Organisms and Life Processes – Lecture Review

A comprehensive set of question-and-answer flashcards covering cell structures, life processes, enzyme activity, respiration, transport mechanisms, and organisation levels discussed in the lecture notes.

Name the eight life processes shared by most living organisms.

Nutrition, respiration, excretion, response to stimuli, movement, control of internal conditions, reproduction, and growth & development.

What is cytoplasm?

The living, jelly-like material inside a cell where metabolic reactions occur.

Which organelles are visible only with an electron microscope and not a light microscope?

Most organelles such as ribosomes, detailed mitochondria structure, and internal membranes.

List the structures common to both animal and plant cells.

Nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.

Which three structures are found only in plant cells?

Cell wall, permanent vacuole, and chloroplasts.

State the function of the nucleus.

Contains chromosomes/genes that control cell activities by coding for proteins.

What is the role of ribosomes?

Sites where proteins are assembled from amino acids using genetic instructions.

Why are mitochondria abundant in muscle and nerve cells?

They release most of the cell’s energy through aerobic respiration, which these cells need in large amounts.

Give two characteristics of the cell membrane.

Partially/selectively permeable and forms a boundary controlling substance movement in and out of the cell.

What material makes up the plant cell wall and what is its function?

Cellulose; provides strength, shape, and protection while being freely permeable.

State two functions of the permanent vacuole in mature plant cells.

Stores cell sap (water, sugars, ions) and helps maintain cell rigidity via turgor pressure.

What pigment is contained in chloroplasts and what is its role?

Chlorophyll; absorbs light energy for photosynthesis.

Define metabolic reactions.

All the chemical reactions that take place in a cell; their sum is the cell’s metabolism.

Why are enzymes described as biological catalysts?

They speed up metabolic reactions without being used up themselves.

Differentiate between extracellular and intracellular enzymes.

Extracellular enzymes act outside cells (e.g., digestive enzymes); intracellular enzymes function inside cells.

Explain the lock and key model of enzyme action.

A substrate fits precisely into an enzyme’s active site, allowing a specific reaction to occur.

What is meant by the optimum temperature of an enzyme?

The temperature at which the enzyme catalyses the reaction at its fastest rate.

What happens to enzymes above their optimum temperature?

They become denatured; heat permanently alters the active site so the substrate no longer fits.

Most cellular enzymes have an optimum pH of 7. Which enzyme works best at pH 2 and where?

Pepsin in the stomach.

Define ‘substrate’ in enzyme activity.

The molecule upon which an enzyme acts.

In the amylase-starch experiment, which reagent indicates the presence of starch?

Iodine solution (blue-black in starch, yellow when starch is gone).

What two harmless products does catalase produce from hydrogen peroxide?

Water and oxygen.

Provide the word equation for aerobic respiration.

Glucose + oxygen → carbon dioxide + water (+ energy).

Write the balanced symbol equation for aerobic respiration.

C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy).

What molecule is described as the energy ‘currency’ of the cell?

ATP (adenosine triphosphate).

How is ATP regenerated during respiration?

Energy from glucose oxidation adds a phosphate to ADP to reform ATP.

Give the anaerobic respiration equation in yeast.

Glucose → ethanol + carbon dioxide (+ some energy).

Give the anaerobic respiration equation in overworked muscle cells.

Glucose → lactate (+ some energy).

What is meant by ‘oxygen debt’?

The volume of oxygen required after exercise to oxidise accumulated lactate.

Define diffusion.

Net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.

List four factors that increase the rate of diffusion.

Steeper concentration gradient, larger surface area to volume ratio, shorter diffusion distance, and higher temperature.

What is active transport?

Energy-requiring movement of substances against a concentration gradient using ATP-powered membrane pumps.

Give one human and one plant example of active transport.

Glucose absorption in the small intestine; mineral ion uptake by root hairs.

Define osmosis in cells.

Net movement of water from a concentrated solution to a more concentrated solution across a partially permeable membrane.

Why do alveoli and intestinal villi have large surface areas?

To speed diffusion and absorption by providing more membrane for exchange.

What is mitosis?

Cell division that produces two genetically identical daughter cells for growth and repair.

Explain cellular differentiation.

Process by which cells become specialised in structure and function under genetic control.

Place these in order of increasing complexity: organ, tissue, system, cell.

Cell → tissue → organ → organ system.

Name three organ systems of the human body.

Examples: digestive, circulatory, respiratory (gas exchange), excretory, nervous, endocrine, reproductive.

How is a sperm cell adapted for its function?

Has a tail for swimming and a head packed with paternal genes.

Why is the plant cell wall described as freely permeable?

Its pores allow water and dissolved substances to pass through unhindered.

How do enzymes enable reactions to proceed rapidly at body temperature?

They lower the activation energy required for the reaction.

Why does increasing temperature (below optimum) speed enzyme reactions?

Molecules gain kinetic energy, collide more frequently with the active site.

In the amylase experiment, how is reaction rate calculated?

Rate = volume of starch (5 cm³) ÷ time taken for iodine to remain yellow.

What was demonstrated with germinating peas in a vacuum flask?

Respiration releases heat, increasing temperature in living peas compared with dead peas.

What indicator detects carbon dioxide from respiring organisms?

Hydrogen carbonate indicator (orange to yellow in CO₂).

Why is a cell membrane called ‘selectively permeable’?

It allows some substances to pass freely while restricting or controlling others.

State one advantage of a small cell size related to diffusion.

Higher surface area to volume ratio, allowing quicker diffusion of materials.

What powers membrane ‘pumps’ involved in active transport?

Energy released from ATP breakdown.

Why are thousands of different enzymes possible in cells?

Enzymes are proteins, and proteins can have an enormous variety of amino-acid sequences and shapes.

Which experiment uses buffer solutions to test enzyme activity across pH values?

The catalase–hydrogen peroxide investigation with potato extract.