Plant Cell – Exam Review

Definition

• Plant cells: eukaryotic, true nucleus, specialized organelles

• Distinctive features vs. animal cells: rigid $ext{cell wall}$, plastids, large central vacuole

General Characteristics

• Shape: rectangular, larger than animal cells

• Surrounded by $ext{cell membrane}$ (semi-permeable) + external cellulose wall

Cell Wall

• Composition: cellulose, hemicellulose, pectin, lignin, glycoproteins

• Layers: primary, secondary, middle lamella

• Functions: structural support, shape, mechanical protection, molecular filtration

Cell Membrane

• Thin lipid–protein bilayer inside wall

• Regulates selective entry/exit (nutrients in, toxins out)

Nucleus

• Stores DNA; controls division, metabolism, growth
  • Nucleolus: ribosome production
  • Nuclear pores: passage of proteins & nucleic acids

Plastids

• Own DNA; synthesize/store key molecules
  • Chloroplasts – chlorophyll, photosynthesis (light + $ext{CO}<em>{2}$ + $ext{H}</em>{2} ext{O} \rightarrow$ glucose)
  • Chromoplasts – red/orange/yellow pigments in fruits/flowers
  • Leucoplasts – store starch, lipids, proteins

Central Vacuole

• Occupies $\approx$ $30\%$ of mature cell volume

• Tonoplast membrane; contains cell sap

• Maintains turgor pressure, storage of ions & enzymes

Other Key Organelles

• Golgi apparatus: modify & direct macromolecule transport

• Ribosomes: protein synthesis (“protein factories”)

• Mitochondria: carbohydrate breakdown (\rightarrow) ATP ("powerhouse")

• Lysosomes: digestive enzymes; intracellular waste disposal (“suicidal bags”)

Specialized Plant Cell Types

• Parenchyma – living, flexible; photosynthesis, storage, gas exchange

• Collenchyma – flexible support in growing regions

• Sclerenchyma – rigid support (lignified)

• Xylem – water & mineral conduction root(\rightarrow)shoot

• Phloem – transport of photosynthate (food) throughout plant

Core Functions

• Photosynthesis (chloroplast): converts solar energy to chemical (ATP, glucose)

• Transport: xylem & phloem move water, minerals, food

• Storage: vacuole & leucoplasts accumulate nutrients

• Structural integrity: cell wall + turgor maintain shape & support

Frequently Tested Facts

• Organelles unique to plants: cell wall, chloroplasts, plastids, large central vacuole

• Cell wall polymer: cellulose (linear $\beta(1\rightarrow4)$ glucose chain)

• Photosynthesis site: chloroplast thylakoid membranes