Cell Membranes Flashcards

1
Q

state three functions of the membrane at the surface of cells

A

•they are a barrier between the cell and it’s environment, they partially permeable, they control which substances enter and leave the cell, they let some molecules through but not others, substances can move across plasma membrane by diffusion, osmosis or active transport
•allow recognition by other cells
•allow cell communication

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2
Q

describe three functions of membranes within the cell

A

•membranes around organelles divide the cells into different compartments, act as barrier between the organelle and cytoplasm
•membranes within cells can be the sites of chemical reactions
•they can form vesicles to transport substances between different areas of the cell

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3
Q

give three molecules that are present in animal cell membrane

A

proteins
lipids
carbohydrates

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4
Q

what is the fluid Mosaic structure?

A

fluid mosaic model describes the arrangement of molecules in the membrane

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5
Q

explain why the plasma membrane can be described as having a fluid mosaic structure

A

•in the model, phospholipid molecules form a continuous double layer
•this bilayer is fluid because the phospholipid molecules are constantly moving
• cholesterol molecules are present within the bilayer
• protein molecules are scattered through the bilayer like tiles in a mosaic
• some proteins have a polysaccharide (carbohydrate) chain attached to them, these are glycoproteins
• some lipids have a polysaccharide chain attached to them, these are glycolipids

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6
Q

what is the structure of a phospholipid molecule

A

they have a head and a tail

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7
Q

describe the head and tail of a phospholipid molecule

A

head is hydrophilic, it attracts water
tail is hydrophobic, it tells water
•molecules automatically arrange themselves in a bilayer, head faces put towards the water on either side of the membrane

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8
Q

Describe the centre of the fluid mosaic model

A

The centre of the bilayer is hydrologic, so membrane doesn’t allow water soluble substances through it and acts as a barrier to dissolved substances
( fat soluble substances can dissolve in the bilayer and pass directly through the membrane)

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9
Q

what type of molecule is cholesterol?

A

Cholesterol is a type of lipid

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10
Q

what does cholesterol molecule do to the membrane?

A

Cholesterol gives the membrane stability

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11
Q

How does cholesterol molecules give the membrane stability?

A

cholesterol molecules fit between the phospholipids, they bind to the hydrophobic tails of the phospholipids,
Causing them to pack more closely together, which makes the membrane less fluid and more rigid

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12
Q

what does protein do for the membrane

A

protein controls what enters and leaves the cell

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13
Q

what are the three types of proteins in membrane

A

•some proteins form channels in the membrane, these allow small or charged particles through
•some proteins are carrier proteins, they transport molecules and ions across the membrane by active transport and facilitated diffusion
•some proteins act as receptors for molecules in cell signalling, when a molecule binds to the protein a chemical reaction is triggered inside the cell

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14
Q

what do glycolipids and glycoproteins do for the membrane

A

Glycolipids and glycoproteins act as receptors for messenger molecules

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15
Q

different functions of Glycolipids and glycoproteins in the membrane

A

Glycolipids and glycoproteins stabilise the membrane by forming hydrogen bonds with surrounding water molecules
• sites where drug, hormones and antibodies bind
• act as receptors for cell signalling

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16
Q

What is cell signalling

A

Cells need to communicate with each other to control process inside the body and to respond to changes in the environment

17
Q

How do cells communication with each other using a messenger molecule?

A

•one cell releases a messenger molecule
•this molecule travels to another cell
•the messenger molecule is detected by the cell because it binds to a receptor on its cell membrane

18
Q

What are Receptor proteins:

A

Receptor proteins have a specific shape, only messenger molecules with a complementary shape can bind together to different cells have different type of receptors, they respond to different messenger molecules

19
Q

what is a cell called when it responds to a particular messenger molecule?

A

Target cell

20
Q

Describe using an example how cells communicate with another

A

Glucagon is a hormone that’s released when there isn’t enough glucose in the blood. It binds to receptors on liver cells, causing the liver cells to break down stores of glycogen to glucose

21
Q

What happens when drugs bind to cell membrane receptors

A

Many drugs work by binding to receptors in cell membranes.
They either trigger a response in the cell, or block the receptor and prevent it from working.