Unit 1: Building Blocks of Life

Question 1

Describe the chemical elements that make up biological molecules

Answer 1

Oxygen, Carbon, Hydrogen, Nitrogen, Calcium, Phosphorus, Potassium, Sulfur, Sodium, chlorine, Magnesium

Question 2

Describe how hydrogen bonding occurs e.g. in water molecules

Answer 2

Hydrogen Bonds are weak electrostatic bonds due to uneven distribution of electrons in some atoms. In water molecules hydrogen from one molecule bonds to another molecule’s oxygen through a hydrogen bond.

Question 3

Explain the concept of monomers and polymers

Answer 3

Monomers are single units. Polymers are many monomers bound together.

Question 4

Explain the importance of condensation and hydrolysis reactions in a range of biological molecules

Answer 4

Condensation reaction is a reaction in which two molecules combine to form a single molecule. A small molecule, often water, is removed during a condensation reaction. When water is removed a covalent bond is formed. I.e. When Glucose and Fructose go through a condensation reaction Sucrose is formed.
Hydrolysis reaction is a chemical reaction in which water is used to break down the bonds of a particular substance. I.e. When Sucrose goes through a hydrolysis reaction Glucose and Fructose are formed.

Question 5

Explain the synthesis and breakdown of a disaccharide and polysaccharide by the formation and breakage of glycosidic bonds

Answer 5

Disaccharides and polysaccharides are formed when two hydroxyl groups interact to form a strong covalent bond called the glycosidic bond. Every glycosidic bond results in one water molecule being removed, thus glycosidic bonds are formed by condensation.

Question 6

Describe the structure of starch and how it relates to its biological function.

Answer 6

Starch is an amylose(linear chain) and branched amylopectin(branched chain) Storage Carbohydrate. Starch is stored as granules in chloroplasts.

Question 7

Describe the structure of glycogen and how it relates to its biological function

Answer 7

Glycogen is an amylose chain with more branches. This makes glycogen more compact than starch for the storage in the liver and muscle cells. Glycogen breaks down to release energy.

Question 8

Describe the structure of cellulose molecules and how it relates to its biological function

Answer 8

Cellulose is chains of beta glucose(do not form helices like amylose chains) and are stronger. Cellulose is cross linked to form microfibrils of the cell wall.

Question 9

Describe the general structure of an amino acid

Answer 9

Amino group(H2N), C - H, Side Chain(known as R), Carboxyl Group(CO2H)

Question 10

Describe the synthesis and breakdown of dipeptides and polypeptides by the formation and breakage of peptide bonds.

Answer 10

When more amino acids are added to a dipeptide, a polypeptide chain is formed.
Formation of peptide bonds: Condensation reaction occurs when the OH- from the carboxylic group of one amino acid, and H- from the second amino acid’s amine group form covalent peptide bonds and release a water molecule.
Breakage of peptide bonds: Hydrolysis reaction adds the water molecule back into the amino acid to break the peptide bond.

Question 11

Describe the levels of protein structure

Answer 11

Primary: sequence of amino acids(determined by inherited genetic information).
Secondary: elements are stabilised by hydrogen bonds between specific local sequences of amino acids the polypeptide backbone(usually are the a helix and the B strands that make up B pleated sheets).
Tertiary: elements of the secondary structure come together to form a 3-dimensional fold(overall shape is stabilised by interactions between R groups).
Quaternary: result when two or more polypeptide chains form an interacting complex.

Question 12

Describe the structure and function of globular proteins including a conjugated protein

Answer 12

Globular proteins usually have a spherical shape caused by tightly folded polypeptide chains. The chains are usually folded so that hydrophobic groups are on the inside, while the hydrophilic groups are on the outside.

Question 13

Compare the properties and functions of fibrous proteins

Answer 13

Fibrous proteins are formed from parallel polypeptide chains held together by cross-links. These form, rope-like fibres, with high tensile strength and are generally insoluble in water.
Collagen: the main component of connective tissue such as ligaments, tendons, cartilage.
Keratin: the main component of hard structures such as hair, nails, claws and hooves.
Silk: forms spiders’ webs and silkworms’ cocoons.

Question 14

Identify the key inorganic ions that are involved in biological processes

Answer 14

Nitrate,Phosphate, Chloride, Calcium, Sodium, and Iron Ions

Question 15

Describe the structure of a triglyceride and a phospholipid as examples of macromolecules

Answer 15

Triglycerides are three fatty acids joined to glycerol by an ester linkage.
Phospholipids include Hydrophobic tails(made of fatty acids and glycerol) and Hydrophilic Heads(made of phosphate and choline)

Question 16

Explain the synthesis and breakdown of triglycerides by the formation and breakage of ester bonds between fatty acids and glycerol

Answer 16

Condensation reaction between glycerol and a fatty acid form a triglyceride. this is an ester bond that can be broken down by hydrolysis reaction.

Question 17

Explain how the properties of triglycerides relate to its function in living organisms

Answer 17

Triglycerides are a major component of blood and covers the internal organs and protects them from physical ‘trauma’ or ‘shock’.

Question 18

Explain how the properties of phospholipids relate to its function in living organisms

Answer 18

When phospholipids are added to water, they self-assemble into double-layered structures called bilayers. The Hydrophobic tails point toward the interior resulting in a bilayer arrangement found in cell membranes. The existence of cells depends on phospholipids.

Question 19

Explain how the properties of cholesterol molecules relate to its functions in living organisms

Answer 19

Cholesterol, a type of steroid, is a component in animal cell membranes and a precursor from which other steroids are synthesized. Synthesised in the liver- also obtained from eating animal products. Needed for cell membranes, brain and nerve tissue, steroid hormones and Vitamin D. A high level of cholesterol in the blood clogs arteries, by forming plaques, and may contribute to cardiovascular disease.

Question 20

Understand the difference between prokaryote and eukaryote cell structure

Answer 20

Eukaryotic cells have a nucleus and other membrane-bound compartments. Prokaryote cells are about 1um^3 while eukaryote cells are 1000x larger at about 1000um^3.

Question 21

Understand the reason why eukaryote cells are compartmentalised into organelles

Answer 21

Eukaryote cells are compartmentalised into organelles to make diffusion of molecules take a shorter amount of time and chemical reactions occur faster.

Question 22

Describe the structure and function of the main eukaryote organelles

Answer 22

Plasma membrane: surrounds the contents of the cell and defines its outer boundary. Acts as a barrier, Controls transport into and out of the cell, Passes signals from the environment to the cell, Connects to other cells, concentrates enzyme activity.
Mitochondria: mainly responsible for producing energy for the cell. Plastic and can change shape and move around the cell. Inner membrane contains the electron transport chain and ATP synthase molecules. Contain their own DNA
Nucleus: home to DNA and is the control centre of the cell. nuclear pores allow signals to enter the nucleus and mRNA to leave the nucleus.
Nucleolus: region within nucleus that is the site of ribosome biogenesis. Highly dynamic and can change over time.
Ribosomes make proteins(‘read’ the sequence of mRNA and link together the appropriate individual amino acids to make the protein).
Endoplasmic reticulum: Rough contains ribosomes and is the site of protein synthesis. Smooth is the site of a variety of metabolic processes such as steroid metabolism.
Golgi: made up of membranes. packages proteins into membrane-bound parcels which are then transported to other parts of the cell or for secretion.
Endosomes: membrane enclosed vesicles that are created when the plasma membrane pulls large particles into the cell. transported into the cell where they fuse with lysosomes.
Lysosomes: variety of powerful degradative enzymes that breakdown proteins and other biological molecules into their constituent parts. Part of cell’s recycling system.
Cytoskeleton: series of fibres that runs throughout the cell. Provides mechanical strength and support for cells, allows cells to change shape and move, provides the cell’s transport system to move organelles and vesicles around, separates chromosomes and splits cells in half during cell division.
Vacuole: functions as storage for water and nutrients but also helps maintain pressure on the cell wall.
Cell wall: provides more support and strength than the plasma membrane.
Chloroplasts: similar to mitochondria but in plants. make carbohydrates through photosynthesis. double membrane with own DNA

Question 23

Explain the evolutionary origins of mitochondria and chloroplasts

Answer 23

It is thought that both mitochondria and chloroplasts were originally free-living prokaryote cells that were phagocytosed by a cell and kept rather than broken down for parts. This symbiosis between the two cells eventually evolved into the organelles we see today. This is known as the endosymbiotic theory.

Question 24

Describe the structure of a light microscope and explain the function of the main components

Answer 24

Light source, condenser lens, specimen, objective lens, eyepiece lens, image viewed directly.

Question 25

Describe some commonly used stains to study cell structure

Answer 25

Hematoxylin and Eosin stain: most commonly used stain, Hematoxylin stains(purple) acidic structures such as nucleus. Eosin stains(pink) basic structures such as the cytoplasm.
Azan trichrome stain: nuclei are stained bright red, collagen, basement membrane and mucin are stained blue, muscle and red blood cells are stained orange to red.

Question 26

Describe the principles of fluorescence microscopy and other key microscopy techniques

Answer 26

First barrier filter: lets through only blue light with a wavelength between 450 and 490nm.
Beam-splitting mirror: reflects light below 510 nm but transmits light about 510nm.
Second barrier filter: cuts out unwanted fluorescent signals, passing the specific green fluorescein emission between 520 and 560nm.

Question 27

Explain how microscopy can be used to understand the structure and function of cells

Answer 27

Transmission electron microscopy provides the highest resolution possible. Uses antibodies labelled with gold to detect cellular structures.

Question 28

Describe the main stages of the cell cycle in eukaryote cells and explain what happens in the cells during each stage

Answer 28

G1 Phase: protein synthesis- which means there is also lots of gene transcription and RNA synthesis occurring. duplicate organelles in order that each daughter cell will have enough to meet its needs. Highly metabolically active and require lots of energy.
S Phase: Begins to duplicate DNA. An extra copy of each chromosome is made and the two copies are joined at the centromere.
G2 Phase: Another rapid period of growth as the cell readies itself for mitosis. Checks its DNA to make sure it has been copied correctly.
M Phase: Nuclear envelope breaks down, the mitotic spindle forms and the chromosomes are separated.
Stages of M phase: Prophase(chromatin in the nucleus condenses into chromosomes and become visible), Prometaphase(microtubules emerge from spindle poles and start searching for chromosomes), Metaphase(chromosomes align at the centre of the cell), Anaphase(each chromosome’s sister chromatids separate), and Telophase(the chromosomes have reached the opposite ends of the cell).

Question 29

Explain the role of the cytoskeleton in cell division

Answer 29

Provides intracellular shape, facilitates locomotion, assists transport, forms spindle apparatus, resists compression, enables cell migration, facilitates cytokinesis.

Question 30

Describe the differences in cell division between plant, animal, and bacterial cells

Answer 30

Plants: Cell division is controlled by the activity of cyclin dependent kinase.
Animals: G1, S, G2, M
Bacterial: Chromosome replication begins, replication continues, replication finishes, two daughter cells result.

Question 31

Explain the function of cell cycle checkpoints

Answer 31

End of G1: DNA damage checkpoint: entrance into S is blocked if genome is damaged.
S: DNA damage checkpoint: DNA replication halted if genome is damaged.
End of G2: entrance into M blocked if DNA replication is not completed.
M: Anaphase blocked if chromatids are not properly assembled on mitotic spindle.

Question 32

Explain why multicellular organisms have a diverse range of cell types

Answer 32

Multicellular organisms are composed of more than one cell, with groups of cells differentiating to take on specialized functions.

Question 33

Describe the different types of stem cells and their roles

Answer 33

Totipotent: Capable of producing any cell type.
Pluripotent: Capable of producing any cell within a major lineage.
Multi-potent: Capable of producing a restricted set of related cells

Question 34

Describe the different types of tissues- epithelial, connective, muscle, and neuronal

Answer 34

Epithelial: linings and main components of most organs
Connective: mainly binds and supports other tissues. Contains sparsely packed cells scattered throughout an extracellular matrix. Matrix consists of fibres in a liquid, jellylike, or solid foundation
Muscle: skeletal(next to bones), smooth(intestines), cardiac(heart).
Neuronal: Neurons and Glia cells

Question 35

Describe the different ways that cells are connected to each other in tissues

Answer 35

Cells are joined together and attached to the extracellular matrix. This happens through different types cell junctions(Tight junction, desmosomes, gap junction) and involves the cytoskeleton

Question 36

Describe the key features of bacteria, archaea, fungi and protists, including size range, genome structure, cell structure and replication strategies

Answer 36

Bacteria: single-celled prokaryotes, asexual reproduction by binary fission. free-living, commensals, mutualists, Pathogens, 1 circular chromosome, no nucleus, may have one or more plasmids, cell morphologies(spherical, rods, spirals), peptidoglycan in cell wall.
Archaea: Single-celled prokaryotes, asexual reproduction, lack peptidoglycan in cell wall, unique cell membrane lipids, 1 circular chromosome, no nucleus, may have one or more plasmids, Forms(spherical, rods, spirals, rectangles/squares, lemon-shaped), free-living(many are extremophiles), commensals.
Fungi: Single-celled and multicellular eukaryotes, asexual and sexual reproduction, chitin in cell wall, multiple linear chromosomes within the nucleus, yeasts or moulds or both, decomposers, mutualists, pathogens.
Protists: single-celled and multicellular eukaryotes(slime molds, algae, amoebae), asexual or sexual reproduction, multiple linear chromosomes within the nucleus, most unicellular, some multicellular, free-living, pathogenic, mutualistic.

Question 37

Describe the key features of viruses including size range, genome structure and capsid structures

Answer 37

Particles: genome in a protein coat.
May have an envelope, multiply only in living cells and often cause disease.
Are not living-no metabolism. Do not grow-they are assembled from constituent parts.
Virus-specified proteins are synthesized using host ribosomes.

Question 38

Explain why viruses are considered non-living and provide an overview of the general virus replication cycle

Answer 38

Viruses are considered non-living as they only replicate through living cells.
1. Entry and uncoating.
2. Replication(Viral DNA is replicated)
3. Transcription and manufacture of capsid proteins
4. Self-assembly of new virus particles and their exit from the cell.

Question 39

Explain the term ‘niche’ and describe how this relates to the different types of environments that microbes inhabit

Answer 39

Niche: set of environmental conditions in which a species of microbe can replicate.

Question 40

Explain the difference between a pathogen, commensal and mutualist

Answer 40

Pathogenic: interact with host organism; host damaged
Mutualistic: interact with host organism; both partners benefit
Commensal: interact with host organism; one partner benefits, other unaffected

Question 41

Describe some of the ways in which microbes affect our health, food and environment

Answer 41

Microbes have been used for centuries to make fermented foods such as yoghurt, kimchi, vinegar, soy sauce, bread, beer and wine. Microbes causing food spoilage lead to food waste.

Question 42

Describe some of the ways in which microbes can be used to benefit society

Answer 42

Bacteriophages: used to increase food security by reducing bacterial diseases of crop plants and livestock.
Microbes have enormous metabolic diversity and some can be used to clean up pollution such as crude oil spills: bioremediation.