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Biology

Organelles: Function and Structure

  • Cell Membrane: Protective barrier that regulates what enters and exits the cell; made of a phospholipid bilayer with embedded proteins.

  • Cytoplasm: Gel-like fluid that fills the cell and holds organelles; site for metabolic processes.

  • Nucleus: Control center containing genetic material (DNA); surrounded by the nuclear envelope.

  • Nuclear Membrane/Envelope: Double membrane that encloses the nucleus, regulating the movement of substances in and out.

  • Nucleolus: Found within the nucleus; responsible for ribosome production.

  • Vacuoles: Storage organelles for nutrients, waste products, or other materials; larger in plant cells.

  • Mitochondria: Powerhouse of the cell; produces ATP through cellular respiration.

  • Golgi Body/Apparatus: Modifies, sorts, and packages proteins and lipids for transport.

  • Lysosomes: Contains digestive enzymes to break down waste materials.

  • Endoplasmic Reticulum (Smooth & Rough): SmoothER synthesizes lipids; RoughER has ribosomes on its surface for protein synthesis.

  • Centrioles: Involved in cell division; help organize microtubules.

  • Ribosomes: Sites of protein synthesis; found in cytoplasm or attached to RoughER.

  • Chromatin: Complex of DNA and protein; condenses to form chromosomes during cell division.

  • Cell Wall: Rigid outer layer in plant cells, providing structure and support; made of cellulose.

  • Chloroplasts: Site of photosynthesis in plant cells; contains chlorophyll.

Differences Between Plant and Animal Cells

  • Plant cells have a cell wall, chloroplasts, and large vacuoles; animal cells do not.

  • Animal cells have centrioles and smaller vacuoles compared to plant cells.

Diffusion and Osmosis

  • Diffusion: Movement of particles from an area of higher concentration to one of lower concentration.

  • Osmosis: Diffusion of water across a selectively permeable membrane.

The Cell Cycle

  • Components: Interphase, Mitosis, Cytokinesis.

  • Interphase: Cell grows and duplicates its DNA (includes G1, S, and G2 phases).

Mitosis

  • Process of cell division resulting in two identical daughter cells.

  • Stages: Prophase, Metaphase, Anaphase, Telophase.

Cytokinesis

  • Division of the cytoplasm after mitosis; in plants, a cell plate forms; in animals, the membrane pinches.

Specialized Cells

  • Shape/features enhance function (e.g., neurons with long axons for signal transmission).

Mutations and Cancer

  • Mutation: A change in DNA sequence; can lead to cancer if it affects cell regulation.

  • Cancer: Uncontrolled cell division; causes include genetic factors, environmental exposure. Treatments may include surgery, radiation, chemotherapy.

  • Comparison: Cancer cells grow uncontrollably and don’t carry out normal functions.

Reasons for Cell Division

  • Growth, repair, reproduction, and maintenance of tissues.

Definitions

  • Metastasis: Spread of cancer cells to other parts of the body.

  • Malignant: Cancerous tumors that invade nearby tissues.

  • Benign: Non-cancerous tumors that do not spread.

  • Biopsy: Removal of tissue for diagnostic examination.

Tissue Functions

  • Epithelial: Covers surfaces and lines cavities; protects, absorbs, secretes.

  • Connective: Supports and binds other tissues; stores energy.

  • Muscle: Responsible for movement.

  • Nervous: Transmits impulses and processes information.

Blood Circulation

  • Blood moves through the heart (right atrium, right ventricle, lungs, left atrium, left ventricle, aorta) to deliver oxygen and nutrients to the body.

  • Components of Blood: Red blood cells (carry oxygen), white blood cells (immune response), platelets (clotting), plasma (liquid component).

Circulatory and Respiratory System Interaction

  • Blood transports oxygen from lungs to cells and carbon dioxide from cells to lungs for exhalation.

Respiratory System Pathway**

  • Air travels from the nose/mouth, down the trachea, into the bronchi, and into the lungs.

Breathing Mechanism

  • Inhalation: Diaphragm contracts, creating negative pressure; air flows in.

  • Exhalation: Diaphragm relaxes, pressure increases; air is expelled.

Digestive System Pathway**

  • Food travels from the mouth, down the esophagus, into the stomach, small intestine, large intestine, and out the rectum.

Epiglottis Function

  • Prevents food from entering the trachea during swallowing; crucial for protecting the airways.

Functions of Organs

Circulatory System

  • Heart: Pumps blood throughout the body.

  • Blood Vessels (arteries, veins, capillaries): Transport blood to and from the heart.

  • Blood: Carries oxygen, nutrients, and waste products.

Respiratory System

  • Nose/Mouth: Entry point for air; warms and filters it.

  • Trachea: Airway that conducts air to the lungs.

  • Lungs: Site of gas exchange (oxygen in, carbon dioxide out).

  • Diaphragm: Muscle aiding in inhalation and exhalation.

Digestive System

  • Mouth: Begins digestion via chewing and saliva.

  • Esophagus: Transports food to the stomach.

  • Stomach: Digests food with acids and enzymes.

  • Small Intestine: Absorbs nutrients from food.

  • Large Intestine: Absorbs water and prepares waste for removal.

  • Rectum: Stores waste before elimination.

Interactions Between Organ Systems

  • The circulatory system delivers nutrients and oxygen absorbed from the digestive system to cells and removes waste. The respiratory system supplies oxygen to the circulatory system and removes carbon dioxide.

Diseases Affecting Each System

  • Circulatory System: Heart disease, hypertension, stroke.

  • Respiratory System: Asthma, chronic obstructive pulmonary disease (COPD), pneumonia.

  • Digestive System: Gastroesophageal reflux disease (GERD), irritable bowel syndrome (IBS), Crohn's disease.

Functions of Plant Parts

  • Leaves: Photosynthesis, gas exchange.

  • Stem: Support, transportation of nutrients and water.

  • Roots: Absorption of water and minerals, anchorage.

Main Body Systems in Plants

  • Shoot System: Includes stems, leaves, flowers; functions in photosynthesis and reproduction.

  • Root System: Anchors the plant, absorbs water and nutrients.

Three Tissues in Plants

  • Dermal Tissue: Protects the plant and prevents water loss.

  • Vascular Tissue: Transports water (xylem) and nutrients (phloem).

  • Ground Tissue: Photosynthesis, storage, and support.

Stomata and Guard Cells

  • Stomata: Openings on leaf surfaces for gas exchange.

  • Guard Cells: Surround stomata and regulate their opening and closure based on environmental conditions (e.g., humidity, light). Stomata open during the day for photosynthesis and close at night to conserve water.

Pollination

  • Pollination occurs when pollen from the male part of a flower (anther) reaches the female part (stigma). It is essential for reproduction and the production of seeds, which leads to the growth of new plants.