Membrane Transport and Tissues

Question 1

Phospholipid

Answer 1

Made up of a glycerol backbone with a phosphate group (phosphatidylcholine) and two fatty acid chains attached (for example, maybe oleic acid and palmitic acid)

Amphipathic: has polar and non polar regions

Question 2

Micelle

Answer 2

A structure formed from phospholipids aggregating in an aqueous solution so that the polar heads are turned outward and nonpolar tails are turned inward

Question 3



liposome

Answer 3

artificial phospholipid bilayer vesicle

formed from suspension of phospholipid molecules

Question 4

Leaflets

Answer 4

Inner and outer layer of phospholipid bilayer membrane

Question 5

Plasma membrane of Eukaryotic cell

Answer 5

Made up of phospholipid bilayer, contains glycolipids and steroids like cholesterol

Regulates substances that enter and leave cell as well as facilitating cell to cell communication

Glycolipids found on outer leafet only

Question 6

Peripheral Proteins in Membrane

Answer 6

Aka extrinsic proteins

Located on surface of membrane and generally polar or hydrophilic, can’t flip sides easily

Can be ionically bonded to polar head of phospholipid or integral protein

Can contain a carbohydrate (would be a glycoprotein), carbohydrate protrude outside of cell

Question 7

Integral Proteins in Membrane

Answer 7

Aka intrinsic proteins

Amphipathic proteins that can cross the membrane from inside of the cell to the outside

Can contain carbohydrate (making it a glycoprotein), carbohydrate protrude towards outer cell

Question 8

Fluid mosaic model

Answer 8

Refers to the fluidity of the plasma membrane due to the ability of the phospholipids and proteins to slide past each other

Forces holding membrane together are intermolecular, parts can slide laterally, but not separate

Mosaic refers to asymmetrical layout of a membrane’s lipids and proteins

Question 9

Membrane protein functions

Answer 9

Can act as:

• transporters: proteins select which solutes to enter and exit
• receptors: receive chemical signals from cellular environment
• attachment sites: anchor to the cytoskeleton
• identifiers: other cells can recognize
• adhesive proteins: adhesion from one cell to the next
• enzymes: control chemical reactions

Question 10



Brownian Motion

Answer 10

The constant, irregular motion of very fine particles (such as fine dust or smoke) suspended in a fluid and observed with a microscope. Brownian motion is taken as evidence for molecules, which collide with the observed particles and cause the jitter motion.

Leads to the tendency of solutions to mixc completely with each other over time

Question 11

Diffusion:

Answer 11

tendency of atoms, molecules, and ions in a liquid or air solution to move from areas of higher concentration to areas of lower concentration, thus becoming more evenly distributed. In general, diffusion is more rapid over shorter distances, larger concentration gradients, and higher temperatures.

Question 12

Electrochemical Gradient

Answer 12

Combination of chemical concentration gradient and electrical gradient

Chemical concentration gradient:
Series of vectors pointing in direction of lower concentration for a solute

Electrical gradient:
Series of vectors pointing in the direction that a positively charged particle will tend to move

Question 13

Membrane Permeability

Answer 13

Increasing polarity and size leads to decreased permeability in membrane

Large steroid hormone diffuses easily

Water diffuses slowly across membrane
Most diffusion of polar or small molecules takes place through incidental holes called leakage channels created by irregular shapes of integral proteins

Question 14

Passive diffusion

Answer 14

Movement across the membrane through leakage channels without the assistance of membrane proteins

No ATP required, down the concentration gradient

Question 15

Membrane channels

Answer 15

Aka carrier proteins

Proteins embedded in the cell membrane that assist molecules in moving across membrane

Question 16

Facilitated Diffusion

Answer 16

Diffusion that occurs down the concentration gradient through membrane channels

No ATP required

Glucose transported this way

Question 17

Active transport

Answer 17

Movement of a compound against its electrochemical gradient

Requires expenditure of energy

Primary active transport: direct use of ATP

Secondary active transport: ATP creates electrochemical gradient which is then used to acquire or expel a second molecules against its gradient

Question 18

Osmotic Pressure

Answer 18

When concentrations of molecules on either side of membrane are not equal, a pulling pressure is generated to equal out the gradient

Water will move towards areas of higher concentration

Colligative property: based on the number of particles present rather than the type

Question 19

Endocytosis

Answer 19

Cells acquire substances from extracellular environment by membrane surrounding the contents and allowing the entry of a vesicles to the interior of the cell

Vesicle can fuse with Golgi apparatus or targeted for destruction by lysosome

Question 20

Phagocytosis

Answer 20

Cell membrane protrudes outward to engulf and envelop particulate matter

Triggered by binding of matter to protein receptors on cell

E.g., macrophages

Question 21

Pinocytosos

Answer 21

Extracellular fluid is engulfed by small invaginations of cell membrane

Performed by most cells in random non-selective fashion

Question 22

Receptor-mediated endocytosis

Answer 22

Specific uptake of macromolecules by ligand binding to receptor protein on cell membrane and then moved to a Claritin coated pit which forms a coated vesicle

Uptake of hormones or nutrients

Question 23

Exocytosis

Answer 23

Reverse of endocytosis, where substances leave the cell in a vesicle that fuses with the cell membrane

Question 24

Stages of cell cycle of typical somatic cell

Answer 24

First Growth phase (G1)
Synthesis (S)
Second Growth Phase (G2)
Mitosis or Meiosis (M)

Interphase: G1, S, G2

Question 25

G1 of Cell Cycle

Answer 25

Cell grows in size, producing new organelles and proteins RNA and protein synthesis ER creates phospholipids and new portions of the cell membrane as secretory vesicles Cell growth assessed at G1 checkpoint

Question 26

G1 Cell Checkpoint

Answer 26

Assessed size of cell If cell size is large enough (ratio of cytoplasm to DNA exceeds threshold), then cell moves to S phase, otherwise moves to G0 phase

Question 27

G0 Cell Cycle Phase

Answer 27

Non-growing state distinct from interphase Causes variations in cell cycle length between cells Some cells remain in G0 permanently (neurons)

Question 28

S Cell Cycle Phase

Answer 28

Cell focused on DNA replication, exact duplicate of each chromosome is created Organelle and protein production slows

Question 29

G2 Cell Cycle Phase

Answer 29

Cellular organelles duplicate RNA and protein synthesis 10-20% of cell life cycle G2 checkpoint at end of the G2 checks for mitosis promoting factor

Question 30

G2 Cell Checkpoint

Answer 30

If mitosis promoting factor (MPF) is high enough, mitosis is triggered

Question 31

M Cell Checkpoint

Answer 31

End of Mitosis, checks if chromosomes are aligned correctly score dividing

Question 32

Two types of Cancer Mutations

Answer 32

Tumor repressor: deactivation of checkpoint protein | Oncogene: activation of a gene that causes proliferation of cell

Question 33

Fibroblast

Answer 33

Cells that can secrete fibrous proteins such as elastin and collagen which forms a molecular network that holds cells in place Network known as extracellular matrix

Question 34

Extracellular Matrix

Answer 34

Molecular network that holds cells in place Varies greatly from cell type to cell type Can be liquid or solid May provide structural support, determine cell shape and motility, and affect cell growth

Question 35

Three classes of molecules that comprise animal cell matrices

Answer 35

1. Glycosaminoglycans and proteoglycans Provides pliability to matrix, over 90% of matrix by mass 1. 2. Structural proteins Provide matrix with strength (collagen) 1. 3. Adhesive proteins Help individual tissues stick together

Question 36

Basal lamina

Answer 36

Thin sheet of matrix material that separates epithelial cells from support tissue Acts as a sieve-like barrier, selectively allowing passage of some molecules, but not others

Question 37

Glycocalyx

Answer 37

Separates cell membrane from ECM, some animal cells contain this layer Involved in cell-to-cell recognition, adhesion, cell surface protection, and permeability Same material as ECM

Question 38

Tight junctions

Answer 38

Form watertight seal from cell to cell that blocks water, ions, and other molecules from moving around and past cells Barrier to protein movement between apical and basolateral surfaces of cell (apical side of cell faces lumen of cavity)

Question 39

Desmosomes

Answer 39

Join two cells at a single point, strongly attached directly to cytoskeleton of cell Do not prevent fluid from circulating around cell, but found in tissues that experience a lot of stress due to sliding (skin or intestinal epithelium)

Question 40

Gap junctions

Answer 40

Small tunnels that connect cells, facilitate movement of small molecules and ions between cells

Question 41

Cell communication with non adjacent cells

Answer 41

Cell sends out chemical message or hormone which can picked up receptor of other cell If hormone small and lipophilic (steroid), can cross membrane and bind to receptor in cell (cytosol or nucleus) to change transcription If hormone large and lipophobic (protein), binds to receptor on surface of cell which can change membrane permeability, or deactivate/activate other membrane proteins, or activates an intracellular second messenger

Question 42

Intracellular second messenger

Answer 42

Activated as the second part of a signal cascade with a hormone binding to outside the cell possibly as first signal cAMP, cGMP, or calmodulin

Question 43

Four types of tissue

Answer 43

Epithelial: separates free body surfaces from surroundings Muscle Connective: characterized by an extensive ECM (blood, lymph, bone, cartilage, connective tissue) Nervous

Question 44

Organs

Answer 44

Various types of tissues work together to form