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Biology A level > Cells & DNA > Flashcards

Cells & DNA Flashcards

2.1.1 euk cells, 2.1.3 Microscopes, 4.2 protein synthesis, 4.3/8.1 mutations and gene DNA replication, 4.3 Meosis, 4.1 prok cells, 1.5.2 semi conservative replication, 2.2 cell cycle, mitosis, 2.1.2prok vs euk, 2.2 Binary fission

1
Q

Nucleus

A

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

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2
Q

Nucleus structure

A

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

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3
Q

5 parts of nucleus

A

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

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4
Q

Ribosomes

A

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

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4
Q

Ribosomes function

A

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

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5
Q

Vesicle

A

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

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6
Q

vesicle function

A

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

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7
Q

Centrioles structure

A

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

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8
Q

Centrioles function

A

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

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9
Q

Vacuole structure

A

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

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10
Q

Vacuole function

A

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

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11
Q

Function of a vacuole

A

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

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12
Q

cell membrane

A

a phospholipid bilayer with intrinsic and extrinsic protein molecules.

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13
Q

cell membrane function

A

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.

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14
Q

Rough endoplasmic reticulin

A

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.

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15
Q

Rough endoplasmic reticulin function

A

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

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16
Q

Ribosomes made from…

A

RNa/ rRNA, Proteins

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17
Q

DNA vs mRNA

A
  • deoxyribose vs ribose
  • thymine vs uracil
  • long vs short
  • double stranded vs single stranded
  • Hydrogen bonds vs no HB
  • Complementary base pairing vs no
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18
Q

why is the Resolution in Electron microscopes higher?

A

shorter wavelength between electrons
longer wavelength In light rays

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19
Q

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

A

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

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20
Q

Bacteria structure (not in plants)

A

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

21
Q

Virus structure not in Bacteria

A

Capsid
Reverse transcriptase
RNA genome
Envelope

22
Q

Describe and explain the arrangement of genetic material in prophase:

A

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

23
Q

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

A

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

24
Q

describe how Monomers join to form the primary structure of protein

A

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

25
Q

State how Enzymes help reactions to proceed quickly at lower temps

A

Lowers activation energy

26
Q

Genes definition

A

A sequence of DNA bases that codes for a polypeptide

27
Q

MRNA Euk cells vs prok cells

A

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

28
Q

ATP in translation

A

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

29
Q

How do parent DNA strands separate

A

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

30
Q

Water properties for importance in organisms

A

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

31
Q

Compare and contrast the structure of starch and cellulose

A

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

32
Q

Describe the structure of DNA and Chromosomes

A

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

33
Q

Non competitive inhibitor in enzymes

A
  • 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
34
Q

Meosis key words (6marker)

A

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

35
Q

viral replication

A

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

36
Q

binary fission

A

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

37
Q

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

A

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

38
Q

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.

A

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;

39
Q

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

A

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

40
Q

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)

A

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

41
Q

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)

A

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

42
Q

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

A

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

43
Q

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)

A

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

44
Q

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

A

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

45
Q

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

A

3d image

46
Q

why use a buffer solution

A

controls PH

47
Q

Describe the structure of DNA and structure of a chromosomes

A
  • 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
48
Q

Describe the process of semi-conservative replication of DNA.

A
  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;
49
Q

Describe the structure of DNA.

A
  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;
  1. (Hydrogen bonds/pairing) between adenine, thymine and cytosine, guanine;
50
Q

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

A

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;

Biology A level (18 decks)

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