1. What do you remember?

2. Membrane held in place by mostly hydrophobic interaction
“Fluid Mosaic Model”
Membrane held in place by mostly hydrophobic interaction
Most lipids and some proteins drift randomly

4. Factors influencing fluidity
1) Phospholipid structure

7. 2)

8. flowchart

9. Transport What types of molecules can do this? Passive transport
Diffusion
Down concentration gradient
Simple vs. Facilitated
Simple diffusion  molecules diffuse through the lipid portion
What types of molecules can do this?

10. Facilitated Diffusion
Requires help (Protein)
Why would it need help?
Examples:
carrier/transport proteins
ion channels
gated ion channels
aquaporins

12. Osmosis Diffusion of water -through a selectively permeable membrane
Uses aquaporins
Comparative terms
Hypertonic
Hypotonic
Isotonic
ALWAYS refer to SOLUTE concentration

14. Which direction will water move? What will happen to fluid levels?B B A
Selectively permeable membrane
Which side has a higher solute concentration?
Which side has a higher water concentration?
Which side is hypertonic?
Which side is hypotonic?

21. Active Transport
Movement of a solute against its concentration gradient
-many times use ATP as energy ex: Na+/K+ pump
Proton pump is major electrogenic pump in plants, fungi, and bacteria

22. Cotransport
Use the concentration gradient produced by one pump to move a second molecule against its concentration gradient
high sucrose
low sucrose
Ex: Plants use this to load sugar (from photosynthesis) into specialized cells (phloem) so it can be transported throughout the plant

23. https://highered. mheducation. com/olcweb/cgi/pluginpop. cgi

24. Apply to a functioning neuron

27. Resting potential  charge difference on either side of membrane

28. Na+ is main cation Negatively charged proteins are main anions
K+ is main cation

30. Na+ channels behind (toward the cell body) cannot be reactivated for a period of time
Ensures that action potentials are one way

32. Saltatory conduction

39. Local signaling Synaptic signaling Electrical signal triggers
release of neurotransmitter.
Synaptic signaling
Neurotransmitter
diffuses across
synapse.
Figure Local and long-distance cell signaling by secreted molecules in animals (part 2: local signaling, synaptic)
Target cell

40. https://youtu.be/JjHMGSI_h0Q

42. Local signaling Target cells Paracrine signaling
-ex: growth factors used to stimulate target cells to grow and divide
Secreting
cell
Figure Local and long-distance cell signaling by secreted molecules in animals (part 1: local signaling, paracrine)
Secretory
vesicles
Local regulator
-ex: growth factor

43. Long-distance signaling  endocrine signaling …hormones!!!
Target cell
specifically
binds
hormone.
Endocrine cell
Hormone
travels in
bloodstream.
Figure Local and long-distance cell signaling by secreted molecules in animals (part 3: long distance signaling, endocrine)
Blood
vessel

44. Cell signaling occurs in 3 stages
EXTRA-
CELLULAR
FLUID
CYTOPLASM
Plasma membrane
Reception
Receptor
Figure 5.20-s1 Overview of cell signaling (step 1)
Signaling
Molecule
-ligand

45. EXTRA- CELLULAR FLUID CYTOPLASM Plasma membrane Reception Transduction
Receptor 1 2 3
Relay molecules
Figure 5.20-s2 Overview of cell signaling (step 2)
Signaling
molecule

46. EXTRA- CELLULAR FLUID CYTOPLASM Plasma membrane Reception Transduction
Response
Receptor 1 2 3
Activation
Relay molecules
Figure 5.20-s3 Overview of cell signaling (step 3)
Signaling
molecule

47. Reception Gate closed Ions Signaling molecule (ligand) Plasma
membrane
Ligand-gated
ion channel receptor
Figure 5.22-s1 Ion channel receptor (step 1)

48. Gate open Gate closed Ions Signaling molecule (ligand) Cellular
response
Plasma
membrane
Ligand-gated
ion channel receptor
Figure 5.22-s2 Ion channel receptor (step 2)

49. Gate open Gate closed Ions Signaling molecule (ligand) Cellular
response
Plasma
membrane
Ligand-gated
ion channel receptor
Gate closed
Figure 5.22-s3 Ion channel receptor (step 3)

50. G protein-coupled receptor
Inactive
enzyme
Signaling
molecule
Activated
GPCR
Figure 5.21-s1
GTP
Plasma
membrane
Activated
G protein
CYTOPLASM
G protein-coupled receptor
-large class of receptors that have a variety of responses
-similar in structure … evolved early in life’s history
Figure 5.21-s1 A G protein-coupled receptor (GPCR) in action (step 1)

51. Activated G protein and activated protein is the transduction
Inactive
enzyme
Signaling
molecule
Activated
GPCR
Figure 5.21-s2
GTP
Plasma
membrane
Activated
G protein
CYTOPLASM
Activated
enzyme
Figure 5.21-s2 A G protein-coupled receptor (GPCR) in action (step 2)
GTP
Activated G protein and activated protein is the transduction
Cellular response

52. Why can aldosterone do this?
Hormone
(aldosterone)
EXTRA-
CELLULAR
FLUID
Receptor inside cell
Why can aldosterone do this?
Figure 5.23
Plasma
membrane
Receptor
protein
Hormone-
receptor
complex
Target cells are kidney
Cause Na+ to be reabsorbed into the blood
Result on blood volume and pressure?
Figure 5.23 Steroid hormone interacting with an intracellular receptor
DNA
mRNA
New
protein
NUCLEUS
CYTOPLASM

54. Many signal cascades utilize protein kinases
Kinases phosphorylate other molecules (often proteins)
Responses can be amplified

55. Phosphorylation cascade
Signaling molecule
Activated relay molecule
Receptor
Inactive
protein
kinase 1
Active
protein
kinase 1
Inactive
protein
kinase 2
Phosphorylation cascade
ATP
ADP P
Active
protein
kinase 2
Figure 5.24 A phosphorylation cascade PP P i
Inactive
protein
ATP
ADP P
Active
protein
Cellular
response PP P i

56. Ex: breaking down glycogen
First messenger
(signaling molecule
such as epinephrine)
Adenylyl
cyclase
G protein
GTP
G protein-coupled
receptor
ATP
Second
messenger
cAMP
Figure 5.25 cAMP as a second messenger in a G protein signaling pathway
Protein
kinase A
Cellular responses
Ex: breaking down glycogen

57. Response could be activated enzyme
or turning on a gene
Growth factor
Reception
Figure 5.26
Receptor
Phosphorylation
cascade
Transduction
CYTOPLASM
Inactive
transcription
factor
Active
transcription
factor
Figure 5.26 Nuclear response to a signal: the activation of a specific gene by a growth factor
Response P
DNA
Gene
NUCLEUS
mRNA

58. Other roles of membrane proteins
Signaling
molecule
Figure 5.7
Receptor
Enzymes
ATP
Signal transduction
(a) Transport
(b) Enzymatic activity
(c) Signal transduction
Figure 5.7 Some functions of membrane proteins
Glyco-
protein
(d) Cell-cell recognition
(e) Intercellular joining
(f) Attachment to the
cytoskeleton and extra-
cellular matrix (ECM)

59. Intercellular joining
Examples in animal cells
-tight junctions
-gap junctions
-desmosomes

60. Prevent leakage of fluid from between cells
Tight Junctions
Prevent leakage of fluid from between cells

61. Function like rivets, anchoring cells together
Function like rivets, anchoring cells together. Membrane proteins are attached to intermediate filaments (part of cytoskeleton). Found in cells that undergo mechanical stress (epithelial in intestines, skin)

63. Gap Junctions
Allow for passage of molecules from cytoplasm of one cell to the next. Allows for direct communication. Found in cardiac muscle and some neurons. Speeds impulse transmission

64. Cardiac muscle cells

65. Animal junctions review

66. Plant cell junctions