Biological Molecules, Enzymes & Ecology – Review

Question-and-Answer flashcards covering biological molecules, food tests, enzymes, ecology, environmental impact, and conservation topics from Chapters 4, 5, 18, and 19.

What three elements are found in all biological molecules?

Carbon (C), Hydrogen (H) and Oxygen (O)

Which two additional elements are found in nucleic acids but not in most carbohydrates or lipids?

Nitrogen (N) and Phosphorus (P)

What is the basic building block of carbohydrates?

Simple sugars called monosaccharides

Give two examples of monosaccharides.

Glucose and fructose

What disaccharide is formed from two glucose molecules?

Maltose

Name three polysaccharides and one function for each.

Starch – energy storage in plants; Glycogen – energy storage in animals; Cellulose – structural support in plant cell walls

Which type of biological molecule is composed of glycerol and three fatty acids?

A triglyceride (lipid)

State three functions of lipids in organisms.

Long-term energy storage, thermal insulation, protection of organs

What molecule forms the main component of cell membranes?

Phospholipids (a type of lipid)

Proteins are polymers of what monomers?

Amino acids

What type of bond links amino acids in a protein?

Peptide bond

List three functional roles of proteins besides enzymes.

Hormones (e.g., insulin), antibodies, structural proteins (e.g., keratin, collagen)

What are the subunits of nucleic acids called?

Nucleotides

Name the four bases found in DNA.

Adenine, Thymine, Cytosine, Guanine

Which DNA bases pair together?

A with T, C with G

Which food-test reagent turns blue-black in the presence of starch?

Iodine solution

What positive result indicates a reducing sugar after Benedict’s test and heating?

Brick-red precipitate

Which reagent is used in the Biuret test for proteins, and what color indicates a positive result?

Biuret solution; purple/violet color

What observation indicates lipids in the ethanol emulsion test?

A cloudy/milky layer forms

Define an enzyme.

A biological catalyst made of protein that speeds up chemical reactions without being used up

What is meant by an enzyme’s ‘active site’?

The specific region where the substrate binds

Describe the lock-and-key model of enzyme action.

The substrate fits exactly into the enzyme’s active site like a key in a lock

What happens to an enzyme at temperatures above its optimum?

It denatures (permanently loses its shape and function)

How does substrate concentration affect enzyme activity before saturation?

Higher substrate concentration increases reaction rate until all active sites are occupied

Name the enzyme that breaks starch into maltose.

Amylase

Which enzyme hydrolyzes proteins into amino acids?

Protease

What are the products of lipid digestion by lipase?

Fatty acids and glycerol

Define ‘population’ in ecology.

A group of individuals of the same species living in a habitat

What is a community in ecological terms?

All the populations of different species in a habitat

List the order of feeding levels from producer to top predator.

Producer → Primary consumer → Secondary consumer → Tertiary consumer

Approximately what percentage of energy is transferred from one trophic level to the next?

About 10%

Which ecological pyramid best represents the actual transfer of energy?

Pyramid of Energy

Give two abiotic factors that can affect an ecosystem.

Light intensity and temperature (others include water availability, soil pH)

Give two biotic factors that can affect an ecosystem.

Predation and competition (also disease)

State one plant adaptation to reduce water loss.

Waxy leaves (thick cuticle)

Name two animal adaptations to cold climates.

Thick fur and hibernation (migration is another)

Which gas released from burning fossil fuels contributes most to global warming?

Carbon dioxide (CO₂)

What pollutant gas causes acid rain?

Sulfur dioxide (SO₂)

Outline the first two steps of eutrophication.

1) Excess nitrates enter water; 2) Algal bloom blocks sunlight

Why does eutrophication often lead to fish deaths?

Bacteria decompose dead plants, using up oxygen, leading to low dissolved oxygen for fish

Give two harmful effects of deforestation.

Increased CO₂ (global warming) and habitat loss (also soil erosion)

How can overfishing disrupt marine ecosystems?

It depletes fish stocks and disrupts food chains

List three conservation methods used to protect biodiversity.

Protected areas, captive breeding programs, seed banks

Define sustainable development.

Using resources to meet present needs without compromising future generations

Give one example of a sustainable energy source.

Solar energy (wind energy is another)

Name two actions individuals can take to promote sustainability.

Recycle/reuse materials and reduce deforestation (also conserving energy)

What property makes plastic a persistent land pollutant?

It is non-biodegradable