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Lipids Flashcards

1
Q

What is the main characteristic of lipids?

A

Their insolubility in water

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2
Q

What is the function of phospholipids and cholesterol?

A

Structural components of membranes that form the outer boundary of eukaryotic cells and separate different organelles

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3
Q

What is the function of triaglycerols/triglycerides?

A

Energy storage in fat cells (adipose tissue). They break down when energy is needed and release energy rich fatty acids (lipolysis) into bloodstream

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4
Q

What is the function of cholesterol and fatty acids?

A

They are precursors of important signalling molecules (steroid hormones and prostaglandins)

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5
Q

Describe the basic structure of a fatty acid

A

An unbranched hydrocarbon chain with a carboxyl group at one end. The hydrocarbon chain can either be saturated or unsaturated

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6
Q

What does the properties of fatty acids depend on? (2)

A

The length of the hydrocarbon chain

If any double bonds are present and how many

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7
Q

How many carbons do liquid fatty acids have

A

1-8

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8
Q

Which form of unsaturated fatty acids is more stable, cis or trans?

A

Trans however, most are found in the cis form

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9
Q

Do double bonds in fatty acids increase or decrease the melting point?

A

Decrease

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10
Q

What is an essential fatty acid?

A

A fatty acid with 2 or 3 double bonds, they cannot be synthesised and have to be present in the diet

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11
Q

What 2 categories are polyunsaturated fatty acids found as?

A

Omega 3 (n3, fish oils) and omega 6 (n6, plant oils), the n numbers refer to where the first double bond is found

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12
Q

How is a molecule of triacylcglycerol formed?

A

The condensation reaction between 3 fatty acids and a molecule of glycerol which forms an ester bond between them

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13
Q

What are fats and oils

A

Triacylglycerols, solid = fat, liquid = oil

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14
Q

What lipid is the most important for structure?

A

Phospholipids

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15
Q

Describe the structure of a phospholipid

A

1 or 2 fatty acids and a phosphate group bonded to a glycerol molecule. The phosphate group is often linked to a small ionic nitrogen-containing group such as choline

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16
Q

What makes phospholipids ampipathic?

A

They have a hydrophilic polar head group (phosphate) as well as a hydrophobic fatty acid tail

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17
Q

How many carbons is cholesterol made from?

A

27

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18
Q

Describe the structure of choleserol

A

A 27 carbon chain with 4 rings and an aliphatic chain

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19
Q

Where is cholesterol obtained from and where is it synthesised?

A

Obtained from the diet and synthesised in the liver from carbohydrate precursors

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20
Q

What is cholesterol a precursor for?

A

Steroid hormones, vitamin D and bile acid synthesis

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21
Q

Describe the structure of waxes and their uses

A

Complicated mixtures of long chain alkanes with high melting points, no double bonds and are chemically inert, they provide a waterproof coating for organisms

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22
Q

What is the role of sphingolipids and give and example

A

Protect the external surfaces of cells, e.g ceramide

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23
Q

What is the role of glycolipids?

A

Cell recognition and cell signalling

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24
Q

What is the basic structure for membranes?

A

Double layer of lipid molecules which are embedded with different protein molecules. Most also contain carbohydrates

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25
What are glycoproteins and glycolipids?
When sugar side chains attach to proteins and lipids
26
What differences in membranes allows them to have different functions?
Differences in material used as well as the ratio between lipid and protein
27
Why and how do phospholipids with single fatty acid chains form micelles?
When in aqueous environments, the polar head groups face outwards with the hydrophobic tails facing inwards
28
What structure do phospholipids with 2 fatty acid chains form in aqueous environments?
A bilayer, rather than a micelle, the phospholipids arrange themselves in 2 rows with the polar head groups facing outwards
29
What is the lipid bilayer permeable and impermeable to?
Permeable to lipid soluble molecules and small uncharged molecules. Impermeable to ions and most water-soluble molecules
30
What is required to transport ions across the lipid bilayer?
Transporter proteins and aquaporins (channel proteins that transport water)
31
What does the fluidity of a membrane depend on?
The liquid composition
32
When is the packing of lipids at its most dense?
When both of the fatty acid chains are long and saturated (straight chains)
33
Why does double bonds in fatty acids make the structure looser?
It makes kinks preventing the fatty acids being packed together tightly
34
Why does cholesterol increase membrane fluidity?
It is rigid and kinked, it takes the place of a phospholipid and disrupts the stacking of fatty acids
35
Why are lipids of biological membranes always fluid at room temperatures?
They contain unsaturated fatty acids and cholesterol
36
What is a liposome?
An artificial bilayer that forms in certain conditions to self seal, it is a small hollow sphere of lipid membrane.
37
How can liposomes be used to help with drug delivery to target organs?
Non-lipid soluble material can be packaged into the centre of a liposome. When the liposome comes together with plasma membranes, the material is directly delivered into the interior of the cell
38
Describe the structure of a liposome
A spherical lipid bilayer where the polar head groups of one layer surrounds the outside and the polar head group of the other layer bunch together on the inside forming a small hollow
39
What is the fluid mosaic model of membrane structure?
There is a lipid bilayer in which proteins float like tiles of a mosaic and are responsible for the membranes functions
40
What are transmembrane protein?
Proteins that span the membrane (go across both layers in the bilayer)
41
What are peripheral proteins?
Proteins that only attach to the interior or exterior face of the bilayer
42
In the fluid mosaic model, what type of interactions are the lipid-lipid and lipid-protein interactions?
Non-covalent
43
Can all proteins move in the membrane?
No, most can however, some are anchored to the cell's cytoskeleton
44
Give some exampled of functions of the proteins that are found in the membrane
Pumps, channels, receptors, enzymes
45
Describe the term membrane asymmetry and what causes it
The idea that the inside and outside of the cell membrane are distinct as although proteins can move around, the can't travel to the other lipid layer in the bilayer. They also cannot change their orientation once part of the cell membrane
46
Why is membrane asymmetry important?
It allows messages and materials to be sent in the right direction across the membrane
47
What property of membranes allow them to fuse together
They are fluid
48
Give 3 examples of when membranes fuse
Male and female gametes to form a zygote Transport of materials through vesicles Viruses entering their host cell
49
What are the 2 classifications of membrane proteins?
Peripheral and integral
50
What are peripheral proteins?
Proteins that are loosely attached to the membrane and are easily removed by mild treatment such as changing pH
51
What are integral proteins?
Proteins that embedded in the membrane and are only removed by disruption of the membrane such as detergents
52
What allows membrane proteins to be sufficiently anchored n hydrophobic environments of the membrane?
They have one or more hydrophobic regions
53
Which parts of a protein are the hydrophilic regions?
The regions with amino acids that have polar or charged side groups
54
Which part of a cell is responsible for maintaining the internal environment (pH, osmolality, ions)
The plasma membrane
55
Generally, what are the 2 types of transport into and out of cells?
Passive diffusion and active transport
56
What are the 2 types of passive diffusion and how are they different?
Simple (across membrane unaided) | Facilitates (using carrier proteins)
57
What is active transport?
The transport of ions or solutes across the membrane against the concentration gradients and requires ATP either directly or indirectly
58
What is a uniport protein?
A transport protein that transports one solute form one side of the membrane to the other
59
What is a co-transport system?
When the transfer of one solute depends on the simultaneous or sequential transfer of a second solute
60
What is the difference between symport and antiport co-transport systems?
``` Symport = solutes travel in the same direction Antiport = Solutes travel in opposite directions ```
61
Give an example of a symport co-transport system
The uptake of sugars and amino acids into some animal cells is linked to the inward movement of Na+
62
Give an example of an antiport co-transport system
The sodium pump Na+/K+ ATPase transports K+ in and Na+ out against their concentration gradients
63
Describe how glucose is transported from the diet into the bloodstream
At the cell/blood surface, the antiport (ATPase) of K+ pumps K+ into the cell and Na+ out of the cell. This lowers Na+ in the cell meaning that Na+ then flows back into the cell but through a symport transporter down the concentration gradient. The co-transporter molecule for this is glucose from the diet (intestine). This then increases the glucose in the cell (epithelial) causing glucose to passively diffuse out of the cell via a glucose transporter and into the blood
64
What is the function of ion pumps in the internal membranes of cells?
They allow organelles such as mitochondria and the endoplasmic reticulum to maintain an internal ionic environment different from the surrounding cytoplasm
65
Give an example of an ion pump on the internal membrane and its function
The endoplasmic reticulum has a Ca2+-ATPase which pumps Ca2+ out of the cytoplasm and builds up a store in the E.R which can be released easily
66
Describe how the active transporter Human P-glycoprotein works
It has 2 transmembrane domains (TMD) and 2 nucleotide-binding domains (NBD). The intracellular NBDs hydrolyse ATP in the cell and use the energy to transport foreign molecules out of cells. However, sometimes it transports out drugs such as anticancer drugs and can be responsible for drug resistance
67
What are the 2 types of gated ion channels?
Voltage gated ion channels | Ligand-gated ion channels
68
What is endocytosis?
The process by which cells take in large quantities of materials
69
What is pinocytosis?
The process where cells uptake fluid
70
What is phagocutosis?
The process where cells engulf large quantities or large particles
71
What is the function of macrophages?
They engulf dead cells and cell debris (phagocytosis)
72
Why does the fact that membranes are fluid help with endocytosis?
It allows membranes to flow around large particles
73
What happens when endocytic vesicles fuse with lysosomes?
The contents inside the vesicles are broken down by lysosomal enzymes
74
Describe receptor-mediated cytosis
Specific molecules bind to receptors on the extracellular membrane. This then triggers an endocytic vesicle to be created allowing the material to be transported into the cell
75
Give an example of a molecule that is transported into the cell by receptor-mediated cytosis
Cholesterol. It is synthesised in the liver and transported in the bloodstream as LDL particles. Cells have LDL receptors on their surfaces. Enzymes in the endocytic vesicle that is created allow the cholesterol to be released for its use.
76
What is the part of the cell's surface called where receptor-mediated endocytosis occurs?
Calthrin-coated pits
77
Describe exocytosis
A vesicle inside the cell travels to the cell membrane, fuses with it and releases its contents outside of the cell
78
Describe regulated secretion
Proteins are secreted form a cell in large amount when a specific signal is detected for example from a hormone or neurotransmitter
79
What can trigger exocytosis?
Stimuli, for example a sudden increase in calcium ion concentration inside a cell. However, exocytosis can also be continuous
80
What does compartmentalisation in cells allow?
Different processes to occur without disrupting other parts of the cell
81
What is cell differentiation?
The process where a cell changed from one cell type to another
82
What is an embryonic stem cell?
The cells of the zygote that can differentiate into all cell types of the adult organism
83
What does pluripotent mean?
A cell that is capable of differentiating into all cell types
84
What are somatic cells?
Any cell in the body except sperm and egg cells. They have differentiated from embryonic stem cells and only express certain parts of the genome in order to specialize for different functions
85
What are germ line cells?
Any cells that give rise to gametes
86
What are adult stem cells?
Cells that have the ability to indefinitely divide to give rise to specialised cells.
87
What are epithelial tissues?
A group of cells that cover the exterior of surfaces of the body, line internal cavities and passageways and form certain glands
88
What is the function of connective tissues?
To bind cells and organs together
89
What do muscle tissues do?
Contract forcefully when excites, providing movement
90
What is the function of nervous tissue?
Allows the generation and propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body

PHAY0003 (22 decks)

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