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Ch7 Flashcards

1
Q

what’s the nickname of the cell membrane

A

The cell membrane is often referred to as “the edge of life” because it defines the boundaries of the cell and regulates the movement of substances in and out.

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2
Q

membrane functions

A
  • Allow some substances to leave or enter the cell
  • Maintain internal and external cell environments
  • Display cell antigens/markers
  • Hold receptors for large molecules
  • Seal, fuse, and remain flexible as the cell changes shape
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3
Q

describe the structure of phospholipids.

A

Phospholipids have a glycerol backbone attached to a phosphate group and 2 fatty acid chains. Phospholipids are amphipathic, meaning they have both hydrophobic and hydrophilic ends.

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4
Q

Result of phospholipid structure in water

A

Cell membrane forms spontaneously as a lipid bilayer.

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5
Q

Function of protein channels in lipid bilayer

A

Protein channels penetrate the lipid bilayer to prevent complete impermeability. Allow specific molecules that are too large or too polar to cross the membrane.

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6
Q

Role of hydrophobic amino acids in proteins

A

Hydrophobic amino acids allow proteins to embed themselves in the phospholipid tail region of the plasma membrane since the membrane is hydrophobic there.

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7
Q

Lipid bilayer membranes are permeable to:

A

IN GENERAL:
- Other lipids - Nonpolar molecules
- Small polar molecules

SPECIFIC EXAMPLES of some of these molecules are in parentheses:
- Nonpolar molecules (e.g., O₂, CO₂)
- Small polar molecules (e.g., H₂O)

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8
Q

Lipid bilayer membranes are impermeable to:

A

IN GENERAL:
- Ions
- Large polar molecules

SPECIFIC EXAMPLES of some of these molecules are in parentheses:
- Ions (e.g., Na⁺, K⁺, Cl⁻)
- Large polar molecules (e.g., sugars C₆H₁₂O₆, proteins)

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9
Q

3 main types of globular proteins embedded within the cell membrane

A
  1. Integral Protein: permanently attached
  2. Transmembrane Protein: an integral protein that crosses the entire membrane
  3. Peripheral Protein: not permanently attached
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10
Q

Functions of Integral Proteins

A
  1. Channels
  2. Receptor proteins
  3. Cell surface markers (with carbohydrate chains attached to proteins)
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11
Q

Receptor proteins

A

Transmembrane proteins. They bind to signaling molecules outside the cell, such as hormones.

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12
Q

Function of receptor proteins

A

Transmit signals through molecular switches to internal signaling pathways.

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13
Q

Result of signal transduction in cells

A

Triggers a response, such as making more of a specific protein or opening a protein channel.

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14
Q

what’s a ligand

A

A generic term for a molecule that binds to a receptor protein.

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15
Q

Receptor/Channel Protein

A

A protein that allows the binding of a ligand, leading to a cellular response.

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16
Q

Cell surface markers are integral proteins or lipids with carbohydrate “flags” attached. These are called…

A

These markers are called glycoproteins or glycolipids.

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17
Q

Function of cell surface markers

A

They identify your body’s cells as belonging to you and are useful in cell-cell recognition and adhesion.

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18
Q

Role of cell surface markers in the immune system

A

They help in the rejection of foreign cells by the immune system.

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19
Q

Importance of cell adhesion

A

Cell adhesion helps cells stick together to become tissues.

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20
Q

Definition of “glyco”

A

“Glyco” refers to carbohydrate.

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21
Q

Glycoprotein

A

A glycoprotein is a protein with a carbohydrate chain.

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22
Q

Glycolipid

A

A glycolipid is a lipid with a carbohydrate chain.

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23
Q

Unsaturated lipid tails

A

Unsaturated lipid tails have C-C double bonds, resulting in a bent chain. They are less tightly packed, leading to lower melting points and maintaining fluidity and flexibility of the cell membrane at lower temperatures.

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24
Q

Saturated lipid tails

A

Saturated lipid tails have C-C single bonds, resulting in a straight chain. They are more tightly packed, leading to higher melting points and decreased fluidity, strengthening the cell membrane at higher temperatures.

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25
Membranes in living organisms vary in composition due to different habitats.
The composition of membranes in living organisms changes based on their habitat to maintain proper fluidity and function.
26
Ideal ratio of saturated and unsaturated fatty acids
The ideal ratio of saturated and unsaturated fatty acids is regulated to maintain membrane fluidity, keeping it fluid yet strong enough to avoid puncture. This is dependent on the temperature of the environment the organism lives in.
27
Temperature's effect on cell membranes
The temperature a cell experiences affects its membrane composition. For example, fish in Antarctic water have more unsaturated fatty acids in their membranes than fish in warmer water.
28
Role of unsaturated fatty acids in cold environments
Unsaturated fatty acids have a lower melting point, which increases membrane fluidity in cold environments.
29
Ratios of fatty acid types of a fish in Antarctic water
Fish in Antarctic water have higher percentages of unsaturated fatty acids in their membranes to maintain fluidity in cold temperatures.
30
Cholesterol is found in _______________ in eukaryotes.
Cholesterol is located in between phospholipids in cell membranes.
31
Role of cholesterol in membrane fluidity.
Cholesterol acts as a modulator to membrane fluidity by stabilizing membranes at high temperatures and preventing stiffness at low temperatures.
32
Selectively permeable
property of biological membranes which allows some substances to pass more easily than others.
33
Function of channel proteins
Move molecules across the membrane that the membrane is impermeable to; May provide a hydrophilic tunnel through the membrane; May physically bind to a substance to move it across
34
Specificity of channel proteins
Channel proteins are specific for the substance they move.
35
Movement across the cell membrane can be passive
Passive transport means the cell does not have to expend energy; molecules are moving down their concentration gradient (from high to low concentration)
36
Movement across the cell membrane can be active
Active transport is an energy-requiring process where a transport protein pumps a molecule across a membrane against its concentration gradient.
37
Passive Transport: Simple Diffusion
The net movement of a substance down a concentration gradient, resulting from random molecular movement. It continues until equilibrium is reached and is not selective. Example: O₂ and CO₂ move through phospholipids based on size and nonpolar vs. polar properties.
38
Facilitated diffusion
Involves the diffusion of solutes across a membrane (from high to low concentration) with the help of transport proteins. No energy is needed.
39
True or False: Channels in facilitated diffusion are selective to what they transport.
TRUE
40
True or False: In facilitated diffusion, molecules move down a concentration gradient.
TRUE
41
Osmosis
The diffusion of water across a selectively permeable membrane.
42
Water Movement in Osmosis
Water moves down its concentration gradient from more water availability to less water, or from a less concentrated solution to a more concentrated solution.
43
Equilibrium in Osmosis
Osmosis continues until equilibrium is reached, where water molecules move in both directions at the same rate.
44
cytosol
Cytosol is the solution inside cells, consisting of water and dissolved substances.
45
extracellular fluid
Extracellular fluid is the solution outside cells, consisting of water and dissolved substances.
46
A solution is hypertonic.
A hypertonic solution has a higher concentration of solutes outside the cell than inside.
47
A solution is hypotonic.
A hypotonic solution has a lower concentration of solutes outside the cell than inside.
48
A solution is isotonic.
An isotonic solution has equal concentrations of solutes inside and outside the cell.
49
Definition of solute.
Solute is what dissolves in a solvent, such as salt in water.
50
Definition of solvent.
Solvent is the substance doing the dissolving, like water in our body.
51
Discuss what is happening to the cell when it is in a HYPERTONIC solution
A solution with a greater solute concentration compared to that inside a cell. More water is available in the cell, so water leaves the cell; the cell shrinks and goes through crenation (cell forms rounded edges).
52
Discuss what is happening to the cell when it is in a HYPOTONIC solution
A solution with a lower solute concentration compared to that inside a cell. More water is outside the cell, so water enters the cell. Cell swells; possibly bursts.
53
Discuss what is happening to the cell when it is in a ISOTONIC solution
A solution with an equal solute concentration compared to that inside a cell. There is an equal amount of water inside and outside the cell; no net movement of water. Cell size maintains.
54
Definition of hypotonic
Hypotonic: A solution with a lower concentration of solutes compared to another solution.
55
Definition of hypertonic
Hypertonic: A solution with a higher concentration of solutes compared to another solution.
56
Direction of water movement in solutions
Water moves from a hypotonic solution to a hypertonic solution because the hypotonic solution has less solute and more free water.
57
Plasmolysis
Occurs in a hypertonic environment where cells shrivel and usually die. The cell membrane pulls away from the cell wall. (This only happens in cells with cell walls)
58
Turgid
Occurs in a hypotonic environment where water moves into the cell, causing it to swell. The cell becomes swollen due to water (high turgor pressure). (This only happens in cells with cell walls)
59
Describe how an Animal cell's ideal osmotic environment is isotonic.
In an isotonic environment, the concentration of solutes is equal inside and outside the cell, allowing for normal cell function without net movement of water.
60
Describe how a Plant cell's ideal osmotic environment is hypotonic.
In a hypotonic environment, the concentration of solutes is lower outside the cell, causing water to enter the cell, which is ideal for plant cells as it maintains turgor pressure.
61
What is the ideal osmotic environment for animal cells?
Isotonic
62
What is the ideal osmotic environment for plant cells?
hypotonic
63
True or False: Animal cells can be turgid.
FALSE; Only cells with cell walls can be turgid. If animal cells had a net movement of water going into the cell, they would lyse (burst) since they do not have cell walls to prevent that.
64
identify the solute if salt is being dissolved into water.
salt
65
identify the solvent if sugar is being dissolved into water.
water
66
Example of Cotransport in Plants
Plants use a proton pump coupled with sucrose-H⁺ cotransporter protein to load sucrose into specialized cells. Sucrose is moved against its concentration gradient without spending any additional energy since is comes in with the H+ ions that are moving down their concentration gradient passively through the cotransporter.
67
Types of active transport commonly used in cells
- Protein pumps (e.g., Na+ / K+ pump, H+ pump) - Cotransport - Endocytosis - Exocytosis
68
Describe how movement across the cell membrane can be active.
Active transport requires energy. It involves moving ions or molecules against the concentration gradient, from low to high concentration.
69
Proton Pump
Pumps protons (H⁺ ions) out of the cell, creating a proton gradient with higher concentration outside the membrane. This membrane potential can perform work when protons diffuse back through a different protein channel.
70
Energy for Cotransport
The energy required to move a substance against its concentration gradient is provided by the movement of another substance along its gradient in concentration.
71
How does the Na+/K+ pump maintain membrane potential?
+3 charge moves out of the cell while +2 charge enters, leading to a negative charge inside the cell.
72
In endocytosis, what protein helps vesicle formation?
Clathrin
73
Movement across the cell membrane can be passive.
Passive transport does not require energy. Examples include diffusion, facilitated diffusion, and osmosis.
74
Phagocytosis example
Phagocytosis is when an immune system cell engulfs a bacteria or virus to be destroyed by a lysosome.
75
Describe Vesicles
Vesicles are small dynamic structures that are continuously made, moved, and merged within cells.; they are formed by pinching off a small area of membrane from a larger one.
76
Direction of molecule movement in active transport
From an area of low concentration to an area of high concentration
77
Endocytosis
Endocytosis involves the plasma membrane folding in to form a vesicle that brings substances into the cell. Proteins in the membrane use ATP energy for this process.
78
Exocytosis
Exocytosis is the bulk movement of substances out of a cell; involves membrane-bound secretory vesicles budding from the ER or Golgi and migrating to the plasma membrane. The vesicle fuses with the membrane, allowing products to be incorporated into the membrane or released into the extracellular environment. For example, pancreas cells produce insulin and release it into the blood through exocytosis.
79
Cotransport (Coupled Channels)
The coupled transport of chemical substances across a cell membrane.
80
Discuss the concentration gradients of Na+ and K+ as they are moved using the Na+/K+ pump
Both are moved against their concentration gradients.
81
Membrane potential
The negative charge inside the cell compared to outside is called membrane potential.
82
Sodium-Potassium Pump function
Actively pumps Na+ ions out of the cell and K+ ions into the cell to maintain membrane potential.
83
Pump cycle details of Sodium-Potassium pump
In every pump cycle, 3 Na+ leave and 2 K+ enter the cell. This costs 1 ATP
84
What does it mean to say active transport is energetically "uphill"
Uses energy from ATP to move molecules from low to high concentration

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