04/13/23 DNM 100 1

CELL

S.S.MOORTHY SEMENCHALAMM.Sc. Comm Health (Occ Health) UKM

B.HSc. Nursing (Aust)Dip Med Sc. (Moh)

Learning OutcomesAt the end of this session, the students will be able to:

• Define cell and organelle• State the function of each organelles • List generalizes cells

– Nucleus– Mitochondria – Golgi apparatus – Ribosome – Lysosome – Rough and smooth endoplasmic reticulum

• Understand the cell membrane transportation across cell membrane

• Discuss cell division – mitosis and meiosis

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Cell Theory – 4 basic Concepts

• Cell is the basic unit of structure and function of all living organisms

• The activity of an organism depends on both the individual and collective activity of its cells

• The biochemical activities of cells are determined by their specific sub-cellular structures

• Continuity of life has a cellular basis (cells come from cells)

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Structure of a Generalized Cell

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Terminology

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The Cytoplasm is the viscous, semi-fluid (gel-like) matter between the cell membrane and the nucleus

The aqueous or watery component of the cytoplasm is the Cytosol, which includes ions and soluble macromolecules

The insoluble constituents of the cytoplasm include the Organelles and the Cytoskeleton

The space outside cells is called the Interstitium. The extracellular fluid is called Interstitial fluid (containing sugars, amino acids, vitamins, hormones, salts, and waste products.

Plasma Membrane (Cell Membrane)• Every cell is surrounded by a cell membrane• It separates the cell’s cytoplasm from its external environment• It also regulates the passage or transport certain molecules in

and out of the cell, while preventing the passage of others (“selective semi-permeable membrane”)

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Plasma Membrane (Cell Membrane)

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• Cell membrane is made of protein and lipid (fatty substance) molecules, which arranged in a double layer

Head (polar)

- Hydrophilic -

Tails (nonpolar)

- Hydrophobic -

Cell membrane

Phospolipid

Nucleus

• The largest organelles• It contains the body’s genetic material, which

directs the activities of the cell called genes (chromosomes)

• Human somatic cells have 46 chromosomes, 23 inherited from each parent.

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04/13/23 DNM 100

Mitochondria• The ‘powerhouses’ of the cell• Generate most of the ATP ( adenosin triphosphate ) cellular

energy• Active cells, such as those found in the muscles, liver, and

kidneys, have a large number of mitochondria (high rate ATP usage)

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• Consists of stacks of closely folded flattened membranous sacs

• It is present in all cells but is larger in those that synthesis and export protein

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Golgi apparatus

• Tiny granules composed of RNA and protein • Synthesised protein from amino acid• Free ribosome's make protein for use within the same cell

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Ribosomes

Endoplasmic Reticulum (ER)

• Two types: 1) Smooth ER 2) Rough ER

• Smooth ER – synthesises lipids and steroid hormones. It is also associated with the detoxification of some drugs

• Rough ER – studded with ribosomes

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04/13/23 DNM 100

Lysosomes• Formed by the Golgi apparatus• Contain a variety of enzymes involved in breaking down large

molecules (e.g. carbohidrate and protein) into smaller particles that are either recycled or expelled from the cell as waste material

• Intracellular digestive system ( destroy cellular debris from damaged cells)

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Cell Membrane Transport

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Passive Transport - requires no ATP (energy) inputDiffusion Simple Diffusion

Facilitated Diffusion Osmosis

Filtration

Active Transport - metabolic energy ATP requiredPrimary Active TransportSecondary Active Transport

Vesicular TransportExocytosisEndocytosis

Passive Transport: Diffusion

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Diffusion is a physical process whereby molecules of gases, liquids, or solid particles scatter themselves evenly through a medium. Molecules are in constant motion (kinetic energy) and move around in a random fashion, colliding with other molecules and/or walls of the container.

Molecules move from areas where they are in higher concentration to areas where their concentration is lower

Passive Transport: Diffusion

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Molecules move from areas where they are in higher concentration to areas where their concentration is lower

Passive Transport: Diffusion

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The driving force for diffusion is the kinetic energy of the particles

The speed or rate of diffusion is influenced by:

Molecular size (the smaller, the faster)

Temperature (the warmer, the faster)

Cell Membrane – Semi-Permeable

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The plasma membrane is a selectively permeable barrier. It only allows “selected” substances to pass through.

Passive Membrane Transport: Facilitated Diffusion

Some molecules, combine with protein carriers move through transmembrane protein channels

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Passive Membrane Transport: Facilitated Diffusion

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Passive Transport: OsmosisOsmosis - movement of water across a semi

permeable membrane.

*Driven by a difference in solute concentrations on the two sides of the membrane.

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Osmolarity

- Total concentration of solute particles in a solution

Effect of Membrane Permeability on Diffusion and Osmosis – Membrane Permeable to Solute

and Water

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Solution tonicity

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Isotonic – solutions with the same solute concentration as the cytosol

Hypertonic – solutions having greater solute concentration than the cytosol

Hypotonic – solutions having lesser solute concentration than the cytosol

Hypotonic Isotonic Hypertonic

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Passive Transport: FiltrationThe movement of water and solutes across a

membrane due to some mechanical force, such as blood pressure and gravity

Pressure gradient pushes solute-containing fluid from a higher-pressure area to a lower-pressure area

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Filtration also occurs in the kidney (glomerulus).

Active Transport

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•Process whereby molecules move across the cell membrane from an area of lower concentration to an area of higher concentration (against the concentration gradient)

•Requires the high energy chemical compound ATP which is supplied by cell metabolism (adenosine triphosphate)

Vesicular Transport• Transport of large particles, macromolecules, and fluid

across plasma and intracellular membranes

– Exocytosis – (Exo = out) – moves substance from the cell interior to the extracellular space

– Endocytosis – (Endo = in) – moves substance from the outside into the intracellular space

- Phagocytosis (cell eating) – substances engulfed by the cell membrane are within particles

- Pinocytosis (cell drinking) – substances engulfed by the cell membrane are in solution

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Exocytosis

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Hormone secretion, neurotransmitter release, mucus secretion, ejection (excretion) of wastes

Endocytosis - Phagocytosis

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Phagocytosis – pseudopods extend, engulf solids, and bring them into the cell (phagosome may fuse with a lysosome → phagolysosome)

bacteria, cell debris

Endocytosis - Pinocytosis

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Pinocytosis – fluid-phase endocytosis – cell membrane invaginates (infolds) and brings extracellular fluid and solutes into the cell

Principle of cell division

• A cell has its own life span• Eventually cells damage, get worn out and die.

They are replaced by a process of cell division for growth, repair & replacement.

• Humans have 46 chromosomes (23 pairs).– 22 pairs somatic (body) chromosomes – 1 pair is sex chromosomes.

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• Nuclear division involves 5 main phases:1) INTERPHASE- Cell is engaged in metabolic activity and

prepare for mitosis / meiosis2) PROPHASE- Chromatin in the nucleus begins to condense &

become visible. Centrioles begin to move to opposite ends of the cells

3) METAPHASE- Spindle fibers align the chromosomes along the middle of the cell nucleus

4) ANAPHASE- Paired chromosomes separate at the kinetochores and move to opposite side of the cell

5) TELOPHASE- Chromatid arrive at the respective poles, and cytokinesis (partitioning) begins

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Principle of cell division

Cell division: Mitosis

• Mitosis is a somatic (body) cell division• A cell undergoes nuclear division and produce 2

identical daughter cells.• Each daughter cell has the same number and kind

of chromosomes as the original cell (46)• Somatic cell division replaces dead or injured cells

and adds new ones for tissue growth.

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04/13/23 DNM 100

Cell division: Meiosis• Meiosis is a reproductive cell division( eggs & sperm ).• A cell undergoes nuclear division and produces 4

identical daughter cells.• Each daughter cell has half of chromosomes of the

original cell (23)• Reproductive cell division produces gametes (sperm and

ova)• Two stages: Meiosis I and Meiosis II

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04/13/23 DNM 100

04/13/23 DNM 100

QUESTIONS PLEASE..