Cell Structure and Function

• Cells are the basic units of life.
• All living things consist of one or more cells.
• All cells originate from pre-existing cells.

Cell Types

• Nerve, blood, skin, and leaf cells are examples of different cell types.

Structures Unique to Animal Cells

• Cilia, flagella, and centrioles are exclusively found in animal cells.

Structures Unique to Plant Cells

• Cell walls, large vacuoles, and chloroplasts are unique to plant cells.

Cell Composition

• Cells are composed of organelles that perform specific functions.
• Organelles are contained within the cytoplasm, which is primarily water.

Cell Wall

• Protects and supports cells.
• Composed of cellulose.
• Absent in animal cells.

Cell Membrane

• Protects cells, and monitors and controls the movement of materials in and out.
• Present in all cells.
• Made of phospholipids that are in constant motion.
• Proteins in the membrane act as channels.

Cytoplasm

• Encompasses everything within the cell membrane, excluding the nucleus.
• The cytosol is a jelly-like substance.

Nucleus

• The control center of the cell, containing chromosomes (DNA).

Nucleolus

• A dense region within the nucleus where ribosomes are produced.

Mitochondrion

• Oval-shaped organelle that provides energy (ATP) to cells.
• The site of aerobic cellular respiration.
• ATP powers other organelles for cell processes.
• Aerobic cellular respiration: sugar + O2 → CO2 + H2O + energy (ATP).

Ribosome

• Microscopic spheres attached to the endoplasmic reticulum or floating in the cytoplasm.
• Synthesizes protein within the cell.

Endoplasmic Reticulum

• A network of canals that transports materials throughout the cell.
• Rough ER has ribosomes attached, while smooth ER does not.

Golgi Apparatus

• Flattened sacs that produce vesicles (transport sacs).
• Modifies and stores cellular secretions, such as proteins.

Lysosome

• Saclike structure formed by the Golgi apparatus.
• Contains enzymes that break down molecules or worn-out cell parts.

Vacuole

• Fluid-filled space for storing water, sugar, and proteins.
• Regulates water in plants.
• Helps store food or transport organisms.

Centriole

• Small protein structures essential for cell division.
• Absent in plant cells.

Chloroplast

• Found in green plants and some protists.
• Converts sunlight into food for the cell via photosynthesis.

Cilia and Flagella

• Fine protein fibers used for locomotion.
• Cilia are short and numerous.
• Flagella are long and few.

Cytoskeleton

• Protein fibers that anchor organelles and provide cell structure.

Cell Size

• Small size allows efficient diffusion due to the relationship between size and volume.

Human Organ Systems

Organ Systems

• Circulatory, respiratory, and digestive systems.
• These systems interact to maintain bodily functions.

Circulatory System Functions

• Transports nutrients and oxygen to body cells, removes wastes and carbon dioxide.

Circulatory System Components

• Heart, blood vessels, and blood.

Heart

• Cardiac muscle tissue enables the heart to contract as a unit.
• Epithelial tissue protects.

Blood Vessels

• Arteries carry blood away from the heart.
• Veins carry blood toward the heart.
• Capillaries surround body cells and allow the exchange of oxygen and nutrients.

Blood

• Red blood cells transport oxygen.
• White blood cells destroy foreign microbes.
• Platelets are involved in blood clotting.
• Plasma is a protein-rich liquid that carries blood cells.

Respiratory System Functions

• Provides oxygen and removes carbon dioxide.

Respiratory System Components

• Mouth, nose, trachea, lungs, and diaphragm.

Mouth and Nose

• Facilitate chewing and air intake.

Trachea

• Allows air to pass from the mouth and nose.
• Cartilaginous rings keep it open.
• Ciliated epithelium moves mucus and debris away from the lungs.

Lungs

• Non-muscular organs filled with alveoli.
• Alveoli are air sacs surrounded by capillaries.
• Alveoli are the site of gas exchange.

Diaphragm

• Dome-shaped muscle attached to the bottom of the lungs.

Digestive System Functions

• Takes food into the body, breaks it down, absorbs nutrients, and excretes solid waste.

Digestive System Components

• Mouth, esophagus, stomach, small intestine, and large intestine.

Mouth

• Breaks down food through chewing and digestive enzymes.
• Saliva is produced by epithelial tissue.

Esophagus

• Smooth muscles move food to the stomach through peristaltic movements.

Stomach

• Stores food and mixes it with digestive juices.

Small Intestines

• Digestion and absorption of nutrients occur here.

Large Intestines

• Water is reabsorbed into the body, and solid waste is excreted.

Interaction of Systems

• Oxygen moves from air in the respiratory system to blood in the circulatory system.
• Carbon dioxide moves from blood to air.

Cellular Respiration

• Glucose + Oxygen → Carbon Dioxide + Water
• The respiratory system brings oxygen and removes carbon dioxide.
• The digestive system brings nutrients (glucose).
• The circulatory system transports gases and nutrients.

The Cell Cycle Mitosis Cancer

Cell Theory

• All living things consist of cells.
• Cells are the smallest functional units of living organisms.
• All cells originate from pre-existing cells.

Cell Size Constraints

• Volume increases faster than surface area as cells grow.
• Cells divide when they become too large to absorb enough nutrients.

Reasons for Cell Division

• To increase the number of cells.
• To replace dead, damaged, or old cells.
• To make exact copies (clones).

Cell Types

• Plant cells have a cell wall, a large central vacuole, and chloroplasts, but they lack centrosomes and lysosomes.
• Animal cells lack a cell wall (irregular shape), have numerous small vacuoles, no chloroplasts, but have centrioles/centrosomes and lysosomes.
• Examples include fat, sex, immune, muscle, bone, nervous, and blood cells.

Prokaryotes

• Simple structure without a prominent nucleus.
• Small size.
• Cell wall contains peptidoglycan.
• Small ribosomes.
• Unicellular.
• Lack organelles.
• Examples: bacteria and archaea.

Eukaryotes

• Complex structure with a prominent nucleus.
• Large size.
• Cell walls contain chitin or cellulose.
• Large ribosomes.
• Unicellular or multicellular.
• Membrane-bound organelles.
• Examples: humans, plants, fungi, and protists.

The Cell Cycle

• Body cells undergo a cycle of growth and division.

Cell Cycle Parts

• Interphase: cell repairs, energizes, grows, and prepares for division.
• Mitosis & Cytokinesis: division into two identical daughter cells.

Interphase

• The longest stage (90% of the cell cycle).
• Three phases:
  • First Gap Phase (G1): cell grows, new proteins and organelles are made.
  • Synthesis Phase (S): DNA is replicated (chromatin).
  • Second Gap Phase (G2): cell prepares for division.

Cell Division

• Mitosis: division of the nucleus.
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• Cytokinesis: division of the cytoplasm/organelles.
• Results in two daughter cells.

Chromosomes

• Contain hereditary information within the nucleus.
• Human cells have 23 pairs of chromosomes.
• Composed of DNA and proteins.
• A gene is a segment of DNA that codes for a particular trait.

Prophase

• Chromatin condenses into chromosomes (sister chromatids).
• Centrioles move to each pole.
• The nucleus and the nuclear membrane break down.

Metaphase

• Spindle fibers attach to centromeres.
• Chromosomes line up at the metaphase plate.

Anaphase

• Spindle fibers shorten.
• Centromeres split.
• Sister chromatids separate and move to opposite poles as daughter chromosomes.

Telophase

• Spindle fibers disappear.
• Chromosomes decondense into chromatin.
• The nuclear membrane reappears around DNA.

Cytokinesis

• Cell membrane pinches inwards.
• Cytoplasm splits in half.
• Daughter cells return to interphase.

Purpose of the Cell Cycle

• Necessary for the body to function, especially for replacing damaged or injured cells.
• Nerve cells do not undergo mitosis.

G0 Phase

• Cells can enter a resting phase (G0).
• Nerve cells in the brain stop dividing and cannot re-enter the cell cycle.

Cell Death

• Necrosis: cell death due to external factors.
• Apoptosis: programmed cell death.

Cancer

• Genetic mutations lead to abnormal cell division.
• Cancer cells divide uncontrollably and do not undergo apoptosis.
• They divide without limit forming a tumor.
• Cancer cells can spread, replicate uncontrollably, and invade neighboring cells.

Normal Cells vs. Cancer Cells

• Normal cells make exact copies, reproduce for a limited number of divisions, stick together, and self-destruct.
• Cancer cells make copies, do not stop reproducing, behave independently, and may move to other locations.

Cell Specialization

Why Specialize?

• Single-celled organisms perform all functions in one cell.
• Multicellular organisms are more complex, needing specialized cells.

Cellular Differentiation

• The process of creating specialized cells.
• All cells originate from the zygote (fertilized egg).
• During development, cells change their shape, contents, and function.

Causes of Specialization

• Cytoplasm differences: asymmetric distribution of organelles and factors.
• Environmental conditions: variations in temperature and nutrients.
• Neighbouring cells: substances produced by nearby cells.
• All these factors may result in the expression of different genes.

Stem Cells

• Cells that can differentiate into many different cell types.
• Daughter cells have the same DNA, but different genes may be turned on or off.

Types of Stem Cells

• Embryonic: differentiates into any cell type (research restricted).
• Pluripotent: umbilical blood stem cells used to treat disorders and cancers.
• Adult Stem cells: exist in some tissues.

Tissue Types

• Tissues are collections of similar cells performing specific functions.

Animal Tissue Types

• Epithelial: lines surfaces and forms a barrier.
• Muscular: moves the body or organs by contracting and relaxing.
• Connective: strengthens, supports, and protects, found in an extracellular matrix.
• Nervous: neurons send and receive signals to coordinate body actions.