College Bio Chapter 4

Nucleus

Stores DNA, controls cell activities, and contains the nucleolus where ribosome subunits are assembled.

Ribosome

Makes proteins; found free in cytoplasm or attached to rough ER; composed of rRNA and protein.

Rough Endoplasmic Reticulum (Rough ER)

Produces and modifies proteins for secretion or membranes; has ribosomes attached.

Smooth Endoplasmic Reticulum (Smooth ER)

Synthesizes lipids, detoxifies drugs, and stores calcium; found abundantly in liver and muscle cells.

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids from the ER into transport vesicles.

Lysosome

Contains digestive (hydrolytic) enzymes; breaks down old organelles, waste, and foreign material.

What are lysosomes filled with?

Hydrolytic enzymes in an acidic environment.

Mitochondria

Site of cellular respiration; produces ATP; known as the "powerhouse" of the cell.

Lysosome vs. Mitochondria

Lysosomes digest and recycle materials; mitochondria generate ATP (energy).

Tay-Sachs Disease

Caused by defective lysosomal enzyme; leads to buildup of fatty substances in neurons.

Chloroplast

Performs photosynthesis—converts light energy into glucose; found only in plant and algal cells.

Contractile Vacuole

Pumps out excess water; found in freshwater protists like paramecium.

Central Vacuole (plants)

Stores water, nutrients, and waste; maintains turgor pressure for plant structure.

Organelles found only in plant cells

Cell wall, chloroplasts, central vacuole.

Phospholipids in membranes

Form bilayers in water; hydrophilic heads face water, hydrophobic tails face inward.

Where are ribosomes assembled?

In the nucleolus inside the nucleus.

Where are ribosomes found?

Free in cytoplasm, attached to rough ER, and inside mitochondria or chloroplasts.

Antibiotics - what do they target?

Target bacterial ribosomes or cell wall synthesis; do not harm human ribosomes.

Prokaryotic Cells

No nucleus or membrane-bound organelles; smaller; bacteria and archaea.

Eukaryotic Cells

Have a nucleus and membrane-bound organelles; include plants, animals, fungi, and protists.

Messenger RNA (mRNA)

Carries genetic code from DNA to ribosomes for protein synthesis.

Ribosomal RNA (rRNA)

Forms part of the structure of ribosomes and helps catalyze protein synthesis.

Transport Vesicles

Move proteins/lipids between ER, Golgi, and plasma membrane; part of the endomembrane system.

Major lipids in cell membranes

Phospholipids, cholesterol, glycolipids.

Muscle contraction and organelles involved

Smooth ER (sarcoplasmic reticulum) releases calcium ions that trigger muscle contraction.

Chromatin

Loosely packed DNA in the nucleus during normal cell activity.

Chromosome

Condensed DNA form visible during cell division.

Plasma Membrane

Selectively permeable barrier controlling what enters and leaves the cell; maintains homeostasis.

Endomembrane System

Network of membranes (nuclear envelope, ER, Golgi, lysosomes, vacuoles, plasma membrane) that modify and transport materials.

Detoxification of drugs occurs where?

Smooth ER, especially in liver cells.

Term: What's stored in central vacuoles of plants?

Water, ions, sugars, pigments, and waste products.

What organelle synthesizes proteins for export?

Covered with ribosomes that make proteins destined for secretion or for use in membranes.

What organelle breaks down waste using digestive enzymes?

Contains hydrolytic enzymes that digest worn-out organelles, waste, and foreign material.

Why don't antibiotics harm human cells?

Because antibiotics target bacterial structures, such as bacterial ribosomes or cell walls, which are different or absent in human cells.

What structure makes up most of the plasma membrane?

Phospholipid bilayer. Hydrophilic heads face outward; hydrophobic tails face inward. Also contains proteins and cholesterol.

Where are ribosomes assembled?

Nucleolus

What's the main difference between chromatin and chromosomes?

Chromatin = loose, uncoiled DNA during normal cell function. Chromosomes = tightly coiled, condensed DNA visible during cell division.

Which organelle is defective in Tay-Sachs disease?

Lysosome-Missing enzyme prevents breakdown of fatty substances in nerve cells, leading to buildup and cell damage.

What type of vacuole helps freshwater protists survive?

Contractile vacuole-Pumps out excess water to prevent the cell from bursting (found in freshwater protists like paramecia).