Biology paper 1

What are biological molecules?

Molecules made and used by living organisms e.g. Carbohydrates, Proteins, Lipids, DNA, ATP, Water, Inorganic Ions.

What are the functions of carbohydrates?

Energy source (glucose in respiration), energy store (starch in plants, glycogen in animals), structure (cellulose in cell wall of plants).

What are the building blocks for carbohydrates called?

Monosaccharides.

What examples of monosaccharides are there?

Glucose (alpha and beta), galactose, fructose.

What is the formula for monosaccharides?

C6H12O6 (isomers = same formula but different arrangement).

What is the difference between alpha and beta glucose?

On Carbon 1, alpha glucose has a OH group on the bottom and beta glucose has a OH group on the top.

How are monosaccharides joined together?

By a condensation reaction (removing water) – between 2 OH groups.

What is the bond in carbohydrates called?

Glycosidic bond (1,4 – between carbon 1 and carbon 4).

What are examples of disaccharides?

Maltose (glucose + glucose), lactose (glucose + galactose), sucrose (glucose + fructose).

What is the formula for disaccharides?

C12H22O11.

How are polymers separated?

By hydrolysis (add water).

What is a polysaccharide?

Many monosaccharides joined by condensation reaction/glycosidic bonds.

What are examples of polysaccharides?

Starch, Glycogen, Cellulose.

What are starch and glycogen used for?

Energy stores (starch in plants, glycogen in animals), they are made out of many alpha glucose.

What is cellulose used for?

To form the cell wall in plants, made out of many beta glucose.

What is the structure of starch?

Made from Amylose (long straight chain of alpha-glucose which is coiled) and Amylopectin (straight chain of alpha-glucose with side branches).

What is the structure of glycogen?

Straight chain of alpha-glucose (1,4-glycosidic bond) with side branches (1,6-glycosidic bond).

What are properties of starch and glycogen as energy stores?

Insoluble (do not affect water potential of the cell), coiled/branched (compact, more can fit into a cell).

How do you test for starch?

Add iodine, turns blue/black.

How do you test for reducing sugar?

Heat with Benedict's, turns brick red.

How do you test for non-reducing sugar?

Heat with Benedict's – no change, add dilute hydrochloric acid (hydrolyse glycosidic bond), then add sodium hydrogen carbonate (neutralises solution), heat with Benedict's - turns brick red.

What are the two types of proteins?

Globular and Fibrous.

What are globular proteins?

Soluble proteins with a specific 3D shape e.g. enzymes, hormones, antibodies, hemoglobin.

What are fibrous proteins?

Strong/insoluble/inflexible materials e.g. collagen and keratin.

What are the building blocks for proteins?

Amino acids.

How do amino acids differ?

They have different R groups (e.g., glycine has a hydrogen in its R group).

How are amino acids joined together?

By a condensation reaction between the carboxyl group of one and an amine group of another, leaving a bond between carbon & nitrogen (called a peptide bond).

What is primary structure in proteins?

Sequence of amino acids, polypeptide chain (held by peptide bonds).

What is secondary structure in proteins?

The primary structure coils to form a helix, held by hydrogen bonds.

What is tertiary structure in proteins?

Secondary structure folds again to form the final 3D shape, held together by hydrogen/ionic/disulfide bonds.

What is quaternary structure in proteins?

Made of more than one polypeptide chain.

What is a test for protein?

Add Biuret, turns purple.

What is an enzyme?

A biological catalyst that speeds up the rate of reaction without being used up.

What makes an enzyme specific?

It has a specific active site shape; only complementary substrates can bind.

What is the lock and key model?

The active site shape is rigid, only exactly complementary substrates can bind.

What is the induced fit model?

The active site changes shape to fit the substrate.

How does substrate concentration affect enzyme activity?

As concentration increases, the rate of reaction increases until active sites are saturated.

How does temperature affect enzyme activity?

Increased temperature increases kinetic energy, up to a point called optimum, beyond which enzyme denaturation occurs.

How does pH affect enzyme activity?

Changing pH away from optimum can denature the enzyme.

What are competitive inhibitors?

Substances that occupy the active site and prevent substrates from binding.

What are non-competitive inhibitors?

Substances that bind to another site on the enzyme causing a conformational change.

What are the three types of lipids?

Triglycerides, Phospholipids, Cholesterol.

What is the structure of a triglyceride?

Made of 1 glycerol and 3 fatty acids joined by ester bonds.

Difference between saturated and unsaturated fats?

Saturated fats have no carbon double bonds, while unsaturated fats have carbon double bonds in the fatty acid R group.

What are nucleic acids?

Polymers made from nucleotides (DNA and RNA).

What is DNA?

DeoxyriboNucleic Acid that carries genes, found in all organisms.

What is the structure of DNA?

DNA is a double helix formed by nucleotides joined by hydrogen bonds based on complementary base pairing.

What is ATP and its role?

Adenosine Triphosphate is an energy carrier molecule that delivers energy for life processes.

What is the structure of ATP?

Made from 1 adenosine and 3 phosphates.

How does ATP release energy?

By hydrolysis reaction, breaking down ATP to ADP + Pi.

What role does water play in biology?

Acts as habitat, solvent, and helps in maintaining hydrostatic pressure.

What are inorganic ions?

Salts/minerals that do not contain carbon and are charged (e.g., Na+, Cl-).

What are the 5 kingdoms of living organisms?

Animal, Plant, Bacteria, Fungi, Protoctista.

What is the difference between eukaryotic and prokaryotic cells?

Eukaryotic cells have membrane-bound organelles while prokaryotic cells do not.

What are the two forms of reproduction?

Sexual and Asexual.

What is a zygote?

A fertilized egg that develops into an organism.

Define a tissue, organ, and organ system?

Tissue = a group of specialized cells, Organ = made of different tissues, Organ system = different organs working together.

How is color produced in flowers?

Due to pigments that absorb certain wavelengths of light.

What is biomass?

The total mass of organic material in an area or volume.

What is homeostasis?

The regulation of internal conditions to maintain a stable environment within an organism.