For high school bio students

1. CELL AND ITS STRUCTURE

2. Chapter Outlines:
i) What is a cell and how is it seen
ii) Eukaryotic cells have internal membranes that compartmentalize their
functions
iii) The eukaryotic cell’s genetic instructions are housed in the nucleus and
carried out by the ribosomes
iv) The endomembrane system regulates protein traffic and performs
metabolic functions
v) Mitochondria and chloroplasts change energy from one form to another
vi) The cytoskeleton is a network of fibers that organizes structures and
activities in the cell
vii) Extracellular components and connections between cells help coordinate
cellular activities
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So at first what is A CELL?
 Cell is a structural and functional unit of life.
So What types of cell Are there:
 Eukaryotic cell
These are cells with a true nucleus, and contain many membrane-bound organelles.
These include the animal cells, human cells, plant cells and even fungi.
• Prokaryotic cells
Cells that do not contain any true nucleus and
also no other membrane bound organelles.
Now generally, eukaryotes cells have a typical size of 10-
20µm. While prokaryotes cells have a typical size of 0.1
to 5.0µm. Meaning eukaryotes are generally bigger than
prokaryotes.

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Other terms you need to know:
• Organnelles:
They are functionally and structurally distinct part of a cell.
And are surrounded by membranes for compartmentalization.
• Ultrastructure of Cells
Not necessarily surrounded by membranes surrounded by membranes
detailed structures of a cell
Only can be seen under an electron microscopes
• Types of Microscopes:
• Light microscope
• Electron Microscope

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Cell membrane:

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Nucleus
General Function:
• Contains genetic information for the
synthesis of protein
• Also the site of transcription of genes and
production of mRNA.
Has three components:
• Nuclear envelope
• Nucleolus
• Chromatin
• Nucleoplasm

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Ribosomes:
• Is the Smallest Organelle
• It is not bound by a membrane
• Is made up of rRNA, that is synthesized in nucleolus +
some protein
• It has two subunits
Large subunit and small subunit.
Function
Is the site of protein synthesis
There are two types of ribosomes:
 70S
Are smaller in size and can be found in mitochondria
and chloroplasts of eukaryotes
 80S
Are larger and can be found in cytoplasm and RER of all
eukaryotes

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Rough Endoplasmic Reticulum

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Smooth Endoplasmic Reticulum
It is an ER without ribosomes.
Function
Is the site of lipid and steroid synthesis
Golgi Apparatus
• Is made up of cisternae
• Have layered appearance
• No connection between members
• Not continuous with nuclear envelope
• Swellings at end of sacs for vesicle formation
• Constantly being formed and broken down
• Being formed by: Transport vesicles from RER on the cis face
• Broken down to form: Secretory vesicle and lysosomes on
transface

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Mitochondria
Function
• Is the site of aerobic respiration
And synthesizes ATP/produces energy in the form of ATP

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Chloroplasts

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Cell Wall
• Is a thick, rigid layer which is made up of cellulose
• It is permeable as there are spaces/gaps between fibres.
Plasmodesmata
• Is strands of cytoplasm passing through channels

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Vacuoles

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Centrioles and Centrosomes
Functions
• Is involved in cell division
 Replicates before each cell division and moves to
opposite poles.
 Centrioles are found in pairs at right angles from
each other
 These two form centrosome
• Modified centrioles are also found elsewhere
• Acts as a Microtubule Organizing Center(MTOC)

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Microtubules
Function
• Makes up the cytoskeleton (together with actin filaments)
This in therefore provides the mechanical support
Also it acts as an intracellular transport system for movement of vesicles or
other components

19. THANK YOU