cells - cell transport

Question 1

homeostasis

Answer 1

need of an organism to stay stable by regulating internal conditions

Question 2

stimulus

Answer 2

change in environment

Question 3

response

Answer 3

a change in the organism, as a result of a stimulus

Question 4

Feedback mechanisms

Answer 4

evolved to help maintain homeostasis in organisms as they respond to stimuli

• These mechanisms use the output of a system to signal a change in input so that a system response can be stabilized or amplified.
• Can be positive or negative
• In a positive feedback loop, the output (or product) of a system intensifies the response.
• In a negative feedback loop, the output (or product) of a system causes a counter response to return to a set point.

Question 5

cell membrane

Answer 5

• Homeostasis is maintained through regulation at the organ system level all the way down to the cellular level.
• Much of homeostasis on the cellular level is maintained by the cell membrane controlling the movement of things in and out of the cell.
• The cell membrane is selectively permeable = picky about what goes in and out.

CAN pass easily: things that are small, nonpolar, hydrophobic and/or neutral, as well as water
CANNOT pass easily: polar and/or large molecules

• The transport of materials into and out of the cell is classified as either passive or active.

Question 6

Cell Transport

Answer 6

Passive Transport requires no extra energy by the cell because molecules move from high concentration (squished together) to low concentration (spread out) areas down the concentration gradient.
Ex. Simple diffusion, facilitated diffusion, and osmosis

Active Transport requires extra energy (ATP) to be spent to bring materials into the cell or expel materials out of the cell moving from low to high concentration against the concentration gradient.
Ex. Molecular pumps, exocytosis, and endocytosis

Question 7

solute, solvent, and solution

Answer 7

Solute: what gets dissolved (Ex. Lemonade powder)

Solvent: does the dissolving (Ex. Water)

Solution: uniform mixture of two or more substances (Ex. Lemonade)

Question 8

concentration & concentration gradient

Answer 8

Concentration: amount of solute dissolved in solvent
Symbol for abbreviation = [ ]

Concentration gradient: Difference in concentration of a substance from one location to another

Question 9

simple diffusion

Answer 9

• passive transport

The spreading out of molecules across a membrane until equilibrium is reached
Equilibrium = equally concentrated on both sides of the membrane
Molecules move down a concentration gradient, from high [ ] to an area of low [ ]
Ex. O2 and CO2, and other small, nonpolar molecules

Question 10

Facilitated Diffusion

Answer 10

A transport protein helps to facilitate the diffusion of molecules that normally couldn‘t pass through the cell membrane
Transport proteins can act as a channel or a carrier
Molecules move down a concentration gradient, from high [ ] to an area of low [ ]
Ex. Large molecules like glucose (sugar = C6H12O6) and polar molecules like calcium (Ca+2)

• passive transport

Question 11

osmosis

Answer 11

• passive transport

The simple diffusion of water across the cell membrane.
Water molecules move down a concentration gradient, from high [water] to an area of low [water] until equilibrium is reached.
High water concentration means low solute concentration.
Low water concentration means high solute concentration.

Question 12

hypotonic, hypertonic, isotonic

Answer 12

Hypertonic solutions: water [ ] is lower than the cell’s cytoplasm.
Net movement of water out of cell 🡪 Cell shrivels

Hypotonic solutions: water [ ] is higher than the cell’s cytoplasm.
Net movement of water into a cell 🡪 Cell swells

Isotonic solutions: identical water [ ] to cell’s cytoplasm 🡪 Cell stays the same

Question 13

molecular pumps

Answer 13

• active transport

When a cell uses energy to pump molecules across the membrane, against the [ ] gradient, through a protein channel.
This allows a cell to concentrate key molecules within the cell, or remove waste quickly from the cell.
Ex. Potassium (K+), chlorine (Cl-) and sodium (Na+) = ions (charged particles)

Question 14

endo/exocytosis

Answer 14

Endocytosis uses vesicles to move large particles into the cell.
Ex. When white blood cells engulf bacteria in order to fight infection.
Exocytosis uses vesicles to export materials out of the cell.
Ex. When nerve cells secrete neurotransmitters to send signals throughout the body.

• active transport (uses vesicles)

Question 15

2 types of endocytosis

Answer 15

2 Types of Endocytosis:
Phagocytosis = cell “eating”
Cell engulfs solids into vesicle and “digests” them

Pinocytosis = cell “drinking”
Cell engulfs liquids into vesicle and “digests” them