Biology Final Exam Notes

CELL STRUCTURE AND FUNCTION

LEVELS OF ORGANIZATION

• Atom

• Molecule

• Macromolecule

• Organelle

• Cell

• Tissue

• Organ

• Organ system

• Organism

WHAT ARE CELLS?

• Cells are the smallest units of life.

• All living things are made up of cells.

• All cells arise from the reproduction of other cells.

WHICH OF THESE ITEMS ARE CELLS?

• • Glucose

• • Carbon Atom

• • Influenza Virus (900 pm)

• • E. coli Bacterium (3 μm)

• • Baker's Yeast (4 μm)

• • Sperm Cell (130 μm)

• • Human Egg Cell (130 μm)

• • Paramecium (210 μm)

• • Amoeba Proteus (500 μm)

• • Coffee Bean (8 mm)

HOW ARE ORGANISMS ORGANIZED INTO CELLS?

• Organisms can be:

  • Multicellular: composed of many cells (e.g., Bacteria, Yeast, Algae)

  • Unicellular: composed of one cell (e.g., Protists)

• Multicellular organisms have specialized cells (e.g., Red Blood Cells, Skin Cells, Muscle Cells, Nerve Cells).

WHY AREN'T VIRUSES CELLS?

• Viruses are not classified as living; they require human cells for reproduction.

• They consist of DNA enclosed in a protein coat.

WHY ARE CELLS SO SMALL?

• Most cells are microscopic to facilitate quick transport of materials in and out through the cell membrane.

PROKARYOTIC VS EUKARYOTIC CELLS

Prokaryotic Cells

• Typically unicellular.

• Smaller and simpler than eukaryotic cells.

• Lacks membrane-bound organelles.

• DNA is not enclosed.

• Usually possesses a cell wall (e.g., Bacteria).

Eukaryotic Cells

• Can be unicellular or multicellular.

• Larger and more complex.

• Contains membrane-bound organelles.

• Examples include plants, animals, fungi, and protists.

MAJOR PARTS OF PROKARYOTIC CELLS

• Ribosome

• Loose DNA

• Cell wall

• Cell membrane

• Cytoplasm

• Cilia

• Flagella

MAJOR PARTS OF EUKARYOTIC CELLS

• Nucleus

• Endoplasmic reticulum

• Ribosomes

• Mitochondria

• Lysosomes

• Golgi apparatus

• Cytoplasm

• Cell membrane

• Flagella

• Vacuole

FUNCTIONS OF ORGANELLES

• Cell Membrane: Selectively permeable, surrounded by lipids and proteins.

• Nucleus: Control center holding DNA, organized into chromosomes.

• Cytoplasm: Gel-like matrix holding organelles.

• Ribosomes: Site of protein synthesis.

• Mitochondria: Powerhouse, produces ATP.

• Chloroplast: Photosynthesis in plant cells.

• Cell Wall: Provides support and structure in plant cells, made of cellulose.

CELL TRANSPORT

• Definition: Movement of molecules across cell membranes.

TYPES OF TRANSPORT

A. Passive Transport

• No energy required.

• Movement from high concentration to low concentration.

Types of Passive Transport:

1. Diffusion: Movement of molecules from high to low until equilibrium (e.g., gas exchange in lungs).

2. Osmosis: The diffusion of water across the membrane.

3. Facilitated Diffusion: Molecules enter through protein channels (e.g., glucose).

B. Active Transport

• Requires energy.

• Movement from low concentration to high concentration.

• Examples include Endocytosis (transport into the cell) and Exocytosis (transport out of the cell).

OSMOSIS IN CELLS

In Plant Cells

• Cells can maintain structure due to a rigid cell wall.

• Behavior in different environments:

  • Equal environment: No change

  • Hypotonic environment: Gains water

  • Hypertonic environment: Loses water

In Animal Cells

• Animal cells do not have a cell wall, making them vulnerable to osmotic changes.

• Behavior in different environments:

  • Equal environment: No change

  • Hypotonic environment: Can swell

  • Hypertonic environment: Can shrivel

Ecosystems

Producer

• Consumer: Organisms that obtain energy by eating other organisms.

• Decomposer: Organisms that break down dead or decaying organic matter, returning nutrients to the soil and environment.