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A Level Biology > Topic 2 > Flashcards

Topic 2 Flashcards

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1
Q

What are the role of goblet cells

A

They produce mucus

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2
Q

What is the role of the mucus

A

It traps any dust,mucus and microorganisms found in our airways

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3
Q

How is mucus removed

A

It’s moved by waves of beating cila

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4
Q

Why is it hard for mucus to be moved in sufferers of cystic fibrosis

A

The mucus had little water in it so it’s very sticky

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5
Q

Why are low levels of oxygen created in mucus with people who cf

A

Oxygen diffuses to slowly through mucus

Epithelial cells use up more oxygen in cf patients

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6
Q

How are lung infections common with suffers of CF

A

As anaerobic conditions are created in the lungs due to low oxygen levels which enables harmful bacteria to thrive

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7
Q

How can white blood cells cause the mucus to be sticky

A

As when they break down they release DNA causing mucus to be even sticker

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8
Q

Explain how the lungs are adapted for gas exhahgrv

A

Large surface area for alveoli

Numerous capillaries good blood supply, maintains the concentration gradient, ventilation of lungs maintains the concentration gradient

Thin walls of capillaries and alveoli short distance between alveoli to travel

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9
Q

What are the 3 properties of gas exchange

A

Surface area
Concentration gradient
Thickness of gas exchange surface

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10
Q

Explain the relationship between surface area and rate of diffusion

A

They are directly proportional so as rate of diffusion increases so does surface area

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11
Q

Explain the relationship between concentration gradient and rate of diffusion

A

They are directly proportional so the greater the concentration gradient the faster the rate of diffusion

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12
Q

Explain the relationship between thickness of gas exchange surfaces and rate of diffusion

A

They are inversely proportional the thicker the surface area the slower the diffusion

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13
Q

What is fick law

A

Surface area*difference in concentration gradient
/
Thickness of gas exchange surface

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14
Q

What is diffusion

A

Net move of particles from an area of low concentration to an area of high concentration along a concentration gradient

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15
Q

How are concentration gradient mainted

A

By cells continuously using substances they have absorbed and producing waste products from them

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16
Q

What happens to organisms when they get larger

A

Their surface area per unit volume diminishes

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17
Q

Why can’t larger organisms rely on their general body for diffusion

A

As it’s too slow and the distance between cells is long

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18
Q

Describe why someone with cf will have breathing issues

A

Sticky,vicious mucus is produced

This mucus blocks the movement of air in bronchi.

Reduce gas exchange surface as reduces surface area for alveoli

Anaerobic conditions creating as a result of mucus leaves lung vulnerable to infection

The lung elasticity damaged as mucus makes it harder to breath out air

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19
Q

What do all amino acids contain

A

Amine group
Carboxylic acid group
Hydrogen
Residual group

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20
Q

What examples of protein are their in the body

A

Enzymes
Hormones
Antibodies

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21
Q

What is the primary structure of an amino protein

A

The sequence of amino acids in a polypeptide chain

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22
Q

What is the reaction called when two amino acids combine and what is the bond produced called

A

The reaction is called s condensation reaction and peptide bond is produced and water is released

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23
Q

How do secondary structures form in proteins

A

When in amino acids the polypeptide chains interact and coil up and fold

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24
Q

What are the two things formed in secondary structures

A

A helix

B pleated sheets

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25
Q

What is alpha helix

A

When hydrogen bonds form between the negative carboxylic acid and the positive amine group

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26
Q

What are beta plated sheets

A

When amino acids fold back on themselves and hydrogen bonds form linking them together

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27
Q

What is the tertiary structure of a protein

A

When the polypeptide chain folds to make a 3D shape which is held by chemical bonds between r groups

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28
Q

What are the 3 types of bond that can form between r groups in proteins

A

Hydrogen bonds
Ionic
Disulphide covalent bonds

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29
Q

When is a molecule described as a protein

A

When it’s 3D structure is functional

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30
Q

What is Quanternary structure

A

When the protein had more than one polypeptide chain

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31
Q

What are the two types of protein

A

Globular

Fibrous

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32
Q

Give characteristics of globular proteins

A

The polypeptide chain is folded into a spherical compact shape

They are soluble as they contain hydrophilic side chain

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33
Q

Give some characteristics of fibrous proteins

A

They remain as long chains that cross linking polypeptide chains which gives them strength

They are insouble proteins and are used as structural molecules

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34
Q

What problems does CF create in persons digestive system

A

The sticky mucus blocks the pancreatic duct so digestive enzymes can’t be released

Causes damage to the pancreas
Can cause diabetes due to enzymes damaging insulin producing cells

Malabsorption syndrome in which the rate of digestion is reduced as not all nutrients are absorbed

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35
Q

What are enzymes

A

Biological catalysts and globular proteins that speed up rate of reaction

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36
Q

Give 3 theories that explain the effect of enzymes active site

A

Lock and key theory
Induced fit theory
Activation energy

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37
Q

What is the lock and key theory

A

Substrate molecules bind into an active site as they have a complementary shape they produce an enzyme substrate complex in which they form a temporary bond

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38
Q

What are catabolic reactions

A

When enzymes break down larger molecules into smaller molecules

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39
Q

What are anabolic reactions

A

When enzymes build up reactions

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40
Q

How do u work out intial rate of reaction

A

Change in y

Change in X

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41
Q

What is activation energy

A

The amount of energy needed to break bonds to start a reaction

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42
Q

What is the structure of a membrane

A

Two layers of phospholipids which contain fatty acids

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43
Q

What is the phospholipid structure

A

Two fatty acid tails phosphate heads that are hydrophilic tails and the tails are hydrophobic

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44
Q

What two arrangements can phosphate lipids form

A

Bilayer

Micelles

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45
Q

Why do phsolipids form a bilayer

A

As it’s the most stable arrangement the head comes in contact with water tails face away

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46
Q

What are micelles and why isn’t the favoured arrangement

A

When they arrange themselfves in spherical clusters but it’s to bulky to fit

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47
Q

What things are found on a cell surface membrane

A

Glycoproteins
Glycolipids
Proteins
Cholesterol

48
Q

What is the fluid mosaic model

A

The arrangement of cell membranes and that some proteins have the ability to move around and move freely

49
Q

Name ways substances transport across a memebrane

A 
Osmosis 
Diffusion
Active transport 
Endocytosis
Exocytosis
50
Q

What is diffusion

A

The net movement of ions from an area of high concentration to a region of lower concentration

51
Q

What is facilitated diffusion

A

When polar molecules or ions larger than co2 need to cross the membranes with the help of carrier proteins and they go through channel proteins

52
Q

In facilitated diffusion how the carrier proteins carry molecules

A

The ion or molecule binds onto a specific site in the protein which makes it change shape

53
Q

What is osmosis

A

The net movement of water molecules from an area of solution with lower concentration of solute to a solution with a high concentration of solute through a partially permeable membrane

54
Q

What is active transport

A

Movement of substances against a concentration gradient which requires energy

55
Q

How does active transport work

A

The substance to be transported binds on to a carrier protein

A phosphate by hydrolysis is removed from ATP from ADP which becomes hydrated and a lot of energy is released as a result of the bond formed

This causes the shape of the carrier protein to change and the substance is released

56
Q

What is exocytosis and how does it work

A

When substances like proteins and polysaccharides are released from the cell

The cell membrane is fused with vesicles and they transport substances out of the cell

57
Q

What is endocytosis

A

This is when substances are taken into the cell by vesicles

58
Q

When theirs excess water in the mucus how is it released

A

The sodium pump pumps sodium ions outside the cell into the basal end into the tissue fluid

Due to an electrical created as a result of this cl ions go into the tissue fluid via a diffusion

Water via osmosis diffuses into the tissue fluid from the basal membrane due to the increase in solute concentration

The solute concentration in the basal membrane(epithelial cell)increases as a result and water from the mucus diffuses into the epithelial cell

59
Q

What happens where their is to little water in the mucus

A

Cl ions are secreted into the mucus and they go via CFTr channel

The CFTr channel protein prevents the sodium pump from pumping sodium ions so they build up in the mucus

Due to increase in solute level water from the tissue fluid water diffuses into the mucus making to more viscous

60
Q

What is wrong with people with cf Cftr protein

A

It’s not present or doesn’t function properly

61
Q

Explain why people with Cf lungs can’t regulate water in mucus

A

Their cftr protein isn’t functioning properly

Meaning it can’t regulate the sodium channel properly so more sodium ions travel through into tissue fluid in which a electrical gradient is created so cl ions go from the mucus into epithiel cells into the tissue fluid

Due to the higher solute level in the tissue fluid water via osmosis is continuously drawn out of the mucus into then tissue fluid making mucus sticky

62
Q

What is induced fit theory

A

That a substrate will cause the active site of a enzyme to change so it can fit in

63
Q

What type of nucleic acid is DNA

A

deoxyribosenucleic acid

64
Q

What are 3 molecule are found in mononucleotides

A

a deoxyribose
A phosphate group
Organic base with nitrogen

65
Q

What are the bases in DNA molecules

A

Adenine
Guanine
Thymine
Csytine

66
Q

What base pair are complementary and what bond forms between them

A

A and T
C and G

Hydrogen bonds

67
Q

What reaction causes between mono nucleotides and what bond forms between two nucleotides

A

Condensation reactions occur between a sugar of one nucleotides and a phosphate group of another

It’s forms a phosphodiester bond

68
Q

What are the differences between RNA and DNA

A

RNA contains a ribose sugar not deoxyribose

RNA contain a uracil base that replaces the thymine

RNA can leave nucleus

RNA has one strand and DNA has two strands

69
Q

Give the names of RNA involved in protein synthesis

A

Messenger RNA
Transfer RNA
Ribsomal RNA

70
Q

Describe what happens in transcription

A

RNA polymerase causes hydrogen bonds between bases to be exposed as the DNA molecule unwinds

The exposed bases on the DNA template strand pair up with free RNA nucleotides from the nucleus and the mrna forms alongside the DNA template strand

RNA polymerase creates phosphodiester bonds between the adjacent mrna nucleotides forming the mrna

Then it’s released through nuclear pore and exits the nucleus

71
Q

What is the template strand

A

The Dna strand that the mrna is copied from

72
Q

What is the role of tRNA and describe some of its features

A

It transfers amino acids to the ribosomes and it has a anticodon that is complementary to the mrna codon

73
Q

Describe the process of translation

A

The mrna on the ribosome has its first base exposed a tRNA with a complementary is attracted to it and forms hydrogen bonds with it

The next codon on the mrna is exposed and it attracts another tRNA which is carrying a amino acid and it to binds on to the codon on the mrna

The amino acids that are held in place forms peptide bonds with one another and it occurs as a result of a condensation reaction

The first tRNA will return back to the cytoplasm to collect another amino acid and the process continues until a stop codon is reached which results in the polypeptide chain to stop growing and it detached from the ribosome

74
Q

What is meant by the genetic code being degenerate

A

It means that several genetic code can code for the same amino acid

75
Q

What is meant by the genetic code being non overlapping

A

It means that the codes are adjacent to one another and that they don’t overlap

76
Q

Outline the steps in DNA replication and state what it’s called

A

DNA polymerase causes the hydrogen bonds between DNA to break causeing the DNA strand to unravel

Alongside each single strand of DNA free DNA nucleotides line up and hydrogen bonds form between there bases DNA polymerase links the adjacent nucleotides together via condensation reaction resulting in phosphodiester bonds forming between them

It’s known as semi conservative replication as it contains an old DNA strand and a new one

77
Q

Describe the procedure in meelson and stahl experiment

A

They used DNA from escherichia bacteria which had grown in a medium which contained only a heavy type of nitrogen

They then put the bacteria in a medium that had nitrogen 14(so it had heavy and light nucleotides)

They allowed the bacteria and DNA to divide and replicate they then extracted and centrifuged the DNA after

78
Q

What were the initial findings in melson and stahl experiment and what do after

A

They found just a middle band meaning they could discount the conservative theory of DNA replication

So they let the DNA undergo to more rounds of replication.

79
Q

After the second round of replication what did melson and stahl find

A

They found two bands in the middle of the tube a light and medium band which supports semi conservative replication as it shows that a new DNA strand is made from both old and new strand

80
Q

What types of mutations can take place in DNA

A

Mutation
Deletion
Insertion
Substitution

81
Q

What is the locus

A

It’s the position at which two copies of a particular gene are located on two pairs of chromosomes

82
Q

What are alleles

A

They are alternative forms of genes

83
Q

What is the genotype

A

This is all the alleles that make up a persons genetic make up

84
Q

What is a homozygous genotype

A

When a person has 2 identical copies of an allele for a gene

85
Q

What is a heterozygous genotype

A

When a person has 2 different copies of an allele for a gene

86
Q

What is a recessive allele

A

It needs two identical copies of the allele to produce a phenotype

Not expressed when there’s a dominant allele

Needs 2 alleles in order to be expressed

87
Q

What is monohybrid inheritance

A

When a characteristic is only controlled by one gene

88
Q

What is the purpose of genetic screening

A

It’s used to confirm the results of genetic testing and identify carriers

89
Q

What is a dominant allele

A

Only needs one copy of an allele to produce a phenotype

90
Q

Give 3 examples of prenatal testing

A

Chronic villus sampling

Amniocentesis NIPD

91
Q

What happens in aminocentesis

A

It’s the insertion of a needle into the amniotic to collect fetal cells that have fallen of placenta and fetus

It occurs 15-17 weeks into pregnancy

92
Q

What happens to in CVs

A

Insertion through abdomen wall or vagina to collect sample of placenta tissue

Happens in 8-12 weeks into pregnancy

93
Q

What is the issue with both amniocentesis and chronic villus sampling

A

They carry a risk of miscarriage

1% risk of miscarriage form amniocentesis

1-2% risk of miscarriage for cvs

94
Q

What is NIPD

A

It’s analyses DNA fragments in mothers bloods

Doesn’t require insertion of needle so it’s no risk of miscarriage

95
Q

What happens in PGD

A

IVF is used to create embryos that are tested,the cells in the embryos are tested via genetic screening then it’s decided wheather or not to place In the uterus

96
Q

What is the issue with PGD

A

IVF is expensive and stressful and low success rate

97
Q

What is activation energy

A

The amount of energy needed to break bond to start a reaction

98
Q

What are catabolic reactions

A

Enzymes break down larger molecules into smaller molecules

99
Q

What are anabolic reactions

A

When enzymes build up reactions

100
Q

Give differences between globular and fibrous proteins

A

Globular-soluble,compact 3D shape,enzymes,hydrophilic

Fibrous-insouble,straight chains,mainly secondary structure,hydrophobic

101
Q

What was the issue with the original 3 layer protein sandwich

A

It didn’t allow for phosphate head to come in contact with water

It allowed for hydrophobic amino acids to be kept in and have contact with water

102
Q

Give examples of evidence that support the fluid mosaic model

A

Change in interpretation of electron micrograph

Experiments showing two types of proteins

Human and mouse cell experiment

Freeze fracture

103
Q

What things comprise a cell membrane in accordance to the fluid mosaic model

A

Phosplipid bilayer
Glycoproteins
Glycolipids(lipids with polysaccharides attached

104
Q

What is incomplete dominance

A

When the trait from a dominant allele isn’t completely shown over the trait produced by a recessive allele,both alleles influence phenotype

105
Q

How does improvements in electron micrograph interpretation provide evidence for the fluid mosaic model

A

The new evidence states that the phosphate heads are at darker regions or the membrane and that they are more electron dense and the lipid tails were at the lighter parts of the membrane

106
Q

Suggest why phosphate heads are at the darker edges of the membrane

A

Due to the polar nature of the phosphate head

107
Q

State what experiments have shown about proteins in the fluid mosaic model and how they support the model

A

Experiments show that there are two types of proteins

Some which can be dissociated from the membrane by ionic strength(easily dissociated)

Other proteins in the membrane which are harder to dissociate

Supports integral(they are fully embedded in the phoslipids and peripheral proteins which are loosely attached

108
Q

Describe the procedure with the mouse and human cell and state how it supports the
Fluid mosaic model

A

They marked proteins in each cell and then fused them together after 40 mins they found that the proteins had intermixed

Supports the model as the only way they could have achieved this was by diffusion through the membrane showing that it’s fluid

109
Q

What did freeze fracture show about the fluid mosaic model

A

The membranes were frozen and split along weak points between the lipid layer

Using electron microscopy they found a mosaic like surface with lipid tails along with larger proteins scattered among them

110
Q

What are the functions of glycoproteins and glycolipids

A

Helps in cell to cell recognition

Glycolipids aid in receptors

111
Q

What do both endocytosis and exocytosis require

A

ATP

112
Q

Why are membrane more fluid when they have more unsaturated fatty acids

A

They contain a double bond that means they have a kink in there chain so they don’t pack close together

113
Q

What is the role of cholesterol in the membrane

A

They are between phospholipids and it mains fluidity

114
Q

State how enzymes can reduce activation energy

A

The charged groups in the enzyme and substrate interact causing the bonds in the substrate to change and distort

Which assist in bonds breaking or making

115
Q

Describe the structure of collagen

A

3 polypeptide chains that are cooled tightly around one another

Every third amino acid has a small R group

Chains are held by covalent cross links

Used to function as support tissue

A Level Biology (9 decks)

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