Lecture 04 Cytoplasmic components; - PowerPoint Presentation

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Lecture 04

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Cytoplasmic components;

their organization

&

functions

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Cytoplasm

The part of the cell between the cell membrane and the nuclear membrane is called the cytoplasm.

The cytoplasm consists of the

matrix

and the

organelles

.

The

matrix is a transparent semi fluid substance.

The organelles are found embedded in the cytoplasm.

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O- 65%

C- 18.3%

H- 11%

N- 2.5%

S, P, K, Mg,

Ca

, Cu, B, Zn,

Cl

, Al etc.

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Parts of cytoplasm

Cytosol

Ectoplasm

Mesoplasm

Endoplasm

Hayaloplasm

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Functions

It is the

seat

of all metabolic and bio-chemical processes taking place in a

cell.

It is involved in

the storage of raw materials or reserve food

required by the cell.

It brings about exchange of materials between the cell organelles.

It exchanges materials with the surrounding environment such as extra cellular

fluid.

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Mitochondrion

These may be cylindrical, rod-shaped or spherical and distributed in the cytoplasm. Each mitochondrion is bound by a double membrane.

New

mitochondrions

are formed by division of

mitochondrion

already existing in a

cell.

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Structure

The mitochondrion cover consists of two membranes - external and internal.

The

external membrane smooth, it does not form any cords and excrescences.

The

internal membrane, on the contrary, forms numerous cords which are referred to a mitochondrion cavity.

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Cords of an internal membrane name

cristas

("Cristae" - a crest, an excrescence).

In the central cavity, it contains granular matrix that fills the cavity.

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Functions of Mitochondrion

Power house of cell

TCA Cycle

ATP formation

Secretes biological energy (ATP) to other organelles

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Plastids

Plastids are present in the cytoplasm of all plant cells.

In cells of

animals, plastid is

absent. Distinguish three basic types of plastids:

Leucoplast

Amylopast

- storing starch

Elaioplast

-storing oils and fatty substances

Aleuroplast

- storing protein

Green

– chloroplasts

Chromoplast

Red

, orange and yellow –

chromoplasts

Colourless

- leucoplasts.

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Chloroplast

From a cytoplasm the chloroplast is delimited by

two membranes

-

external

and

internal

.

The external membrane smooth, without cords and excrescences, and internal

membrane surrounds the

stroma

and the grana.

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The ground substance or matrix of chloroplast

is called

stroma

. It is composed of

proteinaceous

material

.

Within

the

stroma

, a large number of granules

are lying embedded

called

grana

.

Each

granum

(stack) consists of varying number of

disks or a

pile of flattened vesicles arranged one on top of

the other

.

Each disk is called

thylakoid

.

There

are

lamellae

(

stroma

lamellae

) or tubules present

in low

density in the matrix,

interconnecting the

grana

.

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Thylakoids

are

of disk-shaped

membranous

structures

in the

chloroplasts that

contain chlorophyll

.

Photosynthesis

takes place

on thylakoid membrane where the chlorophylls are present

.

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Function of the chloroplast

The function of the chloroplast is

to the

trap solar energy for photosynthesis

. Chloroplast is the basic

organoid

of

plants cell

in which

photosynthesis occurs,

i.e. Formation of organic substances (carbohydrates) from inorganic (СО

2

and Н

2

О

) materials by the

use of energy of a sunlight

.

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Chromoplasts

are in different colorful parts of plants like stalks, leaves, petals and fruits. Presence of

chromoplasts

results yellow, orange and red coloring.

Leucoplasts

are in a cytoplasm of cells of unpainted parts of plants, for example in stalks, roots, tubers. It is of three types

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Golgi

apparatus

The

Golgi apparatus

(also called the

Golgi body

,

Golgi complex

,

dictyosome

, or more colloquially

Golgi

) is an organelle

found in most eukaryotic cells

.

It

was identified in

1898

by the Italian physician

Camillo

Golgi

and was named after him.

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Structure

The Golgi body is composed of

stacks of membrane-bound structures

known as

cisternae

(singular:

cisterna

).

Each cisterna comprises a flattened membrane disk.

The Golgi complex is made of several flattened membranes sacs, but can be ultimately divided into two sections: the

Cis

Golgi

and the

Trans Golgi Network (TGN

)

.

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The cisternae stack has five functional regions:

Cis

-Golgi network region

Cis

-Golgi region

Medial-Golgi region

Trans-Golgi region

Trans-Golgi network region

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The

Cis

-Golgi

functions as the

receiving end

for newly synthesized proteins from the lumen of the Endoplasmic Reticulum (ER).

Vesicles

containing proteins from the ER merge with the

Cis

-Golgi,

allowing the proteins to enter the Golgi complex.

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As the

Cis

-Golgi

receives proteins from the ER, the proteins then begin their

modification,

moving along membrane to membrane towards the

TGN (Trans Golgi Network).

At

the other end of the G

olgi

complex, the newly modified protein arrives at the TGN where it is then send off to different parts of the cell via a transport vesicle.

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Vesicles from the endoplasmic reticulum fuse with the

cis

-Golgi network

through the stack to the

trans-Golgi network

Sent to the required destination

How the Golgi apparatus works ??

subsequent

progress

Here, they

are packaged

Each region contains different enzymes which selectively modify the contents depending on where they reside.

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The main function is to modify, sort and package the macromolecules that are synthesized by the cell

(

Post

office)

.

It modifies the proteins which are prepared by the

RER.

The enzymes in the cisternae have the ability to modify proteins by the addition of carbohydrate (

glycosylation

) and

phosphate

(phosphorylation

)

.

Function

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They are also involved in transport of lipid molecules around the cell.

They create lysosomes too.

This is also a major site of carbohydrate synthesis process.

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Endoplasmic

reticulum

The e

ndoplasmic reticulum

(

ER

) is a

eukaryotic organelle

that forms an interconnected network of

tubules

,

vesicles

, and

cisternae

within cells.

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The general structure of the endoplasmic reticulum is an extensive membrane network of

cisternae

(sac-like structures) held together by the

cytoskeleton

.

The

phospholipid membrane

of ER encloses

a space, the

cisternal

space (or lumen), from the cytosol.

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The

three varieties are

Rough endoplasmic reticulum

The surface of the rough endoplasmic reticulum (RER) is studded with protein-manufacturing ribosomes

giving

it a "rough"

appearance.

Smooth endoplasmic reticulum

Sarcoplasmic reticulum

The sarcoplasmic reticulum (SR), from the Greek

sarx

, "flesh", is a special type of smooth ER found in smooth and striated muscle.

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It plays major role in the production, processing and transport of protein and lipid molecules.

ER produces

transmembrane

proteins and lipids for its membrane, as well as the membrane of lysosome, secretory vesicles,

golgi

apparatus, cell membrane and plant cell vacuoles.

Function

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“If the farmer is poor then so is the whole country”

__

Polish proverb