ZooLec 5: Cells Part 3 (Cytoplasm & Nucleus) BORROWED

Cytoplasm

Gel-like substance enclosed by the cell membrane; contains organelles and supports metabolic processes

3 elements of cytoplasm

Cytosol, Organelles, Inclusions

Cytosol

Liquid portion of cytoplasm; mainly water with dissolved ions, organic molecules, and proteins

Organelles

Membrane-bound structures such as mitochondria, ER, Golgi bodies; carry out essential cellular functions

Inclusions

Non-membrane-bound particles; stored nutrients like glycogen or starch

Organelles classification

Membranous (membrane-bound) and Nonmembranous (not membrane-bound)

Endomembrane system

Organelles working together to modify, package, and transport lipids and proteins

Nucleus

Control center of cell; contains DNA

Multinucleate cells

Cells with many nuclei

Anucleate cells

Cells with no nucleus (e.g., red blood cells lose their nucleus over time)

Nuclear envelope

Double membrane surrounding nucleus with pores controlling entry/exit of molecules

Nucleoplasm

Gel-like substance filling nucleus; contains chromatin

Nucleolus

Dense structure in nucleus; site of ribosome synthesis

Progeria nucleus

Nucleus abnormality linked to premature aging

Chromatin

DNA wrapped around proteins

Nucleosome

DNA wrapped around histone proteins

Histone

Protein that enables DNA packaging into nucleosomes

Mitosis

Cell division duplicating the genome and distributing identical copies into daughter cells

DNA

Deoxyribonucleic acid; blueprint for protein synthesis

Gene

Segment of DNA that codes for one polypeptide

Exon

DNA/RNA segments that code for proteins

Intron

Non-coding regions removed during RNA splicing

Central Dogma of Biology

DNA → RNA → Protein

Protein synthesis

Process of making proteins using mRNA as blueprint; ribosomes and tRNA assemble amino acids into polypeptides

Transcription

Process of forming RNA from DNA

Translation

Process of converting mRNA into polypeptides

Ribosomes

Cell's protein synthesis machinery

Free ribosomes

Produce proteins used within cytosol

Bound ribosomes

Produce proteins for secretion outside cell or for membranes

Endoplasmic reticulum (ER)

Network of membranes for protein and lipid synthesis

Rough ER

Site of protein synthesis; studded with ribosomes

Smooth ER

Site of lipid synthesis; lacks ribosomes

Golgi apparatus

Modifies, sorts, and packages proteins and lipids from ER for secretion; made of flattened sacs (cisternae)

Lysosome

Organelle with hydrolytic enzymes; digests biomolecules, repairs cells, involved in apoptosis (programmed cell death)

Vacuoles

Storage organelles in plants

Mitochondria

Site of cellular respiration; powerhouse of the cell

Mitochondria outer membrane

Smooth surface

Mitochondria inner membrane

Folded into cristae to increase surface area

Endosymbiont theory

Mitochondria originated as free-living prokaryotic cells engulfed by ancestral eukaryotes

Peroxisome

Organelle for fatty acid breakdown; produces and detoxifies hydrogen peroxide

Cytoskeleton

Network of protein filaments in cytoplasm providing structure and facilitating transport

Centrosome

Region where microtubules grow; contains centrioles

Cilia

Short, numerous hairlike projections; move fluids across cell surface

Flagella

Long, whip-like structures; propel cells through water

Extracellular matrix (ECM)

Structure outside plasma membrane; provides support and anchorage for cells

Cell junctions

Connections between cells for adhesion and communication

Tight junctions

Seal neighboring cells; form water-tight barriers

Gap junctions

Allow communication and rapid signal transmission between cells