Physio 4

1. Cell Structure
& Function

2. 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.

3. Definition of Cell
A cell is the smallest unit that is
capable of performing life
functions.

4. Cell Classified to function
1. Muscle cell
2. Nerve cell
3. Epithelial cell
4. Connective tissue cell

5. Examples of Cells
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria

6. Two Types of Cells
•Prokaryotic
•Eukaryotic

7. Prokaryotic
• Do not have
structures
surrounded by
membranes
• Few internal
structures
• One-celled
organisms,
Bacteria

8. Eukaryotic
• Contain organelles (little organs) surrounded by
membranes
• Most living organisms
Plant Animal

9. “Typical” Animal Cell

10. • Cells are surrounded by cell membrane
• The interior of the cell is divided:
1. Nucleus
2. Cytoplasm
The Cytoplasm contains two components
1. Cell organelles
2. Cytosol

11. Cell Parts
Surrounding the Cell

12. Cell Membrane
Function of cell membrane
1. Regulate the passage of
substance into and out of
cell and between cell
organelles and cytosol.
2. Link adjacent cells together
3. Detect chemical
messengers arriving at the
cell surface

13. The Cell Membrane Structure

14. Overview
• Cell membrane separates living cell from
nonliving surroundings
– thin barrier = 8nm thick
• Made of phospholipids, proteins & other
macromolecules

15. Phospholipids
Fatty acid
Phosphate
• Fatty acid tails
– hydrophobic
• Phosphate group head
– hydrophilic
• Arranged as a bilayer

16. Phospholipid bilayer
polar
hydrophilic
heads
nonpolar
hydrophobic
tails
polar
hydrophilic
heads

17. More than lipids…
• In 1972, S.J. Singer & G. Nicolson proposed that membrane
proteins are inserted into the phospholipid bilayer
• Two types of membrane protein
1. Integral membrane
2. Peripheral membrane

18. Membrane is a collage of proteins & other
molecules embedded in the fluid matrix of
the lipid bilayer
Extracellular fluid
Cholesterol
Cytoplasm
Glycolipid
Transmembrane
proteins
Filaments of
cytoskeleton
Peripheral
protein
Glycoprotein
Phospholipids

19. Membrane Proteins
• Proteins determine membrane’s specific functions
– cell membrane & organelle membranes each have
unique collections of proteins
• Membrane proteins:
– peripheral proteins
• loosely bound to surface of membrane
– integral proteins
• penetrate lipid bilayer, usually across whole membrane
• transmembrane protein

20. Proteins domains anchor molecule
• Within membrane
– nonpolar amino acids
• hydrophobic
• anchors protein
into membrane
• On outer surfaces of
membrane
– polar amino acids
• hydrophilic
• extend into extracellular
fluid & into cytosol
Polar areas
of protein
Nonpolar areas of protein

21. Many Functions of Membrane Proteins
Outside
Plasma
membrane
Inside
Transporter Cell surface
receptor
Enzyme
activity
Cell surface
identity marker
Attachment to the
cytoskeleton
Cell adhesion

22. Membrane carbohydrates
• Play a key role in cell-cell recognition
– ability of a cell to distinguish one cell from
another
– important in organ &
tissue development

23. Membrane Junctions
• Some cell not anchored to other cells but
suspend in the fluid.
• Most cells are packaged into tissues and
are not free to move.
• Many cells physically joined by
specialized types:
1. Desmosomes
2. Tight junctions
3. Gap junctions

24. Inside the Cell

25. Nucleus
• Almost all cells contain a single nucleus.
• Directs cell activities
• Separated from cytoplasm by nuclear membrane
• Function-Stores and transmits genetic information in the
form of DNA. Genetic information passes from the
nucleus to the cytoplasm

26. Nuclear Membrane
• Surrounds nucleus
• Made of two layers
Nuclear envelope
Nuclear pores
• Openings allow
material to enter and
leave nucleus
http://library.thinkquest.org/12413/structures.html

27. Chromosomes
• In nucleus
• Made of DNA
• Contain instructions
for traits &
characteristics
http://library.thinkquest.org/12413/structures.html

28. Nucleolus
• Inside nucleus
• Contains RNA to build
proteins
http://library.thinkquest.org/12413/structures.html

29. Endoplasmic Reticulum
• Moves materials around
in cell
• Smooth type (Agranular):
lacks ribosomes. Site of
lipid molecule
synthesized
• Rough type (Granular):
ribosomes embedded in
surface. Packaging of
proteins to be secreted or
distributed.
http://library.thinkquest.org/12413/structures.html

30. Ribosomes
• Composed of proteins
and several RNA
molecules
• Proteins factories of
the cell
• Either bound to the
organelle or found
free in the cytoplasm
http://library.thinkquest.org/12413/structures.html

31. Golgi Apparatus
• Most cells have
single Golgi
apparatus.
• Protein 'packaging
plant'
• Move materials within
the cell
• Move materials out of
the cell
http://library.thinkquest.org/12413/structures.html

32. Lysosome
• Spherical or oval
• Typical cell may contain
several hundreds
• Digestive enzyme for
proteins, fats, and
carbohydrates
• Transports undigested
material to cell
membrane for removal
• Cell breaks down if
lysosome explodes
http://library.thinkquest.org/12413/structures.html

33. Mitochondria
• Spherical rode like structure
• 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