Biology Chapter: Cells and Organelles

Eukaryotic vs. Prokaryotic Cells

• Eukaryotic cells have less surface area per unit volume, making exchange processes less efficient.
• Prokaryotic cells have more surface area per volume, making nutrient and energy uptake easier.
• Eukaryotic cells have DNA enclosed in a nucleus.
• Prokaryotic cells have loose DNA.
• Eukaryotic cells contain membrane-bound organelles.
• Prokaryotic cells lack membrane-bound organelles.

Vacuoles

• Vacuoles are large vesicles used for storage of water, and other substances.

Chloroplasts

• Chloroplasts are specialized organelles responsible for harnessing energy through photosynthesis.
• Thylakoids are stacked to form grana.
• Stroma is the fluid surrounding the grana.

Mitochondria

• Mitochondria are responsible for cellular respiration, converting fuel into usable energy (ATP).
• Cristae are the folds of the inner membrane.
• Matrix is the fluid in the mitochondrion.

Nucleus

• The nucleus contains DNA which is organized into chromatin.
• The nucleus is encased by an envelope (double membrane).
• The nucleolus is found inside the nucleus and is responsible for ribosome production. Made of rRNA and proteins.
• Ribosomes are made in the nucleolus.

Endoplasmic Reticulum (ER)

• Smooth ER is involved in lipid synthesis, detoxification, and calcium storage.
• Rough ER is the site of protein synthesis and modification.
• Rough ER has ribosomes attached to its surface.

Golgi Apparatus

• The Golgi apparatus modifies, sorts, and packages proteins for shipping.
• Proteins are modified before being shipped in vesicles.

Lysosomes

• Lysosomes are sacs of digestive enzymes.
• Phagocytosis is "cell eating."
• Autophagy is the recycling of cellular components.

Cytoskeleton

• Microtubules: Involved in cell division, movement of cilia and flagella.
• Intermediate filaments: Provide structural support and anchor.
• Microfilaments (actin): Crucial in muscle contraction.

Membrane Proteins

• Membrane proteins have various functions allowing communication with the external environment like transport.
• Integral membrane proteins are embedded in the membrane, and peripheral proteins are loosely attached.

Plasma Membrane

• The plasma membrane regulates what enters and leaves the cell.
• The plasma membrane is fluid due to unsaturated fatty acid tails, and cholesterol.
• Cholesterol helps maintain membrane fluidity.

Active Transport

• Active transport moves molecules against their concentration gradient, requiring energy (ATP).

Passive Transport

• Passive transport moves molecules down their concentration gradient, requiring no energy(ATP). -Simple diffusion means movement until equilibrium is reached at random. -Osmosis is a type of diffusion where water moves across a selectively permeable membrane, from an area of high water concentration to an area of low water concentration.

Cell Signaling

• Reception: A signaling molecule binds to a receptor protein.

• Transduction: The signal is converted into a form that can trigger a specific cellular response.

• Response: The cell responds to the signal by altering its activities.

  -Different signaling pathways can exist from local or long distances such as endocrine system, nervous system signaling and paracrine signaling, etc.

Metabolism

• Anabolic pathways synthesize larger molecules from smaller ones (absorbing energy).
• Catabolic pathways break down larger molecules into smaller ones (releasing energy).
• Energy coupling uses an exergonic reaction to drive an endergonic reaction.
• Enzymes are biological catalysts that speed up metabolic reactions.