Cell Membranes And Cell Transport

Question 1

Phospholipids are similar to triglycerides but?

Answer 1

One of the fatty acids is replaced by Phosphate group

Question 2

 Describe the structure of phospholipids 

Answer 2

Phospholipids are shown as a phosphate head and 2 fatty acid tails. Phosphate heads are hydrophilic, and the fatty acid tails are hydrophobic. When added to water, they form a bilayer, which head facing out towards water on either side and hydrophobic tails in the centre.

Question 3

Describe the phospholipids in a cell membrane

Answer 3

Membrane acts as a barrier to water soluble substances because I cannot get through the hydrophobic centre of the phospholipid bilayer

Question 4

Describe the plasma membrane

Answer 4

-separate cells contents from the outside environment
-Controls the passage of substances into and out of cells
-Allows vesicles to fuse, is it during exocytosis
-Is involved in cell recognition and cell signalling

Question 5

Describe organelle membranes

Answer 5

-divide this, so into compartments of specialised functions
-Controls the passage of substances into and out of organelles
-Isolate, potentially harmful enzymes in lysosomes
-Provide surfaces for holding chlorophyll
-provides surfaces for producing atp

Question 6

As well as phospholipids, what else or cell membrane is made up of

Answer 6

Proteins, glycoproteins, and glycolipids and cholesterol

Question 7

Describe the proteins in the cell membranes

Answer 7

Has surface proteins, which span part of the membrane and are involved in cell recognition and cell signalling and transmembrane proteins Channell proteins which spans the whole membrane and which allows large polar molecules in hours to pass through it 

Question 8

Describe the fluid mosaic model

Answer 8

The phospholipid can move around, making the membrane fluid and the proteins are scattered throughout it like tiles in a mosaic. Some of the proteins are fixed position but some can move sideways through the membrane. 

Question 9

Describe the glycoproteins in glycolipids in a cell membrane

Answer 9

Protein is a carbohydrate attached to a protein of hydra attached, a lipid. He’s always reject from the outside surface of the cell surface membrane as there is a recognition and cell signalling.

Question 10

Describe cholesterol in the cell membrane

Answer 10

Cholesterol is a type of liquid is in between phospholipid more closely and stabilises membranes by making them less fluid and more rigid. This helps animal cells maintain a shape. Cholesterol is also hydrophobic to reduces permeability to water.

Question 11

Cell membranes are Persian partially permeable what does this mean?

Answer 11

They allow some substances to pass through, but not others

Question 12

Describe why cell membranes are partially permeable

Answer 12

-small molecules can squeeze in between the phospholipids
-Large nonpolar are lipid soluble, so can get through the bilayer because they can dissolve in it
-large polar molecules and ions are water soluble so cannot get through the bilayer because they can’t dissolve. They can only get through the membrane by carrier proteins or Channell proteins.

Question 13

What are the four ways in which substances can get across membranes

Answer 13

Simple diffusion, facilitated diffusion, osmosis which are passive processes (they do not use energy in the form of ATP )
and active transport which is an active process (uses energy in the form of ATP )

Question 14

What is diffusion?

Answer 14

Diffusion is the movement of molecule or ions from an area of higher concentration to an area of lower concentration 

Question 15

What is the simple diffusion?

Answer 15

The diffusion of small molecules and lipidsoluble molecules directly through the phospholipid bilayer of cell membranes

Question 16

Why does diffusion happen?

Answer 16

Because molecules and ions have their own kinetic energy and they move about in random directions

Question 17

Is molecules are at a higher concentration outside the cell them inside a cell what happens?

Answer 17

There will be a net movement of these into the cell, until equilibrium is reached

Question 18

What happens at equilibrium?

Answer 18

Turn the uniform distribution of molecules inside, and outside of the cell and diffusion occurs in both directions. At the same time, it does not stop it’s just there is no net movement 

Question 19

Rate of diffusion increases with what?

Answer 19

A higher temperature increase kinetic energy of molecules and ions
A larger Surface area allows for more points of contact
Higher concentration gradient mean is that there’s a big difference in concentration
A lower thickness of exchange surface beans as a shorter diffusion pathway 

Question 20

What is facilitated diffusion?

Answer 20

Special type of diffusion, which is aided by channel proteins or carrier proteins in the cell membrane

Question 21

What happens during facilitated diffusion?

Answer 21

Ions in large water, soluble molecules, such as glucose get across membranes. The substances cannot cross memories by simple diffusion because they cannot cross the hydrophobic centre of the bilayer. 

Question 22

Apart from all the same factors, a simple diffusion, what else affects the rate of facilitated diffusion

Answer 22

The number of transmembrane proteins
Fusion parties at a certain concentration of the diffusing substance does a transmembrane protein become saturated. Their numbers are limited, and they can only heard of certain number of market opens at a time. 

Question 23

What do you channel proteins allow through the cell membrane?

Answer 23

Ions such as calcium, 2+

Question 24

What do you carrier proteins alarm through the cell membrane?

Answer 24

Water soluble molecules for example glucose

Question 25

What is active transport?

Answer 25

The movement of ions or molecules across the cell membranes against a concentration gradient, requiring the use of the energy in the form of ATP

Question 26

Why is active transport necessary?

Answer 26

Diffusion only works from high to low concentration, but sometimes cells the more of a substance in the cytoplasm that is present outside the cell.
Diffusion is slow, cells can obtain substances more quickly by actively pumping them inside the cell

Question 27

What’s the difference between active transport and facilitated diffusion?

Answer 27

Active transport uses carrier proteins, where is facilitated diffusion use his carrier protein and channel proteins
Active transport is it is an active process and facilitated diffusion is a passive process
Active transport moves molecules up a concentration gradient where is facilitated diffusion moves down a concentration gradient