1. Cells: The Living Unit

2. Cells – general 4 aspects of cell theory –
A cell is the basic structural & functional unit of life
Cell properties directly relate to the properties of life
The activity of an organism depends on the activities of individual and collective cells
Principle of complementarity –
Activities of cells are dictated by specific structures of cells
Continuity (the smooth working) of life is based on a cellular level
Cells come from pre-existing cells

3. Cells – general cont. Characteristics of cells –
Cells vary greatly in their size, shape, and function
All cells are composed primarily of carbon, hydrogen, nitrogen, and oxygen (CHON)
All cells have the same basic parts & some common functions
All general cells contain a plasma membrane, cytoplasm, and nucleus

4. Cell diversity

5. Plasma membrane structure
Defines the extent of the cell
Separates bodies major fluid components
Intracellular fluid within cells
Extracellular fluid outside cells
The plasma membrane is composed of a double layer of phosopholipids embedded with smaller amounts of cholesterol and glycolipids and proteins

6. Plasma membrane structure cont.
Fluid mosaic model =
Membrane structure composed of a double layer (bilayer) of lipid molecules with protein molecules dispersed in it.
Proteins which “float” within the bilayer form an ever changing mosaic pattern
Composed of…
Double layer of phospholipids (lying tail to tail with their polar heads exposed to the water inside and outside the cell) embedded with cholesterol, proteins, and glycolipids

7. Plasma membrane structure cont.
Surfaces of the plasma membrane –
Outside surfaces of the cell contain more lipids
Contains glycolipids (sugar lipid)
Helps to make the outer surface more polar
Inside contains integral proteins, phospholipids, & cytoskeleton
Phospholipids –
Modified lipid containing phosphorus
2 components –
Hydrophilic –
Polar “head”
Has a charge
Water loving
Hydrophobic –
Nonpolar “tail”
Does not have a charge
Water hating

8. P.M.

9. Plasma membrane structure cont.
Plasma membrane proteins –
Integral proteins are firmly inserted into the plasma membrane
Have both hydrophobic and hydrophilic regions
Some protrude from only one side of the plasma membrane
Usually involved in receptors for hormones or chemical messengers or act as chemical relay messengers
Transmembrane proteins span the entire plasma membrane
Mainly involved in transport
Channel proteins –
Have a pore in which water soluble molecules pass
Carrier proteins –
Bind to substances to move them through the membrane

10. P.M

11. Plasma membrane structure cont.
Peripheral proteins are not embedded in the plasma membrane, but attach to integral proteins or to phospholipids
Can be removed w/o disturbing the plasma membrane
Contain filaments that helps support the membrane on the cytoplasmic side
Some involved in changing the cells shape (during division)
The glycocalyx is the fuzzy, sticky, carbohydrate-rich area surrounding the cell
“sugar covering”
Provides a highly specific biological markers
Recognize self from non-self

12. P.M.

13. Specialization of the plasma membrane
Microvilli –
“shaggy hairs”
Fingerlike extensions of the plasma membrane that increase the surface area of the cell
Most often found in cells with an absorptive function
Kidneys and intestines
Contains actin –
Contractile protein that helps stiffen the microvilli to keep them erect

14. Specialization of the plasma membrane cont.
Membrane junctions –
Many cells are close together and in tight communities
Glycoproteins act as the cells “adhesive”
Wavy contours of cells edges allow cells to stick together in a tongue and grove fashion
Special membrane junctions are formed
Tight Junctions
Desmosomes
Gap Junctions

15. Specialization of the plasma membrane cont.
Tight junctions
Integral proteins on adjacent cells fuse together to form impermeable junctions
Prevents molecules from passing through the extracellular space between cells

16. Specialization of the plasma membrane cont.
Membrane junctions cont. -
Desmosomes –
Anchoring junctions
Scattered like rivets to prevent the cells separation
Held together by linker proteins that extend from the plaque on the cytoplasmic face
Linker proteins span from one cell to the other & attach themselves to the other cells plaque
Reduces the chances of ripping the cell when tension is applied

17. Desmosomes

18. Specialization of the plasma membrane cont.
Membrane junctions cont. –
Gap junctions –
Communication junction
Allows chemical substances to pass between adjacent cells
Connected by connexons – hollow tubules that allow the cells to communicate because their cytoplasm's are so close
Allows small molecules to pass between two cells
In electrically charged tissues

19. Gap junctions

20. P.M. Functions – general Cells are “bathed” in interstitial fluid –
Contains important substances cells need to survive
Cells extract nutrients to remain healthy
Where the cells eject their waste
The plasma membrane is a selectively permeable barrier, regulating how substances pass into and out of the cell
Allows some substances to pass while excluding others

21. P.M. Functions cont. Solute – Solvent – Concentration gradient –
Substance being dissolved within a solution
Ex. Sugar, salt, calcium, etc.
Solvent –
Substance in which solutes are dissolved
“vat” in which substances are dissolved
Typically water
Concentration gradient –
The difference in solute concentration inside and outside the cell

22. Passive processes Passive processes – Does not require energy (ATP)
Move substances down (or with) a concentration gradient
Substances move from areas of higher concentration to areas of lower concentration
Types –
Diffusion
Simple diffusion
Facilitated diffusion
Osmosis
Filtration

23. Passive processes Diffusion –
The tendency of molecules/ions to scatter evenly throughout the environment
Substances move directly through the plasma membrane if its…
Lipid soluble
Small enough to pass through membrane channels
Assisted by carrier proteins
Goal of diffusion – to reach equilibrium – where molecules are moving equally in all directions – there is no net movement – molecules are balanced on each side

24. Passive processes cont.
Diffusion cont –
Move from areas of higher concentration to areas of lower concentration – move down the concentration gradient
Molecules move very quickly & erratically
Bounce off each other
They don’t like to be close they naturally move to areas where numbers are lower (move from high to low)
The greater the concentration difference the faster the diffusion process
Movement occurs due to the kinetic energy of the molecules
The smaller the molecule the faster the diffusion
Warmer the temp the faster the diffusion

25. Diffusion

26. Passive processes cont.
Diffusion cont. –
Simple diffusion –
Unassisted diffusion of lipid-soluble or very small particles
Substances that are nonpolar
Oxygen, carbon dioxide, alcohol, fat-soluble vit
Down the concentration gradient
Facilitated diffusion -
Substances are moved through the plasma membrane by binding to protein carriers or by membrane channels
Transport proteins change shape to allow substances (glucose & simple sugars) through
Transported down the concentration gradient

27. Passive processes

28. Passive processes cont.
Osmosis –
Diffusion of water
Water is polar, but it is a small molecule that can slip through the plasma membrane as the membrane changes shape
Occurs until solute concentrations are balanced
Movement occurs due to solute concentrations
Water moves when solute concentrations differ
Requires less energy to move water than a solute
Osmolarity – the total number of all solute particles w/in a solution
Osmotic pressure – the cells ability to resist further (net) water movement – when solute concentrations are equal

29. Osmosis

30. Passive processes cont
Osmosis cont. –
Tonicity –
A solutions ability to change the tone or shape of cells by altering their internal water volume
The number of nonpenetrating solutes
Isotonic –
Solutions with the same concentration of nonpenetrating solutes on either side of the cell or the total solute concentration
Solutes are equal inside and outside the cell
Cells keep their “normal” shape because there is no net movement of water
Body fluids = isotonic

31. Passive process cont. Osmosis cont. – Hypertonic – Hypotonic –
Solutions with high concentrations of solutes
Cells loose water trying to equalize the solutes
Loosing water causes them to shrink or crenate
Hypotonic –
Solutions that contain fewer solutes
The solution bathing the cell is more dilute than the cell itself
Cells take on water as it tries to equalize the lower number of solutes on the inside of the cell
Cells take on so much water they eventually burst or lyse
Rehydrating – sports drinks, cola, and apple juice are hypotonic increasing the amount of water cells absorb, causing rehydration

32. Tonicities

33. Passive processes cont.
Filtration –
A pressure-driven process that forces water and solutes through a membrane or capillary wall by fluid or hydrostatic pressure
Passive processes
Involves a pressure gradient that pushes the solute fluid (filtrate) from higher-pressure areas to lower-pressure areas
Not a selective process
Anything that is small enough will be pushed, by pressure, through the plasma membrane

34. Active processes
Cells use energy, ATP, to move substances against their concentration gradient
Active transport –
Uses solute pumps to move substances against their concentration gradient
Energy is needed either directly or indirectly
Provide movement for substances who can’t pass by diffusion
Ions such as Na+ and K+ need a protein transport (solute pump) to move across the membrane against their concentration (moving them uphill)

35. Active processes cont. Active transport cont. –
Primary active transport –
Energy provided directly by the hydrolysis of ATP
Causes the transport protein to change shape which pumps the bound solute across the membrane
Sodium potassium pump
K+ higher inside the cell
Na+ higher outside the cell
They leak across the plasma membrane along their concentration gradient – the pump is needed to keep K+ higher inside and Na+ higher outside

36. Active processes cont. Active transport cont. –
Secondary active transport –
The driving forces of primary transport can indirectly drive the transport of other solutes
As sodium is transported it drags other solutes with it – they are cotransported (sugars and amino acids)
Even though solutes are cotransported which is passive – they would not be able to be transported w/o the energy required movement of sodium

37. Active transport

38. Active transport cont. Active transport cont – Vesicular transport –
Means by which large particles (macromolecules) & fluids are transport across the plasma membrane
Energized by ATP
Two types –
Endocytosis
Exocytosis

39. Active transport cont. Vesicular transport – Exocytosis –
“out of the cell”
Used to move substances from inside the cell to the extracellular environment
Hormone secretion, neurotransmitting, ejection of waste, mucus secretion
Substance to be secreted is enclosed in a membranous sac called a vesicle

40. Exocytosis

41. Active transport cont. Endocytosis – “into the cell”
Move substances into the cell using protein-coated vesicles
Clathrin-coated
Non-clathrin-coated (Caveolae or coatomer)
Moved into the cell by extensions of the plasma membrane

42. Active transport cont. Endocytosis cont –
3 Types of Clathrin-coated vesicles
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Phagocytosis –
“cell eating”
Cytoplasmic extensions = pseudopods – protrude from cell and cover/contain large/solid material
Formed vesicle = phagosome
Fuses with a lysosome to digest the contents

43. Active transport cont. Endocytosis cont –
Pinocytosis (fluid phase endocytosis)
Infolding of the plasma membrane
Contains extracellular fluid w/ dissolved molecules
Allows the cell to “sample” the contents of the extracellular fluid
Important for cells that absorb nutrients

44. Active transport cont. Receptor-mediated endocytosis –
Most common method for specific uptake
Enzymes, insulin, hormones, and iron
Flu viruses utilize this method to attack our cells
Receptors = membrane proteins that only bind with certain substances
Create a vesicle = coated pit
Contents dissolved/utilized within the cell

45. Enodcytosis

46. Active transport cont. Non-clathrin-coated vesicles
Caveolae – inpocketings of plasma membrane
Caveolin proteins
Capture specific molecules (folate, tetanus toxin)
Close association with lipid rafts, important for cell signaling
Coatomer (COP1 and COP2) proteins
Vesicular trafficking

47. Membrane potentials
A membrane potential is a voltage across the cell membrane that occurs due to a separation of oppositely charged particles.
In a resting stage a cell exhibits a resting membrane potential – the cell is polarized – the inside of the cell is more negative than the outside
Charge only exists at the membrane
Charges within in the cell are neutral
Determined by…
Concentration gradient of potassium (K+) and sodium (Na+)
More K+ within cells
More Na+ in the extracellular fluid
K+ diffuses out of the cell – cells is impermeable to Na+
Now more positive charges are outside the cell giving it its negative charge

48. Cellular environmental interactions
Membrane receptors –
Diverse groups of integral proteins and glycoproteins that serve as binding sites
Function in:
Contact signaling –
Touching of cells
Method for recognizing other cells
Bacteria and viruses utilize this method
Electrical signaling –
Responding to the changes in voltage
Neural and muscle tissue
Chemical signaling –
Job of most membrane receptors
Nervous & endocrine systems

49. Developmental aspects of cells
Aging –
Due to wear-and-tear
Accumulation of free radicals
May be a result of autoimmune responses & progressive weakening of the immune system
Apoptosis –
Programmed cell death
Cell suicide
Cancer = cells fail to go through apoptosis
Strokes & heart attacks increase the rate of apoptosis

50. The rest of the material is not necessary for the test.

51. Components of the cell
The cytoplasm is the cellular material between the cell membrane and the nucleus, and is the site of most cellular activity.
Major elements of the cytoplasm –
Cytosol –
Fluid in which the other cytoplasmic elements are suspended
Largely water w/ salts, proteins, sugars & other solutes
Cytoplasmic organelles –
Major components/workings of the cell
Cytoplasmic inclusions –
Not a functional unit
Chemical substances
Ex: lipid droplet in a fat cell

52. Components of the cell Organelles – Mitochondria – Ribosome –
Sausage-shaped organelle
Powerhouse of the cell
Produce ATP
The more mitochondria – the more energy a particular cell needs
Large quantities in liver and muscle cells
Ribosome –
Consist of proteins & ribosomal RNA
Site of protein synthesis

53. Components of the cell cont.
Endoplasmic reticulum –
Continuous with the nuclear membrane
“network within the cell”
Two types –
Rough endoplasmic reticulum –
Contains ribosomes making it appear rough
Manufactures all proteins secreted from the cell
Produces components of the membranes
Liver & secretory cells
Smooth endoplasmic reticulum –
Continuation of the RER
Lipid & cholesterol synthesis
Synthesis of steroid-based hormones (sex hormones)
Absorbtion, synthesis & transort of fats
Detoxification of drugs
Breakdown of glycogen to form free glucose

54. Components cont. Golgi apparatus – Lysosomes –
Moves & directs cellular proteins
Modifies, concentrates, & packages proteins
Proteins bud off in vesicles from the ER & bind with the golgi in order to be modified
Golgi vessicles are created allowing proteins to be transferred to the plasma membrane in order to be excreted into the extracellular space
Lysosomes –
Involved in digestion & phagocytosis (bacteria, viruses, & toxins)
Degrading nonfunctional/worn-out organelles
Break down nonuseful tissues

55. Components cont. Peroxisomes – Cytoskeleton –
Digestion of alcohol
Cytoskeleton –
Cells skeleton
Supports cell structure & generates cell movements
Centrosomes & centrioles –
Organizes mircrotubules
Arranged at right angles to each other
Organize mitotic spindles
Form base of cilia and flagella
Cellular extensions –
Cilia –
Occur in large numbers
Move together in order to move substances
Propels other substances
Flagella –
Single
Whip like motion
Sperm
Propels itself

56. Nucleus Control center of the cell Nuclear envelope – Nuclear pores –
Binds the nucleus
Double layer membrane
Continuous with rough ER
Nuclear pores –
Regulates entry and exit of large particles
Nucleoli –
Site of ribosome production
Contain DNA
Chromatin –
DNA (genetic materials) & histone proteins
Nucleosomes –
Eight histone proteins & DNA molecule
Chromosomes –
Condensed chromatin
Utilized when cells are going to divide