Cell Structure and Function

• Small cells possess a high surface area-to-volume ratio (SA:V).
• Nutrients and gases diffuse more quickly and efficiently in cells with a large SA:V.
• Larger cells have a smaller SA:V ratio, which slows diffusion.

Organelle Functions

• Nucleus: Stores DNA and controls cell activities.
• Ribosomes: Synthesize proteins.
• Rough Endoplasmic Reticulum (ER): Contains ribosomes and aids in protein production and transport.
• Smooth ER: Synthesizes lipids and detoxifies the cell.
• Golgi Apparatus: Packages and ships proteins and lipids.
• Mitochondria: Produces energy (ATP) through cellular respiration.
• Chloroplast: Site of photosynthesis in plant cells.
• Lysosomes: Breaks down waste and old cell components.
• Vacuole: Stores water, nutrients, and waste.
• Cell Membrane: Regulates the entry and exit of substances from the cell.
• Cell Wall: Provides structure and support in plant cells.
• Cytoplasm: Jelly-like fluid that houses organelles and facilitates chemical reactions.
• Centrioles: Help organize cell division in animal cells.

Plant vs. Animal Cells

• Cell Wall: Present in plant cells but absent in animal cells.
• Chloroplasts: Present in plant cells, enabling photosynthesis; absent in animal cells.
• Vacuole: Plants have one large central vacuole, while animals have small or many vacuoles.
• Shape: Plant cells are typically rectangular or boxy, whereas animal cells are round or irregular.
• Centrioles: Usually absent in plant cells but present in animal cells to aid cell division.
• Energy: Plants make energy from sunlight and respiration, while animals get energy from food through respiration.
• Lysosomes: Rare in plant cells but common in animal cells.

DNA

• DNA stands for Deoxyribonucleic Acid.
• DNA is the genetic blueprint for all living organisms.

Mitosis Stages

• Mitosis involves one cell dividing into two identical daughter cells.
• Mitosis is used for growth, repair, and asexual reproduction in body cells.

Prophase

• Chromatin condenses into visible chromosomes, each with two sister chromatids.
• Spindle fibers form.
• Nuclear membrane breaks down.

Metaphase

• Chromosomes align in the middle of the cell.
• Spindle fibers attach to the centromeres of each chromosome.

Anaphase

• Sister chromatids are pulled apart to opposite ends of the cell.
• Each side now has a complete set of chromosomes.

Telophase

• Two new nuclear membranes form around the separated sets of chromosomes.
• Chromosomes begin to uncoil into chromatin.
• Cell splitting begins.
• Cytoplasm divides, resulting in two identical daughter cells.

End Result of Mitosis

• Mitosis ensures each daughter cell receives an exact copy of the parent cell’s DNA.

Detailed Mitosis Stages

• Prophase: Chromatin condenses into visible chromosomes, each with two sister chromatids joined at a centromere.
• The nucleolus disappears, and the nuclear envelope breaks down.
• Centrosomes move to opposite poles of the cell, forming the mitotic spindle.
• Metaphase: Chromosomes line up at the cell's equator (metaphase plate) via spindle fibers attached to their centromeres.
• Anaphase: Centromeres split; spindle fibers pull sister chromatids apart, now considered individual chromosomes, toward opposite poles.
• Telophase: Chromosomes de-condense back into chromatin; two nuclear envelopes reform around each set of chromosomes, and nucleoli reappear.
• The cell now has two nuclei, each with a full set of chromosomes.
• Mitosis ensures genetic consistency from one cell generation to the next.

Key Mitosis Terms

• Chromosome: Coiled DNA and protein structure carrying genetic information; humans have 46 chromosomes (23 pairs).
• Sister Chromatids: Identical chromosome copies joined at a centromere, formed during DNA replication.
• Centromere: The point where sister chromatids join and where spindle fibers attach during mitosis.
• Spindle Fibers: Microtubule threads that pull chromosomes apart during mitosis.
• Centrioles: Cylindrical structures in animal cells that organize spindle fibers during mitosis.
• Chromatin: Loose, uncoiled DNA in the nucleus during interphase; condenses into chromosomes during prophase.

Cell Cycle Checkpoints

• Cell cycle checkpoints are control mechanisms ensuring proper function before cell progression.
• Checkpoints prevent errors like DNA damage or mutations from being passed on.

Major Checkpoints

• G1 Checkpoint: Occurs at the end of G1 phase; checks for cell size, nutrient availability, DNA damage, and division necessity.
• G2 Checkpoint: Occurs at the end of G2 phase; checks for complete and correct DNA replication, cell readiness for mitosis, and DNA errors.
• M Checkpoint (Spindle Checkpoint): Occurs during metaphase; checks for proper chromosome attachment to spindle fibers and correct chromosome alignment.

Checkpoint Outcomes

• If issues arise at a checkpoint, the cell can pause to fix the problem.
• Apoptosis (self-destruction) occurs if damage is too severe.
• Faulty checkpoints can lead to uncontrolled cell division and cancer.

Cell Division

• Cell division is essential for growth, healing, reproduction, and maintenance.
• Mitosis is for body cells.

Tumors

• Definition: Mitosis and Cancer
• Normal mitosis is tightly controlled in healthy cells.
• Cancer cells exhibit uncontrolled mitosis due to mutations that regulate cell division.

Benign Tumors

• Non-cancerous growths.
• Slow-growing.
• Do not invade nearby tissues.
• Do not spread (metastasize).
• Can be surgically removed.

Malignant Tumors

• Cancerous growths.
• Grow quickly.
• Invasive and spread to nearby tissues.
• Metastasize to other body parts through blood or lymphatic system.
• Often require aggressive treatments.

Causes of Cancer

• Genetic mutations: Inherited or spontaneous DNA changes disrupting normal cell growth.
• Environmental factors: Exposure to carcinogens causing DNA mutations.
• Lifestyle factors: Poor diet, lack of exercise, and alcohol consumption increase cancer risk.
• Infections: Viruses and bacteria can trigger cancer.
• Age: Risk increases with age due to accumulated mutations.

Impact of Cancer

• Tumors displace healthy tissue and block vital pathways.
• Metastasis affects multiple organs.
• Organ function impairment leads to serious complications like organ failure and loss of function.

Treatment Options

• Surgery: Removal of tumors.
• Radiation therapy: Uses high-energy radiation to destroy cancer cells.
• Chemotherapy: Drugs that kill fast-dividing cells.
• Immunotherapy: Boosts the body's immune system to fight cancer.
• Targeted therapy: Targets specific molecules involved in cancer cell growth.
• Hormone therapy: Blocks hormones that promote cancer growth.
• Stem cell/bone marrow transplants: Regenerate healthy blood cells.

Tumors: Summary

• Benign tumors are non-cancerous and typically easier to treat.
• Malignant tumors are cancerous and require more aggressive treatments.
• Cancer cells divide uncontrollably due to genetic mutations.

Levels of Organization

• Cell: The basic unit of life.
• Tissue: A group of similar cells performing a specific function.
• Organ: A structure made of different tissues performing a specific function.
• Organ System: A group of organs performing complex functions.

Platelets (Thrombocytes)

• Function: Involved in blood clotting to stop bleeding.
• Structure: Small cell fragments.

Stem Cells

• Function: Undifferentiated cells that can develop into different cell types.
• Types:
  • Embryonic stem cells: Pluripotent, can become any cell type.
  • Adult stem cells: Multipotent, can form a limited range of cell types.

Specialized Cell Functions

• Nerve cells transmit signals.
• Skin cells protect and regulate temperature.
• Intestinal lining cells absorb nutrients.
• Red blood cells carry oxygen and carbon dioxide.
• White blood cells protect against pathogens and infections.

Tissue Types

• Epithelial:
  • Structure: Tightly packed cells, avascular, forming layers.
  • Function: Protection, absorption, secretion.
  • Examples: Skin, intestines, glands.
• Nervous:
  • Structure: Neurons (cell body, dendrites, axons), glial cells.
  • Function: Communication, processing information.
  • Examples: Brain, spinal cord, nerves.
• Connective:
  • Structure: Cells + extracellular matrix (fibers, ground substance).
  • Function: Support, transport, protection.
  • Examples: Bone, blood, adipose tissue.
• Muscle:
  • Structure: Long muscle fibers, striated or smooth.
  • Function: Movement, posture, heat production.
  • Examples: Skeletal muscle, cardiac muscle, smooth muscle.

Organ Structures

• Heart: Cardiac muscle for pumping, epithelial for lining, connective for structure, nervous for regulation.
• Stomach: Smooth muscle for digestion, epithelial for acid secretion, connective for structure, nervous for regulation.
• Small Intestine: Smooth muscle for peristalsis, epithelial for absorption, connective for structure, nervous for motility control.
• Esophagus: Smooth muscle for peristalsis, epithelial for lubrication, connective for flexibility, nervous for regulation.
• Organ Systems: Various tissues in each organ system work together for specific functions.

Digestive Organs and Functions

• Mouth: Chewing and saliva (amylase) start digestion (Mechanical and Chemical)
• Esophagus: Transports food to the stomach (Mechanical).
• Stomach: Churns food with gastric juices; begins protein digestion (Mechanical and Chemical).
• Small Intestine: Most digestion and nutrient absorption occur (Chemical).
• Large Intestine: Absorbs water, salts, and some vitamins (Absorption only).
• Anus: Eliminates feces (None).
• Salivary Glands: Produce saliva with amylase (Chemical).
• Liver: Produces bile to emulsify fats (Chemical).
• Gallbladder: Stores and concentrates bile (None).
• Pancreas: Produces digestive enzymes and regulates blood sugar (Chemical).

Circulatory Organs

• Heart: Pumps blood throughout the body
• Structure: Four chambers: two atria and two ventricles.
• Functions: Right side sends blood to the lungs, the left side sends it to the body.
• Lungs: Oxygen enters, and carbon dioxide is removed.
• Structure: Bronchi, bronchioles, and alveoli.
• Blood: Transports oxygen, nutrients, hormones, and waste.
• Structure: Red blood cells, white blood cells, plasma, and platelets.

Blood Vessels

• Arteries: Carry blood away from the heart (usually oxygen-rich).
• Veins: Carry blood toward the heart (usually oxygen-poor).
• Capillaries: Connect arteries to veins.

Diffusion of Oxygen and Carbon Dioxide

• Lungs: Oxygen diffuses from alveoli into red blood cells; carbon dioxide diffuses from blood into alveoli.
• Body Tissues: Oxygen diffuses from blood into cells; carbon dioxide diffuses from cells into the blood.

Respiratory System

• The respiratory system facilitates breathing and gas exchange.
• Nose/Nasal Cavity: Filters, warms, and moistens air.
• Pharynx (Throat): Connects the nose/mouth to the larynx; a pathway for air and food.
• Larynx (Voice Box): Contains vocal cords, prevents food from entering the windpipe.
• Trachea (Windpipe): Carries air from the throat to the lungs.
• Bronchi: Two branches from the trachea to each lung.
• Bronchioles: Smaller branches inside the lungs leading to alveoli.
• Alveoli: Tiny air sacs for gas exchange.
• Diaphragm: Muscle under the lungs that aids breathing.

Breathing

• Inhalation (Breathing In):
• Diaphragm contracts and moves down.
• Rib muscles contract, lifting the ribs.
• Chest cavity gets larger. - Air flows into lungs.
  • Inside pressure decreases.
• Exhalation (Breathing Out):
• Diaphragm relaxes and moves up.
  • Rib muscles relax, ribs move down.
  • Chest cavity gets smaller.
  • Air flows out of the lungs.
  • Inside pressure increases.

Cellular Analogies

• Nucleus: Factory manager; controls cell activities and stores DNA.
• Ribosomes: Workers make proteins (cell's products).
• Endoplasmic Reticulum (ER): Assembly line; Rough ER makes and transports proteins; Smooth ER makes lipids and detoxifies.
• Golgi Apparatus: Packaging and shipping center; modifies, packages, and ships proteins.
• Mitochondria: Power plant; produces energy (ATP) from food.
• Chloroplasts (in plants): Solar panels; convert sunlight into energy (photosynthesis).
• Cell membrane: Factory gates; controls what enters and leaves the cell.
• Lysosomes: Recycling and waste center; break down waste.
• Cytoplasm: Factory floor; jelly-like fluid where things move around.
• Vacuole: Storage room; stores water, nutrients, and waste.
• Cell wall (in plants): Outer fence; provides extra support and protection outside the membrane.