1.2 - 2.1 - bio mols 1 and eukaryotic cells

Question 1

v
How are triglycerides formed

Answer 1

When a glycerol molecule reacts with 3 fatty acids to form an ester bond. (Condensation reaction as h20 removed)

Question 2

Saturated lipids
Unsaturated

Answer 2

S - contain single bonds
U - contain carbon carbon double bonds , creating kinks in the chains so its harder for them to pack together tightly as it increases the space between phospholipids

Question 3

How does the structure of lipids relate to its role in , waterproofing, energy transfer , insulation

Answer 3

Water - they are
non polar and hydrophobic so they won’t dissolve in water
Energy -

Question 4

What is a phospholipid?
How can the structure of a phospholipid control what enters and leave a cell ?

Answer 4

A lipid made of one phosphate molecule , glycerol mol and 2 fatty acids
Phosphate heads are hydrophilic and the tails are hydrophobic

Question 5

Explain the arrangement of phospholipids in a membrane

Answer 5

-Bi layer
Phosphate head orientated outside, so they can interact with the aq envir
Fatty acid tails within the bilayer as they turn away from the solution

Question 6

Amino acids combine in a long chain to produce proteins in

Answer 6

Condensation reaction

Question 7

The primary structure ..
Secondary structure of protein …

Answer 7

of a protein is the linear sequence of amino acids joined by peptide bonds
The curling or folding of the poly peptide chain into alpha helixes and beta pleated sheats due to the formation of hydrogen bonds .

Question 8

How are polypeptides formed (lots of amino acids join )

Answer 8

The amino group of an aa reacts with the carboxyl group of another aa in a condensation reaction where a water molecule is lost.

Question 9

How is a peptide bond formed

Answer 9

When 2 amino acids join together

Question 10

Tertiary structure
Quaternary structure

Answer 10

3D folding of the secondary structure , joined by disulfide bonds
3D arrangement of more than one tertiary polypeptide

Question 11

How do hydrogen bonds form
How do disulfide bonds form?

Answer 11

In aa the negative charges on the oxygen of the carboxyl group and positive charges on the hydrogen atoms attract .
Oxidation reaction takes place between the two sulphur containing groups resulting in a covalent bond

Question 12

How do ionic bonds form?

Answer 12

They form between some of the strongly positive and negative amino acid sidechains.

Question 13

In a phospholipid the head is

Answer 13

Polar and hydrophilic , because it has a charge it’s attracted to water
Non - polar hydrophobic

Question 14

Cholesterol …

Answer 14

Is a molecule made in the liver regulates fluidity and permeability of the cell membrane

Question 15

Lipids containing saturated fatty acids are more likely to be

Answer 15

Solid at room temp than those containing unsaturated fatty acids

Question 16

plasma membranes are composed of proteins arranged randomly amongst the phospholipids. what are they

Answer 16

extrinsic proteins - occur on the surface of the bilayer or partially embedded in it

intrinsic - extend thru the whole membrane form one side to another

Question 17

why should cell surface membranes be flexible ?

Answer 17

so the cell can change shape slightly as its water content changes

Question 18

functions of proteins in the membrane are to:

Answer 18

1. provide structural support
2. act as carriers transporting water soluble substances across the membrane
3. form recognition sites by identifying cells

Question 19

why are cholesterol molecules distributed across the phospholipid bilayer?

Answer 19

to help it stay fluid in different environmental conditions
-it also holds the phospholipids together so they dont separate too far letting unwanted substances in

Question 20

What’s the function of the nuclear membrane/envelope in a nucleus
Nuclear pores
Nucleolus

Answer 20

Controls exit of materials in and out nucleus
Hole in the nuclear envelope , allowing mrna molecules to pass thru after transcription
Contains almost pure DNA and protein

Question 21

In a mitochondria what are the
Mitochondrial dna
Cristae (highly folded inner membrane)
Outer membrane

Answer 21

Allows mitochondrial enzymes to be created
Increases SA for enzymes involved with respiration to attach to
Controls passage of substances in and out cell

Question 22

In a mitochondria what’s the function of
Matrix (cytoplasm )
Ribosome
ATpase enzyme

Answer 22

Fluid filling mitochondrion
Site of protein synthesis
Enzyme used in respiration

Question 23

70s ribosomes
80s

Answer 23

Found in prokaryotic cells
Made up of a smaller 30 sub unit and larger 50s

Eukaryotic cells , 40s small and 60s large

Question 24

What’s the job of a SER

Answer 24

Synthesises , stores and transports lipids and steroids

Question 25

Describe the structure of an ER

Answer 25

Double membrane highly folded into cisternae forming a channel thru out the cell , folding increase sa for reactions In the cell

Question 26

List properties of fibrous proteins

Answer 26

Long parallel polypeptide chains with occasional cross linkages that form into fibres
They are insoluble and tough
Mainly secondary struc

Question 27

Collagen..

Answer 27

Is a fibrous protein and provides strength to other structures
The Fibres are strong bc of it being made of 3 polypeptide chains held by hydrogen bonds
- flexible due to kinks in protein chain

Question 28

Globular proteins …

Answer 28

Tertiary / quaternary struc
Folds into spherical globular shape
Holds molecules in position in cytoplasm

Question 29

Haemoglobin…

Answer 29

-globular protein and water soluble
4 polypeptide chains held tog by disulfide bonds

Question 30

Glycoproteins ?
Lipoproteins ?

Answer 30

Protein w carbohydrate prosthetic group
Protein w lipid prosthetic group

Question 31

What’s a monosaccharide, disaccharide and polysaccharide

Answer 31

M - single carbohydrate monomer
D- 2 carbohydrate monomers joined together
P - many monosaccharides joined

Question 32

What’s a glycosidic bond ?

Answer 32

A covelant bond formed when 2 monosaccharides join in a condensation reaction , a mol of water is removed and a disaccharide formed

Question 33

A glycosidic bond between 2 monosaccharides is split by

Answer 33

Hydrolysis where water is added to the bond

Question 34

What is starch amylose?

Answer 34

-made up of alpha glucose molecules joined by 1.4 glycosidic bonds , unbranched polymer
- as chain lengthens molecules spiral making it more compact for storage

Question 35

What is starch amylopectin?

Answer 35

• branched polymer of glucose molecules
• branching chains = more terminal glucose molecules can be broken off rapidly when needed
  -1.4 AND A FEW 1.6 bonds

Function: releases glucose rapidly when needed

Question 36

What is glycogen? polyosaccharide

Answer 36

• Alpha glucose, 1.4 and many 1.6 glycosidic bonds,
  branched meaning glucose broken down rapidly making it a source of glucose for cellular respiration

Question 37

What is cellulose? Structure and function

Answer 37

Beta glucose, 1.4 glycosidic bonds, hydrogen bonds hold molecules together, unbranched
- provides strong cell wall to prevent cell lysis ( H 2 )

Question 38

How does the Golgi apparatus and rer work together?

Answer 38

• Rer packages proteins into vesicles which pinch off
• vesicles then fuse w Golgi body emptying contents into golgi sacs
• golgi modifies protein , by adding carbohydrate
• if modified protein leaves the cell it’s packaged into vesicles and fuses w cell surface membrane for exocytosis
• golgi produces lysosomes

Question 39

What are lysosomes and how does it work

Answer 39

-Spherical vesicles containing digestive enzymes
- they destroy old surplus organelles

• materials from outside the cell fuse w cell membrane it’s taken into cell ,packaged into membrane bound vesicles . Lysosome fuses with v, releasing its contents digesting it

Question 40

Define apoptosis

Answer 40

The breakdown of worn out damaged or diseased cells by lysosomes

Question 41

Describe the structure of plant cell walls

Answer 41

1. Middle Iamella is made of pectin and forms calcium pectate which binds to cellulose on either side
2. Primary wall - made of microfibrils and matrix built up on either side of iamella, microfibrils in same direction so very flexible
3. Secondary wall - microfibrils lie at diff angles as cell ages

Question 42

What is plasmodesmata in plant cells

Answer 42

Strands of cytoplasm which stretch between cells , water can move from cell to cell via this route (symplast pathway)

Question 43

Vacuoles ..

Answer 43

Surrounded by tonoplast membrane , cell sap from vac moves into cell by osmosis making cytoplasm press against cell wall keeping cells turgid .

Question 44

Chloroplasts..

Answer 44

Have a double membrane, the inner membrane is highly folded to form thylakoids.
It absorbs light energy for photosynthesis and converts it into chemical energy .

Question 45

Amyloplasts

Answer 45

Colourless organelles and are developed from leucoplasts , they store starch

Question 46

In Complex organisms cells are organised into..

Answer 46

Tissues - a group of specialised cells carrying out particular function in body
Organs - structure made up of several types of tissues grouped together to carry out a particular function in the body
Organ system - group of organs working together to carry out particular function in the body .

Question 47

Explain how the properties of water molecules result in surface tension

Answer 47

-Water molecules are polar
-therefore form hydrogen bonds therefore are cohesive

Question 48

Why is water a polar molecule ?

Answer 48

Covelantly bonded , electrons attracted to stronger positive charge of the atom w the largest no of protons , in this case oxygen .
End of molecule has slight - charge , hydrogen end = slightly +

Electrons held closer to oxygen atom than hydrogen , water form’s hydrogen bonds, cohesive

Question 49

Importance of water :
1.high specific heat capacity
2. Maximum density 4 degrees

Answer 49

1. H bonds between molecules means it takes a lot of energy to separate them so temps of lakes etc don’t change much throughout the year , making good habitats
2. When cooled to 4 degs mols are closest together , ice floats forming an inuslating layer protecting aquatic organisms

Question 50

Importance of water :
3. Incompressibility
4. Polar solvent

Answer 50

3. Water is a liquid so can’t be compressed
4. Water contains hydrogen bonds . water is a solvent so polar molecules can dissolve in water