1. Cells
Chapter 3

2. Generalized View of the Cell
There are three main parts to a cell and each part has a very specific function.
Read pages to discover them on your own….

3. The Plasma Membrane Sturdy barrier; made mainly of proteins and lipids
Lipid bilayer made of three types of lipid molecules: Phospholipids (lipids that contain phosphorus), cholesterol , glycoproteins (lipids that contain carbohydrates)
Two types of proteins:
Intergral protein extend through
(2) Peripheral loosely attached to interior/exterior
example: glycoproteins –proteins attached to carbohydrates
Selectively permeable--controls what in/out;
to water, most nonpolar lipid soluble molecules: fatty acids, fat-soluble vitamins, steroids, oxygen, carbon dioxide
Impermeable to: ions (cross through ion channels), charged or polar molecules: glucose, amino acids (these cross through integral protein assist, channels; transporters change shape from one side to other)
Receptors (integral proteins) recognize & bind to specific molecules; i.e. hormones
Enzymes (integral and peripheral proteins)
Membrane glycoproteins and glycolipids = cell identity markers  id same cell tissue or foreign cells (danger)

4. Transport Across the Plasma Membrane
Fluids in average body = ~60%
ICF -- inside the cell (cytosol)
ECF – outside the cell
Interstitial fluid (between cells of tissues)
Plasma (blood vessels)
Lymph (lymphatic vessels)
Cerebrospinal fluid (within and around brain/spinal cord)
Materials dissolve into these body fluids; direction of movement dependent upon concentration (amount of solute in solution) 

5. Concentration Gradients
Differences between ICF and ECF in solute concentration
3% salt solution % salt solution
??? Water ??? Water
Passive Active
High to low Low to high
No energy needed Energy needed
Would this be passive or active

6. Concentration Gradients
Differences between ICF and ECF in solute concentration
3% salt solution % salt solution
97% Water % Water
Passive
High to low until dynamic equilibrium reached
Down concentration gradient
No energy needed

7. Passive Processes Does not require the use of energy
Diffusion defined:
Substance moves due to kinetic energy
Movement from high concentration to low concentration
Movement of more molecules in one direction is called net diffusion
Movement ‘down the concentration gradient’
Continues until equilibrium is reached

8. Two types of diffusion
Simple diffusion: lipid-soluble substances, simple cross membrane down the gradient
Facilitated diffusion: ions, through pores of ion channels of integral proteins
NO ENERGY NEEDED
Simple: oxygen, carbon dioxide, nitrogen gases; fatty acids, steroids, fat-soluble vitamins (A, D, E, and K), glycerol, small alcohol and ammonia, water, (polar) and urea (polar)
SIMPLE DIFFUSION ALLOWS GAS EXCHANGES BETWEEN BODY AND BLOOD CELLS AND BLOOD AND AIR WITHIN THE LUNGS
ALLOWS WASTE TO LEAVE THE BODY
Facilitated through pores: ions of potassium, chloride, sodium, calcium through gated
Facilitated: through integral protein assist; substance binds to specific transporter, transporter changes shape, release substance on other side (hormone directed process)
glucose, fructose, galactose, urea, and some vitamins

9. Osmosis
Net movement of water down the gradient; lower solute concentration to higher solute concentration through
Lipid bilayer
Integral proteins
Book problem and packet, sac permeable to water not sucrose; filled with solution is 20% sucrose & 80% water placed in 100% water
Mine one side 20 sucrose 80 water, mine moves from high water concentration to low, levels go up because water moves in but sucrose cannot move out, pressure forces some water back out thus maintaining equilibrium, movement equal back and forth
Do practice problem in packet
WILL LEVELS CONTINUE TO GO UP UNTIL =???? YES!!!! YOUR LEVELS CONTINUE TO GO UP UNTIL EQUILIBRIM IS REACHED
20% sucrose
80% water

10. Osmotic Pressure
Pressure exerted on plasma membrane due to a solution containing solute particles that cannot pass through membrane
Higher solute concentration = higher osmotic pressure
Lower solute concentration = lower osmotic pressure

11. Osmotic Solutions
Isotonic solution: cells maintain normal shape and volume; concentration of solutes equal on both sides of membrane
Hypotonic solution: higher concentration of water outside; higher concentration of solutes than cytosol inside cell
Water molecules will enter cell faster than they leave it = cell will swell, eventually burst
Bursting of red blood cells referred to as hemolysis
Hypertonic solution: higher concentration of water inside; lower concentration of solutes than cytosol inside cell
Water molecules will leave cell faster than they enter it = cell will shrink
Shrinkage of red blood cells referred to as crenation

12. Short Video Review

13. Passive or Active?
Have I been talking about passive, active, or passive and active transport?

14. Active Transport
From low to high concentration; ‘up the concentration gradient’
Requires the use of energy
Comes from splitting of ATP molecule
Changes shape of transporter protein, called a pump
Transports ions: Na+, K+, H+, Ca+2, I-, Cl-
Example: sodium-potassium pump
40% of a cell’s ATP expended on active transport
Drugs like cyanide can turn off ATP production--FATAL
Sodium-potassium pump expels sodium (3) from cell and brings in potassium (2) and acts as an enzyme to split ATP
Also extremely important because it maintains osmotic balance of fluids out v. inside the cell by constantly regulating sodium and potassium that easily leaks into and out of a cell; osmotic balance is needed for the ability of cells to generate electrical signals for action potentials

15. Cyanide
Cyanide can be a colorless gas, such as hydrogen cyanide (HCN) or cyanogen chloride (CNCl), or a crystal form such as sodium cyanide (NaCN) or potassium cyanide (KCN).
Cyanide sometimes is described as having a “bitter almond” smell, but it does not always give off an odor, and not everyone can detect this odor.
You could be exposed to cyanide by breathing air, drinking water, eating food, or touching soil that contains cyanide.
Cyanide enters water, soil, or air as a result of both natural processes and industrial activities. When present in air, it is usually in the form of gaseous hydrogen cyanide.
Smoking cigarettes is probably one of the major sources of cyanide exposure for people who do not work in cyanide-related industries.

16. Transport in Vesicles
Vesicles small sacs formed by budding off of membranes
Transport substances within the cell from one structure to another
Energy source again is ATP
Take in substances from ECF and transport substances out to ECF
Endocytosis: materials moved into cell
Phagocytosis  ‘to eat’ - solids
Bulk-phase endocytosis(pinocytosis)  liquids
Exocytosis: materials moved out of cell

17. Endocytosis
Endocytosis: capturing substance or particle from outside the cell by engulfing it within membrane folds from the cell membrane and releasing it into cytosol.
There are two main kinds of endocytosis:
Phagocytosis
Bulk-phase endocytosis (pinocytosis)

18. Phagocytosis Phagocytosis ”cellular eating” Occurs only in phagocytes
Particles bind to plasma membrane receptors
Projections called pseudopods extend surround particles and portions of the membrane fuse to form a vesicle
Extensions of the plasma membrane and cytoplasm
Pseudopods vesicle formed called a phagosome
Phagosome enters the cell, fuses with lysosomes
Lysosome enzymes break down phagosome’s contents
Any undigested content remains in the phagosome, now called a residual body
Occurs only in phagocytes
(certain white blood cells
and macrophages), cells
specialized to engulf and
destroy bacteria, viruses,
aged dying cells, and foreign
matters protecting body from
disease

19. Bulk-phase endocytosis (pinocytosis)
Bulk-phase endocytosis (pinocytosis) ”cellular drinking”
Plasma membrane folds inward, forming a vesicle allowing tiny droplets of extracellular fluid that contain dissolved substances to be surrounded
Vesicle detaches or “pinches off” of the plasma membrane and enters the cytosol
Liquid is encircled within a pinocytic vesicle
Vesicle fuses with a lysosome, enzymes degrade engulfed solutes
Degraded solutes; like amino acids and fatty acids leave the lysosome to be used elsewhere in the cell

20. Exocytosis
Exocytosis: process of vesicles fusing with the plasma membrane and secretes their contents to the outside of the cell.
All cells do exocytosis process, but most important in:
Secretory cells
Release digestive enzymes, hormones, mucus, and other secretions
Nerve cells
Release neurotransmitters

21. Cytoplasm
Consists of all the cellular contents between the plasma membrane and the nucleus and includes both cytosol and organelles.

22. Cytosol
Cytosol is the liquid portion of the cytoplasm that surrounds the organelles and makes up about 55% of the cell’s volume.
75%-90% of cytosol is water, the rest is composed of dissolved solutes and suspended particles.
Examples: ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, and waste.
Site of many chemical reactions
Maintain cell structure and enable cell growth

23. Cytoskeleton Extends throughout cytosol
Network of three different types of protein filaments:
Microfilaments
Intermediate filaments
Microtubules

24. Microfilaments Contribute to cell strength and shape Function:
Provide mechanical support and help generate movement
Anchor cytoskeleton to integral proteins
Provide support for microvilli
Microvilli
Fingerlike projections of the plasma membrane
Increase cell surface area
Found mostly in areas with great absorption needs like the small intestines
Help cells attach to one another or extracellular materials
Involved in muscle contractions, cell division, and cell locomotion
Migration of embryonic cells
Invasion of tissues by white blood cells (WBCs) to fight disease
Migration of skin cells in wound healing

25. Intermediate Filaments & Microtubules
Found in parts of cells subjected to tension (stretching)
Hold organelles in place
Attach cells to one another
Microtubules
Long, hollow tubes
Help determine cell shape
Function as transport system for
Organelle movement
Secretory vesicles
Migration of chromosomes
Create movement of cilia and flagella

26. Organelles
Functions and identification of the organelles are your responsibility since this a total biology review area
Information found on pages of your textbook
Assign for homework, then do lysosomes, peroxisomes, and proteasomes slides and assign functions of the rest for homework…

27. Lysosomes Membrane-enclosed vesicles
May contain up to 60 different digestive enzymes
Fuse with other vesicles during endocytosis
Recycle the cell’s own structures (worn-out organelles)  autophagy
May destroy own cell  autolysis
This cause tissue deterioration after death
Faulty lysosomes can contribute to certain diseases, i.e. Tay-Sachs disease
Page 13 of packet…. Tay-sachs children jewish nerve cells accumulate glycolipid ganglioside causes muscle rigidity leads to blindness, dementia, lose of coordination die by age 5

28. Peroxisomes Smaller than lysosomes
Contain enzymes called oxidases that oxide (remove hydrogen atoms from) various substances
Creating a by-product of hydrogen peroxide H2O2
Potentially toxic compound associated with free radical superoxides
BUT peroxisomes also contain catalase which breaks down H2O2
Oxidize toxic substances
Abundant in liver

29. Proteasomes Tiny, barrel-like structure
Destroys unneeded, damaged, or faulty proteins from the cytosol
Contain enzyme called protease
Cuts proteins into small peptides
So other enzymes can break them down to amino acids from which new proteins can be built
Remind them to do rest on their own…

30. Nucleus On your own, this is also a biology review topic
Label the diagram on page 14 of your packet
List the functions of the nucleus also
Information found on page 62 of your textbook

31. Gene Action: Protein Synthesis
On your own, this is also a biology review topic
Information found on pages of your textbook.
Show next slide and briefly refresh them on synthesis process…

32. Protein Synthesis
DNA transcribed in nucleus to mRNA, leaves nucleus goes to ribosome there translated into amino acids, peptide bonds form between amino acids and polypeptide chain grows….

33. Somatic Cell Division
Damaged, diseased, or worn out cells are replaced
Two types of cell division:
Reproductive cell division-meiosis
Will be discussed in later chapters
Somatic cell division-mitosis
Division into two identical cells
Division occurs through a sequence of changes called the cell cycle
Two major parts to cell cycle
Interphase: when cell is not dividing
Mitotic phase: when cell is dividing
Somatic cell replacement replaces dead and injured cells and adds ones for tissue growth

34. Interphase 1st step is DNA replication
Then production of new organelles and cytoplasmic components fro the new cell
High metabolic activity
A lot of cell growth

35. Mitotic Phase
Mitosis followed by Cytokinesis (splitting of the cytoplasm)
Chromosomes are visible during this phase under a microscope
Can you identify this phase? CLICK…prophase
Can you identify this phase? CLICK…anaphase

36. Nuclear Division: Mitosis
Four stages:
Prophase
Chromatin condenses into visible chromosomes
Centrioles migrate to opposite poles
Mitotic spindles form attach to centromeres of
chromatids
Nuclear envelop breaks down
Metaphase
Chromatids line up at equator (metaphase plate)
Anaphase
Centromeres split chromatids into chromosomes
Chromosomes dragged towards the poles
Telophase
Chromosomes uncoil into chromatin
Nuclear envelops reforms
Nucleolus reappear
Mitotic spindles break down

37. Cytoplasmic Division: Cytokinesis
Division of cytoplasm and organelles between two new cells
Begins with formation of a cleavage furrow in plasma membrane that pinches inward
Cells return to Interphase

38. Complete Process of Somatic Cell Division

39. Cellular Diversity
Average humans has about 100 trillion cells of varying sizes
Cell size is measured in micrometers (µm)
1 micrometer = 1 one-millionth of a meter
Largest cell in human body is an oocyte with a diameter of 140 µm
Average hair strands is ~100 µm in diameter
Cells can be round, oval, flat, cube-shaped, column-shaped, elongated, star-shaped, cylindrical, or disc-shaped
Shape is related to function

40. Round: oocyte Oval: Liver Flat: Squamous Cube-shaped: Cubiodal Column-shaped: Collumnar Elongated: Collagen Star-shaped: Natural Killer Cells Cylindrical: Skeletal Disc-shaped: RBCs
Round =female egg
Oval = liver cell
Flat = epithelial; connective tissue
Cube= epithelial; connective tissue
Column = muscle
Elongated =
Star-shaped =
Cylindrical = skeletal muscle cells
Disc-shaped = red blood cells

41. Aging and Cells As we age our cells ability to divide is diminished.
DNA sequences that code for cell division break down.
Free radical control becomes limited.
Autoimmune responses slow down.