Explanation

Step 1: Follow the order of operations (PEMDAS/BODMAS)

First, calculate 6 × 4 × 0.5

Step 2: Calculate 6 × 4

6 × 4 = 24

Step 3: Multiply 24 by 0.5

24 × 0.5 = 12

Step 4: Add 2 to the result

2 + 12 = 14

Explanation

120 × 0.3 = 36

Explanation

0.8 ÷ 0.1 = 8

Explanation

0.2 × 0.02 = 0.004

Explanation

The backbone of DNA consists of alternating deoxyribose sugar and phosphate groups, linked by phosphodiester bonds.

Key Information:

Sugar-Phosphate Backbone:

• Provides structural stability to the DNA double helix.
• Directionality: 5’ (phosphate) to 3’ (sugar) orientation.

Nitrogenous Bases (A, T, C, G):

• Attached to the sugar but not part of the backbone.
• Form hydrogen bonds to create base pairs (A-T, C-G).

Explanation

Nucleic acids (DNA/RNA) are present in:

Nucleus:

• Contains genomic DNA (eukaryotic cells).

Mitochondria:

• Have their own mtDNA (vital for energy production).

Chloroplasts (in plants/algae):

• Contain cpDNA for photosynthesis-related functions.

Explanation

ATP (Adenosine Triphosphate) is called the energy currency of the cell because it stores and provides energy for cellular activities.

It releases energy when converted to ADP (Adenosine Diphosphate), which is then recycled back into ATP through cellular respiration.

Explanation

The increase in length (or volume) of solids when heated is specifically called thermal expansion.

Key Information:

Thermal Expansion:

• Occurs due to increased atomic vibrations with temperature.
• Linear expansion: Change in length (e.g., railroad tracks expanding in summer).
• Volumetric expansion: Change in 3D dimensions (e.g., mercury in thermometers).

Explanation

Cholesterol is a vital precursor in the biosynthesis of:

Vitamin D:

• Cholesterol converts to 7-dehydrocholesterol in the skin, which forms vitamin D₃ under UV light.

Steroid Hormones:

Cholesterol is the backbone for:

• Sex hormones (testosterone, estrogen, progesterone).
• Adrenal hormones (cortisol, aldosterone).

Explanation

Exponential notation (scientific notation) is used to express very small (e.g., 0.0000001) or very large (e.g., 1000000000) quantities compactly by representing numbers as powers of 10.

Key Information:

Format: a × 10^n, where 1 ≤ a < 10 and n is an integer.

Used for very large or very small numbers.

Examples:

• Large number: 6.022 × 10^23 (Avogadro's number)
• Small number: 1.6 × 10^-19 (Charge of an electron)