrose

Transported in the phloem of flowering plants.

Lactose

Found in mammalian milk.

reducing sugar

sugar that can donate an electron to (or reduce), another chemical, in this case Benedict’s reagent.

Polysaccharides

large complex molecules known as POLYMERS. Polymerisation is the process of bonding many MONOMERS by condensation reactions to form one large molecule.

Starch

Found in plant cells as small grains, especially in seeds and storage organs, like potato tubers. It is an energy source in plants and is used by animals as an important component of food, as an energy source.

Amylose

A long, linear, unbranched chain of α-glucose molecules. It is wound tightly into a coiled shape, making the molecule very compact and so a good energy store. It has α-1,4-glycosidic bond forming between the 1st carbon atom (C1) on one glucose monomer and the 4th carbon atom (C4) on the adjacent one.

Amylopectin

A long-branched chain of α-glucose. Its side branches allow the enzymes that break down the molecule to get to the glycosidic bonds easily This means glucose can be released quickly, due to there being lots of ends. There are α-1,4-glycosidic bonds between the monomers in the main chain and α-1,6-glycosidic bonds between the monomers of the main chain and the side branches.

Glycogen

Glycogen is the animal cell equivalent of starch. Glycogen is a large insoluble molecule that is stored as granules in the liver and muscle cells.

Structural polysaccharides

Structural polysaccharides are needed to provide strength and support.

Cellulose

Found in plant cellulose cell walls (fruit and vegetables). Chains are Made up of long chains of β-glucose monomers.

Chitin

made of β-glucose subunits in which alternating units are rotated through 180o to each other. Linked by β-1,4- glycosidic bonds. The subunits are called glucosamine. The acetylamine group allows even more hydrogen bonds to form between chains than in cellulose making chitin stronger than cellulose.