Chapter 3 Part 1: Cells-The Living Units

Question 1

Cell Theory

Answer 1

• the cell is the basic structural and functional unit of life
• organismal activity depends on individual and collective activity of cells
• cellular activity depends on the relative number of specific sub cellular structures
• continuity of life has a cellular basis. Cells can only arise from other cells

Question 2

Plasma Membrane (general)

Answer 2

• selectively permeable barrier surrounding the cell
• plays a dynamic role in cellular activity
• provides biological markers for cell-cell recognition

Question 3

Fluid Mosaic Model

Answer 3

Plasma membrane is a bilayer of lipids with imbedded, dispersed proteins

Question 4

Membrane Lipids

Answer 4

• phospholipids have hydrophobic “tails” and hydrophilic “heads”
• hydrophobic tails make up the interior of the membrane
• glycolipids: are lipids with bound carbohydrate chains on the outer surface of the cell membrane
• cholesterol: helps stabilize the membrane fluidity

Question 5

Integral Proteins

Answer 5

Firmly embedded in the cell membrane

Most protrude from both sides of the membrane as transmembrane proteins

Question 6

Peripheral Proteins

Answer 6

More loosely attached at the surface

Question 7

Glycoproteins

Answer 7

Have attached carbohydrate chains

Question 8

Functions of Membrane Proteins

Answer 8

• Transport
• Enzyme Activity
• Receptors for signal transduction
• Intercellular joining
• Cell-cell recognition
• Attachment to the cytoskeleton and extracellular matrix

Question 9

Glycocalyx

Answer 9

Carbohydrate area on the cell surface (glycolipids and glycoproteins)
Provides biological markers for cell recognition and instruction

Question 10

Specialization of the Cell Membrane

Answer 10

Microvili and Membrane junctions

Question 11

Microvili

Answer 11

Fingerlike projections on the cell membrane that increase Membrane surface area

Question 12

Membrane Junctions

Answer 12

Tight Junctions
Anchoring Junctions
Gap Junctions

Question 13

Tight Junctions

Answer 13

Impermeable (watertight) junction of interlocking Proteins encircling the cell

Question 14

Anchoring Junctions

Answer 14

Anchors 2 cells together

-desmosomes: anchoring junctions that consist of an internal protein plaque and external linker proteins

Question 15

Gap Junctions

Answer 15

Collection of hollow protein channels (connexons) that allow substances to pass between cells

Question 16

Plasma Membrane Functions

Answer 16

Membrane Transport
Membrane Potential
Cell-environment Interactions

Question 17

Membrane Transport: Passive Processes

Answer 17

no cellular energy required
Diffusion: the tendency for molecules or ions to disperse evenly
*concentration gradient: a difference in concentration of a substance between 2 areas (drives diffusion)

Question 18

Passive Processes: simple diffusion

Answer 18

• Non-polar and lipid-soluble substances

- Diffuse directly through the lipid bilayer

Question 19

Passive Processes: Facilitated Diffusion

Answer 19

• Small lipid insoluble solutes
• Diffuse through channel proteins
• Large polar molecules such as simple sugars combine with carrier proteins which move them across

Question 20

Passive Processes: Osmosis

Answer 20

-osmosis: diffusion of water across a semipermeable membrane
(occurs when the concentration of water on opposite sides of a membrane)
Osmolarity: total concentration of solute particles in a solution

Question 21

Osmotic Pressure

Answer 21

Pressure required to resist further water entry into a cell

• equal to hydrostatic pressure inside the cell
• in plant cells, creates internal pressure and stops net water movement
• animal cells tend to shrink or swell in response to osmotic imbalances

Question 22

Tonicity

Answer 22

Measure of the ability of a solution to change cell shape or tone by promoting water flow

• hypertonic
• hypotonic
• isotonic

Question 23

Hypertonic

Answer 23

• a solution with high concentration of solutes than inside the cell
• cell loses water and shrinks

Question 24

Hypotonic

Answer 24

• a solution with lower concentration of solutes than inside the cell
• cell gains water and swells

Question 25

Isotonic

Answer 25

-a solution with the same concentration of solutes than inside the cell

Question 26

Passive Processes: Filtration

Answer 26

The passage of water and solute through a membrane by hydrostatic pressure (ex: filtration if urine through the kidney tubes) - pressure gradient pushes fluid from a higher pressure area to a lower pressure area

Question 27

Active Processes

Answer 27

Use ATP to move solutes across a membrane 2 Major Mechanisms: Active Transport Vesicular Transport

Question 28

Symport Systems

Answer 28

2 substances are moved across a membrane in the same direction

Question 29

Antiport Systems

Answer 29

2 substances are moved across a membrane in opposite directions

Question 30

Active Transport

Answer 30

Primary: direct result of hydrolysis of ATP causing conformational change in the Transport protein. (e.g. Na+-K+ pump) Secondary: use of an exchange pump (e.g. Na+-K+ pump) indirectly to drive the Transport of other solutes

Question 31

Vesicular Transport

Answer 31

Transport of large particles and macromolecules across plasma membrane in membrane vesicles.

Question 32

Exocytosis

Answer 32

moves substances from the cell interior to the extracellular space

Question 33

Endocytosis

Answer 33

enables large and macromolecules to enter cell

Question 34

Phagocytosis

Answer 34

Pseudopodia engulf solids and bring them into cell's interior

Question 35

Pinocytosis

Answer 35

Cell drinking

Question 36

Receptor-Mediated endocytosis

Answer 36

Uses receptors in pits all the major mechanisms for specific uptake of macromolecules

Question 37

Membrane Potential

Answer 37

*Voltage across a membrane *Resting Membrane Potential -results mostly from Na+ and K+ concentration gradients across the membrane due to: ~differential permeability of the plasma membrane to Na+ and K+ ~sodium potassium pump

Question 38

Cell-Environment Interactions

Answer 38

Role of Cell Adhesion Molecules | Role of membrane receptors

Question 39

Cell Adhesion Molecules

Answer 39

- Anchor cells to the extracellular matrix and each other - assist in movement of cells last one another - direct white blood cells to injured or infected areas - respond to tension at the cell surface

Question 40

Roles of Membrane Receptors (Proteins and Glycoproteins)

Answer 40

- contact signaling - electrical signaling - chemical signaling - g protein-linked receptors and second messengers

Question 41

Contact Signaling

Answer 41

Important in normal tissue development and immunity

Question 42

Electrical Signaling

Answer 42

Voltage regulated "ion" gates in nervous and muscle tissue respond to voltage changes

Question 43

Chemical Signaling

Answer 43

Signal chemicals it ligands (e.g. Neurotransmitters and hormones) bind to membrane receptors

Question 44

G protein linked receptors

Answer 44

Binding of a ligand activated a g-protein, causing the release of a second messenger (e.g. Cyclic AMP)