Characteristics of Living Organisms

• The study notes cover characteristics of living organisms, classification systems, organization of the organism, movement into and out of cells, biological molecules, enzyme action, and plant nutrition.

Characteristics of Living Organisms

• Living organisms exhibit movement, respiration, sensitivity, growth, reproduction, excretion, and nutrition.
• Movement involves a change in position or place.
• Respiration involves chemical reactions in cells that break down nutrient molecules to release energy for metabolism.
• Sensitivity involves the ability to detect and respond to changes in the internal or external environment.
• Growth is defined as a permanent increase in size and dry mass.
• Reproduction is the process of creating more organisms.
• Excretion refers to the removal of waste products of metabolism.
• Nutrition involves taking in materials for energy, growth, and development.

Concept and Uses of Classification Systems

• Organisms can be classified into groups based on shared features.
• A species is a group of organisms that can reproduce fertile offspring.
• The binomial system is an internationally agreed system where the scientific name of an organism is made up of two parts: genus & species.
• Dichotomous keys can be constructed and used based on identifiable features.
• Classification systems aim to reflect evolutionary relationships.
• DNA base sequences are used as a means of classification.
• Organisms that share a more recent ancestor have more similar DNA base sequences.

Classification Features

• Main features are used to place animals and plants into appropriate kingdoms.
• Classifying organisms uses features identified in sections 1.3.1 and 1.3.2.
• Organisms are placed into one of five kingdoms: animal, plant, fungus, prokaryote, protoctist by using features identified in sections 1.3.4 and 1.3.5.
• Main features can be used to place organisms into groups within the plant kingdom, including: Ferns and flowering plants (dicotyledons and monocotyledons).
• Viruses are characterized by a protein coat and genetic material.

Cell Structure

• Plant cells are compared to animal cells based on cell wall, cell membrane, nucleus, cytoplasm, chloroplasts, ribosomes, mitochondria, vacuoles.
• Bacterial cell structure includes cell wall, cell membrane, cytoplasm, ribosomes, circular DNA, and plasmids.
• New cells are produced by division of existing cells.
• Specialized cells have specific functions.
  • Ciliated cells facilitate movement of mucus in the trachea and bronchi.
  • Root hair cells are responsible for absorption.
  • Palisade mesophyll cells conduct photosynthesis.
  • Neurons conduct electrical impulses.
  • Red blood cells transport oxygen.
  • Sperm and egg cells (gametes) are involved in reproduction.
• Cell, tissue, organ, organ system, and entire organism are structural terms.
• Formula: Magnification = image size actual size

Movement into and out of Cells

• Diffusion moves particles from a high to low concentration area due to random movement.
• Energy for diffusion comes from the kinetic energy of random molecule and ion movement.
• Some substances move into and out of cells by diffusion through the cell membrane.
• Diffusion is important for gas and solute movement in living organisms.
• Factors that influence diffusion are: surface area, temperature, concentration gradient, and distance.
• Water diffuses through partially permeable membranes by osmosis.
• Water moves into/out of cells through the cell membrane.
• Plants are supported by water pressure inside the cells pressing outwards on the cell wall.
• Osmosis: Net movement of water molecules from high to low water potential through a partially permeable membrane.
• Active transport: movement of particles through a cell membrane from low to high concentration, which uses energy from respiration.
• Protein carriers transport molecules/ions across a membrane during active transport.

Biological Molecules

• Chemical elements make up carbohydrates, fats and proteins.
• Large molecules are made from smaller ones.
  • Starch, glycogen, and cellulose from glucose
  • Proteins from amino acids
  • Fats and oils from fatty acids and glycerol
• Iodine solution tests for starch
• Benedict's solution tests for reducing sugars
• The biuret test is for proteins
• Ethanol emulsion tests for fats and oils
• DCPIP test for vitamin C
• DNA molecule structure:
  • Two strands coiled together forming a double helix.
  • Each strand contains chemicals called bases.
  • Bonds between base pairs hold the strands together.
  • Bases pair: A with T, and C with G

Enzyme Action

• A catalyst increases the rate of reaction without changing itself.
• Enzymes are proteins that function as biological catalysts in metabolic reactions.
• Enzymes are important for necessary reaction rates for all living organisms.
• Enzyme action: the shape of the active site of an enzyme matches its substrate and in product formation.
• The effect of temperature and pH changes on enzyme activity are described.
• Enzyme action involves: active site, enzyme-substrate complex, substrate, and product.
• Enzymes are specific due to the complementary shape to the active site.
• Changes in temperature alter enzyme activity.
• Changes in pH alter enzyme activity in terms of shape and fit/denaturation.

Plant Nutrition

• Photosynthesis synthesizes carbohydrates from raw materials using light energy.
• Photosynthesis word equation: carbon dioxide + water glucose + oxygen (in the presence of light and chlorophyll).
• Chlorophyll is a green pigment found in chloroplasts.
• Chlorophyll transfers light energy into chemical energy for creating carbohydrates.
• Carbohydrate use and storage:
  • Starch as an energy store
  • Cellulose to build cell walls
  • Glucose supplies respiration energy
  • Sucrose transports in the phloem
  • Nectar attracts pollination insects
• Nitrate ions create amino acids.
• Magnesium ions create chlorophyll.
• Investigate the importance of chlorophyll, light and carbon dioxide (appropriate controls).
• The effects of changing light intensity, carbon dioxide concentration and temperature alter the rate of photosynthesis.
• Light and dark conditions alter gas exchange in aquatic plants using hydrogencarbonate indicator solution.
• State the balanced chemical equation for photosynthesis as: 6CO2 + 6H2O → C6H12O6 + 6O2
• Limiting factors of photosynthesis vary as a result of different environmental conditions.
• Leaves have large surface area and are thin (photosynthesis adaptation).

Leaf Structure

• Key leaf structures in dicotyledonous plants: chloroplasts, cuticle, guard cells, stomata, upper/lower epidermis, palisade/spongy mesophyll, air spaces, vascular bundles, xylem and phloem.
• The structures adapt in leaves for photosynthesis.