Unit 1 Biology- Terms and Definitions

Cohesion

The ability of like molecules to stick together. Water’s high cohesion causes high surface tension, which allows insects to use the water surface as a habitat and helps in the transportation of water through plant xylem.

Adhesion

The ability of dissimilar molecules to stick together. Water’s adhesive forces help pull water up through the plant's xylem and into the roots.

Capillary Action

the movement of a liquid through or along another material against an opposing force. gives water the to travel upward through narrow spaces (such as the xylem) against gravity due to cohesive and adhesive forces. However, it can only pull water a small distance.

Hydrophilic

Substances that attract water (e.g., polar molecules, ionic compounds).

Hydrophobic

Substances that repel water, typically non-polar molecules like hydrocarbons (e.g., fats, CH₄).

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Buoyancy

The ability of an object to float in a fluid, which is equal to the weight of the displaced fluid. Objects with lower density float more easily. For example, fish use swim bladders to regulate buoyancy.

Viscosity

A measure of a fluid’s resistance to flow

Thermal Conductivity

The measure of the rate which heat passes through a material, essential for thermal regulation in organisms and environments, helping to maintain stable temperatures critical for life

Specific heat capacity

The amount of heat required to raise the temperature of a substance. Water has a high specific heat capacity, meaning it can absorb a lot of heat before changing temperature, which helps in regulating body temperature.

Habitable zone

The region around a star where liquid water can exist, crucial for the potential for life.

DNA

The genetic material in all living organisms, containing the instructions for protein synthesis. It is double-stranded and found in the nucleus.

RNA

Involved in protein synthesis, typically single-stranded, and found in the cytoplasm. It is a message carrier and is not inherited.

Nucleotide

The basic building block of nucleic acids, consisting of a phosphate group, a pentose sugar, and a nitrogenous base.

Base Pairing

Adenine (A) pairs with Thymine (T) in DNA, and Uracil (U) replaces Thymine in RNA. Guanine (G) pairs with Cytosine (C). Purines are A and G, and Pyrimidines are T, C, and U.

Amino Acids

The building blocks of proteins. Each contains a carboxyl group (-COOH), an amino group (-NH₂), a hydrogen atom, and a variable R group.

Polypeptide

A chain of amino acids linked by peptide bonds.

Protein denaturation

The loss of a protein's structure due to exposure to heat, pH changes, or UV light.

Describe all four protein structures

• Primary: Linear sequence of amino acids.

• Secondary: Alpha helices or beta-pleated sheets, held together by hydrogen bonds.

• Tertiary: The three-dimensional structure formed by interactions between R groups.

• Quaternary: A multi-subunit structure formed by two or more polypeptides.

Monosaccharides

Simple sugars like glucose and fructose.

Disaccharides

Two monosaccharides joined together (e.g., sucrose, lactose).

Polysaccharides

Long chains of monosaccharides (e.g., starch, cellulose, glycogen).

Glycogen

A storage form of glucose in animals.

Starch

A storage form of glucose in plants

Cellulose

A structural component of plant cell walls, made of beta-glucose.

Lipids

Hydrophobic molecules made of C, H, and O. They include triglycerides (energy storage), phospholipids (cell membranes), and steroids (signaling molecules like cholesterol).

Triglycerides

Made of glycerol and three fatty acids, and can be either saturated or unsaturated.

Phospholipids

Have both hydrophobic (fatty acid tails) and hydrophilic (phosphate group) regions, forming bilayers in cell membranes.

Cholesterol

A type of steroid that affects membrane fluidity and is a precursor to steroid hormones.

Anabolic metabolism

Builds molecules for growth, repair, and energy storage, often requiring energy (endergonic reactions).

Catabolic metabolism

Breaks down molecules for energy production, releasing energy (exergonic reactions).

Enzyme

A biological catalyst that speeds up chemical reactions by lowering the activation energy required.

Active site

The region on an enzyme where the substrate binds.

Substrate

The molecule upon which an enzyme acts.

Factors which affect enzyme activity

Temperature, pH, and substrate concentration can influence the enzyme’s effectiveness.

Competitive inhibition

An inhibitor competes with the substrate for the enzyme’s active site.

Non-competitive inhabition

An inhibitor binds elsewhere on the enzyme, changing its shape and function.

Allosteric reaction

Enzyme activity is controlled by molecules binding to sites other than the active site.