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Biology > Topic 2 - B > Flashcards

Topic 2 - B Flashcards

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1
Q

What is the fluid mosaic model?

A
  • Arrangement of molecules in the cell membrane
  • Phospholipid bilayer is fluid because it is constantly moving.
  • Because the fatty acids are hydrophobic and unsaturated.
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2
Q

What is the role of cholesterol in cell membranes ?

A
  • Gives membranes stability
  • Fits between phospholipids and binds to hydrophobic tail which causes them to pack more closely
  • Without it cells would burst as it would be too fluid
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3
Q

Why is fluidity needed in cell membranes?

A
  • Diffusion of substances across the cell membrane

- Membrane moves to change shape e.g. phagocytosis

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4
Q

What is the role of extrinsic (peripheral) proteins in cell membranes?

A
  • Don’t span the entire membrane
  • Can attach onto an intrinsic (integral) protein
  • Communication and cell signalling
  • Transfer molecules within the membrane
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5
Q

The difference between cholesterol in hot and cold temperature?

A
  • When HOT it interacts with fatty acid tails to decrease fluidity
  • When COLD it prevents membrane from solidifying to maintain fluidity
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6
Q

What are the roles of glycoproteins in cell membranes?

A
  • Proteins with carbohydrates attached
  • Important in cell recognition and immunity
  • Structural support (found in collagen)
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7
Q

Describe the roles of carrier proteins in cell membranes?

A
  • Used for active transport and facilitated diffusion of molecules
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8
Q

Describe the roles of channel proteins in cell membranes?

A
  • Used as a pathway for facilitated diffusion of large (sugars) or charged (ions) molecules
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9
Q

Why can’t ions diffuse through cell membranes?
Why can’t large molecules diffuse through cell membranes?
- LIMITATIONS OF PHOSPHOLIPID BILAYER

A
  • Charges are repelled by hydrophobic tails in the interior of the phospholipid bilayer
  • They are too big as the membrane is selectively permeable and they would be considered impermeable
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10
Q

What are intrinsic proteins?

A
  • Do span the entire membrane

- Carrier and Channel proteins

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11
Q

What is the definition of simple diffusion?

A

The passive, net movement of molecules or ions from an area of high concentration to an area of low concentration down a concentration gradient until dynamic equilibrium is reached.

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12
Q

What is Fick’s Law?

A

rate of diffusion = surface area x difference
in conc.
/
diffusion pathway
(membrane thickness)

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13
Q

How does surface area affect rate of diffusion?

A
  • More membrane means more opportunity for net movement

- Increases rate of diffusion

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14
Q

How does diffusion pathway (membrane thickness) affect rate of diffusion?

A
  • The thinner the pathway the shorter distance the molecules have to travel
  • Increases rate of diffusion
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15
Q

How does the difference in conc. affect rate of diffusion?

A
  • The greater the difference

- The faster the rate of diffusion

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16
Q

What is the definition of facilitated diffusion?

A

The passive, net movement of large molecules or ions through a carrier or channel protein from an an area of high concentration to an area of low concentration until dynamic equilibrium is reached.

17
Q

What are the similarities of facilitated diffusion and simple diffusion?

A
  • Passive process
  • Polar molecules move down a concentration gradient from an area of high concentration to an area of low concentration
  • Dynamic equilibrium is reached
18
Q

State the differences of facilitated diffusion and simple diffusion?

A
  • Facilitated occurs at specific points of membrane which has channel or carrier proteins whereas simple diffusion occurs all over the membrane.
  • Simple diffusion involves small, non-charged molecules whereas facilitated diffusion involves large (sugars) and charged (ions) molecules.
  • Channel proteins only allow water soluble molecules through
  • Carrier proteins only allow specific targeted molecules through
19
Q

What is the definition of Osmosis?

A

The net movement of water from a region of high water potential to a region of low water potential through a partially permeable membrane until dynamic equilibrium is reached.

20
Q

Explain water potential?

A
  • Water potential is the liklihood of water molecules moving in or out of a cell
  • It is measured in kiloPascals
  • Pure water has the highest water potential value at 0 kPa
  • Solutions that have a lower water potential than water are negative
  • The greater the number of water molecules, the higher the water potential
21
Q

What is the definition of active transport?

A

The movement of molecules or ions from an area of low concentration to an area of high concentration, against a concentration gradient - energy in the form of ATP is required.

22
Q

How does active transport happen?

A
  • A phosphate group from the molecule of ATP attaches itself onto the carrier protein
  • Causing it to change shape
  • As the protein changes shape the phosphate group pumps the molecule or ion into the cell
23
Q

What is endocytosis?

A
  • The process which moves macro molecules or large particles into a cell
  • E.G. phagocytosis of pathogens and large particles
  • E.G. pinocytosis of water and solutes in the water
24
Q

What is exocytosis?

A
  • The process which moves macro molecules and large particles out of a cell
  • E.G. (reverse of endocytosis) materials inside a cell are packed in a vesicle which fuses to the plasma membrane
25
Q

Explain the roles of guard cells?

A
  • They control the stomata being opened and closed
  • Allow diffusion of gases in and out the cell
  • E.G if a cell is filled with water it is turgid and the stomata are opened to lose water and make the cell flaccid
26
Q

What is a protoplast?

A
  • The nucleus and cytoplasm of a plant cells including the organelles it contains
27
Q

Explain the concept of incipient plasmolysis?

A
  • Midpoint whereby no water is moving in or out of cell by osmosis
  • Plants cells have a turgo pressure of 0
28
Q

Describe plasmolysis?

A
  • When the cytoplasm shrinks away from the cell wall as a result of osmosis
  • Protoplast lost contact with the cell wall and loss of water makes cell plasmolysed
29
Q

Explain a hypotonic solution?

A
  • When a solution has a higher water potential than the cell immersed in it
  • A tissue placed in their would gain mass
30
Q

Explain a hypertonic solution?

A
  • A solution with low water potential than the cell immersed it in
  • A tissue placed their would lose mass
31
Q

Describe the relationship between surface area and volume ratio?

A
  • As organisms get larger their surface area: volume ratio get smaller
  • A large surface is needed for specialised exchanges surface and circulatory
32
Q

What are co-transporters?

A
  • They are a type of carrier proteins that can move 2 molecules at the same time
  • They can use the concentration gradient of one molecule to move the other against its concentration gradient
  • Very important for the absorption of glucose and amino acids
33
Q

Explain the process of glucose re-absorption?

A
  1. Sodium ions actively transported out of epithelia cells into blood stream (NA+/K+ pump are used)
  2. This creates a concentration gradient
  3. Sodium ions diffuse down a concentration gradient from lumen to epithelia via Sodium-Glucose symporter
  4. Glucose is transported across into the epithelial cell
  5. High concentration of glucose in epithelial cell so glucose will move into blood stream by facilitated diffusion using a glucose transporter
34
Q

What is the ratio of the sodium - potassium pump?

A
  • Pump moves sodium in one direction ad potassium in the other at a 3:2 respective ratio
35
Q

Explain the functions of ATP the sodium - potassium pump regarding sodium?

A
  • ATP is bound to the protein which has a high affinity for sodium and binds to 3
  • ATP is hydrolysed into ADP and the protein is phosphorylated by a phosphate changing its tertiary structure
  • Now the sodium is in the other side of the membrane
36
Q

Explain the functions of ATP the sodium - potassium pump regarding potassium?

A
  • Protein now has a low affinity sodium and releases them
  • But has a high affinity for potassium and binds with 2
  • Causes dephosphorylation of the protein so it revert to its original shape
  • Now the potassium is on the other side of the membrane

Biology (5 decks)

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