pdt-3rd chap(cell strct n funtn of organelles)

8/9/2019 PDT-3rd Chap(Cell Strct n Funtn of Organelles)

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At the end of this topic, students should beable to :

Learning outcomes :

Identify the structure and state the function of :

Cell wall

nucleus

Nucleolus

mitochondria

Rough and smooth endoplasmic reticulum

Golgi bodyribosome

s

lysosomes

Chloroplasts

Centrioles

describe the structure and properties of cellmembrane according to Fluid Mosaic Model

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Key Terms

selectively permeable

Mitochondria

Cell wall

Ribosome

Nucleus

Nucleolus

Golg body

Lysosomes

Chloroplast

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CELL MEMBRANE

A cell is separated from its environment bya plasma membrane which is selectively

permeable.

The plasma membrane is commonlydescribed as a FLUID MOSAIC MODEL.


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Phospholipidbilayer

Structure of cell membrane

FLUID

- Refers to phospholipid molecules that movefreely, so the plasma membrane is quite fluidand flexible.

MOSAIC

- Refers to the proteins that are embedded in

the membrane

Consist of

- phospholipids bilayer - Glycoprotein

- Glycolipid - Cholesterol

- Protein

FLUID MOSAIC MODEL

Cell Wall

Structure :

Found only in plant cell

surrounds the plasma membrane

Made up of cellulose

Function :

Maintains the shape of the cell

Protects the cell

Cell Wall


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Nucleus

Structure :

one in each cell

Shape : Round or oval

surrounded by nuclear envelope

consists of nucleoplasm that contains

Chromatin

Nucleolus

Function :

Acts as the centre to control cell activities

Nucleus

Nucleolus

Structure : Found within the nucleus Shape : Round or oval

Function : Synthesise rRNA

Nucleolus


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Mitochondria

Mitochondria

Structure :

Found in all eukaryotic cells

Double membrane organelle :

Inner membrane

Cristae (foldings of inner membrane)

Outer membrane

Contains semifluid matrix

Function :

sites of cellular respiration generating ATP

A membranous system which is continuouswith the outer nuclear membrane

Two types of ER that differ in structure andfunction

Rough endoplasmic reticulum (RER)

Smooth endoplasmic reticulum (SER)

Rough and Smooth EndoplasmicReticulum

Rough ER (RER) has ribosomes attached to it

Rough Endoplasmic Reticulum


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Smooth ER (SER) lacks ribosomes.

Smooth Endoplasmic Reticulum

Functions of EndoplasmicReticulum

Rough ER

Involves in intracellular transport of proteins

Smooth ER

Participates in the synthesis of lipids,phospholipids & steroids

Participates in carbohydrate metabolism

Detoxifies drugs and poisons

Golgi Body Golgi body


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Structure

Stacks of flattened sacs

Functions :The site of biochemicals synthesis:

Formations of lysosomes

Assembling glycoproteins bycombining carbohydrates and proteins

Production of digestive enzymes

Golgi Body

Ribosomes


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Structure :

Without membrane

Can be found :

freely in cytoplasm

Attached to RER

each consisting of 2 subunits

large subunit

small subunit

Function :

the site of protein synthesis

Ribosomes

Structure :

Small spherical vesicles.

Contain a variety of hydrolytic enzymes which can digestmaterial within the cell

Functions :

Break down macromolecules such as proteins,polysaccharides and nucleic acids

Digest old and worn out organelles (autophagy)

Destruction of cells by their own lysosomes

- important during metamorphosis and development

Lysosomes

Chloroplasts

Structure :

Surrounded by a double membrane

Outer membrane Inner membrane

Thylakoid membrane : part of inner

membrane system

Contain photosynthetic pigments

Stroma : gel-like matrix

Function :

sites of photosynthesis.

Chloroplasts


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Centrioles

1 set of tripletmicrotubules

Structure :

found in animals cells.

Pair of cylindrical structures located in thecentrosome.

Each cylinder consists of nine sets of tripletmicrotubules arranged in a ring.

Functions :

as organisers of spindle fibres during cell division

produce basal bodies from which flagella and ciliadeveloped.

Centrioles


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Key Terms

Selectively permeable

Hypotonic

Hypertonic

Dynamic equilibrium

Passive transport

Active transport

Passive Transport

The diffusion of a substance

across a biological membrane

down concentration gradient

without the supply of energy (ATP).

TYPES OFPASSIVE

TRANSPORT(Not require energy)

Diffusion FacilitatedDiffusion

Osmosis

Definition:

Movement of the substances (molecules, ions &atoms) from a region of higher concentration to a

lower concentration.

Movements of individual molecules are random

DIFFUSION


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The phospholipid bilayer is permeable to very small

uncharged molecules like oxygen and carbondioxide.

These molecules diffuse freely in and out of the

cell through the phospholipid bilayer.

The phospholipid bilayer is not permeable to charged

ions

DIFFUSION

DIFFUSION

e.g. a permeable membrane separating asolution with dye molecules from pure water,

until both solutions have equal concentrations ofthe dye - dynamic equilibrium

each substance diffuses down its own

concentration gradient

DIFFUSION of two solutes

OSMOSIS

Definition

The passive movement of water molecules

across a selectively permeable membrane from the hypotonic solution to the hypertonic

solution

The movement continues until both solutions are

isotonic.


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OSMOSIS

OSMOSIS

when the two solutions are isotonic :

water molecules move at equal rates

from one to the other

with no net movement

OSMOSIS

The Concepts of Water Potential

Definition :

the physical property that predicts

the direction in which water molecules will flow

determined by solute concentrationsolute concentration and applied

pressurepressure.

OSMOSIS


The symbol : a Greek alphabet, psi, The units : kilopascalskilopascals (kPakPa) @ megapascals (MPa)


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OSMOSIS

Pure water has the highest water potential which isset at zero

Dissolving solute molecules in pure water willreduce the water potential (more negative) as theconcentration of water molecules lower

OSMOSIS The concept of water potential

Morenegative

LessNegative

Water Potential,

Solute Potential, s

Pressure Potential, p

OSMOSIS


The three quantities

The combined effects of pressure and [solute] onwater potential are incorporated into the followingequation:

= s + p *

OSMOSIS

The Concepts of Water Potential(in plant cell)

p: due to the presence of cell wall


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OSMOSIS

Definition (the concept of water potential)

The passive movement of water molecules

across a selectively permeable membrane from the solution of higher water potential to the

solution of lower water potential.

FACILITATED DIFFUSION

Definition :

Diffusion of solutes across a membrane with thehelp of transport proteins.

The movement is spontaneous.bound to specific transport proteinsdown their concentration gradients.without using energy

1. Carrier protein

MODES OF FACILITATED DIFFUSION

2. Channel protein

depends on the types of the transport proteins :


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the movement of a substance across abiological membrane

Active transport

DEFINITION

against its concentration gradient

with the help of energy input andspecific transport protein

to bind the carrier &the solute together

to enable the carrier to

translocate the soluteacross the membrane

to separate the solutefrom the carrier

Active transport

The ATP is needed

pdt-3rd chap(cell strct n funtn of organelles)

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