Chapter 3

Question 1

what are cells?

Answer 1

Cells: The structural unit of all living things.

Question 2

What are the 4 main postulates of cell theory?

Answer 2

• Cell is the basic structural and functional unit of life.
• Activity of organism depends on individual and collective activity of its cells.
• Biochemical activities of cells are dictated by their shapes and forms and by the number of their specific subcellular (macromolecule) structures
• Continuity of life has a cellular basis

Question 3

What do membranes do?

Answer 3

organize the chemical activities of life

Question 4

what does the plasma membrane do?

Answer 4

controls the flow of molecules in and out of all cells

Question 5

how are phospholipids structured?

Answer 5

structured similar to a fat molecule, but contains a phosphate group and has only two fatty acids

Question 6

What do phospholipids consist of?

Answer 6

-Choline
-Phosphate
-Glycerol
-Two fatty acids chains

Question 7

What makes up the hydrophilic head?

Answer 7

Choline, phosphate, and glycerol make up the hydrophilic head

Question 8

What makes up the hydrophobic tail?

Answer 8

Two fatty acids chains make up the hydrophobic tail

Question 9

what are plasma membranes made up of?

Answer 9

Plasma membranes are made up of a phospholipid bilayer

Question 10

What is the plasma membrane made up of and what is the model of it called?

Answer 10

Plasma membrane is made up of many thousands of proteins and phospholipids (mosaic) and moves together in a fluid motion: fluid mosaic model

Question 11

Function of the cell membrane?

Answer 11

• Plays a dynamic role in cellular activity
• Must allow transport across membrane to bring material in, transport waste out
• Separates intracellular fluid (ICF) from extracellular fluid (ECF)
• Interstitial fluid (IF) = ECF that surrounds cells

Question 12

What is fluidity maintained by and what does it prevent?

Answer 12

Fluidity is maintained by occasional unsaturated fatty acid tails (double bonds-kinks) in the phospholipids which prevents tight packing

Question 13

What does cholesterol do in an animal cell?

Answer 13

In animal cells, cholesterol helps to stabilize (makes less fluid) the membrane at body temperature, but also helps to maintain fluidity at lower temperatures – accounts for 20% of membrane lipid

Question 14

what are the functions of Integral (membrane bound) proteins

Answer 14

-Attaching membrane to cytoskeleton
-Identification tagging
-Forming junctions between cells
-Molecular assembly lines
-Receptors for chemical messages
-Signal transduction: relay of chemical messages from outside to inside cell
-Help move substances across the membrane

Question 15

functions of Peripheral proteins?

Answer 15

• Support membrane
• Act as enzymes
• Motor proteins involved in cell shape change and muscle contraction

Question 16

Lipid Rafts?

Answer 16

• 20% of outer surface contains lipid rafts

- Concentrating platforms for receptor molecules required for cell signaling.

Question 17

what is Glycolcalyx?

Answer 17

refers to sticky outer coating of cells

Question 18

What acts as biological markers?

Answer 18

Each sugar chain is different so provides highly specific biological markers

Question 19

What are the three factors that bind cells together?

Answer 19

1. Glycoproteins in the glycocalyx act as an adhesive
2. Wavy contours of membranes fit together in tongue and
   groove fashion
3. Specialized cell junctions

Question 20

what are the three general types of cell junctions in animal cells?

Answer 20

Tight junctions: junctions that bind cells very tightly together, forming leak proof, impermeable, sheets (eg. Digestive tract)
Anchoring junctions: (also called Desmosomes) rivet cells together with cytoskeletal fibers, forming strong sheets which are capable of stretching or mechanical stress (Eg. Heart muscle and skin)
Gap junctions: channels that they allow the flow of small molecules between adjacent cells – communication channels (Eg. Flow of ions in gap junctions in the cells of heart muscle coordinates their contraction)

Question 21

What is selective permeability?

Answer 21

Selective permeability: capability of a membrane to select (permit) some substances to cross the membrane more readily than others

Question 22

What molecules are soluble in lipids and can easily pass through membranes through simple diffusion

Answer 22

Small, nonpolar, hydrophobic molecules

Question 23

What molecules are imbedded by the hydrophobic core of the membrane

Answer 23

Large, polar, hydrophilic molecules

Question 24

what is diffusion?

I energy required?

Answer 24

• Diffusion: the net movement of particles down its concentration gradient - from an area of high concentration to an area of low concentration until equilibrium is reached
• no

Question 25

What is passive transport?

Answer 25

Passive Transport: diffusion of a substance across a membrane down its concentration gradient (requires no input of energy)

Question 26

what is Facilitated diffusion?

Answer 26

• Facilitated diffusion: diffusion of substance across a membrane down its concentration gradient that is facilitated (assisted) by membrane-bound proteins (a form of passive transport)
• Can be controlled or regulated

Question 27

What are the two general types of membrane transport proteins and what are some facts about them?

Answer 27

~Channel proteins: an open channel that allows specific molecules or ions to pass freely across the membrane
-Aquaporins are channels specific for water transport
-Selective due to pore size and charges of amino acids lining channel
-Leakage channels – always open
-Gated channels – controlled by chemical or electrical signals
~Carrier proteins: similar to induced fit this protein has specific binding sites for a particular ion or molecule and will change shape to move substances across the membrane.
-Can work with or without energy (ATP)
-Transport large polar molecules such as amino acids and sugars.

Question 28

What is osmosis?

Answer 28

• Osmosis: a physical process in which water diffuses, without input of energy, across a semi-permeable membrane
• Direction of water flow in osmosis is determined by total overall solute concentration (not water volume), and continues until equilibrium is reached
• Salt sucks or Solute sucks

Question 29

what is osmolarity?

Answer 29

Osmolarity: total concentration of all solute particles in solution

Question 30

what is tonicity?

Answer 30

• describes the tendency of a cell in a given solution to either gain or lose water
• Depends on solute concentration and solute permeability of the membrane

Question 31

What is hypertonic?

Answer 31

• Hypertonic: hyper-above… So a hypertonic solution has a high concentration of solute relative to the other solution (i.e. the cell’s cytoplasm).
• When a cell is placed in a hypertonic solution, the water diffuses out of the cell causing the cell to shrivel.

Question 32

What is hypotonic?

Answer 32

• Hypotonic: hypo-below… So a hypotonic solution has a low concentration of solute relative to the other solution (i.e. the cell’s cytoplasm).
• When a cell is placed in a hypotonic solution, the water diffuses into the cell causing the cell to swell and possibly explode.

Question 33

what is isotonic?

Answer 33

Isotonic: no net movement of molecules due to equal concentrations on either side of a semi-permeable membrane.