Chap 2 - Organelles and their functions

8/14/2019 Chap 2 - Organelles and their functions

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CHAPTER 2

PROKARYOTIC ANDEUKARYOTIC CELLS


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Cell Theory

1965 - Robert Hooke, an English scientist, observed a thin slice

of cork under a compound microscope which consists of

small boxes and named it as cells.

1838 - Matthias Schleiden, German botanist, suggested that all

plants consists of cells.

1839 - Theodore Schwann, a German zoologist, suggested thatanimals also consists of cells. He came up with two

theories:

a. All organisms consists of one or more cells.

b. A cell is the basic unit of structure and

function for all living organisms

1849 - Rudolf Virchow, a German scientist, came up with

another theory : all cells originate from pre-existing cells.


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Robert Hookes

compound microscope

a) The small units of a thin slice of cork

observed by Hooke. b) The plant cell

a. b.


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Cellular Structure and Function

Cytology - the study of cells and their submicroscopic structure

By using electron microscope, the microscopic structure of cells canbe observed.

Two types of cell:

1. Prokaryotic cell

pro before ; karyon nucleus

Prokaryotic cell, the DNA is concentrated in a region called the

nucleoid with no membrane enclosed it.

ex. Bacterial cell and Cyanobacteria

2. Eukaryotic cell

eu true

It has true nucleus bounded by a membranous nuclear envelope.

ex. Fungal cells, animal cells and plant cells


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A comparison between Prokaryotic Cell and Eukaryotic Cell


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All cells have the following structures:

i. Plasma membrane which functions as a barrier between

external and internal parts of a cell.

ii. Nucleus which contains genetic information and controls cell

activities.

iii. Cytoplasma which is a liquid medium where chemical

reactions and metabolism occurs, the site for synthesis of

enzyme, proteins and other materials needed by the cell.


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A view of the Eukaryotic CellsA

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Nucleus

Contains most of the genes

~ 5 m

Nuclear envelope enclosesthe nucleus

Chromosomes, a structure

that carries genetic

information

Chromatin, a complex of

proteins and DNA that builds

up chromosome

Nucleolus a mass of densely

stained granules and fibersadjoining part of the chromatin

Nuclear matrix a framework

of fibers extending throughout

the nuclear interior


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Nuclear envelope

Double membrane, each a lipid

bilayer with associated proteins,

separated by a space of 20-40 nm

Perforated by micropores ~ 100nm

that regulates the entry and exit of

certain large macromolecules and

particles

Chromosomes

An organized unit of DNA, carries the genetic information

Each chromosome is made up of a material called chromatin a

complex of proteins and DNA

A typical human cell has 46 chromosomes

a combination of 23 chromosomes of egg and sperm cells


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Nucleolus

a mass of densely stained

granules and fibers adjoining

part of the chromatin

rRNA is synthesized from

instructions in the DNA with the

protein from cytoplasm, into itssmall and large ribosomal

subunit in nucleolus

It will exit the nucleus to the

cytoplasm and assemble to

become the ribosome


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Ribosomes: Protein factories in the cell

Made of ribosomal RNA and protein that carry out protein synthesis

Cells that have a high protein synthesis have a large number of this cell

Not enclosed in membrane

2 types of ribosome based on its location:

1. Free ribosomes : suspended in the cytosol and build protein that

function in the cytosol. Ex: enzyme for sugar breakdown

2. Bounded ribosomes : attached to the outside of the endoplasmicreticulum or nuclear envelope; make proteins for insertion into membranes,

for packaging within certain organelles such as lysosomes


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The Golgi Apparatus (GA) : Shipping and receiving center

Functions: Center for manufacturing, warehousing, sorting and shipping

Consists of flattened membranous sacs cisternae that stack together

Vesicles concentrated in the vicinity of the GA are engaged in the

transfer of material between GA and other structures.


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Lysosomes : Digestive Compartments

A membranous sac of hydrolytic

enzymes that is used to digest

macromolecules

Lysosomal enzymes works in acidic

environment and perform

autodigestion which destroy the cell

itself

Hydrolytic enzymes and lysosomal

membrane are made by RER andthen transferred to the GA for

processing

Functions:

1. Intracellular digestion

2. Involved in phagocytosis.

Ex. InAmoeba

3. Autophagy recycle of cells

own organic materials


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Vacuoles : Diverse Maintenance Compartments

Found in plant or fungal cell

In mature plant cells, vacuoles enclosedby a membrane called tonoplast which

is selective in transporting solutes

Functions:

1. Hydrolysis (=lysosomes)

2. As food vacuoles

3. Contractile vacuoles

regulates water in the cell

4. As a storage cells in seed

5. As disposal sites for metabolic by-products

6. Protect the plant by containing compounds that are poisonous


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Mitochondria and chloroplasts:

Change energy from one form to another

Semiautonomous organelles that grow and reproduce within

the cell

Contains small amount of DNA that programs the synthesis of

proteins

Mitochondria

Chloroplast


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Mitochondria : Chemical energy Conversion

Functions : Sites of cellular

respiration, the metabolic process

that generates ATP from ADP by extracting

energy from sugars, fats and other

fuels with the help of oxygen.

Enclosed by two membranes, a

phospholipid bilayer withembedded protein

The outer membrane is smooth,

inner membrane is convoluted

forming cristae that increase the surface area for cellular respiration

Consists of two compartments : intermembrane space and

mitochondrial matrix

Mitochondrial matrix contains many enzymes, mitochondrial DNA and

ribosomes


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Chloroplasts : Capture of light energy

A type ofplastids

3 types of plastids:

1. Amyloplasts colourless plastids that store starch, particularly

in root and tuber

2. Chromoplasts contain pigments that give fruits and flowers

their orange and yellow hues

3. Chloroplasts contain the green pigment chlorophyll, along

with enzymes and other molecules that function in

photosynthetic production of sugars


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Lens-shaped, ~ 2 m by 5 m, enclosed by two membranes

separated by intermembrane space

Within the cell, there are thylakoids a flattened interconnectedsacs; a stack of thylakoids is called granum

The fluid outside the thylakoids is called stroma which contains the

chloroplasts DNA, ribosomes, starch and lipid granules and some

enzymes

Three compartments : the intermembrane space, the stroma and

the thylakoid space


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Differences Between Animal and Plant cells

Animal Cells Plant Cells

Only have cell membrane. Have cell membrane and therigid cell wall.

Do not chloroplasts. Have chloroplasts.

Have small or no vacuoles atall.

Have large vacuoles.

Have centrioles. Do not have centrioles.

Food storage : glycogen Food storage : starch


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Unicellular and Multicellular

Organisms

Two categories of cell

1. Unicellular organism

Single-celled organisms which function

as one unit to carry out activities like

growth, reproduction. Motility,excretion, transportation, respiration

and digestion.

Ex. Paramesium2. Multicellular organism

Consists of multiple cells. They depend

on coordination and cooperation

between different types of cells for

proper function.

Ex. Human, Fish, Elephant.

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Chap 2 - Organelles and their functions