Chapter 5 The working cell: part 2

1
Chapter 5 The working cell part 2
2
More definitions

• Phospholipid
• Selectively permeable
• Osmosis
• Diffusion
• Hypertonic, Hypotonic, Isotonic
• Passive and active transport
• Facilitated diffusion

3
Function of the plasma membrane

• Keeps contents of the cell inside and foreign
  particles outside
• It is selectively permeable allows in some
  substances and excludes others

4
Phospholipid molecules

• The backbone of the plasma membrane
• Each molecule has
• -Polar heads
• (hydrophilic water-loving)
• -Nonpolar tails
• (hydrophobic or water-hating)

5
Phospholipidshave polar and nonpolar parts
6
Plasma membrane structure

• Has double layer (phospholipid bilayer)
• Tails on the inside (away from water)
• Heads on the outside (facing water)
• There are also additional components
• proteins
• steroids
• carbohydrates

7
Structure of the plasma membrane
8
Function of proteins

• Serve as receptors for hormones
• Are enzymes themselves
• Attach the membrane to the cytoskeleton
• Form junctions between adjacent cells
• Help move substances across the cell membrane

9
Carbohydrates in the membrane

• Carbohydrate lipid glycolipid
• Carbohydrate protein glycoprotein
• Both act as cell identification tags that are
  recognized by other molecules
• Immune system recognize some cells as foreign
• When doing a transfusion, you must use compatible
  blood types

10
Glycolipid recognition blood type antigens

• Type A has A glycolpids
• Type B has B glycolipids
• Type AB has both glycolipids
• TYPE O has no glycolipids

11
Passive transport

• Requires no work or energy from the cell
• Molecules move from an area of high concentration
  to an area of low concentration
• Diffusion is a type of passive transport
• At equilibrium, the molecules still move but
  there is not net change in concentration.
• Example dye in water

12
Examples of passive transport
13
Passive transport special types

• Osmosis - water
• Facilitated diffusion - uses transport proteins

14
Osmosis

• Diffusion of water
• Movement of water from an area of high to an area
  of low concentration
• Osmosis will be influenced by the amounts of
  salts or sugars dissolved in the water

15
Osmosis terms

• Solute
• the molecule which is dissolved in water
• Salts, sugars, etc.
• Solvent
• The molecule that does the dissolving water

16
More osmosis terms

• What is the relationship of the solute
  concentration outside the cell compared to inside
  the cell?
• Equal to cell isotonic
• Higher than cell hypertonic
• Lower than the cell hypotonic

17

• In osmosis, water moves from high to low
  concentration
• If there is high solute, then there is low water
• If there is low solute, then there is high
  concentration of water

18
Hypertonic vs. Hypotonic

• In a hypertonic solution, there are more solutes
  and less water outside the cell, so water leaves
  the cell
• In a hypotonic solution, there are less solutes
  but more water outside the cell so water enters
  the cell

19
Osmosis
20
Water moves from hypotonic to hypertonic solutions
21
Facilitated diffusion

• Deals with large molecules
• Too big to pass through the phospholipid bilayer
• Need protein carrier molecules
• Like all diffusion, molecules move down their
  concentration gradient

22
Active transport

• Moves molecules against the concentration
  gradient
• Molecules are moved from an area of low
  concentration to an area of high concentration
• Requires energy ATP

23
Exocytosis

• A process of transferring large particles inside
  a vesicle from the inside to the outside of a cell

24
Endocytosis

• A process of taking in large molecules from the
  outside the cell by forming vesicles from the
  membrane

25
Three types of endocytosis

• Phagocytosis
• Amoeba take in food by using extensions called
  pseudopods pack food in a vacuoles
• Macrophages also take in foreign particles
• Pinocytosis
• Take in solutes dissolved in water, not specific
• Receptor-mediated endocytosis
• Specific process
• Substance binds to a specific receptor and then
  gets internalized in vesicles formed from the
  membrane

26
THREE TYPES OF ENDOCYTOSIS
27
Cholesterol gets internalized by
receptor-mediated endocytosis

• Cholesterol is found in membranes
• What class of molecules does it fall under?
• Problems result if there is too much cholesterol
  in the blood

28
Hypercholesterolemia

• More than twice the level of cholesterol in the
  blood
• No functioning LDL receptors or low numbers of
  the receptors
• LDLS accumulate in the blood
• LDLS can then deposit cholesterol in the lining
  of blood vessels blockage

29
LDL MEDIATED ENDOCYTOSIS