A2.2 Cell structure

What is the cell theory?

• All living organisms = 1 or more cells

• Cell = basic unit of structure and function

• Cells arise only from pre-existing cells

What are the functions of life present in all cells?

Metabolism, Response, Homeostasis, Growth, Reproduction, Excretion, Nutrition

What is light microscopy?

Uses light, lower res

What is the role of fluorescent stains and immunofluorescence?

Highlight proteins/organelle locations

What is electron microscopy?

• TEM (Transmission) → internal ultrastructure

• SEM (Scanning) → 3D surfaces

What is cryo-EM?

Proteins imaged at atomic detail

What is the structure of prokaryotic cells?

• Cell wall of peptidoglycan, plasma membrane controls entry/exit

• Cytoplasm contains 70S ribosomes and nucleoid with naked DNA

• May have pili, flagella, plasmids

What is the process of life in the unicellular organism paramecium?

Heterotroph (cannot produce own food), cilia for movement, contractile vacuoles for osmoregulation

What is the process of life in the unicellular organism chlamydomonas?

Photosynthesis, flagella for movement, phototaxis (moving towards/away from light)

What are the steps for temporary mount in microscopy?

Specimen → drop water/stain → cover slip at angle (avoid bubbles)

What stains are used for microscopy?

Methylene blue (animal), iodine (plant)

What is the formula for magnification?

Magnification = Image / Actual size

What structures are common to cells in all living organisms?

• Plasma membrane = selective barrier, communication

• Cytoplasm = site of metabolism

• DNA = hereditary material for proteins and RNAs

What are the differences in eukaryotic cell structure?

• Cell wall absent in animal, cellulose in plant, chitin in fungal

• Vacuoles small and temporary in animal, large central in plant, small and variable in fungal

• Plastids absent in animal, chloroplasts and others in plant, absent in fungal

• Centrioles present in animal, absent in plant and fungal

• Cilia/Flagella sometimes in animal (sperm), rare in plant and fungal

How are aseptate hyphae atypical eukaryotic cells?

Multi-nucleated, no cross walls

How are skeletal muscle fibres atypical eukaryotic cells?

Syncytium (many nuclei)

How are RBCs atypical eukaryotic cells?

Enucleated to max out oxygen carrying capacity

How are phloem sieve tube elements atypical eukaryotic cells?

No nucleus, rely on companion cells

What are structures in eukaryotic cells?

• Nucleus

• 80S ribosomes

• Rough ER

• Smooth ER

• Golgi apparatus

• Mitochondria

• Chloroplasts

• Cellulose walls

• Large vacuoles

What are characteristics of the nucleus in eukaryotic cells?

Linear DNA and pores

What are characteristics of the 80S ribosomes in eukaryotic cells?

Free or on rough ER

What are characteristics of the rER in eukaryotic cells?

Protein synthesis

What are characteristics of sER in eukaryotic cells?

Lipids and detox

What are characteristics of the golgi apparatus in eukaryotic cells?

Modifies and packages proteins

What are characteristics of the mitochondria in eukaryotic cells?

Produced energy as ATP, contain DNA and 70S ribosomes

What are characteristics in plant/algal eukaryotic cells?

Chloroplasts, cellulose walls, large vacuoles

How to identify prokaryotes in micrographs?

Small, nucleoid, 70S ribosomes, no nucleus

How to identify plants in micrographs?

Cell wall, chloroplasts, large vacuole

How to identify animals in micrographs?

No wall, no chloroplasts, small vacuoles