Human Physiology:
Cell StructureBYand Function
DR BOOMINATHAN Ph.D.
M.Sc.,(Med. Bio, JIPMER), M.Sc.,(FGS, Israel), Ph.D (NUS, SINGAPORE)
PONDICHERRY UNIVERSITY
Source: Collected from different sources on the internet-http://koning.ecsu.ctstateu.edu/cell/cell.html
Anatomy, physiology, …
• Anatomy is the science of the structure
• Physiology is the science of the function
• Anatomy and physiology are closely linked, in
particular physiology cannot be understood
without anatomy
• In many respects, both are ‘closed sciences’
Physiology
• Some important moments:
• 17th century: William Harvey first describes the closed
circulation
• 19th century: Claude Bernard formulates the modern
version of homeostasis – the constancy of the internal
milieu
• 19th century: Johannes Muller formulates the ‘law of
specific nerve energy’
Physiology
• Some important moments:
• 17th century: William Harvey first describes the closed
circulation
• 19th century: Claude Bernard formulates the modern
version of homeostasis – the constancy of the internal
milieu
• 19th century: Johannes Muller formulates the ‘law of
specific nerve energy’
• In general, a slow development of our modern view of
the function of the body
Systems physiology:
Missing from the scheme:
Structure and motion:
• Skeletal system
• Muscles
Integratory systems:
• Nervous system
• Hormones
Cell Structure
& Function
Source: http://koning.ecsu.ctstateu.edu/cell/cell.html
Unit-I Outline
• Levels of Cellular Organization & functionOrganelles, tissues, organs & systems.
• Cell theory
• Properties common to all cells
• Cell size and shape – why are cells so small?
• Prokaryotic cells
• Eukaryotic cells
– Organelles and structure in all eukaryotic cell
– Organelles in plant cells but not animal
• Cell junctions
History of Cell Theory
• mid 1600s – Anton van Leeuwenhoek
– Improved microscope, observed many living cells
• mid 1600s – Robert Hooke
– Observed many cells
• 1850 – Rudolf Virchow
– Proposed that all cells come from existing cells
Cell Theory
Cells were discovered in 1665 by Robert Hooke.
Early studies of cells were conducted by
- Mathias Schleiden (1838)
- Theodor Schwann (1839)
Schleiden and Schwann proposed the Cell
Theory.
9
Cell Theory
1. All organisms consist of 1 or more cells.
2. Cell is the smallest unit of life.
3. All cells come from pre-existing cells.
Cell Theory
• All living things are made up of cells.
• Cells are the smallest working units of all living
things.
• All cells come from preexisting cells through
cell division.
Cell Theory
Cell Theory
1. All organisms are composed of cells.
2. Cells are the smallest living things.
3. Cells arise only from pre-existing cells.
All cells today represent a continuous line of
descent from the first living cells.
12
Cell Theory
Cell size is limited.
-As cell size increases, it takes longer for
material to diffuse from the cell membrane
to the interior of the cell.
Surface area-to-volume ratio:
as a cell increases in size, the volume increases
10x faster than the surface area
13
Cell Theory
14
Cell Theory
Microscopes are required to visualize cells.
Light microscopes can resolve structures that
are 200nm apart.
Electron microscopes can resolve structures
that are 0.2nm apart.
15
Cell Theory
All cells have certain structures in common.
1. genetic material – in a nucleoid or nucleus
2. cytoplasm – a semifluid matrix
3. plasma membrane – a phospholipid bilayer
16
Definition of Cell
A cell is the smallest unit that is
capable of performing life functions.
Observing Cells (4.1)
• Light microscope
– Can observe living cells in true color
– Magnification of up to ~1000x
– Resolution ~ 0.2 microns – 0.5 microns
Observing Cells (4.1)
• Electron Microscopes
– Images are black and white – may be colorized
– Magnifcation up to ~100,000
• Transmission electron microscope (TEM)
– 2-D image
• Scanning electron microscope (SEM)
– 3-D image
SEM
TEM
Examples of Cells
Amoeba Proteus
Plant Stem
Bacteria
Red Blood Cell
Nerve Cell
Two Types of Cells
•Prokaryotic
•Eukaryotic
Prokaryotic
• Do not have
structures
surrounded by
membranes
• Few internal
structures
• One-celled
organisms, Bacteria
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Prokaryotic Cells
Prokaryotic cells lack a membrane-bound
nucleus.
-genetic material is present in the nucleoid
Two types of prokaryotes:
-archaea
-bacteria
24
Prokaryotic Cells
Prokaryotic cells possess
-genetic material in the nucleoid
-cytoplasm
-plasma membrane
-cell wall
-ribosomes
-no membrane-bound organelles
25
Prokaryotic Cells
26
Prokaryotic Cells
Prokaryotic cell walls
-protect the cell and maintain cell shape
Bacterial cell walls
-may be composed of peptidoglycan
-may be Gram positive or Gram negative
Archaean cell walls lack peptidoglycan.
27
Prokaryotic Cells
Flagella
-present in some prokaryotic cells
-used for locomotion
-rotary motion propels the cell
28
Prokaryotic Cell Structure
• Prokaryotic Cells are smaller and simpler
in structure than eukaryotic cells.
– Typical prokaryotic cell is __________
– Prokaryotic cells do NOT have:
• Nucleus
• Membrane bound organelles
Prokaryotic Cell
TEM Prokaryotic Cell
Eukaryotic
• Contain organelles surrounded by membranes
• Most living organisms
Plant
http://library.thinkquest.org/C004535/eukaryotic_cells.html
Animal
“Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
Plant Cell
http://waynesword.palomar.edu/images/plant3.gif
Eukaryotic Cells
Eukaryotic cells
-possess a membrane-bound nucleus
-are more complex than prokaryotic cells
-compartmentalize many cellular functions
within organelles and the endomembrane
system
-possess a cytoskeleton for support and to
maintain cellular structure
36
Eukaryotic Cells
37
Eukaryotic Cells
38
Eukaryotic Cells
Nucleus
-stores the genetic material of the cell in the
form of multiple, linear chromosomes
-surrounded by a nuclear envelope composed
of 2 phospholipid bilayers
-in chromosomes – DNA is organized with
proteins to form chromatin
39
Eukaryotic Cells
40
Eukaryotic Cells
Ribosomes
-the site of protein synthesis in the cell
-composed of ribosomal RNA and proteins
-found within the cytosol of the cytoplasm
and attached to internal membranes
41
Cell Structure
• All Cells have:
–an outermost plasma membrane
–genetic material in the form of DNA
–cytoplasm with ribosomes
Cell Parts
Organelles
Surrounding the Cell
Cell Membrane
• Outer membrane of cell
that controls movement in
and out of the cell
• Double layer
http://library.thinkquest.org/12413/structures.html
Cell Wall
• Most commonly found
in plant cells & bacteria
• Supports & protects
cells
http://library.thinkquest.org/12413/structures.html
Inside the Cell
Nucleus
• Directs cell activities
• Separated from cytoplasm by nuclear
membrane
• Contains genetic material - DNA
Nuclear Membrane
• Surrounds nucleus
• Made of two layers
• Openings allow material
to enter and leave
nucleus
http://library.thinkquest.org/12413/structures.html
Chromosomes
• In nucleus
• Made of DNA
• Contain instructions for
traits & characteristics
http://library.thinkquest.org/12413/structures.html
Nucleolus
• Inside nucleus
• Contains RNA to build
proteins
http://library.thinkquest.org/12413/structures.html
Cytoplasm
• Gel-like mixture
• Surrounded by cell membrane
• Contains hereditary material
Endoplasmic Reticulum
• Moves materials around in
cell
• Smooth type: lacks
ribosomes
• Rough type (pictured):
ribosomes embedded in
surface
http://library.thinkquest.org/12413/structures.html
Ribosomes
• Each cell contains
thousands
• Make proteins
• Found on ribosomes &
floating throughout the
cell
http://library.thinkquest.org/12413/structures.html
Mitochondria
• Produces energy through
chemical reactions – breaking
down fats & carbohydrates
• Controls level of water and
other materials in cell
• Recycles and decomposes
proteins, fats, and
carbohydrates
http://library.thinkquest.org/12413/structures.html
Golgi Bodies
• Protein 'packaging
plant'
• Move materials within
the cell
• Move materials out of
the cell
http://library.thinkquest.org/12413/structures.html
Lysosome
• Digestive 'plant' for proteins,
fats, and carbohydrates
• Transports undigested material
to cell membrane for removal
• Cell breaks down if lysosome
structure
is disrupted.
http://library.thinkquest.org/12413/structures.html
Vacuoles
• Membrane-bound sacs
for storage, digestion,
and waste removal
• Contains water solution
• Help plants maintain
shape
http://library.thinkquest.org/12413/structures.html
Chloroplast
• Usually found in plant
cells
• Contains green
chlorophyll
• Where photosynthesis
takes place
http://library.thinkquest.org/12413/structures.html
1. Plasma Membrane
• All membranes are phospholipid bilayers
with embedded proteins
• The outer plasma membrane
–isolates cell contents
–controls what gets in and out of the cell
–receives signals
2. Genetic material in the form of
DNA
–Prokaryotes – no membrane around
the DNA (no nucleus)
–Eukaryotes – DNA is within a
membrane (there is nucleus)
3. Cytoplasm with ribosomes
–Cytoplasm – fluid area inside outer
plasma membrane and outside DNA
region
–Ribosomes – make proteins
Cell Structure
• All Cells have:
–an outermost plasma membrane
–genetic material in the form of DNA
–cytoplasm with ribosomes
Why Are Cells So Small? (4.2)
• Cells need sufficient surface area to allow
adequate transport of nutrients in and wastes
out.
• As cell volume increases, so does the need for
the transporting of nutrients and wastes.
Why Are Cells So Small?
• However, as cell volume increases the surface
area of the cell does not expand as quickly.
– If the cell’s volume gets too large it cannot
transport enough wastes out or nutrients in.
• Thus, surface area limits cell volume/size.
Why Are Cells So Small?
• Strategies for increasing surface area, so
cell can be larger:
– “Frilly” edged…….
– Long and narrow…..
• Round cells will always be small.
Eukaryotic Cells
• Structures in all eukaryotic cells
– Nucleus
– Ribosomes
– Endomembrane System
• Endoplasmic reticulum – smooth and rough
• Golgi apparatus
• Vesicles
– Mitochondria
– Cytoskeleton
NUCLEUS
CYTOSKELETON
RIBOSOMES
ROUGH ER
MITOCHONDRION
CYTOPLASM
SMOOTH ER
CENTRIOLES
GOLGI BODY
PLASMA
MEMBRANE
LYSOSOME
VESICLE
Fig. 4-15b, p.59
Nucleus (4.5)
• Function – isolates the cell’s genetic material,
DNA
– DNA directs/controls the activities of the cell
• DNA determines which types of RNA are made
• The RNA leaves the nucleus and directs the synthesis of
proteins in the cytoplasm at a ______________
Nucleus
• Structure
– Nuclear envelope
• Two Phospholipid bilayers with protein
lined pores
–Each pore is a ring of 8 proteins with an
opening in the center of the ring
– Nucleoplasm – fluid of the nucleus
Nuclear pore
bilayer facing cytoplasm
Nuclear envelope
bilayer facing
nucleoplasm
Fig. 4-17, p.61
Nucleus
• DNA is arranged in chromosomes
– Chromosome – fiber of DNA with proteins
attached
– Chromatin – all of the cell’s DNA and the
associated proteins
Nucleus
• Structure, continued
– Nucleolus
• Area of condensed DNA
• Where ribosomal subunits are made
– Subunits exit the nucleus via nuclear pores
ADD
THE
LABELS
Endomembrane System (4.6 – 4.9)
• Series of organelles responsible for:
– Modifying protein chains into their final
form
– Synthesizing of lipids
– Packaging of fully modified proteins and
lipids into vesicles for export or use in the
cell
– And more that we will not cover!
Structures of the
Endomembrane System
• Endoplasmic Reticulum (ER)
– Continuous with the outer membrane of
the nuclear envelope
– Two forms - smooth and rough
• Transport vesicles
• Golgi apparatus
Endoplasmic Reticulum (ER)
– The ER is continuous with the outer
membrane of the nuclear envelope
– There are 2 types of ER:
• Rough ER – has ribosomes attached
• Smooth ER – no ribosomes attached
Endoplasmic Reticulum
• Rough Endoplasmic Reticulum (RER)
• Network of flattened membrane sacs create a
“maze”
– RER contains enzymes that recognize and modify
proteins
• Ribosomes are attached to the outside of the
RER and make it appear rough
Endoplasmic Reticulum
• Function RER
• Proteins are modified as they move through the
RER
• Once modified, the proteins are packaged in
transport vesicles for transport to the Golgi
body
Endomembrane System
• Smooth ER (SER)
– Tubular membrane structure
– Continuous with RER
– No ribosomes attached
• Function SER
– Lipids are made inside the SER
• fatty acids, phospholipids, sterols..
– Lipids are packaged in transport vesicles and sent
to the Golgi
Endomembrane System
Vacuoles
-membrane-bound structures with various
functions depending on the cell type
There are different types of vacuoles:
-central vacuole in plant cells
-contractile vacuole of some protists
-vacuoles for storage
82
Endomembrane System
Endomembrane system
-a series of membranes throughout the
cytoplasm
-divides cell into compartments where
different cellular functions occur
1. endoplasmic reticulum
2. Golgi apparatus
3. lysosomes
83
Endomembrane System
Rough endoplasmic reticulum (RER)
-membranes that create a network of
channels throughout the cytoplasm
-attachment of ribosomes to the membrane
gives a rough appearance
-synthesis of proteins to be secreted, sent to
lysosomes or plasma membrane
84
Endomembrane System
Smooth endoplasmic reticulum (SER)
-relatively few ribosomes attached
-functions:
-synthesis of membrane lipids
-calcium storage
-detoxification of foreign substances
85
Endomembrane System
Endomembrane System
Golgi apparatus
-flattened stacks of interconnected
membranes
-packaging and distribution of materials to
different parts of the cell
-synthesis of cell wall components
87
88
Endomembrane System
Lysosomes
-membrane bound vesicles containing
digestive enzymes to break down
macromolecules
-destroy cells or foreign matter that the cell
has engulfed by phagocytosis
89
90
Endomembrane System
Microbodies
-membrane bound vesicles
-contain enzymes
-not part of the endomembrane system
-glyoxysomes in plants contain enzymes for
converting fats to carbohydrates
-peroxisomes contain oxidative enzymes and
catalase
91
Golgi Apparatus
• Golgi Apparatus
– Stack of flattened membrane sacs
• Function Golgi apparatus
– Completes the processing substances received
from the ER
– Sorts, tags and packages fully processed proteins
and lipids in vesicles
Golgi Apparatus
• Golgi apparatus receives transport vesicles
from the ER on one side of the organelle
– Vesicle binds to the first layer of the Golgi and its
contents enter the Golgi
Golgi Apparatus
– The proteins and lipids are modified as they pass
through layers of the Golgi
– Molecular tags are added to the fully modified
substances
• These tags allow the substances to be sorted and
packaged appropriately.
• Tags also indicate where the substance is to be shipped.
Golgi Apparatus
Transport Vesicles
• Transport Vesicles
– Vesicle = small membrane bound sac
– Transport modified proteins and lipids from the ER
to the Golgi apparatus (and from Golgi to final
destination)
Endomembrane System
• Putting it all together
– DNA directs RNA synthesis  RNA exits
nucleus through a nuclear pore  ribosome
 protein is made  proteins with proper
code enter RER  proteins are modified in
RER and lipids are made in SER  vesicles
containing the proteins and lipids bud off
from the ER
Endomembrane System
• Putting it all together
ER vesicles merge with Golgi body 
proteins and lipids enter Golgi  each is
fully modified as it passes through layers of
Golgi  modified products are tagged,
sorted and bud off in Golgi vesicles  …
Endomembrane System
• Putting it all together
Golgi vesicles either merge with the plasma
membrane and release their contents OR
remain in the cell and serve a purpose
Vesicles
• Vesicles - small membrane bound sacs
– Examples
• Golgi and ER transport vesicles
• Peroxisome
– Where fatty acids are metabolized
– Where hydrogen peroxide is detoxified
• Lysosome
– contains digestive enzymes
– Digests unwanted cell parts and other wastes
Lysosomes (4.10)
• The lysosome is an example of an organelle
made at the Golgi apparatus.
– Golgi packages digestive enzymes in a vesicle. The
vesicle remains in the cell and:
• Digests unwanted or damaged cell parts
• Merges with food vacuoles and digest the contents
• Figure 4.10A
Lysosomes (4.11)
• Tay-Sachs disease occurs when the lysosome
is missing the enzyme needed to digest a lipid
found in nerve cells.
– As a result the lipid accumulates and nerve cells
are damaged as the lysosome swells with
undigested lipid.
Mitochondria (4.15)
•
Function – synthesis of ATP
– 3 major pathways involved in ATP production
1. Glycolysis
2. Krebs Cycle
3. Electron transport system (ETS)
Mitochondria
• Structure:
– ~1-5 microns
– Two membranes
• Outer membrane
• Inner membrane - Highly folded
– Folds called cristae
– Intermembrane space (or outer compartment)
– Matrix
• DNA and ribosomes in matrix
Mitochondria
Mitochondria (4.15)
•
Function – synthesis of ATP
– 3 major pathways involved in ATP production
1. Glycolysis - cytoplasm
2. Krebs Cycle - matrix
3. Electron transport system (ETS) - intermembrane
space
Mitochondria
TEM
Mitochondria
Mitochondria
-organelles present in all types of eukaryotic
cells
-contain oxidative metabolism enzymes for
transferring the energy within
macromolecules to ATP
-found in all types of eukaryotic cells
110
Mitochondria
-surrounded by 2 membranes
-smooth outer membrane
-folded inner membrane with layers
called cristae
-matrix is within the inner membrane
-intermembrane space is located between the
two membranes
-contain their own DNA
111
Mitochondria
112