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CCEA AS Biology Units 1, 2 And 3 > (U1) Molecules > Flashcards

(U1) Molecules Flashcards

1
Q

Why is water a good solvent?

A
  • Due to their polarity, water molecules are attracted to other polar molecules
  • this allows them to form clusters around the solute and therefore dissolve them
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2
Q

What is a polar molecule?

Why is water a polar molecule?

A
  • A molecule where individual atoms have slight, opposite charges due to uneven distribution of covalent bonds (electron slightly more attracted to one of the molecules)
  • the oxygens have a slight -ve charge, hydrogens slight +ve
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3
Q

In what 3 ways is water used within the body?

A
  • most of the reactions in cells take place in aqueous solutions (in water)
  • water acts as a transport medium
  • it has different effects on hydrophobic and hydrophilic molecules (e.g. fat won’t dissolve in water) - key for membrane structure
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4
Q

What are calcium ions used for by humans and plants? (4)

A
  • helps produce calcium pectate for use in plant cell walls
  • a component of bones and teeth
  • key in blood clotting
  • key in muscle contraction
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5
Q

What are Iron ions used for by humans and plants? (2)

A
  • in the haem group of haemoglobin (oxygen carrier in RBCs)
  • key constituent of electron carriers in respiration
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6
Q

What are magnesium ions used for in plants?

A

Helps make chlorophyll able to absorb light

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7
Q

What are potassium ions used for in humans?

A

Maintaining electrical gradients across neurones

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8
Q

What are nitrate ions used for by humans and plants?

A

A component of amino acids, nucleic acids and chlorophyll

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9
Q

What are phosphate ions used for by humans and plants? (2)

A
  • helps form phospholipids for cell membranes
  • component of bio molecules like ATP (adenosine triphosphate) and nucleic acids
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10
Q

What are Hydrogencarbonate ions used for by humans and plants?

A

Used as a natural buffer

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11
Q

What are buffers? (2)

Why are they needed?

A
    • Chemicals or substances that resist changes to pH - meaning pH is maintained
    • when small volumes of acid/alkali are added
    • pH changes can result in enzyme denaturation, buffers prevent this and allow enzymes to operate at their optimum pH
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12
Q

Give 2 examples of buffers

A
  • HCO3- ions
  • blood proteins e.g. albumin
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13
Q

What are ions?

A

Charged particles

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14
Q

Name 7 inorganic ions

and

state their formula

A
  • calcium - Ca2+
  • iron - Fe2+
  • magnesium - Mg2+
  • potassium - K+
  • nitrate - NO3-
  • phosphate - PO43-
  • hydrogen-carbonate - HCO3-
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15
Q

What are organic molecules?

Name 3 examples

A
  • complex carbon containing molecules
  • carbohydrates, proteins and lipids
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16
Q

What are monomers and polymers?

What is the name of the process used to form polymers?

and

what does it entail?

A
  • mono - individual subunits
  • poly - many subunits joined together
  • polymerisation - adding monomers together to form polymers
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17
Q

What elements are contained in carbohydrates?

A
  • carbon
  • hydrogen
  • oxygen
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18
Q

What is the ratio between the number of hydrogen and oxygen atoms in carbohydrates?

A

2 hydrogen : 1 oxygen

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19
Q

What are the 3 types of carbohydrates?

A
  • monosaccharides
  • disaccharides
  • polysaccharides
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20
Q

What are monosaccharides?

Which 3 categories are biologically important?

A
  • simple sugars with different categories depending on no. of carbons
  • important ones:
  1. trioses (3 carbons),
  2. pentoses (5 carbons) and
  3. hexoses (6 carbon)
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21
Q

What are disaccharides? (2)

A
  • Double sugars formed from 2 monosaccharide monomers
  • which join through condensation reactions
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22
Q

What are polysaccharides? (2)

A
  • Complex molecules consisting of many monosaccharide monomers
  • bonded through condensation reactions
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23
Q

What is DNA Helicase

and

How does it work? (3)

A
  • An enzyme
  • breaks hydrogen bonds between complementary bases (ATCG),
  • separating into 2 polynucleotide strands
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24
Q

What is DNA polymerase

and

How does it work?

A
  • an enzyme
  • joins mononucleotides together to form a new polynucleotide strand
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25
Which **2 enzymes** are used in **DNA replication**?
- DNA helicase - DNA polymerase
26
Why is **DNA replication** referred to as being **semi-conservative**?
Each newly synthesized DNA molecule **retains 1 parental strand** and **1 newly synthesized strand**
27
What are **hydrogen bonds**? (Biology) **How** are they **broken**?
- **Weak bonds** between **hydrogen and oxygen ions** in water due to *uneven distribution* of *covalent bonds* - **broken** by **thermal energy**
28
What are **isomers**? Name **2** examples
- Compounds with the **same chemical formula** but *slightly* **different structural formula** - a-glucose and ß-glucose
29
How do the **structures** of **a-glucose** and **ß-glucose** *differ*?
- **a-glucose**: the **hydroxyl group** connected to *carbon 1* **points downward** (hydrogen points up) - ß-glucose: the **hydroxyl group points upward** (hydrogen points down)
30
Which **polysaccharide(s)** contain **a-glucose**?
- starch - glycogen
31
Which **polysaccharide(s)** contain **ß-glucose**?
Cellulose
32
What are the **properties** of **disaccharides**? (**2**)
- soluble in water - sweet tasting
33
What are **condensation reactions**? (*In amylose chains*) (**4**)
- **reversible reactions** where the **Hydroxyl group** of the **Carbon 1** *on a monosaccharide* - and the **hydrogen** (from the *hydroxyl group*) of the **carbon 4** on another - are **ejected** as a **water molecule** - leaving a **1-4 glycosidic bond**
34
What is **hydrolysis**?
- When a **water molecule** is *added* to a **disaccharide** - *breaking* the **1-4 glycosidic bond** - and **separating** it into **monosaccharides**
35
Name **2 disaccharides** and state their **monosaccharide components**
- maltose - 2 a-glucose - sucrose - 1 a-glucose and 1 fructose
36
How is the **structure of fructose** *visibly different* to **glucose**?
- **Fructose** has a **pentagonal** shape, - whereas both forms of **glucose** are **hexagonal**
37
What are the **properties** of **polysaccharides**? (**2**)
- insoluble in water - not sweet
38
What are the **2 forms** of **starch chains**?
- Amylose - amylopectin
39
How is **amylose structured**? (**3**)
- **long chains** of *a-glucose* with alpha **1-4 glycosidic bonds** - that form a **helical structure** *held in place* by **hydrogen bonds** - chains are **unbranched**
40
How is **amylopectin structured**? (**4**)
- **long chains** of alpha **1-4 glycosidic bonds** - with **branched** ends - formed by alpha **1-6 glycosidic bonds** - chains form **helical shape** *held in place* by **hydrogen bonds**
41
How is **amylose different** to **amylopectin**?
- Amylopectin is **branched** and contains **1-6 glycosidic bonds** - amylose does not
42
**Why** is **starch** a **good storage molecule**? (**4**)
- amylose and amylopectin are **compact and dense** *with glucose* - **insoluble / osmotically inert**: doesn’t affect *cell’s water relations* - **large molecule**, so *doesn’t leave cell membrane* - *amylopectin*: *branching creates* **terminal ends - easily hydrolysed** *especially* in **rapid enzymatic breakdown**
43
**Where** is **starch** found? (Amylose and amylopectin) And In what **form**?
- Plant cytoplasm or chloroplasts - starch grains
44
**Where** is **cellulose** found?
Plant cell walls
45
How is **glycogen structured** (**3**) What is its **function** and **where** is it found?
1. - formed of chains of a-glucose - has a-1-4 and a-1-6 glycosidic bonds - meaning it is branched 2. To **store** carbohydrates (for energy) 3. Found as **granules** in *mammalian* **liver** and **muscle cells**
46
How does *glycogen’s* **structure compare** and **contrast** with *amylopectin*? (**6**)
Contrasts: - **glycogen** is **more branched** and **chains** are **shorter** - glycogen has **no unbranched chains** - **glycogen** has *proportionally* **more terminal ends**, enabling ***faster hydrolysis*** Comparisons: - both **compact** and **insoluble** - *don’t affect cell water relations* - both have **a-1-4** and **a-1-6 glycosidic bonds** - both are formed of **a-glucose monomers**
47
How is **cellulose structured** (**5**) What is its **function** and **where** is it found?
1. - **ß-glucose** monomers form **1-4 glycosidic bonds** - *every **2nd** monomer* is **inverted** - forming **long, straight chains** - *nearby* **chains** are **hydrogen bonded together**, forming a **microfibril** - many **microfibrils** *form* a **cellulose fibre** 2. Structural support for plants 3. Plant cell walls
48
What **effect** does the **flipping** of *alternate monomers in cellulose* have on its **structure**? (**2**)
- Chains are very straight - due to the **-CH2OH groups** *alternating* **above** and **below** the chain
49
**Why** do **hydrogen bonds form** between *adjacent **cellulose chains***?
**Oxygen** and the **-CH2OH** are **available** on **both sides** of chains
50
What is the **chemical formula** of **fructose**?
C6H12O6
51
What is the **chemical formula** of **glucose**?
C6H12O6
52
What is the **formula** of **Glycerol**?
C3H8O3
53
What **group** do **fatty acids** belong to?
Carboxylic / organic acids
54
What **elements** do **lipids** contain?
Carbon, hydrogen and oxygen
55
Although **lipids** are *hydrophobic*, what **solvents** do they **dissolve** in?
Organic ones like ether and ethanol
56
What are the **2 main types** of **lipids** Where are they found?
- **triglycerides** - fats and oils - **phospholipids** - cell membranes
57
**How** are **triglycerides formed**? What else is **formed**? What **bonds** are formed? What is **formed** in the **reverse** of this, and what is this **called**?
- **Condensation** reactions between **1 glycerol** and **3 fatty acid** molecules + **3 molecules of water** *liberated* - **ester bonds** - **1 glycerol** and **3 fatty acids** *reformed* - **Hydrolysis** (by adding 3 molecules of water)
58
**Where** do **condensation reactions** occur in **triglycerides**? What is this process **also known as**?
1. Between: - The (**-OH**) group of *glycerol* and - the (**-COOH**) group of *fatty acids* 2. Esterfication
59
What are the **differences** between **saturated** and **unsaturated fatty acids**? (**2**)
- **saturated** consist of chains of **single carbon bonds** and **hydrogen** - **unsaturated** have **at least 1 C=C double bond** - *unsaturated* **aren’t as straight** structurally
60
What is the **name** of an *unsaturated fatty acid* with **1 C=C bond**?
Monosaturated fatty acids
61
What is the **name** of an *unsaturated fatty acid* with **more than 1 C=C bond**?
Polyunsaturated fatty acids
62
**How** are **phospholipids formed**?
- **condensation reactions** between **1 glycerol** molecule and **2 fatty acid** molecules - as well as a **phosphate group** - **replaces a fatty acid** in a triglyceride
63
What are the **properties** of **phospholipids**? (**4**)
- **fatty acid** molecules are **hydrophobic** - **phosphate** makes the **glycerol hydrophilic** and *soluble in water* - they are **polar** - *key in their role in cell membranes* - **cell membranes** contain the **steroid cholesterol**, located *among hydrocarbon chains*
64
What are the **functions** of **triglycerides**? (**3**)
- **energy store** - release more energy per unit mass than carbs - **insulation** (thermally) e.g. as *adipose tissue* - **protection** of **body organs**
65
What **type of lipid** are **fats** and **oils**? What are the **differences** between both *generally*? (**2**)
1. Triglycerides 2. - **fats are solid** at room temp, **oils are liquid** - **fats** are *usually* **animal products** - **oils** are **made by plants**
66
What **elements** are contained in a **protein** molecule?
- carbon - hydrogen - oxygen - nitrogen - *sometimes* sulphur
67
How many **amino acids** are in **1 protein**?
20
68
What is a **protein’s shape** determined by? (**2**)
- It’s *sequence* of amino acids - and the **bonds / attractions** *between their R-groups*
69
How does each **amino acid differ**?
Each has a **different R group**
70
What is the **R group** of **glycine**?
-H
71
What is the **R group** of **alanine**?
**-CH3** (methyl group)
72
What is the **R group** of **cysteine**?
-CH3 -SH
73
What **reaction** is responsible for **linking amino acids**? What **bonds** are produced? What is the **inverse reaction** called?
- Condensation - peptide bonds - hydrolysis
74
What is a **pair** of **bonded amino acids** called?
A *dipeptide*
75
What is a **polypeptide**?
**Many amino acids** joined together
76
What are the **4 levels** of **structure** in a **protein**?
- primary - secondary - tertiary - quaternary
77
What is a **primary structure** *caused* by? (protein)
The *sequence of amino acids* in a **polypeptide chain**
78
What is a **secondary structure** *caused* by? (protein) What **shapes** can they be?
- **hydrogen bonds** between **(-C=O)-** and **(-NH)+** - **a-helix** (held by *hydrogen bonds*) or **ß-pleated sheets** - more rigid and less flexible *(due to hydrogen bonds)*
79
What **bonds/attractions** can be *present between R-groups* in a **tertiary structure**? (protein) What are their **properties**? (**4**)
- **hydrogen bonds** - *weak* and easily broken - **ionic bonds** - strong but *weak* with *pH changes* - **disulfide bonds / bridges** - *very strong* covalent bonds + **hydrophobic interactions** between amino acids and hydrophobic R-groups - R-groups tend to be *surrounded* by other *parts of the polypeptide*
80
**How** are **tertiary protein structures** formed *broadly*? (**3**)
- further **folding** - creating a **3d shape** - due to a **range of bonds** *between* **R-groups** of amino acids in the chain | *bonds covered in another card*
81
What do **quaternary protein structures** *consist of*? (**3**) What are the **2 types**?
1. - *2 or more* polypeptides (Which can be folded into B-pleated sheets or a-helices) - with *some containing* **prosthetic groups - conjugated proteins** 2. **Globular** and **fibrous**
82
What are **prosthetic groups**? What are **proteins** *containing* **prosthetic groups** called?
- **Non-protein components** of proteins e.g. the haem group of haemoglobin (which contains iron) - **conjugated** proteins
83
Name **3 conjugated proteins** Include what **type of protein** they are.
Any 3 from: Globular: - haemoglobin - glycoprotein - enzymes - insulin Fibrous: - collagen - actin - keratin Etc.
84
What are **prions**? (**2**)
- A *type* of **protein** - found in the **mammalian nervous system** and *some other animals*
85
What is the **notation** for: 1. Normal 2. Disease causing *Prions*?
- normal = PrP / PrPc - disease causing = PrPsc
86
**Structurally**, how do *disease causing prions* ***differ* from *normal prions***? (**2**)
- disease causing = **missfolded** - disease causing = *greater proportion* of **ß-pleated sheets** *than* **a-helices**
87
**Why** does the *presence* of **a disease causing prion** pose a *threat*? (**4**)
- causes a **chain reaction** where other **normal prions** become *progressively* **missfolded** - this **increases** *no. of* **disease causing prions** - if at a *threshold level*, **neurodegenerative disorders** can emerge in *nervous tissue* - this can lead to **death**
88
What are the **2 key features** of **disease causing prions**?
- can *replicate* - are *infectious*
89
*How long* can **prions** be **incubated** for?
5 to 20 years
90
Name **3 ways** *diseases caused by prions* can arise.
- *normal prions* **spontaneously** adopt the *PrPsc form* - **mutations** in **DNA bases** *coding for prion proteins* —> *disease-causing form* can be *passed* to offspring - eating **contaminated food** with diseased prions
91
Name **3 prion diseases** and What **animals** they are found in
- **scraple** in *sheep* - ***Bovine Spongiform Encephalopathy* (BSE)** - ‘mad *cow* disease’ - ***variant Creutzfeldt-Jakob disease* (vCJD)** - *in humans* - acquired usually by *eating beef with BSE*
92
What’s the **subunit** of a **nucleic acid**?
A nucleotide
93
What are the **components** of a **nucleotide**?
- phosphate - a Pentose sugar - a base
94
What are the **bases** found in **DNA**? Include *how they pair*
1. - Adenine - Guanine - Cytosine - Thymine 2. AT and CG
95
What are the **bases** found in **RNA**? Include *how they pair*
1. - Adenine - Cytosine - Uracil - Guanine 2. They don’t (single strand)
96
Why are strands of DNA described as being **anti parallel**?
2 strands run in opposite directions
97
What **bonds** are there between *phosphates* and *pentose sugars* in nucleic acids?
Phosphodiester links
98
What are the *differences* between **DNA** and **RNA**? (**4**)
- DNA contains **deoxyribose sugar**, RNA contains **ribose sugar** - subunits of **DNA** are **deoxyribonucleotides**, subunits of **RNA** are **ribonucleotides** - DNA is *longer and double stranded*, RNA is *shorter and single stranded* - DNA contains **thymine**, RNA contains **Uracil** instead
99
What are the **3 types** of **RNA**?
- mRNA - messenger RNA - tRNA - transfer RNA - rRNA - ribosomal RNA
100
What are the *roles* of the **3 types** of **RNA**?
- **rRNA**: *component* of *ribosomes* - **tRNA**: carries *amino acids to ribosomes* where protein synthesis takes place - **mRNA**: carries *code from DNA* in the nucleus *to a ribosome* where protein synthesis takes place
101
What is the **function** of **DNA**? (**2**)
- Acts as the **genetic code** for *amino acid synthesis* - according to **base triplets**
102
What are the **ends** of a **polynucleotide strand** called? **Why** are they called this?
- 5’ ends and 3’ ends - 5’ ends are *closest to the 5th carbon* of a *sugar* - 3’ ends are *closest to the 3rd carbon* of a *sugar*
103
What is a **gene**?
A **sequence of DNA** that *codes for a polypeptide*
104
Outline the *process* of **semiconservative replication** (**4**)
- **DNA helicase** *breaks hydrogen bonds* between complementary bases to reveal *2 polynucleotide strands* - **DNA polymerase** moves along each strand and acts as a *template for the synthesis of a new strand* - DNA polymerase *catalyses* the *joining of free deoxyribonucleotides* to each original strand - **new complementary strands** form - *process continues* along entire length of DNA molecule
105
Outline the **Meselson Stahl experiment** (**4**)
- *cultured E. coli* using **15N** - **15N** *incorporated into* the *bases* of the **DNA in all** the bacteria over time; *bacteria with 14N died and were replaced* - bacteria were *transferred* to a medium with **14N** - bacteria **extracted and analysed** using a *centrifuge* at intervals: 1. While *growing before* **15N** 2. While *growing in* **15N** 3. *1st gen after transfer* to **14N** 4. *2nd gen after transfer* to **14N**
106
*Explain* the **results** of the **Meselson Stahl experiment** (**3**) What **trend** would *results follow after a further gen*?
1. - **gen 0**: all *DNA at bottom* of centrifuge tube - **15N bases** - **gen 1**: *DNA in middle* - *1 strand **15N** bases*, *1 strand **14N** bases* —> medium mass - **gen 2**: *half DNA = medium mass* with **15N and 14N bases**, *other half only DNA* with **14N bases** (top) 2. More DNA with 14N bases, less mixed DNA

CCEA AS Biology Units 1, 2 And 3 (16 decks)

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