CBSE Class 11-science Answered

Plasma membrane

Very thin, flexible and delicate living semi-permeable membrane

Acts as an effective barrier and regulates the entry of certain solutes and ions

Cell wall (only in plant cells)

Freely permeable, mainly composed of cellulose

Gives rigidity and shape to the plant cells and provides protection

Cytoplasm

Contains a mixture of water and soluble organic and inorganic compounds and various cell organelles

Seat of occurrence of glycolysis (production of pyruvic acid)

Endoplasmic reticulum

May be smooth (SER) or rough (RER)

Acts as a supportive framework of the cell

Mitochondria

Double-walled, inner wall thrown into folds called cristae

Seat of aerobic respiration and synthesises respiratory enzymes and energy-rich compounds

Golgi apparatus (in animal cells)

Dictyosomes (in plant cells)

Consists of a set of membrane-bounded, fluid-filled vesicles and vacuoles

Synthesis of the plasma membrane, cell wall etc. and synthesis and secretion of enzymes and hormones

Ribosomes

Single-walled, dense, spherical bodies composed mainly of RNA and proteins

Synthesis of proteins

Lysosomes

Contains 40 different types of enzymes

Intracellular digestion

Centrosomes (only in animal cells)

Contains one or two centrioles which are surrounded by radiating microtubules to form an aster shape

Initiates and regulates cell division

Plastids (only in plant cells)

Double membrane, proteinaceous matrix containing DNA and disc-like structures called thylakoids containing chlorophyll

Chromoplasts: Impart colour to flowers and fruits Chloroplasts: Trap solar energy for photosynthesis Leucoplasts: Store starch

Nucleus

Mostly spherical and dense, surrounded by nuclear membrane with pores

Regulates cell cycle and cell functions

Nucleolus

Round, one or more in number

Participates in protein synthesis by forming and storing RNA

Chromatin fibres

Network of thread-like structures which are made of DNA

Chromosomes carry hereditary information or genes 

Vacuoles

Non-living structures

Storage of water and other substances, food, pigments and waste products

Granules

Small particles, crystals or droplets

Starch (in plant cells), glycogen (in animal cells) and fat-containing granules serve as food for the cell