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Cell Physiology Flashcards

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1
Q
  1. What short term describes the plasma or cell surface membrane?
A

A phospholipid bilayer

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2
Q
  1. What does the term, hydrophobic, mean in relation to phospholipids?
A

Hydrophobic means the fatty acid tails are water repelling or water hating and they will only mix with lipids

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3
Q
  1. What does the term, hydrophilic, mean in relation to phospholipids?
A

Hydrophilic means the phosphate heads are water loving and will not mix with lipid

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4
Q
  1. What term is used to describe the arrangement of all the molecules in the plasma membrane?
A

Fluid Mosaic Model

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5
Q
  1. Describe the “fluid mosaic model”
A

The phospholipids move laterally or sideways, making the structure FLUID; the proteins are irregularly arranged like a MOSAIC, “floating” amongst the lipids.

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6
Q
  1. What are transmembrane, extrinsic and intrinsic proteins?
A

Transmembrane - the proteins go right through the bilayer Extrinsic - the proteins are attached peripherally Intrinsic - the proteins are embedded within one of the layers

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7
Q
  1. What is the GLYCOCALYX?
A

This is the outer layer of our cell membranes, made up of glycoproteins (carbohydrate plus protein) and glycolipids (lipid and carbohydrate), and unique to everyone. These molecules may act as antigens or receptor sites, for example.

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8
Q
  1. What is the role of cholesterol in the cell membrane?
A

It increases the forces of attraction between the fatty acid tails, making he membrane structure more stable

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9
Q
  1. What roles do the proteins in the cell membrane have?
A

Stability and support by anchoring phospholipids * Enzymes * Receptor sites (having a complementary shape to attaching molecules such as hormones * Transport - carriers and channels (see below) * Cell recognition * Antigens in immune response

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10
Q
  1. Define diffusion
A

The net movement of particles down a concentration gradient, from a higher to a lower concentration, until concentrations are equal.

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11
Q
  1. What sorts of molecules can diffuse directly through the phospholipid bilayer?
A
  • Lipid soluble, hydrophobic molecules such as steroids and glycerol * Small uncharged molecules, such as water and carbon dioxide, which move through gaps
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11
Q
  1. What does PASSIVE mean?
A

The process does not require energy (ATP) diant

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12
Q
  1. What factors speed up diffusion?
A
  • Steeper concentration gradient * Short distances (i.e. thin membranes) * Smaller size of molecule * Higher temperature (molecules have more kinetic energy) * Greater surface area
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13
Q
  1. What is ACTIVE TRANSPORT? Give an example.
A

The energy-requiring transport of molecules against a concentration gradient i.e. from a low to a high concentration, using carrier proteins. Eg active transport of minerals into root hair cells

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14
Q
  1. What types of molecules cannot diffuse across the membrane?
A

Water soluble, hydrophilic or polar molecules such as glucose, amino acids and ions

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15
Q
  1. How do water soluble, hydrophilic and polar molecules get across the membrane?
A
  • Channel proteins (which may be gated): Used for diffusion of ions/charged/polar molecules * Carrier proteins: Have specific binding sites and following binding they change shape and release the molecule on the other side of the membrane.
16
Q
  1. Why does active transport require oxygen?
A

Active transport requires energy in the form of ATP, which is made during aerobic respiration and aerobic respiration requires oxygen

17
Q
  1. What does the term, “water potential” mean?
A

Water potential is the TENDANCY to take in water by osmosis from pure water, across a selectively permeable membrane

17
Q
  1. What is OSMOSIS?
A

Osmosis is the DIFFUSION of water molecules from an area of higher water potential to an area of lower water potential (i.e. from a hypotonic to a hypertonic solution), through a partially / selectively permeable membrane

18
Q
  1. What are the two types of transport for moving substances which are too large to move through the membrane or which have to be moved in BULK?
A
  1. Endocytosis - taking substances into the cell 2. Exocytosis - moving substances out of the cell
19
Q
  1. Describe ENDOCYTOSIS
A

A section of the cell membrane surrounds the substance and forms a vesicle/vacuole It pinches off and moves into the cytoplasm where it fuses with lysosomes The lysosome releases its enzymes onto the material and digests it, after which it is absorbed

20
Q
  1. Describe EXOCYTOSIS
A
  • SECRETORY VESICLES pinch off the GOLGI and move towards the cell surface membrane * They merge with the cell membrane and release their contents outside of the cell
21
Q
  1. Why is the water potential of pure water, zero kPa?
A

potential value and it is represented by pure water because it is unable to take in any more water by osmosis. (The water molecules have free kinetic energy, with no solute molecules binding them in hydration shells)

21
Q
  1. What is the difference between phagocytosis and pinocytosis?
A

Both are forms of endocytosis but phagocytosis is taking in solid material while pinocytosis is taking in liquid substances

22
Q
  1. What is the water potential equation?
A

water potential of cell = solute potential + pressure potential

23
Q
  1. What definition for osmosis should you use when using the water potential equation?
A

Osmosis is the movement of water molecules from a higher, or less negative water potential, to a lower, or more negative water potential

24
Q
  1. What do we mean by, solute potential?
A

Solute potential is defined as being the POTENTIAL for a solution to take in water and it is due to the concentration of the solute present. Adding solute decreases water potential and it itself is a negative value.

25
Q
  1. What do we mean by, pressure potential?
A

Pressure potential is the errect of pressure on the solution. Turgid cells will exert a high pressure on their cell walls (which in turn affects ability to take in water). It is often a positive value.

26
Q
  1. Define, HYPERTONIC, HYPOTONIC and ISOTONIC solutions
A

Hypertonic - more concentrated than the cell’s contents (i.e. more ions in solution than cell) Hypotonic - less concentrated that the cell’s contents i.e. fewer ions in solution than in cell) Isotonic - equal concentrations of ions in solution and cell

27
Q
  1. Describe a TURGID plant cell
A

When put into a hypotonic solution, the vacuole takes up water by osmosis and as it swells, it pushes the cytoplasm and cell membrane against the cell wall, exerting a pressure on it. The cell wall limits the expansion and prevents lysis of the cell.

28
Q
  1. Describe a PLASMOLYSED plant cell
A

When put into a hypertonic solution, water leaves the vacuole by osmosis and the cytoplasm and cell membrane begin to pull away from the cell wall, (all of these things make up the protoplast), making the tissues FLACCID rather than TURGID. If the cell continues to lose water, it will plasmolyse and the pressure potential, Yp, becomes zero. The external solution gathers in the space between the cell membrane and the cell wall.

29
Q
  1. What is the difference between incipient plasmolysis and plasmolysis?
A

Incipient plasmolysis is the point at which the cell membrane just loses contact with the cell wall (and Yp becomes 0), while full plasmolysis is when the cell membrane and cytoplasm have pulled away completely from the cell wall.

30
Q
  1. What can we say about water relations at incipient and full plasmolysis?
A

Pressure potential becomes 0 i.e. Yp = 0, therefore, Ycell = Ys

31
Q
  1. What value do we give Ycell at FULL TURGOR?
A

At full turgor, Ycell = O as no further water can enter

32
Q
  1. What will happen to an animal cell such as a red blood cell, if placed in a hypotonic solution?
A

Water will enter the cytoplasm by osmosis, the cell will swell, and as there is no cell wall surrounding the plasma membrane, the cell will undergo LYSIS (it bursts)

33
Q
  1. What would happen the red blood cell in a HYPERTONIC solution?
A

It would lose water by osmosis, shrivel up and CRENATE

Biology (11 decks)

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