Topic 1

Question 1

What are the characteristics of life?

Answer 1

Composed of common elements, made of cells, has genetic information, grows and changes, responds to the environment, uses pre-existing molecules to make new molecules, extracts energy from the environment and uses it, exists in populations and evolves

Question 2

Provide the reasons for viruses being living

Answer 2

They contain nucleic acids, they can replicate, they can evolve

Question 3

Provides the reasons against viruses being living

Answer 3

They cannot replicate by themselves, do not have the same metabolic pathways as other living organisms, not made of cells, can’t extract energy

Question 4

Steps of natural selection

Answer 4

Variation occurs in a population
Individuals with more desirable traits are more likely to survive, thrive, and reproduce
Eventually speciation may occur, where a new species forms

Question 5

Two theories of how life began

Answer 5

Life formed spontaneously on Earth; non-living molecules created
Life came from space, such as from another planet or comet

Question 6

What did the Miller-Urey experiments find?

Answer 6

They tried to replicate Earths atmosphere from when they believed life began. Their findings found the following could be produced.
The bases present in DNA and RNA
All 20 amino acids
Some 3 and 6 carbon sugars
Fatty acids
Vitamin B6, NAD and organic acids

Question 7

What happened for life to arise?

Answer 7

Liquid water appeared

Question 8

What happened during the Cambrian Explosion

Answer 8

A rapid diversification of life, which is when most of the big animal groups appeared.

Question 9

What are stromatolites?

Answer 9

Layers of calcium carbonate that typically form in saline water. The layers trap water and debris which can be fossilised. Some fossilised bacteria has been found from 3.7 B years ago, so life must be older than that.

Question 10

Properties of water that are crucial for life

Answer 10

High vaporisation point, high heat capacity

Question 11

Why does water has such a high boiling point?

Answer 11

Hydrogen bonding

Question 12

Cohesion

Answer 12

Hydrogen bonding between water molecules

Question 13

Adhesions

Answer 13

Attraction of water to other molecules

Question 14

Hydrophilic

Answer 14

Polar molecules are attracted to water

Question 15

Hydrophobic

Answer 15

Non-polar molecules are attracted to each other and not water

Question 16

How does pH affect life?

Answer 16

Influences rate of biological reactions, can affect 3D structure of molecules.

Question 17

What is a macromolecule?

Answer 17

Polymers made up of THOUSANDS of atoms

Question 18

What is a saccharide?

Answer 18

A sugar

Question 19

What are the 3 main types of carbohydrate?

Answer 19

Monosaccharide, disaccharide, polysaccharide

Question 20

How do monosaccharides bond together into di or polysaccharides?

Answer 20

Two hydroxyl groups bond together in a condensation reaction. The bond is called a glycosidic linkage.

Question 21

Who determined the double helix model?

Answer 21

Watson and Crick (1950s)

Question 22

Which bases are single ringed, and which are double-ringed?

Answer 22

Single: cytosine, thymine, uracil
Double: adenine, guanine

Question 23

What do you need to make a nucleotide

Answer 23

A nucleoside ( a base and either ribose or deoxyribose) and a phosphate

Question 24

How do nucleotides make nucleic acids

Answer 24

Condensation reactions. Hydroxyl from the third and fifth carbons bond with the phosphate next to it’s hydroxyl group. This is called a phosphodiester bond. This makes the backbone of the nucleic acid.

Question 25

How do the two DNA strands bond together

Answer 25

The H and NH and the O and the HN groups bond together using hydrogen bonding.

Question 26

Which way does the DNA go?

Answer 26

From the 5 prime to the 3 prime carbons

Question 27

What are the types of RNA

Answer 27

mRNA- messenger tRNA- transfer rRNA- ribosomal

Question 28

How do proteins form?

Answer 28

Amino acids bond together in a condensation reaction (OH reacts with H). The bond is called a peptide bond.

Question 29

Properties of different side-chains

Answer 29

Non-polar, hydrophobic: dispersion forces Polar, electrically charged, hydrophilic: ionic interactions Polar, uncharged, hydrophilic: dipole-dipole or hydrogen bonds

Question 30

What are lipids?

Answer 30

Large groups of molecules that are generally non-polar, and do not make long polymer chains.

Question 31

Saturated fatty acids

Answer 31

Saturated with hydrogen, no double bonds, pack closely together, higher melting point

Question 32

Unsaturated fatty acids

Answer 32

Double bonds instead of hydrogens, which make the backbone more flexible. Tend to have a lower melting point.

Question 33

How to make a triglyceride

Answer 33

Glycerol plus 3 fatty acids that bond using condensation. This is an ester bond.

Question 34

Phospholipids

Answer 34

Non-polar, hydrophilic heads, hydrophobic tails.

Question 35

What was Earth’s early atmosphere like?

Answer 35

No oxygen, high carbon dioxide, ammonia and methane. No ozone layer so intense radiation.

Question 36

Why are photosynthetic Cyanobacteria important?

Answer 36

They turned carbon dioxide from our atmosphere into oxygen, which meant the ozone layer could exist and more life could appear.

Question 37

What are the 3 super kingdom

Answer 37

Archaea, Bacteria, Eukaryotes

Question 38

What makes archaea and bacteria different?

Answer 38

Morphologically, they are the same. When they were sequenced, archaean genes had never been seen before Very different genetically Archway protein synthesis more similar to eukaryotes

Question 39

What do all prokaryotes contain?

Answer 39

A cell membrane DNA inside a nucleoid Cytoplasm Ribosomes

Question 40

Some features of bacteria

Answer 40

Capsule made of polysaccharides Cell wall and a capsule Flagellum (sometimes) Pili

Question 41

What is a ribosome?

Answer 41

Small structure made of 2 subunits of rRNA and proteins. They are responsible for protein synthesis which happens either in the cytosol or on the ER.

Question 42

Features of gram positive bacteria

Answer 42

Stains purple, simple cell wall, single layer, thick cell wall, peptidoglycan layer is thick, no outer membrane, low levels of lipids, less toxic

Question 43

What are the features of gram negative bacteria?

Answer 43

Complex cell wall, double layered thin cell wall, very resistant to antibiotics and often more toxic.

Question 44

Difference in bacterial and archaean environments

Answer 44

Archaea love to live in extreme environments, only some bacteria do

Question 45

What does nitrogen fixing mean?

Answer 45

Bacteria that turn insoluble nitrogen gas into ammonia

Question 46

How is DNA stored in a prokaryote

Answer 46

Loosely clustered in a region called the nucleoid

Question 47

When did eukaryotes evolve?

Answer 47

At least 2.1B years ago

Question 48

Primary endosymbiosis

Answer 48

Prokaryote engulfs another prokaryote. DNA extracted from engulfed prokaryote and organelle formed

Question 49

Secondary endosymbiosis

Answer 49

Eukaryote ears another eukaryote and uses the organelles that it does not have for itself. The excess organelles disappear.

Question 51

What is the endomembrane system?

Answer 51

A system of compartments that include all membrane bound components of the cell except chloroplasts, mitochondria, microbodies

Question 52

Endoplasmic reticulum

Answer 52

Both make carbs and lipids, but rough ER can also make proteins. The bio molecules are then secreted through the endomembrane

Question 53

Golgi apparatus

Answer 53

ORIGAMI MASTER packaging, collecting, distributing biomolecules. Made of golgi stacks. Receives vesicles from ER and then modified in Golgi body. Then leaves in vesicles out of Golgi and out of cell.

Question 54

Vacuoles

Answer 54

Extremely big in plants with a membrane called the tonoplast. Contains enzymes but can also be used for storage of nutrients or maintaining cell pressure.

Question 55

Lysosomes

Answer 55

Cell recycling bins Break down materials via endocytosis or old organelles (like phagocytes) acidic interior, lots of enzymes.

Question 56

Microbodies

Answer 56

Another recycle bin. Not considered part of the endomembrane system. Peroxisomes break down amino acids. Glyoxysomes break down fatty acids.

Question 58

What is the cytosol and what is it’s purpose

Answer 58

Cytosol is a jelly like fluid that helps with structure of a cell and is the site of many biochemical processes. Many biochemical intermediates are shuttles throughout the cytoplasm.

Question 59

What is the cytoskeleton and what is it’s purpose?

Answer 59

Scaffolding in the cytoplasm. It organises cell activities and anchors many organelles. Made of the following proteins: microtubules, microfilaments, intermediate filaments.

Question 60

What are microtubules?

Answer 60

Hollow tubes made of tubulin molecules. They are for movement in organelles, the cell and cell division.

Question 61

What are microfilaments?

Answer 61

Two intertwined strands of actin. Used to maintain shape in cell. Used for movement in cell and cell division. This is what creates the cleavage furrow.

Question 62

What are intermediate filaments?

Answer 62

Fibrous proteins coiled into thicker proteins; these proteins are from the keratin family. Used for structure, anchoring organelles, formation of nuclear lamina.