Cell Biology, DNA and Enzymes

Characteristics of Living Organisms

• Organisms are grouped by shared features.
• Species: organisms that can reproduce fertile offspring.
• Classification sequence: Kingdom → Phylum → Class → Order → Family → Genus → Species (King Philip, Come Over For Good Soup).
• Binomial Nomenclature: system for naming species (Genus species) - genus capitalized, species lowercase.

Features of Organisms

• Animals: Multicellular, ingestive heterotrophs (consume other organisms).
• Plants: Multicellular, photosynthetic autotrophs (make their own food).
• Fungi: Single-celled or multicellular, heterotrophic and saprotrophic, cell walls not made of cellulose.
• Prokaryotes: Single-celled, lack a nucleus and mitochondria, often have plasmids (used in genetic engineering).
• Protists (Protoctists): Single-celled (or multicellular), eukaryotic.

Classification of Plants

• Plants are classified into ferns and flowering plants.
• Ferns: do not produce flowers or seeds, reproduce through spores.
• Flowering plants: reproduce via flowers and seeds, sub-classified into monocots (one cotyledon) and dicots (two cotyledons) based on seed structure.

Viruses

• Viruses are not considered living; they depend on a host cell for reproduction.
• Viral structure: genetic material (RNA or DNA) enclosed in a protein coat.
• Lack cellular structures like mitochondria and ribosomes.

Classification Systems

• Dichotomous keys: use visible features to classify organisms. They provide a series of choices among two options.
• Five-Kingdom classification: a system used to group eukaryotic organisms.

Cells

• All living organisms are composed of cells.
• Typical Eukaryotic Cells (animal and plant):
• Cell Membrane: regulates what enters and exits the cell.
• Cytoplasm: where cellular processes occur.
• Nucleus: contains genetic material (DNA).
• Mitochondria: site of aerobic respiration.
• Ribosomes: site of protein synthesis.

Organelles in Plant Cells

• Vacuole: maintains cell turgor pressure.
• Cell Wall: provides structural support.
• Chloroplasts: site of photosynthesis.

Prokaryotes

• Bacteria are a type of prokaryote
• lack a nucleus and other membrane-bound organelles.
• Typically have a cell wall made of peptidoglycan,
• Have a circular chromosome (DNA).

Levels of Organization

• Cells → Tissues → Organs → Organ Systems → Organism

Movement of Substances Across Membranes

• Diffusion: Movement of particles from high to low concentration (Passive Transport)
• Osmosis: Net movement of water across a semi-permeable membrane from a high to low water potential (Passive Transport).
• Active Transport: Movement of particles from low to high concentrations, requires energy (e.g., transporting certain nutrients/ions.)

Enzymes

• Biological catalysts, speed up chemical reactions; are not consumed by the reaction.
• Lock and Key Model: enzymes and substrates have specific shapes to fit together.
• Affected by temperature and pH: optimal temperatures and pHs for activity, denaturation at extreme values.

Plant Nutrition

• Photosynthesis: Plants synthesize glucose from carbon dioxide and water using light energy (Formula: 6CO2 + 6H2O → C6H12O6 + 6O2)
• Chlorophyll: absorbs light energy for photosynthesis.
• Plants require mineral nutrients (like nitrates (for amino acid production), magnesium (for chlorophyll production)

Human Nutrition

• Balanced diet: contains correct proportions of carbohydrates, proteins, fats, vitamins, minerals, and water essential for good health.
• Digestion: breakdown of large molecules into small ones.
• Enzyme examples in digestion include amylase (for carbohydrates), protease (for proteins), and lipase (for fats)
• Enzymes work best at an optimum pH and temperature.
• Dietary needs vary depending on age, gender, and lifestyle.

Digestion

• Mechanical- breaks down food physically into smaller pieces
• Chemical- uses enzymes like amylase, protease and lipase to break down large food molecules into smaller, more soluble ones.

The Heart- Circulation System

• Double circulation: two circuits in a mammal - pulmonary and systemic
• Pulmonary circulation: heart - lungs - heart (blood picks up oxygen and releases CO2)
• Systemic circulation: heart -body cells - heart

Blood

• Plasma: transports blood cells and dissolved substances.
• Red blood cells: contain hemoglobin to carry oxygen.
• White blood cells: defend against infections.
• Platelets: involved in blood clotting

Gas Exchange

• Lungs: organs for gas exchange, alveoli are the sites for exchange of oxygen and carbon dioxide, have a high surface area to allow efficient gas exchange.
• Breathing is the process of moving air into and out of the lungs.

Excretion

• Removal of waste products from the body (example: urea from the liver through the kidneys)
• Kidneys: filter waste from the blood and produce urine;
• Other organs: lungs(CO2), skin(water), large intestine(indigestible food).

Reproduction

• Asexual reproduction: creation of genetically identical offspring from a single parent.
• Sexual reproduction: fusion of gametes (sperm and egg) from two parents.
• Pollination: transfer of pollen from the stamen (male) to the pistil (female).
• Fertilization: fusion of male and female gametes.
• Sexual characteristics in humans: Develop in puberty.

Homeostasis

• Maintaining a stable internal environment.
• Mechanisms: negative feedback loops, regulation of temperature, blood glucose concentration, osmotic balance.

Hormones

• Chemical messengers produced by endocrine glands, carried in the blood, act on target organs.
• Examples: insulin, glucagon, adrenaline, oestrogen, testosterone.

Nervous System

• Brain and spinal cord (CNS) are the areas of coordination, nerves and neurones are part of the PNS for regulation/coordination.
• Types of neurones : sensory, relay & motor.
• Reflex arc: rapid, automatic response to a stimulus involves sensory, relay and motor neurones.

Genetic Factors

• Chromosomes: contain genetic information in the form of genes,
• Genes: segments of DNA that code for proteins - alleles control how this is expressed.
• Inherited characteristics
• Genetic diagrams like Punnett squares are used to predict possible genotypes and phenotypes of offspring.

Variation and Selection

• Genetic and environmental factors influence variation, continuous variation with a smooth gradient, discontinuous variation with distinct categories.
• Natural selection: organisms with advantageous traits are more likely to survive and reproduce, leading to adaptation.

Environmental Factors

• Organisms interact with their environment.
• Nutrient cycles like carbon and nitrogen cycles.
• Humans influence ecosystems, habitat destruction, monocultures, pollution.

Biotechnology

• Using biological organisms or systems to make products or solve problems,
• Example: gene technology, fermentation.

Test your knowledge of cell structures, functions, and differences between organisms. Explore DNA base pairings and enzyme functions. Understand enzymes, their optimal temperatures, and the molecules they act upon.