BIOLOGY CHAPTER 2 ICSE 9TH

1. Cell : The Unit of Life

2. WHAT IS A CELL ?
• CELL IS THE FUNCTIONAL AND STRUCTURAL UNIT OF LIFE
• SMALLEST PART OF THE BODY
• HAS ITS OWN LIFE
• CAPABLE OF INDEPENDENT EXSISTING AND PERFORMING ESSENTIAL
LIFE FUNCTION
• ALL ORGANISMS START LIFE AS A SINGLE CELL

3. MICROSCOPE INVENTION

4. ROBERT HOOKE

5. ELECRON MICROSCOPE
• 2000x magnification
• Compound microscope uses light to magnify
• Electron microscope uses beam of electron

6. Cell theory
• Cell is the smallest structural unit of life
• Cell is the unit of function for all living things
• All cell arises from pre-existing cell

7. Meaning of cell theory
• Structural unit
• Functional unit
• Cells die and are replaced
• All life starts as a single cell

8. Cells – how many ?

9. Cell - Size
• Smallest cell – bacteria
• Longest cell - nerve cell
• Largest cell – ostrich egg

10. Cell – Shape

11. Circular shape

12. Amoeboid shape

13. Long cells

14. Contractile cells

15. Bean shaped

16. Why are cells small?
• Rapid communication
• Larger surface area volume ratio for greater diffusion

17. ENDOPLAMSIC RETICULAM

18. STRUCTURE AND FUNCTION
• STRUCTURE-
• OUTER END-CONNECTED TO CELL MEMBRANE
• INNER END CONNECTED TO NUCLEAR MEMBRANE
• Ribosomes present : RER.
• Ribosomes absent :
• Functions. 1. Supporting framework.
• 2. Serves as a pathway for distribution.
• 3. Synthesis and transport.

19. RIBOSOMES-

20. STRUCTURE AND FUNCTION
Small granules either scattered freely inside the cytoplasm or on the
ER.
Single walled dense spherical bodies composed mainly of RNA.
Protein synthesis

21. Mitocondria

22. STRUCTURE AND FUNCTION
• Structure.
• 1. Double membrane.
• 2. In a membrane thrown in series of folds called cristae.
• 3. Having their own DNA.
• Functions.
• 1. Cellular respiration.
• 2. Produces energy., chemical energy from the food in the cell to energy
in a form usable to the host cell.
• 3. Energy stored in the form of ATP.
• 4. Energy is used to form various functions of the cells and body .

23. GOLGI APPARATUS

24. STRUCTURE AND FUNCTION
• Structure.
• Granules, filaments. Or rods which are originated from ER
• Small vesicles of different shape.
• Located near the nucleus.
• Consists of tubules, vesicles, an vacuoles.
• Functions.
• Synthesis and secretion of enzymes, hormones.
• Formation of acrosome of sperm. Only in animals and humans.

25. LYSOSOMES

26. STRUCTURE AND FUNCTION
• Structure.
• Membraneous sacs budded off from the Golgi bodies containing
digestive enzymes.
• Intracellular digestion
• Destroy foreign substances.
• Cell is old or damaged, they destroy their own cell an hence Called as
suicide bags.

27. CENTROSOMES

28. STRUCTURE AND FUNCTION
• Location and structure.
• A region surrounding centrioles, located near Nucleus.
• Contains one or two centrioles.
• Centrioles are surrounded by microtubules.
• Functions.
• Initiate and regulate cell division.
• Forms spindle fiber with the help of Aster.

29. PLASTID

30. STRUCTURE AND FUNCTION
• Structure.
• Different shapes ovals spherical, disc like
• Depending on the color they impart they are classified –
• 1 leucoplasts
• 2 Chromoplast
• 3 chloroplasts

31. FUNCTION

32. Nucleus-Most imp part of the cell

33. • Nuclear membrane-nuclear pores
• Nucleoplasm
• Threadlike structure-chromatin fibres
• Chromatin fibres-condense into chromosomes [during cell division]
• Nucleolus – may have one or many-participates in protein sysnthesis
• No. of nucleoli [plural of nucleolus] is fixed

34. chromosomes
• Number of chromosomes are fixed
• They are always present in pairs
• Humans have 46 chromosomes[23 pair]
• Chromosomes have hereditary units called genes
• Genes are made of up DNA

35. NON LIVING OR CELL INCLUSIONS
• GRANULES
• VACUOLES
• Protoplasm-total living substance of a nucleus[cytoplasm+nucleus]

36. DIFFERENCE BETWEEN PLANT AND ANIMAL CELL

37. PROKARYOTIC AND EUKARYOTIC CELL

38. CELLULAR ACTIVITIES
• GROWING
• REPAIR
• MOVEMENT
• FEEDING AND NUTRITION
• CIRCULATION OF BLOOD
• RESPIRATION
• BODY PROTECTION
• SENSARY ORGANS
• THERMO-REGULATION
• REPRODUCTION
• ABSORBTION OF WATER
• LIGHT IS TRAPPED AND COLOUR