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Biology Unit 1 AOS 1 > Plasma Membrane > Flashcards

Plasma Membrane Flashcards

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1
Q

What does the cell membrane allow the cell to sense?

A

Its external environment (extracellular fluid).

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2
Q

What does the cell membrane do with external signals?

A

It relays them to the intracellular fluid to cause appropriate cell responses.

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2
Q

How does the cell membrane help with communication?

A

It communicates with surrounding cells to trigger appropriate responses.

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3
Q

How many layers are in the phospholipid bilayer?

A

Two layers of phospholipid molecules.

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4
Q

What is the structure of the plasma membrane called?

A

Phospholipid bilayer.

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5
Q

What are the two parts of a phospholipid?

A

A phosphate head and two fatty acid tails.

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6
Q

What is the nature of the phosphate head?

A

Polar and hydrophilic (water-loving).

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7
Q

What is the nature of the fatty acid tails?

A

Non-polar and hydrophobic (water-fearing).

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8
Q

What else is embedded throughout the membrane besides phospholipids?

A

Proteins.

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9
Q

Why are phospholipids ideal for forming the plasma membrane?

A

Because their hydrophilic and hydrophobic nature allows them to form a boundary between two liquid environments.

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10
Q

What role do structural proteins in the plasma membrane play?

A

They provide support to the cell.

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10
Q

What are the two liquid environments separated by the plasma membrane?

A

The extracellular (outside the cell) and intracellular (inside the cell) environments.

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10
Q

How do receptor proteins help cells?

A

They allow cells to recognize other structures and communicate.

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11
Q

What function do secretory proteins serve in the plasma membrane?

A

They help cells communicate with each other.

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12
Q

Which proteins assist with the transport of substances across the membrane?

A

Channel and carrier proteins.

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13
Q

What are peripheral proteins in the plasma membrane?

A

Proteins temporarily attached to the membrane.

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14
Q

What are integral proteins in the plasma membrane?

A

Proteins permanently embedded in the membrane.

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15
Q

What are transmembrane proteins?

A

Integral proteins that cross or span the entire membrane.

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16
Q

Why is the cell membrane described as “fluid” in the Fluid Mosaic Model?

A

Because phospholipids continually move laterally (side to side) within the membrane.

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17
Q

Why is the cell membrane described as a “mosaic” in the Fluid Mosaic Model?

A

Because it has proteins and carbohydrates embedded throughout, like a mosaic made of many parts.

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18
Q

What are saturated fatty acids in the phospholipid bilayer?

A

Fatty acids with single bonds between carbon atoms, forming straight tails.

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19
Q

What effect do unsaturated fatty acids have on membrane fluidity?

A

They increase membrane fluidity.

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19
Q

What are unsaturated fatty acids in the phospholipid bilayer?

A

Fatty acids with at least one double or triple bond between carbon atoms, causing a kink in the tail.

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19
Q

Why do unsaturated fatty acids increase membrane fluidity?

A

Because their kinked tails prevent tight packing, keeping the membrane from becoming solid.

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20
How does the kink in unsaturated fatty acid tails affect the phospholipid bilayer?
It adds spaces between phospholipids, affecting membrane fluidity.
21
How do organisms living in low temperatures regulate membrane fluidity?
They use more unsaturated fatty acids in their cell membranes to maintain fluidity.
22
What role does cholesterol play in the cell membrane?
It provides the membrane with flexibility.
23
How does cholesterol affect membrane fluidity?
More cholesterol increases the fluidity of the membrane.
24
Where is cholesterol located in the cell membrane?
It is hydrophobic and located between the hydrophobic fatty acid tails.
25
What does it mean that cell membranes are selectively permeable?
They allow certain molecules to cross (permeable) while blocking others (impermeable).
26
How does the cell membrane's structure aid its function?
It allows the membrane to be differentially selective about molecule movement.
26
What feature of the cell membrane helps control what enters and exits the cell?
The presence of pores (holes) and the membrane’s selective structure.
27
Which molecules can pass directly through the phospholipid bilayer of the cell membrane?
Small molecules and hydrophobic molecules.
27
What is Passive Transport in cells?
Transport of molecules across the membrane without using energy.
27
How do ions and hydrophilic molecules cross the cell membrane?
They move through protein channels in the membrane.
28
Can large molecules like proteins pass through the cell membrane?
No, large molecules like proteins do not pass through the membrane (impermeable).
29
What are the three types of Passive Transport?
Simple Diffusion, Facilitated Diffusion, Osmosis.
30
What is Facilitated Diffusion?
Diffusion of molecules with the help of transport proteins, such as protein channels.
31
What is Active Transport in cells?
Transport of molecules across the membrane that requires energy.
32
What are the three types of Active Transport?
Protein carrier proteins (active uptake), Endocytosis, Exocytosis.
33
What is Simple Diffusion?
Diffusion of molecules directly through the phospholipid bilayer.
34
What is Osmosis?
The diffusion of water molecules across a membrane.
34
What is Diffusion?
The random movement of molecules from an area of high solute concentration to an area of low solute concentration. Diffusion continues until all molecules are evenly spaced (equilibrium is reached). They move due to their kinetic energy.
35
What is a Solute?
A substance dissolved in a solvent.
36
What is a Solvent?
A liquid in which a solute is dissolved.
37
What is a Concentration Gradient?
The difference in concentration between two areas.
38
How do molecules move in Passive Transport?
Molecules move randomly down a concentration gradient.
38
What is a Polar Molecule?
A molecule with a slightly positive or negative side due to uneven distribution of electrons.
38
In which direction do molecules move during Passive Transport?
From an area of high solute concentration to an area of low solute concentration (if permeable).
38
Can water cross the membrane by Simple Diffusion? Why?
Yes, because water is small enough, even though it is polar.
38
What is Simple Diffusion?
Movement of small molecules directly through the phospholipid bilayer down the concentration gradient.
39
What types of molecules move by Simple Diffusion?
Small, hydrophobic (non-polar) molecules like oxygen, carbon dioxide, fat-soluble molecules.
40
Why can small hydrophobic molecules cross the membrane via Simple Diffusion?
Because the membrane is mostly non-polar.
40
Does facilitated diffusion require energy?
No, it is a passive process and does not require energy.
40
How do small polar or charged molecules like amino acids and glucose enter the cell?
They move down the concentration gradient with the help of protein channels or carrier proteins.
40
What kind of molecules do transport proteins specifically transport?
Small, charged, hydrophilic molecules.
41
What type of molecules need assistance from proteins to cross the membrane?
Small polar (hydrophilic) and charged molecules or ions.
42
Are transport proteins selective or non-selective?
Selective—they "select" only certain molecules to cross the membrane.
42
What is osmosis?
The movement of water through a selectively permeable membrane.
42
How does water move through the cell membrane during osmosis?
Through the lipid bilayer (because it is small) or through protein pores called aquaporins.
42
Does osmosis involve the movement of solutes?
No, only water moves, not solutes.
42
In which direction does water move during osmosis?
From a low solute concentration to a high solute concentration.
43
What role does osmosis play in cell homeostasis?
Osmosis helps cells maintain homeostasis by allowing water to enter or exit the cell to dilute or concentrate solutes when the membrane is impermeable to the solute.
44
What happens to a cell in a hypotonic solution?
A hypotonic solution has a lower concentration of solutes and higher water concentration than inside the cell. Water moves into the cell, causing it to swell and potentially burst open (lysis).
44
Why does water move during osmosis?
Because the solute is impermeable and cannot move.
44
What are the three types of tonicity?
Hypertonic, Hypotonic, and Isotonic.
44
What does tonicity describe?
Tonicity describes the concentration of solutes on either side of a membrane.
45
What happens to a cell in a hypertonic solution?
A hypertonic solution has a higher concentration of solutes and lower water concentration than inside the cell. Water moves out of the cell into the solution, causing the cell to shrink.
46
What happens to a cell in an isotonic solution?
The concentration of solutes inside and outside the cell is equal. Water moves equally in both directions, so the cell stays the same size.
47
What prevents bacteria and plant cells from over-expanding?
Their rigid cell walls prevent over-expansion when water enters.
48
What is turgor pressure?
The pressure exerted by water against the plant cell wall when the cell is full of water, making the plant cell turgid (firm).
48
How do protists like Paramecium prevent over-expanding and bursting?
They use contractile vacuoles that collect excess water flowing into the cell and pump it out.
49
How do saltwater fish manage water loss due to osmosis?
Saltwater fish lose water by osmosis but pump salt out of specialized glands to prevent dehydration.
50
Why do freshwater fish gain water by osmosis?
Because the surrounding water is hypotonic (lower solute concentration), freshwater fish gain water through their membranes by osmosis.
50
How do freshwater fish handle the excess water they gain?
They get rid of excess water using their specialized kidneys that produce dilute urine.
51
How does protein-mediated active transport work?
Molecules are moved across the membrane through a transport (carrier) protein against the concentration gradient. This process requires energy from ATP (adenosine triphosphate).
51
What is active transport and how does it move molecules across a membrane?
Active transport requires energy to move molecules across a membrane against their concentration gradient—from an area of low solute concentration to an area of high solute concentration.
51
What do protein pumps do in active transport, and give an example?
Protein pumps transport ions against their concentration gradient (active uptake). Example: Sodium/Potassium pumps are vital for nerve responses. The pump changes shape to move molecules, which requires energy.
51
What is bulk transport and what are its two main types?
Bulk transport moves large substances or groups of substances across the membrane. Endocytosis: Transport of bulky material INTO the cell. Exocytosis: Transport of bulky material OUT OF the cell. Both processes require energy.
52
What is endocytosis and how does it work?
Endocytosis is the process of taking bulky material into a cell using energy. The cell membrane folds inward around solid or liquid material (“cell eating” and “cell drinking”), forming a vacuole that digests or uses the material.
53
How does the cell membrane import substances during endocytosis?
The cell membrane folds around the substance to form a vesicle that contains the substance, bringing it into the cell.
54
What are the two types of endocytosis and how do they differ?
Pinocytosis: "Cell drinking" — the cell membrane folds to take in liquids. Phagocytosis: "Cell eating" — the cell membrane folds to engulf solid objects. Both processes form vesicles to import substances into the cell.
55
What happens during pinocytosis?
The plasma membrane engulfs a drop of extracellular fluid to bring liquids into the cell. Example: Fat droplets moving from the small intestine into cells after digestion.
55
What is exocytosis and how does it work?
Exocytosis is an active process where substances like hormones, enzymes, or wastes are transported out of the cell. Vesicles formed at the Golgi body carry these substances, move to the plasma membrane, fuse with it, and release their contents into the extracellular environment.
55
How is exocytosis important in the nervous system?
Nerve cells release neurotransmitters via exocytosis into the synapse (the gap between neurons) to communicate with other cells.

Biology Unit 1 AOS 1 (4 decks)

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