Cell Structures and Organelles

• Animal cells uniquely feature cilia, flagella, and centrioles.
• Plant cells uniquely possess a cell wall, a large vacuole, and chloroplasts.
• Cells comprise organelles that perform specific functions.
• Organelles reside in the cytoplasm, which is mostly water.

Cell Parts

• The cell wall protects and supports cells and is made of cellulose, absent in animal cells.
• The cell membrane protects cells and regulates material movement; it is present in all cells.
• The cell membrane consists of phospholipids that are in constant motion.
• Proteins within the cell membrane act as channels for larger molecules.
• Cytoplasm includes everything inside the cell membrane but outside the nucleus.
• Cytosol, a jelly-like substance mainly composed of water, fills the cell.
• Organelles are situated within the cytoplasm.

Nucleus and Nucleolus

• The Nucleus is the control center of the cell and contains chromosomes of DNA.
• The Nucleolus is a dense area within the nucleus where ribosomes are produced.

Mitochondrion

• The Mitochondrion is a tiny, oval-shaped organelle that provides cells with energy (ATP).
• Mitochondria is the site of aerobic cellular respiration.
• ATP provides energy for cell processes.
• The equation for this process is: sugar + O2 → CO2 + H2O + energy (ATP).

Ribosome

• Ribosomes are microscopic spheres attached to the endoplasmic reticulum or floating in the cytoplasm
• Ribosomes are responsible for synthesizing proteins within the cell.

Endoplasmic Reticulum

• The Endoplasmic Reticulum is a twisting network of canals.
• The Endoplasmic Reticulum transports materials throughout the cell.
• Rough ER has ribosomes attached, while smooth ER does not.

Golgi Apparatus

• The Golgi Apparatus consists of flattened sacs that produce vesicles or transport sacs.
• The Golgi Apparatus modifies and stores cellular secretions like proteins.

Lysosome

• The Lysosome are sac-like structures formed by the Golgi apparatus.
• Lysosomes contain enzymes that break down large molecules or worn-out cell parts.

Vacuole

• Vacuoles are fluid-filled spaces containing water, sugar, and proteins.
• Vacuoles assist in water regulation in plants.
• Vacuoles also store food or assist in the movement of organisms.

Centriole

• Centrioles are small protein structures critical to cell division.
• Centrioles are not found in plant cells.

Chloroplast

• Chloroplast is found only in green plants and some protists.
• The Chloroplast converts sunlight into food for the cell via photosynthesis.

Cilia and Flagella

• Cilia and Flagella are fine protein fibers used for locomotion.
• Cilia are short and numerous on the cell surface.
• Flagella are long and usually few in number on the cell surface.

Cytoskeleton

• The Cytoskeleton comprises protein fibers that anchor organelles and provide structure to the cell.

Cell Size

• Cells are relatively small because volume increases more rapidly than size therefore diffusion time also becomes longer.

Human Organ Systems

• Circulatory
• Respiratory
• Digestive

Circulatory System

• Circulatory system transports nutrients and oxygen to body cells.
• It removes wastes and carbon dioxide from the cells.
• Components include the heart, blood vessels, and blood.
• The heart's cardiac muscle tissue contracts as one unit.
• Epithelial tissue lines the inside and outside of the heart to protect it from friction.
• Arteries carry blood away from the heart.
• Veins carry blood toward the heart.
• Capillaries surround body cells and allow oxygen and nutrients to enter cells.
• Red blood cells transport oxygen to cells.
• White blood cells recognize and destroy foreign microbes.
• Platelets are cell fragments involved with blood clotting.
• Plasma is a protein-rich liquid that carries blood cells.

Respiratory System

• The Respiratory system provides oxygen and removes carbon dioxide.
• Components include the mouth, nose, trachea, lungs, and diaphragm.
• The mouth and nose are used to chew food, suck in air, and talk.
• Air from the mouth and nose pass through the trachea.
• Cartilaginous rings keep the trachea open.
• The trachea is lined with ciliated epithelium.
• Cilia moves mucus and foreign debris away from the lungs.
• Lungs are non-muscular organs filled with alveoli.
• Alveoli are small air sacs surrounded by capillaries and are the site of gas exchange.
• The diaphragm is a dome-shaped muscle attached to the bottom of the lungs.

Digestive System

• The Digestive system takes food into the body, breaks it down, absorbs nutrients, and excretes solid waste.
• Components include the mouth, esophagus, stomach, small intestines, and large intestines.
• The mouth breaks down food by chewing, and digestive enzymes in saliva produced by epithelial tissue.
• The esophagus propels food to the stomach through peristaltic movements.
• The stomach stores food, and smooth muscle contracts to mix food with digestive juices.
• Digestion and absorption of nutrients occurs in the small intestines.
• Water is reabsorbed into the body in large intestines.
• Solid matter is excreted as feces from the anus.

Interaction of Systems

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

Cellular Respiration

• The equation is Glucose + Oxygen → Carbon Dioxide + Water.
• The respiratory system brings oxygen to mitochondria and removes carbon dioxide as waste.
• The digestive system brings nutrients (glucose) to mitochondria.
• The circulatory system transports gases (CO2) and nutrients (glucose).

The Cell Cycle, Mitosis, and Cancer

• All living things are composed of cells (Cell theory).
• Cells are the smallest functional units of living organisms.
• All cells come from pre-existing cells.
• As cells grow larger, the volume grows faster than the membranes’ surface area.
• Cells divide to increase the number of cells in the body.
• Cells divide to replace dead, damaged, or old cells.
• Cells can make exact copies (clones).
• The human body contains 60 trillion cells.
• Cells take in nutrients and dispose of waste through the cell membrane.

Types of Cells

• Plant cells have a cell wall, large central vacuole and chloroplasts, and lack centrosomes and lysosomes.
• Animal cells lack a cell wall (irregular shape) but have numerous small vacuoles, centrioles/centrosomes, and lysosomes.

Prokaryotes

• Prokaryotes have a simple structure, no prominent nucleus, and are small in size.
• The cell wall has peptidoglycan, small ribosomes, and are unicellular.
• Prokaryotes lack organelles, but have DNA, a cell membrane, and cytoplasm.
• Examples are bacteria and archaea.

Eukaryotes

• Eukaryotes have a complex structure, a prominent nucleus, and are large in size.
• The cell wall has chitin or cellulose, large ribosomes and can be unicellular or multicellular.
• Eukaryotes have membrane-bounded organelles.
• Examples: humans, plants, fungi, and protists.

The Cell Cycle

• Every hour, about 1 billion cells die and are made.
• Body cells undergo several stages in their lifetime called the Cell Cycle.
• Interphase occurs where the cell repairs any damages, re-energizes, grows, and prepares for division.
• Mitosis & Cytokinesis is the division of the cell into 2 identical “daughter”cells.
• The average skin cell life is between 14-28 days, while the red blood cell lives up to 120 days.

Interphase

• Interphase is the longest stage of the cell cycle, taking up 90% of the time.
• First Gap Phase (G1) occurs where cells grow in size, and new proteins and organelles are made.
• Synthesis Phase (S) is where the DNA is replicated (known as chromatin).
• Second Gap Phase (G2) occurs where cells prepare for division.

Cell Division

• Mitosis is the division of the contents of the nucleus: Prophase, Metaphase, Anaphase and Telophase.
• Cytokinesis is the division of the cytoplasm and organelles where original cell splits into two daughter cells.

Chromosomes

• Chromosomes contain hereditary information.
• Chromosomes are contained within the nucleus.
• Human cells contain 23 pairs of chromosomes.
• When a cell divides, each daughter cell gets the same 23 pairs of chromosomes.
• Chromosomes are composed of DNA and proteins.
• A gene is a segment of DNA that codes for a particular trait.

Prophase

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

Metaphase

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

Anaphase

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

Telophase

• Spindle fibres disappear.
• Chromosomes begin to decondense into chromatin.
• The nuclear membrane reappears around the DNA.

Cytokinesis

• The cell membrane pinches inwards.
• Cytoplasm splits in half.
• Daughter cells return to interphase.
• Cellular division is necessary for the body to continue functioning successfully.
• Skin cells, and cells in the digestive tract, continually undergo cell division as they are likely to be damaged or injured.
• Nerve cells do not undergo mitosis, causing spinal cord damage to be so detrimental.

G Phase

• Cells can enter a resting phase called Go.
• For example, nerve cells in the brain stop dividing when the brain is developed and cannot reenter the cell cycle.

Cell Death

• Necrosis: Cells may die due to external factors like toxins, infections, and trauma.
• Apoptosis: The controlled death of old cells like when white blood cells divide to fight viral infections and then undergo apoptosis when no longer required.

Cancer

• Genetic mutations can cause cells to mutate and undergo abnormal cell division.
• Instead of undergoing apoptosis, these cells continue to divide uncontrollably without limit.
• Cell division occurs so fast that cells pile up on top of one another, forming a tumor.
• Tumors reduce the effectiveness of the surrounding tissues.
• Changes to these abnormal cells in the tumor can create cancer which stimulates other cells to start replicating uncontrollably, thus spreading cancer.
• May invade and destroy neighbouring cells.
• Comparison: Normal cells make exact copies, reproduce with a limit, stick together, and self-destruct, while cancer cells reproduce without stopping, do not stick, and may move to other locations.

Cell Specialization

• Single cellular organism performs all required functions in one cell. E.g. Amoeba
• Multicellular organisms are much more complex because the body needs to supply food and nutrients, transport materials, remove wastes and fight infection.
• Cellular Differentiation is the process of creating specialized cells that originate from the zygote (fertilized egg) undergoing mitosis.
• As an embryo develops, cells change their shape, contents and function.
• Cytoplasm differences is from the asymmetric distribution of organelles & other factors in zygote resulting in different daughter cells.
• Environmental conditions such as variations in temperature and nutrients.
• Neighboring cells substances produced by nearby cells can diffuse to nearby cells.
• May result in the expression of different genes within a cell.
• Chemical contamination of the environment can affect cellular development.
• 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 stem cells differentiate into any cell type; research is banned due to ethical reasons.
• Pluripotent stem cells are umbilical (blood).
• Pluripotent stem cells are used to treat most blood disorders & cancers, some immune disorders and bone marrow failure and is retrieved at birth of baby.
• Adult Stem cells exists in some tissues, but can only form specific types of cells with many still being researched.
• Multipotent stem cells are in bone marrow which produces white blood cells, red blood cells and platelets.

Tissue Types

• Tissues are a collection of similar cells that perform specific functions.
• Animals have 4 types of tissue: Epithelial, Muscular, Connective, and Nervous.
• Epithelial tissue Lines the internal and external surfaces of the body and Form a barrier by connecting adjoining cell membranes.
• Muscular tissue moves the body or organ by contracting and relaxing.
• Connective tissue strengthens, supports and protects other tissues where Cells are in an extracellular matrix.
• Nervous tissue is Made of neurons with long projections that send and receive signals, and Coordinates body actions.