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Biology Topic 2 > 2.2 > Flashcards

2.2 Flashcards

1
Q

What is a polymer?

A

A large molecule formed from the linking together of identical or similar subunits (monomers)

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2
Q

What is the amine group?

A

NH2 attached to the central carbon

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3
Q

What is the carboxylic group?

A

COOH attached to the central carbon

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4
Q

What is the residal group?

A

The variable side chain - varies between different amino acids. Attached to the central carbon

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5
Q

What is a fibrous protein?

A

A protein that is un-folded, often with several polypeptide chains cross-linked together for additional strength.

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6
Q

What is a globular protein?

A

A protein where the polypeptide chain is folded into a compact spherical shape.

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7
Q

What is a peptide bond?

A

The bond joining two amino acids in a protein

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8
Q

What reactions joins two amino acids together?

A

Condensation reaction

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9
Q

What is breaking of a bond by the addition of water called?

A

Hydrolysis

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10
Q

What is the primary structure?

A

The sequence of amino acids in a polypeptide chain which determines the final (tertiary) shape of a protein.

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11
Q

What is the secondary structure?

A

Interactions between the R-groups cause the polypeptide chain to form 3D shapes (mainly alpha helix and beta p.s.), prior to folding into the final specific 3D shape.

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12
Q

What is an alpha helix?

A

A common secondary structure where the chain of amino acids is coiled around its long axis, stabilised by hydrogen bonds between C=O of the carboxylic acid and the -NH of the amine group of different amino acids.

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13
Q

What is a beta pleated sheet?

A

Common secondary structure where the polypeptide chain folds back on itself in the same plane, also stabilised by hydrogen bonds.

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14
Q

What is the tertiary structure?

A

The specific 3D structure of a protein - very important in determining its function.

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15
Q

What is the quaternary structure?

A

A protein made of several polypeptide chains held together e.g. haemoglobin

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16
Q

What are conjugated proteins?

A

Proteins containing non-protein material e.g. alpha and beta chain has a heme (iron-containing) group at the centre of the chain.
The non-protein part is called the prosthetic group.

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17
Q

Why do glycoproteins have chains of hydrophilic sugars?

A

To bind to water and to facilitate the swallowing of food.

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18
Q

Why is haemoglobin compact and globular?

A

To transport gases easily through blood vessels

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19
Q

Why is collagen strong?

A

Due to bond between its coils, to provide support for connective tissues.

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20
Q

What are the characteristics of collagen?

A

Three tightly wound peptides
Fibrous protein
Many glycine subunits
Ends of parallel molecules overlap

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21
Q

What are the characteristics of haemoglobin?

A

Globular protein
Four polypeptides
Prosthetic group
Undergoes conformational change

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22
Q

What is a glycoprotein and what is it used for?

A

A protein molecule with a carbohydrate chain attached.

It is used for cell adhesion, cell recognition and as receptors.

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23
Q

What is a glycolipid and what is it used for?

A

A molecule consisting of a lipid and a carbohydrate. Form part of the cell surface membrane.
Have similar functions to glycoproteins in that they help cells to bind to each other to form tissues and they are involved in cell recognition. They act as receptors and are involves in membrane stability.

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24
Q

What is a channel protein?

A

A protein that spans a membrane and is involved in the transport of molecules across the membrane.
They form pores in the membrane for charged particles to diffuse through.
They may open or close in response to a specific messenger or change in voltage (gated channel proteims)

25
Q

What is CFTR?

A

The channel protein that allows diffusion of chloride ions out of an epithelial cell in the lungs, whose malfunctioning causes cystic fibrosis.

26
Q

What is a carrier protein and how does it work?

A

A protein that has specifically shaped binding sites and binds with a specific ion or molecule and helps it cross a membrane.

1) First, a large protein attaches to a carrier protein in the membrane
2) Then, the protein changes shape
3) This releases the molecule on the opposite side of the membrane

27
Q

Define diffusion

A

The net movement of molecules from a high concentration to a low concentration, down a concentration gradient, until an equilibrium is reached. Passive process.

28
Q

Give examples of substances that can diffuse through the lipid bilayer

A

Fastest in small, non-polar molecules e.g. oxygen
Slower in small polar molecules e.g. water
Large uncharged particles
Lipid soluble molecules
Hydrophobic molecules

29
Q

What is facilitated diffusion?

A

Diffusion via a protein channel. Enables large molecules and ions, which can only cross cell membrane with the aid of carrier proteins, to cross the membrane with the aid of proteins.

30
Q

What is osmosis?

A

The net movement of water molecules from a high water potential (dilute solution), to a low water potential (concentrated solution), through a selectively permeable membrane.

31
Q

What is osmotic pressure?

A

Pressure which causes osmosis to occur.

32
Q

What is water potential?

A

The measure of the ability of water molecules to move.

33
Q

What is an isotonic solution?

A

Equally concentrated inside and out

34
Q

What is a hypertonic solution?

A

When water level outside is lower than inside.

35
Q

What is a hypotonic solution?

A

When water level outside is higher than inside.

36
Q

What happens when an animal cell is in a hypotonic solution?

A

Cell fills with water, so it bursts = lysis

37
Q

What happens when a plant cell is in a hypotonic solution?

A

Cytoplasm fills with water and pushes against cell wall, cell is turgid.

38
Q

What happens when an animal cell is put in a hypertonic solution?

A

Cell becomes crenated as the cytoplasm pulls away from cell membrane

39
Q

What happens when a plant cell is put in hypertonic solution?

A

Cytoplasm pulls away from cell wall and is plasmolysed. Cell is flaccid.

40
Q

What is active transport?

A

The movement of molecules and ions across a membrane via a transmembrane protein pump against a concentration gradient. Requires energy from ATP.

41
Q

How does pumping work?

A

A molecule attaches to a carrier protein, the protein changes shape and this moves the molecule across the membrane, releasing it on the other side. It is a selective process and is controlled by the presence/absence of the specific protein pump.
Energy is used because it is a form of active transport.

42
Q

What is exocytosis and how does it work?

A

The bulk transport of material out of cells.
Proteins made in a cell are often modified in the Golgi apparatus. Vesicles are pinched off from the Golgi apparatus and these contain the modified protein. The vesicles move through the cytoplasm and fuse with the cell membrane, releasing the protein from the cell.

43
Q

What is endocytosis and how does it work?

A

The bulk transport of material into the cell.
The cell surface membrane surrounds the particles concerned. The membrane then pinches off to form a vesicle inside the cell containing the ingested substance, before moving into the cytoplasm of the cell.

44
Q

What is the role of cholesterol in the cell membrane?

A

Regulates membrane permeability. It affects the fluidity of the membrane and is important in keeping the membrane stable. Without it, membranes would break and cells would burst open.
The more cholesterol, the less fluid, and the less permeable, the membrane.

45
Q

How do you test for lipids?

A

1) Add the test substance to a test tube containing ethanol and mix
2) Add an equal volume of water to the test mix
3) If the test substance is a lipid, the resulting mix is a cloudy white emulsion, because lipids are soluble in ethanol.

46
Q

State two functions of the R groups in a polypeptide chain

A

1) bonding

2) forming active sites

47
Q

What is the function of a cell membrane?

A

1) keeping all cellular components inside the cell
2) allowing selected molecules to move in and out of the cell
3) isolating organelles from the rest of the cytoplasm, allowing cellular processes to occur separately.
4) a site for biochemical reactions
5) allowing a cell to change shape.

48
Q

Why is the fluid mosaic named like this?

A

It is ‘fluid’ because the proteins and lipids are able to move around within the membrane.

It is ‘mosaic’ because of the mosaic-like make up of the components within the membrane.

49
Q

What is the purpose of the cytoskeleton in the cell membrane?

A

It helps the membrane to maintain its shape and it helps with cell-to-cell attachment. It is also involved in cell movement.

50
Q

What are peripheral proteins on the extracellular side of the membrane used for?

A

They act as receptors for hormones or neurotransmitters, or are involved in cell recognition. Many are glycoproteins.

51
Q

What is the function of integral proteins?

A

Some help transport substances across the membrane, while other integral proteins are receptors for hormones and neurotransmitters, or enzymes for catalyzing reactions.

52
Q

What are peripheral proteins on the cytosolic side of the membrane used for?

A

Peripheral proteins on the cytosolic side of the membrane are involved in cell signalling or chemical reactions. They can dissociate from the membrane and move into the cytoplasm.

53
Q

What processes is the fluid membrane needed for?

A

1) diffusion of substances across the membrane
2) membranes to fuse, e.g. a vesicle fusing with the cell membrane during exocytosis
3) cells to move and change shape, e.g. macrophages during phagocytosis.

54
Q

How does temperature affect membrane permeability?

A

At lower temps, lipids have less kinetic energy so are packed together more tightly, decreasing fluidity.

55
Q

How do lipids affect membrane permeability?

A

Lipids with long, saturated tails have high melting points, which decreases fluidity. The straight, un-kinked fatty acid tails mean the molecules can pack together more tightly, decreasing permeability.

Lipids with short, unsaturated tails have low melting points which increases fluidity The double bonds create kinks so they are loosely packed together.

56
Q

How does cholesterol affect membrane permeability?

A

Higher levels: at body temp, the cholesterol interacts with the phospholipid tails, decreasing fluidity. At lower temps, cholesterol prevents membrane solidifying so it maintains fluidity.
Lower levels: can make membrane too fluid at normal body temp.

57
Q

What are the biological roles of proteins?

A

Structural - main component of body tissues such as muscle
catalytic - all enzymes are proteins
signalling - many hormones and receptors are proteins
immunological - all antibodies are proteins

58
Q

What are the differences between fibrous and globular proteins?

A

fibrous are insoluble in water, globular are soluble
fibrous have stronger intermolecular forces of attraction than globular
fibrous have a thread like structure, while globular are folded
fibrous have helical/sheet structure, while globular is 3D

Biology Topic 2 (6 decks)

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