Lecture 2 Flashcards
Cells are held together physically and functionally by…
junctions which are made up of different types of proteins —> nuts and bolts that anchor cells to one another and anchor cells to their environment (ECM)
what is the ECM
Extracellular Matrix (ECM)
E- outside
C-cell
M- the stuff we live on
The ECM can have variable consistency. Give 2 examples
Both are connective tissue
Bone:
- made up largely of protein and is mineralized
- so super solid ECM
Blood
- very liquidy because it has a lot of water
Name the 3 types of junctions
- Gap junction
- Tight junction
- Anchoring junction
Define gap junctions
- little pores, little holes that allow stuff (mostly ions) to move from one cell to its neighboring cell
- enable communication between cytoplasms of adjacent cells
- found in cardiac muscle
- connexion proteins build a gap junction
Define tight junctions
- adjacent cell membranes are partly fused together creating a barrier
- tightly link cells
- claudin and occludin proteins
Define anchoring junctions
- anchor cells to each other or the ECM or provide strength when tissue is under mechanical stress
- cadherin proteins
what are the 4 major tissue types in the body?
- Epithelial
- Connective tissue cells
- Muscle
- Neural
Describe epithelial tissue
function: protects the internal environment of the body and regulates the exchange of materials between external/internal environments
cell types: exchange, transporting, protective, ciliated, secretory
Define connective tissue cells
function: provides structural support and creates a barrier
- found within the extensive ECM
- made up of collagen
cell types: blood, bone, fibroblasts
Define muscle tissue
function: generate contractile force
cell types: cardiac, skeletal, and smooth
Define Neural tissue
function: neurons carry information in the form of chemical and electrical from one part of the body to another
glial cells are support cells for neurons
Different types of connective tissue
- loose connective tissue
- elastic tissue beneath the skin and between some cells - dense connective tissue
- provides strength and flexibility (tendon and ligaments) - blood
- bone
- adipose tissue
- cartilage
cell membranes are ___________
selectively permeable
what determines the permeability of a molecule
- Presence of transporters or channels for substance
- Size of substance
- Charge of substance
- Hydrophilicity of substance
Highly permeable:
gases, small lipophilic (hydrophobic) molecules, water
impermeable:
ions, lipophobic (polar) and large molecules
Diffusion
- moves from an area of high concentration to a low
- down a concentration gradient
- no use of ATP
Diffusion can be divided into two types across a cell membrane
- Simple diffusion: directly across the phospholipid membrane (small lipophilic molecules)
- Facilitated diffusion: protein-mediate transport
factors affecting diffusion rate
- lipid solubility
- molecular size
- membrane surface area
- concentration gradient
Facilitated diffusion
- protein-mediated channel
- passive transport
- molecule move down their concentration gradient towards equilibrium
Active transport
- requires energy
- molecules move against their concentration gradients
- systems move away from equilibrium
Channels
- water-filled pores linking the extracellular and intracellular environment
- facilitated diffusion (always passive transport
Selective about the substances they allow to pass: - small molecules
- water channels
- ion channels
- most have gates to regulate the flow
- fast
Transporters
- open to one side of the membrane or the other
- may be selective: can carry larger molecules than channels
- facilitated diffusion or active transport
- transport is much slower than channels
Types of channels
- passive/leak channels
- always open and conducting (K+) - Voltage-gated channels
- open and close due to changes in membrane potential - Ligand-gated channels- open when a specific chemical molecule binds to the channel protein
- Mechanically-gated channel: open and close in response to physical disturbance of the membrane
Give an example of ions that use membrane carrier proteins
sodium-glucose transporter
Type of carrier proteins
- uniport carriers (transport one kind of substrate)
- symport carriers (move two or more substrates in the same direction)
- antiport carriers (move substrates in opposite directions)
active transport
- molecules move against a concentration gradient and the system moves away from equilibrium
2 types:
- primary active transport (uses ATP)
- secondary active transport (uses potential energy stored in concentration gradient)
example of secondary active transport
sodium-glucose transporter
Transcellular transport
transport through cells via diffusion, facilitated diffusion, active transport, and endo/exocytosis
ions or molecules pass through apical or basolateral membranes
paracellular transport
- molecules that pass between adjacent cells to get to or from the lumen
- regulated by the presence of tight junctions
