The primary wall of plant cells is mainly composed of cellulose, providing structural support and flexibility for growth.

The plasma membrane is a selectively permeable barrier that regulates the movement of substances into and out of the plant cell.

Chloroplasts contain chlorophyll and are the site of photosynthesis, converting light energy into chemical energy in plant cells.

The endoplasmic reticulum (ER), particularly the rough ER, modifies proteins and facilitates their transport within the cell.

Lignin is deposited in the secondary wall of sclerenchyma cells, providing added rigidity and strength.

The middle lamella, primarily composed of pectins, serves as a glue between adjacent plant cells.

The cell wall is a non-living, rigid structure external to the living protoplast, secreted by the cell.

Fungal cell walls are made of chitin, a nitrogen-containing polysaccharide providing structural support.

The secondary wall typically contains cellulose, hemicellulose, and lignin for added strength and rigidity.

The protoplast, the living contents of the cell, synthesizes and deposits the cell wall materials.

In eukaryotes, the 60S and 40S ribosomal subunits join to form an 80S ribosome for protein synthesis.

Free ribosomes typically synthesize proteins for internal use, such as DNA polymerase, which functions in the nucleus.

Cytosol is the fluid portion of the cytoplasm, excluding organelles, where many cellular processes occur.

Ribosomes carry out protein synthesis (translation), assembling amino acids into polypeptides.

The nucleus is typically the largest and densest organelle, containing the cell’s genetic material.

Mature sieve tube cells, bacteria (prokaryotes), and mammalian red blood cells lack a nucleus.

Gametes are haploid (n = 80), so diploid muscle cells (2n) have twice the chromosomes: 80 × 2 = 160.

Nuclear pore density correlates with the level of gene transcription and transport requirements in eukaryotic cells.

The nucleolus is not a hereditary center; the nucleus contains genetic material. The nucleolus lacks a membrane and synthesizes rRNA.

Haploid (n) is half the diploid (2n) number. For a diploid number of 36, the haploid number is 36 ÷ 2 = 18.