unit review

Cells have tiny parts called organelles that work like little organs to keep the cell alive.

Organelles in both Animals and Plants:
- Nucleus: The "brain" or control center that holds the genetic instructions ( $DNA$ ).
- Mitochondria: The "powerhouse" that turns food into energy ( $ATP$ ) for the cell.
- Ribosomes: Small workers that build proteins.
- Endoplasmic Reticulum (ER): A transport system; the Rough ER has ribosomes and handles proteins, while the Smooth ER makes fats (lipids).
- Golgi Apparatus: The "post office" that packs and sends out proteins.
- Cytoplasm: The jelly-like filling that holds everything in place.
- Cell Membrane: The "security guard" or thin skin that lets things in and out.
- Vacuoles: Storage sacs for water and food. (Plants have one big one; animals have many small ones).
Plant-Only Parts:
- Cell Wall: A tough outer shell for support.
- Chloroplasts: Green parts that catch sunlight to make food (photosynthesis).
Animal-Only Parts:
- Centrioles: Helpers that organize the cell when it is time to divide.

Why do cells split?

The Life of a Cell:

Interphase: The cell grows, copies its $DNA$ , and gets ready to split. This is where the cell spends most of its time.
Mitosis (The 4 Steps):
- Prophase: The cell packs its $DNA$ into visible shapes (chromosomes).
- Metaphase: Chromosomes line up in the middle of the cell.
- Anaphase: The chromosomes are pulled apart to opposite sides.
- Telophase: Two new nuclei form around the separated $DNA$ .
Cytokinesis: The cell pinches in half, creating two new twin cells.

Definition: A disease where cells divide too fast and won't stop.
Causes: Damage to $DNA$ often caused by “carcinogens” like smoking, $UV$ rays from the sun, or bad chemicals.
Staying Safe: Regular doctor check-ups (screening) and living healthy (no smoking, using sunscreen, eating well).
Treatment: Doctors use surgery to cut it out, chemotherapy (strong medicine), or radiation (high energy) to kill the bad cells.

The Food Path: Mouth → Throat → Stomach → Small Intestine → Large Intestine → Exit.

Mouth: Teeth chew food and spit (enzymes) breaks it down chemically.
Esophagus: A tube that squeezes food down to the stomach.
Stomach: Uses strong acid ( $HCl$ ) and enzymes to turn food into liquid.
Small Intestine: The main place where the body sucks up nutrients into the blood.
Large Intestine: Soaks up water and turns the leftover waste into poop.
Helpers: The Liver and Gallbladder handle bile (to break down fat), and the Pancreas makes juices to help digestion.

The Air Path: Nose → Throat → Windpipe (Trachea) → Lung Tubes (Bronchi) → Tiny Air Sacs (Alveoli).

Alveoli: Tiny balloons in the lungs where oxygen enters the blood and carbon dioxide ( $CO_2$ ) leaves it.
Diaphragm: A big muscle under your lungs that pulls down to help you breathe in.

The Blood Path: Right side of heart → Lungs → Left side of heart → Body → Back to heart.

What is in blood?
- Red Cells: Carry oxygen.
- White Cells: Fight germs.
- Platelets: Form scabs to stop bleeding.
- Plasma: The liquid that carries everything else.
The Pipes:
- Arteries: Carry blood away from the heart (thick and strong).
- Veins: Carry blood back to the heart (have "doors" called valves to keep blood flowing one way).
- Capillaries: Tiny tubes where oxygen and food are dropped off to cells.

The Center (CNS): Your brain and spinal cord.
The Rest (PNS): All the nerves that go to your arms, legs, and organs.
Neurons: Special cells that send electrical "text messages" through your body.

This is made of your bones and muscles.
Job: It holds you up, protects your soft insides, and lets you move by having muscles pull on your bones.