Cell structure & functions for class 9 by Susanta Kumar Panda

Our School

Presents……

Definition of Cell…

A cell is the smallest unit

that is capable of performing life functions.

The Cell Theory…

Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

The Two Major Categories of

Cells….

The countless cells on earth fall into two categories:

PROKARYOTIC

They are the simplest form of life.

No nucleus.

Do not have structures surrounded by membranes (organelles)

Few internal structures

They are unicellular_(One-celled organisms).

Example: Bacteria

ribosomes

cell wall

plasma membrane

food granule

prokaryoticflagellum

cytoplasm

nucleoid (DNA)

are the most complex form of life.

They have nucleus

Contain organelles surrounded by membranes

They are multicellular organisms (composed of many cells).

Most living organisms

Examples: animals and plants.

Eukaryotic

EUKARYOTIC

Plant Animal

Prokaryotes & Eukaryotes…

Similarities & differences

Both surrounded by plasma membrane, but very different

Prokaryotes – Archaebacteria and Eubacteria

Eukaryotes – everything else

“Typical” Plant Cell

Difference Between Plant & Animal Cells…

Plants have

Cell wall – provides strength & rigidity

Have chloroplasts, photosynthetic

Animals have

Other organelle not found in plants (lysosomesformed from Golgi)

Centrioles, important in cell division

All living cells (eukaryotes and prokaryotes) have cell membranes

Made mainly of phospholipids and proteins

▪ Animal cell membranes contain cholesterol

Functions:

▪ Separate the cell from the external environment

▪ Controls passage in and out of cell

Outer membrane of

cell that controls

movement in and out

of the cell

Double layer

Membrane Structure

Cell Wall

Rigid structure outside cell membrane

• Found in plants, fungi, bacteria, some protists (not animals)

• Made of cellulose (plants), chitin (fungi) or other material (bacteria)

• Supports and protects cell

Inside the Cell

ORGANELLESCell Parts

CELL STRUCTURE AND FUNCTION

nuclearpores

nuclearpore

nuclear envelope

nucleolus

histone protein

chromosome

DNANucleus

Function

protects DNA

Structure

nuclear envelope

double membrane

membrane fused in spots to create pores

allows large macromolecules to pass through

What kind of molecules need to pass through?

Function

ribosome production

▪ build ribosome subunits from rRNA & proteins

▪ exit through nuclear pores to cytoplasm & combine to form functional ribosomes

smallsubunit

large subunit

ribosome

rRNA &proteins

nucleolus

smallsubunit

largesubunitRibosomes

Function

protein production

Structure

rRNA & protein

2 subunits combine 0.08mm

Ribosomes

RoughER

SmoothER

membrane proteins

Types of Ribosomes

Free ribosomes

◦ suspended in cytosol

◦ synthesize proteins that function

in cytosol

Bound ribosomes

◦ attached to endoplasmic reticulum

◦ synthesize proteins

for export or

for membranes

Function

• processes proteins

• manufactures membranes

• synthesis & hydrolysis of many compounds

Structure

• membrane connected to nuclear envelope &

extends throughout cell

Types of ER

Rough ER (RER) –

Has ribosomes attached

Site of protein synthesis

Smooth ER (SER)

Complex molecules built here

Continuous with RER

Membrane production

Many metabolic processes• synthesis

synthesize lipids

oils, phospholipids, steroids & sex hormones

• hydrolysis

hydrolyze glycogen into glucose

in liver

detoxify drugs & poisons

in liver

ex. alcohol & barbiturates

Produce proteins for export out of cell• protein secreting cells

• packaged into transport vesicles for export

Golgi Apparatus

Function finishes, sorts, tags & ships cell products

ships products in vesicles membrane sacs

Structure Stack of flattened membranes “pita bread” like

transport vesicles

secretoryvesicles

Golgi Apparatus

Vesicles Transport…

ER contents pinch off into vesicles - membrane-bound sacs that store and transport substances in cells

vesiclebuddingfrom roughER

fusionof vesiclewith Golgiapparatus

migratingtransportvesicle

protein

ribosome

The movement of

macromolecules such as

proteins or

polysaccharides into or

out of the cell is called

bulk transport. There are

two types of bulk

transport, exocytosis and

endocytosis, and both

require the expenditure of

energy (ATP).

Produces energy through chemical reactions – breaking down fats & carbohydrates

Controls level of water and other materials in cell

Recycles and decomposes proteins, fats, and carbohydrates

Cytoplasm Cytosol (cytoplasm)

Cellular fluid surrounding organelles

Site of many cellular reactions

Found between cell membrane and nucleus

Lysosomes

Lysosomes – special vesicles that store and transport powerful digestive enzymes and other reactive substances within a cell

Double membrane protects cell from being digested

Break down

Food particles

Unneeded proteins, carbohydrates, etc..

Disease-causing microorganisms

Vacuoles

Large membranous storage sacs found mainly in plants.

Stores water, nutrients, waste products and pigments

○ Give certain plants bright colors (beets, carrots, flowers)

CILIA AND FLAGELLA…

Hairlike organelles that

extend from the

surface of the cell

Assist in movement

Cilia – short and

present in large

numbers

Flagella – long and

less numerous

Chromosomes…

In nucleus

Made of DNA

Contain instructions

for traits &

characteristics

Chloroplast

Usually found in plant cells

Contains green chlorophyll

Where photosynthesis takes place

21/07/2014

v ideo B.av i

21/07/2014

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