Cells & DNA do tonight

Question 1

Nucleus

Answer 1

Chromosomes contain DNA which controls the synthesis of proteins. Ribosomes are formed in the nucleolus

Question 2

Nucleus structure

Answer 2

large organelle enclosed by a double membrane (envelope) perforated by pores. Contains chromosomes and one or more nucleoli.

Question 3

5 parts of nucleus

Answer 3

Nuclear pores - allows passage of large molecules
Nuclear envelope - entry and exit - surrounded by ribosomes
Nucleoplasm
Chromosomes - protein bound DNA
Nucleolous- manufactures rRNA and assembles ribosomes - in nucleoplasm

Question 4

Ribosomes

Answer 4

very small organelle not bound by a membrane. Consists of a large and a small subunit. Made of protein and RNA.

Question 4

Ribosomes function

Answer 4

uses the information in nucleic acid to synthesis proteins.
Protein synthesis

Question 5

Vesicle

Answer 5

contains digestive enzymes
small membrane bound sphere
transport large molecules for exocytosis or to add membrane to different organelles

Question 6

vesicle function

Answer 6

Responsible for destroying worn out organelles and for digesting the content of vacuoles formed by phagocytosis.

Question 7

Centrioles structure

Answer 7

A pair of short cylinders. Each cylinder is made up of nine fibres.

Question 8

Centrioles function

Answer 8

form a spindle- shaped structure of protein fibres on which the chromosomes move during nuclear division.

Question 9

Vacuole structure

Answer 9

a sac bound by a single membrane. Contains cell sap which is a solution of mineral salts, pigments, organic acids and other substances.

Question 10

Vacuole function

Answer 10

stores waste products and other substances. Changes in volume affect the turgidity of the cell.

Question 11

Function of a vacuole

Answer 11

1- support herbaceous plants - turgidity
2- Sugar and AA act as a temporary food store.
3- Pigment - many colour petals - attract pollinating insects

Question 12

cell membrane

Answer 12

a phospholipid bilayer with intrinsic and extrinsic protein molecules.

Question 13

cell membrane function

Answer 13

a partially permeable carrier which controls the passage of substances into and out of the cell
- controls diffusion of molecules and ions between cytoplasm and surrounding fluid.

Question 14

Rough endoplasmic reticulin

Answer 14

Forms a system of channels for transporting materials through the cytoplasm. One type has ribosomes on its surface and is the site of protein synthesis. The other type has no ribosomes and is where steroids and other lipids are synthesised.

Question 15

Rough endoplasmic reticulin function

Answer 15

a complex network of flattened membrane- bound sacs called cisternae. Often has ribosomes on the cytoplasmic side.

Question 16

Ribosomes made from…

Answer 16

RNa/ rRNA, Proteins

Question 17

DNA vs mRNA

Answer 17

• deoxyribose vs ribose
• thymine vs uracil
• long vs short
• double stranded vs single stranded
• Hydrogen bonds vs no HB
• Complementary base pairing vs no

Question 18

why is the Resolution in Electron microscopes higher?

Answer 18

shorter wavelength between electrons
longer wavelength In light rays

Question 19

Describe how to determine size and structure with microscope of an organisms

Answer 19

1- measure and divide by magnification
2- Micrometers to cm x10000
or
1- measure and divide by length of scale bar
2- Multiply by actual length of scale bar

Question 20

Bacteria structure (not in plants)

Answer 20

circular DNA
Meurein cell wall
Smaller/ 70s ribosomes in cytoplasm

Question 21

Virus structure not in Bacteria

Answer 21

Capsid
Reverse transcriptase
RNA genome
Envelope

Question 22

Describe and explain the arrangement of genetic material in prophase:

Answer 22

1- Chromosomes visible
2- still condensing
3- chromosomes arranged randomly/ not lined up
4- Because no spindles

Question 23

Genes - how does it code for production of a polypeptide:

Answer 23

1- Triplet
2- Base/ nucleotide sequence
3- determines order/ Sequences of AA
4- Primary structure in polypeptide determined

Question 24

describe how Monomers join to form the primary structure of protein

Answer 24

1-Condensation reaction between 2 AA 2- creating specific Sequence of AA 3- Joined by peptide bonds

Question 25

State how Enzymes help reactions to proceed quickly at lower temps

Answer 25

Lowers activation energy

Question 26

Genes definition

Answer 26

A sequence of DNA bases that codes for a polypeptide

Question 27

MRNA Euk cells vs prok cells

Answer 27

Euk - pre MRNA only - splicing only - introns removed Prok - introns not present

Question 28

ATP in translation

Answer 28

1- releases energy 2- Peptide bonds form between AA 3- AA join to tRNA

Question 29

How do parent DNA strands separate

Answer 29

1- semi conservative DNA replication 2- Complementary base pairing 3- Hydrogen bonding of bases 4- Condensation of nucleotides 5- DNA polymerase catalyses phosphodiester bonds

Question 30

Water properties for importance in organisms

Answer 30

1- METABLOITE in condensation/ hydrolysis. photosythesis/ respiration 2- SOLVENT so many reactions can occur allowing transport of substance s 3- HIGH SPECIFIC HEAT CAPACITY so buffer to temp changes 4- LARGE LATENT HEAT OF VAPORISATION - so provides a cooling effect through evaporation 5- COHESION between water molecules so supports columns of water in plants 6- COHESION between water molecules provides surface tension supporting organisms

Question 31

Compare and contrast the structure of starch and cellulose

Answer 31

both 1- polysaccharides 2- glycose polymers 3- made of glucose monomers 4- contain glycosidic bonds between molecules 5- contain C, H, O 1- s made of alpha glucose, c- beta glucose 2- s- coiled, C - straight molecule 3- s- branched c- not branched 4- s- no fibrils, c- yes 5- s- 1-6 glycosidic bonds c- doesn't 6- S- 2 types of molecules c - one type 7- S- amylose and amylopectin C - one type

Question 32

Describe the structure of DNA and Chromosomes

Answer 32

1- polymers of nucleotide 2- nucleotide consists of deoxyribose phosphate and an organic/ nitrogenous base 3- phosphodiester bonds between nucleotides 4- DNA double helix held by H bonds 5- HB pairing between AT and CG 6- DNA is associated with histones/ protein 7- During meiosis - when visible chromosome consist of 2 chromatids joined at centromere

Question 33

Non competitive inhibitor in enzymes

Answer 33

- binds to () instead of AS - changes shape of AS - Change tertiary structures - Not complementary so substrate doesn't bind to AS - Not complementary so fewer enzyme substrate complexes

Question 34

Meosis key words (6marker)

Answer 34

2- divisions - meiosis 1, meios 2 DNA Replication in late interphase Seperation of homologous chromosoemes - 1st division Seperation of sister chromatids - 2nd division produce 4 haploid cells

Question 35

viral replication

Answer 35

1- attachment proteins attack to receptors 2- viral nucleic acid enters cell - engulfment, injection for enters 3 - necleic acid replication in cell 4- reverse transcriptase makes DNA from RNA 5- Cells produces viral protein/ capsid/ enzymes 6- Virus assembled and released from cell - bursts/ lysis

Question 36

binary fission

Answer 36

produces 2 daughter cells replication of circular DNA happens in prok cells

Question 37

Suggest how PNA (binds to DNA) affects the transcription of the section of DNA

Answer 37

PNA is complementary to DNA PNA forms base pairs with DNA Preventing/ reducing RNA polymerase activity/ bonding Reducing/ stopping transcription

Question 38

Some cells lining the bronchi of the lungs secrete large amounts of mucus. Mucus contains protein. Name one organelle that you would expect to find in large numbers in a mucus-secreting cell and describe its role in the production of mucus.

Answer 38

Golgi (apparatus); or smooth endoplasmic reticulum Package / process proteins; or Rough endoplasmic reticulum / ribosomes Make polypeptide / protein / forming peptide bonds; or Mitochondria; Release of energy / make ATP; or Vesicles; Secretion / transport of protein;

Question 39

An optical light microscope cannot be used to see a plasma membrane. Explain why.

Answer 39

Does not have the resolution / cannot distinguish between points this close together; As light has longer wavelength;

Question 40

Give one property of the molecules of substance X which allows them to diffuse through the membrane at the position shown (can pass through membrane)

Answer 40

Lipid soluble / small / non-polar / not charged;

Question 41

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical light microscope. (4marks)

Answer 41

Add a drop of water to a glass slide Place a section of a thin tissue sample onto a glass slide Put onto drop of water Add iodine solution to stain it And add cover slip lower with mounted needle - prevents air bubbles

Question 42

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells.

Answer 42

Cell Homogenisation - to break open cells Filter to remove whole cells Isotonic solution - to prevent damage to mitochondria Cold - prevents enzymes activity Buffered solution - prevents enzymes denaturing Spins - centrifugation -at low speed - separates out nuclei into pellet Left over stiff - supernatant - re-spin to get pellet Centrifuge again at higher speed to get mitochondria

Question 43

Starting with mRNA in the cytoplasm, describe how translation leads to the production of a polypeptide. Do not include description of transcription and splicing in your answer. (6marks)

Answer 43

Ms key points - Message RNA attaches to ribosome - Ribosome moves/ recognises to start codon - tRNA brings specific AA to ribosome - Anticodon and codon interaction - complementary in tRNA to mRNA - Ribosome moves and reads next codon - AA joined by peptide bonds Peptide bond formed by condensation reaction

Question 44

Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells. *

Answer 44

TEM uses electrons vs light TEM- uses a greater resolution TEM - can see smaller organisms LM - see living specimens TEM - dead TEM can’t see in colour LM can TEM - longer process to prepare sample LM - quick don’t need to be skilled TEM - thinner specimens

Question 45

What is the evidence that a scanning electron microscope was used to take this photo

Answer 45

3d image

Question 46

why use a buffer solution

Answer 46

controls PH

Question 47

Describe the structure of DNA and structure of a chromosomes

Answer 47

- polymers of nucleotides - nucleotides consist of deoxyribose phosphate and organic nitrfogneous base - Phosphodiester bonds between nucleotides - DNA double helix held by H bonds - 2 strands held by hydrogen bonds - adenine, thymine, cyotsine and guanine - DNA is associated with histones/ proteins - During mitosis/ when visible chromsomeoes cons tis of two chromatids joined at a centromere

Question 48

Describe the process of semi-conservative replication of DNA.

Answer 48

1. DNA helicase unwinds DNA/double helix OR DNA helicase breaks hydrogen bonds; 2. Both strands act as templates; 3. (Free DNA) nucleotides line up in complementary pairs/A-T and G-C; 4. DNA polymerase joins nucleotides (of new strand); 5. Forming phosphodiester bonds; 6. Each new DNA molecule consists of one old/original/template strand and one new strand;

Question 49

Describe the structure of DNA.

Answer 49

1. Polymer of nucleotides; 2. Each nucleotide formed from deoxyribose, a phosphate (group) and an organic/nitrogenous base; 3. Phosphodiester bonds (between nucleotides); 4. Double helix/2 strands held by hydrogen bonds; 5. (Hydrogen bonds/pairing) between adenine, thymine and cytosine, guanine;

Question 50

Describe and explain how the structure of DNA results in accurate replication.

Answer 50

1 two strands therefore semi-conservative replication (possible); 2 base pairing / hydrogen bonds holds strands together 3 hydrogen bonds weak / easily broken, allow strands to separate; 4 bases (sequence) (exposed so) act as template / can be copied; 5 A with T, C with G / complementary copy; 6 DNA one parent and one new strand;