2. INTRO TO CELL, TISSUES, MEMBRANE

INTRODUCTION TO
CELLS, TISSUES,
MEMBRANE

WAN NAPISAH BT WAN OMAR

THE CELL:
STRUCTURE AND
FUNCTIONS

Learning outcome

1. After studying this section, student should be
able to:

2. Describe the structure of the plasma membrane

3. Compare and contrast active, passive and bulk
transport of substances across cell membranes

4. Explain the functions of the principal organelles

5. Outline the process of mitosis.

Introduction

✓ Cells are the body’s smallest functional
units.

✓ The human body develops from a single
cell called the zygote.

✓ Individual cells are too small, can be seen
using microscope only.

✓ A cell consist of plasma membrane
enclosing a number of organelles
suspended in a watery fluid called cytosol.

Simple cell

Protoplasm

✓ Cells are composed of protoplasm, an
aqueous solution of carbohydrates, proteins,
lipids, nucleic acids, inorganic salts
surrounded by a cell membrane.

✓ These component are organized into
structures that have a specific function in the
cell called organells.

Protoplasm

✓ Organelles include : 7. Lysosomes

1. Nucleus 8. Peroxisomes
2. Ribosomes 9. Golgi Apparatus
3. Centrosomes 10. Cytoskeleton
4. Centrioles

5. Endoplasmic reticulum

6. Mitochondria

Protoplasm

✓ Protoplasm inside the nucleus of a cell is
called nucleoplasm.

✓ Outside the nucleus is called cytoplasm.
✓ Cells are microscopic, a special unit of

measurement is used to determine their size.
➢ Micrometer ( )
➢ Micron ( )

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Cell/Plasma membrane

✓ Every cell is surround by a cell membrane/
plasma membrane.

✓ -separates cell from its external environment
and from neighboring cells.

✓ -regulates the passage or transport of certain
molecules into and out

Nucleus

✓ The most important organelle within a cell.

✓ Function:

✓ - to control activities of cell

✓ -facilitate cell division

✓ -various dyes or stains, such as iodine, can be
used to make the nucleus stand out

✓ When a cell reaches a certain size, it divides to
form two new cells.

Nucleus

✓ DNA and protein are arrange in a loose
and diffuse state called chromatin.

✓ Chromatin condenses to form short,
rodlike structures called chromosomes.

✓ The number of chromosomes for the
human being is 46.

✓ Chromosomes store the hereditary
material deoxyribonucleic acid (DNA),
which is passed on from one generation of
cells to the next.

Nuclear membrane

✓ Double layer structure that has openings
(pores) at regular intervals.

✓ Material can pass through these openings
from either the nucleus to the cytoplasm or
the cytoplasm to the nucleus.

✓ Outer layer – continuous with the
endoplasmic reticulum of the cytoplasm and
may have ribosomes.



Nucleoplasm

✓ Clear
✓ Semifluid that fills the spaces around the

chromatin and the nucleoli within the
nucleus.

Nucleolus and the
ribosome

✓ Small round body
✓ Contains ribosome composed of ribonucleic acid

and protein.
✓ Ribosome can pass from nucleus through the

nuclear pores into the cytoplasm
✓ There are ribosome aid in protein synthesis.
✓ Be in clusters called polyribosomes, or attaches

to the walls of the endoplasmic reticulum.

Cytoplasm

✓ Sticky
✓ Semifluid material found between the

nucleus and the cell membrane
✓ Consists of protein, lipids, carbohydrates,

minerals, salts, and water (70%-90%)
✓ Background for all chemical reactions that

take place in a cell.



Centrosome and
centrioles

✓ Centrioles –two cylindrical organelles called
centrosome.

✓ During mitosis, or cell division, two centrioles
separate from each other.

✓ Thin cytoplasmic spindle fibers form between
the two centrioles.

✓ This is called spindle fiber apparatus.
✓ Spindle fibers attach themselves to individual

chromosomes to two daughter cells.

Endoplasmic reticulum

✓ Crisscrossing the cellular cytoplasm is a fine
network of tubular structures called
endoplasmic reticulum (reticulum means
“network”).

✓ Serves as a channel for the transport of
materials in and out of the nucleus.

✓ Sometime act as a storage area.

Endoplasmic reticulum

✓ 2 types : rough and smooth
✓ Rough:
➢ Sites for protein synthesis in the cell.
✓ Smooth:
➢ Cholesterol synthesis, fat metabolism and

detoxification of drugs.



Mitochondria

✓ Most of cell’s energy

✓ Vary in shape and number

✓ Have a double-membrane structure contains
enzymes.

✓ Enzymes help break down carbohydrates, fats
and protein molecules into energy to be stored
in the cell as adenosine triphosphate (ATP).

✓ All living cells need ATP for their activities.

Golgi Apparatus

✓ Golgi bodies or Golgi complex.
✓ -synthesizes carbohydrates and combines

them with protein molecules
✓ -store and packages secretions for discharge

from the cell.
✓ -abundant in the cells of gastric glands,

salivary glands and pancreatic glands.

Lysosome

✓ -oval or spherical bodies in the cellular
cytoplasm.

✓ -contain powerful enzyme that digest
protein molecules.

✓ Helps digest old, worn-out cells, bacteria
and foreign matter.

✓ If a lysosome should rupture- start
digesting the cell’s proteins causing it to
die.

✓ Also known as “suicide bags”.

Peroxisomes

✓ Membranous sacs that
contain oxidase enzymes

✓ These enzymes help digest
fats and detoxify harmful
substances.

Cytoskeleton

✓ -Internal framework of a cell
✓ -consists of microtubules,

intermediate filaments and
microfilaments
✓ -filaments provide support
for the cells

Pinocytic Vesicle

✓ Large molecules such as protein and lipids,
which cannot pass through the cell
membrane, will enter a cell by way of the
pinocytic vesicles.

✓ It is called pinocytosis 0r cell drinking.

Cilia and Flagella

✓ -protrusions from the cell membrane.
✓ Cilia have short hairlike protrusions
✓ Flagella have a singular taillike protrusion
✓ Compose of fibrils that protrude from the cell and

beat or vibrate.
✓ Cilia –move materials across the surface of a cell.
✓ The sperm cell has a flagellum that propels the cell

to reach the egg in the upper part of the fallopian
tube of the uterus of the female.



Cellular Metabolism

✓ For cell to maintain their structure and
function, chemical reaction must occur inside
the cell.

✓ These chemical reactions require energy,
most commonly from a molecule called ATP.

✓ ATP – created from carbohydrates, proteins
and fat we eat.

Cell division

✓ Cell divide for two purpose:
1. Growth or maintenance of cells in the human

body (mitosis)
2. Reproduction (meiosis)
✓ In mitosis each cell carries a complete set of

chromosomes (46)
✓ In meiosis each cell carries only half of the

chromosomes (23).





Meiosis

✓ During meiosis , the ovum from the female
and the spermatozoa from the male reduce
their respective chromosome by half , from46
to 23.

✓ When fertilization occurs, the two sex cells
combine to form a simple cell called the
zygote with the full set of 46 chromosomes
(23 from each parent)

Mitosis

✓ 1st stage – division of the nucleus
✓ 2nd stage – division of the cytoplasm.
✓ All cells do not reproduce at the same rate.

Blood-forming cells in the bone marrow, cells
of the skin and cells of the intestinal tract
reproduce continuously

Phase 1 -interphase

✓ Duplication of the molecules of DNA within a
chromosome is made.

✓ This process is called replication.
✓ Each strand of the replicated chromosome is

called a chromatid.
✓ Two chromatid strands are joined by a small

structure called the centromere
✓ 2 centrioles found in an area called centrosome.

Phase 2 – Prophase

✓ 2 parts of centriole start to separate
✓ Array of cytoplasmic microtubules forms

between them.
✓ -changes in the nucleus as well.
✓ Nuclear membrane start to dissolve and the

nucleolus disappears
✓ The DNA in the chromosomes become more

coiled or condensed and form very deeply
staining, rodlike structures.

Phase 3 – Metaphase

✓ Nuclear membrane has dissolved completely.
✓ Chromatid pairs arrange themselves in a

single file, 1 chromatid pair per spindle fiber
between the 2 centrioles
✓ Area where chromatid pairs align is called the
equatorial plate.

Phase 4 - Anaphase

✓ Chromatid pairs separate and are pulled by
the shortening spindle fibers towards the
centrioles.

✓ 2 chromatid of each replicated chromosome
are now fully separated.

Phase 5 -Telophase

✓ Chromosome migrate to the opposite poles of
the cell.

✓ Start to uncoil to become loosely arrange
chromatin granules.

✓ Nuclear membrane and the nucleolus reappear
to help reestablish the nucleus as a definite
organelle again

✓ When cytoplasmic division is finished , 2 new
daughter cells are formed.