Lecture 3

Question 1

What 4 features do all cells share

Answer 1

DNA in the form of chromosomes, a plasma membrane, ribosomes, cytosol

Question 2

What do the four essential features do?

Answer 2

Chromosomes hold the genetic information of the cell,
Plasma membrane provides a semi permeable membrane which materials can diffuse into and out of the cell through, ribosomes are where proteins are synthesised, cytosol is the jelly like fluid in which organelles are suspended in.

Question 3

difference between prokaryote cells and eukaryote cells

Answer 3

eukaryote has their DNA held in a fixed area called the nucleus, where DNA is in the nucleoid in the prokaryote cells. Eukaryote cells are also bigger 10-100um. Prokaryotes are 1-5um

Question 4

describe composition of the phospholipid bilayer

Answer 4

is made of a bilayer of phospholipids with different proteins attached or embedded into it. The Hydrophobic region is on the interior of membrane, hydrophilic surrounds the hydrophobic middle(interior) coming into contact with aqueous solution on either sides of bilayer. embedded within this are proteins and cholesterol.

Question 5

what affects the fluidity of the plasma membrane

Answer 5

temperature, saturation of phospholipids, the presence of cholesterol

Question 6

what does it mean for an internal membrane to be transmembrane

Answer 6

the protein that is embbeded within the membrane runs the whole range of the membrane.

Question 7

two types of membrane proteins

Answer 7

peripheral or integral. integral means in the membrane and peripheral is outside the membrane

Question 8

6 main roles of membrane-bound proteins

Answer 8

Transport:
Enzymatic activity:
Signal transduction:
Cell-cell recognition:
Intercellular joining:
Attachment to the cytoskeleton and extracellular matrix:

Question 9

Describe membrane protein transport:

Answer 9

A transmembrane protein may provide a hydrophilic channel across the hydrophobic inner for some solutes. Or the protein may actively change shape to move ions across the membrane as ATP is used to pump substances against the conc gradient

Question 10

Describe the enzyme membrane proteins function:

Answer 10

The protein may be an enzyme with its active sides exposed to adjacent solutions allowing the enzyme to do steps in a metabolic pathway

Question 11

Describe a signal transduction membrane proteins function:

Answer 11

A membrane protein may have a specific binding site that fits a specific chemical messenger, hormone for example. These chemicals , may cause the protein to change shape, allowing the protein to relay a message inside the cell. The message is to maybe do a specific metabolic process

Question 12

describe cell-cell recognition membrane protein functions

Answer 12

Some glycoproteins( proteins with added sugar) serve as ID tags that can be recognized by other cell proteins.

Question 13

describe the ntercellular joining membrane protein function

Answer 13

Membrane proteins may join together potentially forming long lasting binding between cells.

Question 14

Membrane proteins that connect to the ECM and cytoskeleton function.

Answer 14

allows a cell to physically connect with protein structures outside the cell (the extracellular matrix) This helps the cell maintain the shape and location of the membrane bound protein. Binding to ECM can make proteins coordinate intra and extra cellular changes.

Question 15

what substances require facilitated diffusion to get across the membrane

Answer 15

Hydrophilic molecules

Question 16

what is a transmembrane protein

Answer 16

a protein that spans the whole membrane range.

Question 17

what does water pass through the plasma membrane in?

Answer 17

Aquaporins

Question 18

Two types of transport proteins

Answer 18

Channel proteins and carrier proteins. Channel proteins provide a hydrophilic channel through the middle of the membrane. Carrier proteins change their shape around the molecule it will transport, these proteins are specific to a given solute

Question 19

what happens to plant and animal cells in hypertonic solution

Answer 19

Animal cells shrink and plant cells plasmolyse.

Question 20

what happens to plant and animal cells in hypotonic solution.

Answer 20

animal cells take in excess water, potentially lysing. Plant cells can’t lyse due to the cell wall, so they are turgid.

Question 21

What happens to plant and animal cells in isotonic solution

Answer 21

plant cells go flaccid and animal cells are normal

Question 22

Facilitated diffusion of some ions requires what

Answer 22

no energy, a concentration gradient and some times an additional ion to bind to the protein, acting as a chemical signal telling the protein to open.

Question 23

what happens to ATP in active transport

Answer 23

as active is against the concentration gradient so energy is needed. ATP provides energy to the proteins, doing so by releasing a phosphate group to the protein, in the process becoming ADP. The release of the phosphate creates the energy

Question 24

what is cotransport

Answer 24

the process of moving a larger molecule across the membrane with another smaller molecule. doing this as the larger molecule cannot diffuse across itself. for example sucrose and hydrogen

Question 25

why is co transport indirect active transport

Answer 25

once the hydrogen and sucrose enter the cell down a concentration gradient, the hydrogen is then moved back out as its not needed in the cell. So there is active transport in a proton pump, as the hydrogen is pumped out of the cell against the concentration gradient, thus requiring energy. The constant hydrogen conc gradient in the cell ensures sucrose can always enter the cell.