2. Overview
• The cell is the basic unit of life
• There are approximately 75 Trillion cells in human body
• Over 260 types of cells in body
i.e. neurons, muscle, bone, blood cells
All types are derived from just 1 fertilized egg
Differentiation
Forming specialized cells from unspecialized cells
• Totipotent – capable of giving rise to any cell type
• Pluripotent – capable of giving rise to several
different cell types
3.
4. Overview
• The cell membrane maintains integrity of cell
• The membrane is a fluid structure with a large portion of membrane proteins
• Selectively permeable - controls what moves into and out of the cell
• Signal transduction – transmission of a signal from the environment, through
the membrane, into the cell
5. Three major components of the cell membrane
1. Phospholipid bilayer
2. Membrane proteins
3. Cholesterol
7. Nonpolar Hydrocarbon tails
Nonpolar tails form the interior of membrane
Polar Phosphate heads
Polar phosphate groups align to face the
extracellular fluid and intracellular fluid
The phospholipid bilayer forms a
fluid, yet stable boundary.
Phospholipids
Cell Membrane
9. The cell membrane is permeable to
small non-polar molecules
• Steroids,
• Gasses (Oxygen and Carbon Dioxide)
Cell Membrane
The cell membrane is
impermeable to polar molecules
• Proteins
• Water
• Sugars
11. 1. Integral Proteins
• Spans the cell membrane
• Includes channel proteins and
transmembrane proteins
Cell Membrane
Membrane Proteins
Transmembrane Protein – class of integral
proteins with an extracellular domain and an
intracellular domain.
12. Cell Membrane
Membrane Proteins
2. Peripheral Proteins
• Weakly bind to the hydrophilic portion of the
membrane
• May be anchored to an integral protein
• Some peripheral proteins serve as
Cellular Adhesion Molecules (CAM)
• Bind cells to neighboring cells or proteins
Peripheral proteins (orange) may be
temporarily attached to the cell membrane,
or attached to a membrane protein.
Integral
protein
Peripheral
protein
Peripheral
protein
13. Organelles
Smooth Endoplasmic Reticulum
• Membranous labyrinth with no ribosomes attached
• Smooth ER synthesizes lipids
Rough Endoplasmic Reticulum
• Membranous labyrinth studded with ribosomes
• Rough ER synthesizes proteins
Golgi Apparatus
• Stacks of flattened membranous sacs.
• Modifies, packages, and ships proteins within vesicles
(membranous sacs) throughout the cell.
14. Organelles
Ribosomes
• Particles of RNA and protein responsible for
protein synthesis
• Ribosomes may be attached to the endoplasmic
reticulum or they may be suspended freely in
the cytosol.
15. Figure 3 OpenStax CC BY
(a)The Golgi apparatus manipulates products from the rough ER, and also produces new organelles called lysosomes. Proteins
and other products of the ER are sent to the Golgi apparatus, which organizes, modifies, packages, and tags them. Some of
these products are transported to other areas of the cell and some are exported from the cell through exocytosis.
Enzymatic proteins are packaged as new lysosomes (or packaged and sent for fusion with existing lysosomes).
(b)An electron micrograph of the Golgi apparatus.
Organelles
16. Organelles
Mitochondrion (plural mitochondria)
• Double-layer membranous organelle that
produces the currency of energy for a cell (ATP)
through cell respiration.
• Powerhouse of the cell Figure 3.4 Mitochondrion. Openstax BBCY
17. Organelles
Lysosomes
• Enzyme-containing sacs
• Digest worn out cell parts or unwanted substances
Peroxisomes
• Enzyme-containing sacs
• Breaks down fats
Lipid bilayer membrane
Enzymes and proteins
18. Centrosome
• Area of the cell that contains two rod-like centrioles
• Used to produce cilia and a flagellum
• Produces spindle fibers during cell division
Organelles
24. Passive (physical)movements
Requires no energy from cell
• Simple Diffusion
• Facilitated Diffusion
• Osmosis
• Filtration
Membrane Transport
Active (physiological) Movements
Requires energy from cell
Active Transport
• Endocytosis
• Exocytosis
• Transcytosis
25. • Net movement of solutes from an area of higher concentration to
an area of lower concentration
• Moving substances eventually become diffuse (evenly distributed)
• Small, non-polar molecules such as O2, CO2, and steroids
Membrane Transport
Simple Diffusion (Diffusion)
26. Membrane Transport
Simple Diffusion (Diffusion)
Concentration Gradient = Difference in
concentration across the cell membrane
• Movement is bidirectional, but
the net movement occurs down
the concentration gradient
27. Membrane Transport
Facilitated Diffusion
• Diffusion across the membrane through
a channel protein or a carrier protein
• Movement is bidirectional, but net
movement occurs down the
concentration gradient
• Facilitated Diffusion transports small, polar
molecules across the cell membrane
(glucose, ions, polar amino acids)
28. Membrane Transport
Osmosis
• Osmosis is the diffusion of only water
through a semipermeable membrane
• Semipermeable membrane is permeable
to water but not to solutes (salts,
sugars, proteins, etc.)
Greater water
concentration
Lesser water
concentration
Semipermeable
membrane
29. • Water moves towards areas of
higher solute concentrations.
• The presence of impermeable solutes
generates an osmotic pressure
Membrane Transport
Osmosis
• Water follows salts
Remember: water follows salts!
30. • An isotonic solution has the same solute
concentration as inside the cell.
• Water enters and leaves the cell at the
same rate.
• A hypertonic solution has a greater solute
concentration than inside the cell.
• Water leaves the cell
• A hypotonic solution has a lesser solute
concentration than inside the cell.
• Water enters the cell causing it to swell
• Cell may lyse (burst)
Membrane Transport
Osmotic Pressure
31. Filtration – separation of larger particles from a solution by passing
the solution across a membrane.
• The movement of fluid through the membrane is caused by a
difference in pressure across the membrane (pressure gradient).
• The fluids that pass through the membrane are called the filtrate.
Membrane Transport
Filtration
32. Blood pressure forces water and smaller solutes through tiny
openings in capillary wall, while larger molecules, proteins, and
cells remain inside the capillaries.
Capillary wall
Membrane Transport
Filtration in the body
33. Membrane Transport
Active Transport
• Carrier proteins use energy to “pump” molecules
against their concentration gradient.
• Active Transport moves molecules from areas of
lower to higher concentration.
34. Membrane Transport
Sodium-Potassium Pump (Na+/K+ ATPase)
• Transports 3 Na+ out of the cell and 2 K+ into the cell
• Na+/K+ pumps create a high extracellular [Na+] and a high intracellular [K+]
• Requires energy (ATP)
36. • Phagocytosis – cell takes in solids
• Pinocytosis – Cell takes in a fluid
Membrane Transport
Endocytosis
The cell membrane surrounds the substance and
forms a vesicle from a portion of the cell membrane.
38. Membrane Transport
Exocytosis
• Exocytosis is similar to endocytosis in reverse
• Cell synthesizes molecules and packages them within
vesicles to be released from the cell
• The vesicle fuses with the cell membrane and the
substance is released into the extracellular space
40. Stages of the Cell Cycle
Interphase
Mitosis
Cytokinesis
Cell Differentiation
The Cell Cycle
41. Interphase is a very active period of the cell’s life
During interphase the cell grows and performs its
routine functions
Interphase can be divided into 3 sub-phases
G1 phase (G = gap)
S phase (S = synthesis)
G2 phase
The Cell Cycle
42. • The cell is active & grows during G1 phase
• G1 phase is followed by a restriction “checkpoint” that
determines the cell’s fate:
The cell may grow & divide
The cell may remain active, but not divide
The cell may undergo apoptosis = programmed cell death
The Cell Cycle
G1 Phase
44. Cell Division - produces 2 daughter cells from 1 cell
• Mitosis - Division of a cell’s chromosomes.
• Karyokinesis - Division of the nucleus
• Cytokinesis - Division of the cytoplasm
Mitosis occurs in Somatic (non-sex) cells –
sex cells are formed from Meiosis
Both daughter cells from mitosis retain the complete genome (46 chromosomes)
The Cell Cycle
45. Prophase
• Chromatin condenses into chromosomes
• Centrosomes move towards opposite poles of cell
• The nuclear envelope breaks down
• Spindle fibers arise from the centrosomes = asters
4 phases of mitosis
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
The Cell Cycle
Mitosis
Use PMAT to remember this order!
46. Metaphase
• Chromosomes align along equator of cell
Anaphase
• Chromosomes move towards opposite poles of cell
• Cytokinesis usually begins during anaphase
The Cell Cycle
Mitosis
47. The Cell Cycle
Telophase
• Chromosomes complete migration
• Nuclear envelopes reform
• Chromosomes begin to unwind
• Cytokinesis completes
Cytokinesis
• Division of Cytoplasm
• Begins during Anaphase &
continues through Telophase
• Microfilament rings pinches off
two cells from one
Mitosis
48. Attribution
• Differentiation: By Mike Jones [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia
Commons http://upload.wikimedia.org/wikipedia/commons/3/3c/Stem_cells_diagram.png
• Carrier protein cell diffusion: Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine.
DOI:10.15347/wjm/2014.010. ISSN 20018762. (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)],
via Wikimedia Commons http://upload.wikimedia.org/wikipedia/commons/9/93/Blausen_0213_CellularDiffusion.png
• Unsaturated phospholipid: By OpenStax College [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via
Wikimedia Commons http://upload.wikimedia.org/wikipedia/commons/3/3c/0301_Phospholipid_Structure.jpg
• Nucleus: By OpenStax College [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
http://upload.wikimedia.org/wikipedia/commons/5/5e/0318_Nucleus.jpg
• Nuclear Pore: CC SA-BY 2.5 Mike Jones, via Wikimedia Commons
http://upload.wikimedia.org/wikipedia/commons/c/c8/NuclearPore_crop.svg
• The Cell Membrane: CC BY-SA 3.0 Mariana Ruiz, via Wikimedia Commons
http://upload.wikimedia.org/wikipedia/en/9/9c/Cell_membrane_detailed_diagram_edit2.svg
• Chromatin: CC BY 3.0 Sha, K. and Boyer, L. A. The chromatin signature of pluripotent cells (May 31, 2009),
StemBook, ed. The Stem Cell Research Community, StemBook, doi/10.3824/stembook.1.45.1.
http://www.stembook.org/node/585
• Chromatin and Chromosome: Openstax College http://cnx.org/contents/f53c4738-3dce-4a11-8560-
526c87ab0938@4/The_Nucleus_and_DNA_Replication
• Diffusion: By LadyofHats Mariana Ruiz Villarreal [Public domain], via Wikimedia Commons
http://upload.wikimedia.org/wikipedia/commons/c/cc/Scheme_simple_diffusion_in_cell_membrane-en.svg
• Erythrocytes and Osmosis: By LadyofHats translated by Drahkrub [Public domain], via Wikimedia Commons
http://upload.wikimedia.org/wikipedia/commons/e/e3/Erythrozyten_und_Osmotischer_Druck.svg
