Cell structure And Function

Question 1

Vacuoles

Answer 1

• non protoplasmic liquid cavities in the cytoplasm
• Large central vacuole — plants 🌵
• Membrane surrounding the large central vacuole– tonoplast
• Solution present in plant cell vacuole — cell sap
• Vacuole – found both in plant and animal cell
  *Single membranous vesicular structure
  *Originated from cell membrane , E.R and golgi complex.
• Animals — formed by phagocytosis
  *Plant vacuole helps in storage of food ( food vacuole ) , defense , acts as lysozyme , elimination of undigested food 🥝🥑 ( contractile vacuole) , support to young plants ☘️
• Maintain turgor
• Membrane separating vacuole from cytoplasm — tonoplast

Question 2

Nucleus

Answer 2

• plants — slightly away from cetre
• Animal — centre ( nucleus )
  *Nucleus — oval or spherical in shape
• Surrounded by double membrane — nuclear envelope/ nuclear membrane
• Double membrane structure
• Two or more nuclei / cell ( coenocytic )
• Perforated by nuclear pores which are composed of specialized protein called nucleoporin
• Sieve tube cells are exceptional cells that donot possesses nucleus
• Nucleus filled with protein rich substance called nucleoplasm or karyolymph
• Nucleoplasm – numerous fine strands in form of network — chromatin network or nuclear reticulum —- composed of nucleic acid — DNA 🧬 + protein
• Chromosomes — hereditary units called genes — carry hereditary information
• Chromosomes – 2 parts
  1) centromere : chromatids ( chromosomes consists of two threads before cell division) are joined by centromere
  2) Arm : part of chromatids from centromere to end
  *Types of chromosomes

_metacentric : chromosomes with equal arms

_ submetacentric : chromosome with unequal arms

_Acrocentric / Sub telocentric: Rod like chromosome with one arm very small and other very long . Centromere is sub terminal

_ Telocentric: location of centromere at the end of chromosome

• Nucleolus—- spherical body / disappear during cell division / synthesis of Ribonucleic acid and ribosome

Question 3

Cell wall

Answer 3

• non living
• Secreted and maintained by living portion of cell called protoplam
  *Middle lamella
  *Primary wall —- 1.3UM ( thick and elastic )
• Secondary wall — 5-10Um ( thick and rigid )
• Cellulose: the main constituent of plant cell wall and use in manufacture of paper