a2.2 cell structure

What does the cell theory predict about newly discovered organisms?

They will consist of one or more cells, as cells are the basic unit of life.

What microscopy skills should IB students learn?

Making temporary mounts, staining, using an eyepiece graticule, focusing with coarse and fine adjustments, calculating actual size and magnification, drawing a scale bar, and taking photos.

What are the advantages of advanced microscopy methods?

• Electron microscopy provides high resolution.

• Freeze-fracture and cryogenic EM show detailed 3D structures.

• Fluorescent stains and immunofluorescence highlight specific structures in light microscopy.

What structures are found in all cells and why?

• DNA: for storing genetic information.

• Cytoplasm: water-based site of metabolic reactions.

• Plasma membrane: controls exchange with the environment.

What components are found in typical prokaryotes (e.g., Bacillus, Staphylococcus)?

Cell wall, plasma membrane, cytoplasm, a loop of naked DNA (nucleoid), and 70S ribosomes.

What are the key features of eukaryotic cells?

Plasma membrane, compartmentalized cytoplasm with 80S ribosomes, a nucleus with DNA bound to histones, and membrane-bound organelles (mitochondria, ER, Golgi, vacuoles, lysosomes), plus a cytoskeleton.

Which life processes occur in unicellular organisms?

Homeostasis, metabolism, nutrition, movement, excretion, growth, response to stimuli, and reproduction.

How do animal, fungal, and plant cells differ structurally?

• Cell walls: present in fungi and plants, not animals.

• Chloroplasts and plastids: only in plants.

• Vacuoles: large central vacuole in plants, small in others.

• Centrioles, cilia, flagella: usually in animals, vary in fungi/plants.

Give examples of atypical cell structures in eukaryotes.

• Multinucleated: skeletal muscle, aseptate fungal hyphae.

• No nucleus: red blood cells, phloem sieve tube elements.

What structures can be identified in micrographs?

Nucleoid region, prokaryotic cell wall, nucleus, mitochondria, chloroplast, sap vacuole, Golgi apparatus, rough/smooth ER, chromosomes, ribosomes, plasma membrane, microvilli.

What should annotated diagrams from electron micrographs include?

Draw and label: nucleus, mitochondria, chloroplasts, sap vacuole, Golgi apparatus, rough/smooth ER, chromosomes, cell wall, plasma membrane, secretory vesicles, microvilli. Include each part’s function.

What is the theory of endosymbiosis?

Mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.
Evidence: 70S ribosomes, circular DNA, independent replication.

What causes cell differentiation?

Differences in gene expression, often triggered by environmental signals, lead to specialized cell types.

Why did multicellularity evolve repeatedly, and what are its benefits?

Evolved in fungi, algae, plants, and animals.
Benefits: Larger size, division of labor, specialized cells and tissues.

Why are the same molecular building blocks used in all cells?

Due to shared ancestry and efficiency: DNA, RNA, proteins, lipids, and carbohydrates are universal and reliable.

What makes a scientific theory compelling?

A strong theory explains many observations and accurately predicts outcomes (e.g., cell theory, endosymbiosis).