Cell Biology Quiz

Cell Morphology

• This presentation covers cell structure and morphology, focusing on various cellular components.

Cytoplasm

• Cytoplasm is a liquid medium within cells, distinct from gaseous, liquid, or solid states.
• Its components are critical to cellular function.

Cytoplasm Structure

• Cytosol : liquid component of cytoplasm.
• Cell organelles : membrane-bound structures with specific functions.
• Cellular inclusions : non-membrane-bound, often storage products.
• Cytoskeleton : protein filaments maintaining shape and supporting movement.

Cytoplasm Topographic Regions

• Cortex : outer layer of the cytoplasm adjacent to the cell membrane.
• Cytocenter, centrosome : area containing centrioles, essential for cell division.
• Endoplasma : innermost region surrounding the nucleus.

Cytosol Composition

• Composed primarily of water (H₂O), amino acids, proteins, enzymes, nucleotides (RNA, DNA), glucose, ATP, and ions.
• Represents a significant proportion (64%) of the total cell volume (in the particular specimen/cell shown).
• Various components, such as mitochondria (1.7%), vacuoles (5.8%), and others, contribute to the composition.

Cell Organelles

• Membrane-bound structures with specific functions within the cell.
• Examples include mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, lysosomes, and peroxisomes.
• These are distinguished by their functions, structure and location within the cell.

Non-Membranous Organelles

• Ribosomes : Involved in protein synthesis; present in both free and bound forms.
• Centrioles : Involved in cell division.
• Ribosomes characteristics:
  • Small subunit – one rRNA molecule and 33 different proteins. Sedimentation coefficient: 40S.
  • Large subunit – three rRNA molecules and 40 different proteins. Sedimentation coefficient: 60S.

Ribosomes Synthesis

• Ribosomes are synthesized in the nucleolus from rRNA and proteins, then transported to the cytoplasm.
• Polypeptide chains – found in the cytoplasm.
• Ribosomal subunits – found in the nucleus.

Endoplasmic Reticulum

• A complex membrane network with flattened sacs and tubes (cisternae).
• Two main types:
  • Rough ER (rER): studded with ribosomes, involved in protein synthesis and modification.
  • Smooth ER (sER): lacks ribosomes, involved in lipid synthesis, carbohydrate metabolism, and detoxification.
• The rER and sER are connected, with sER serving to process and transport molecules that the rER produced.

Golgi Apparatus

• Network of flattened membrane sacs (cisternae) involved in modifying, sorting, and packaging proteins and lipids for secretion or use within the cell.
• Functions include modification of proteins, packaging of proteins, protein sorting, and cell membrane renewal.

Lysosomes

• Membrane-bound organelles containing hydrolytic enzymes for intracellular digestion.
• Function in breaking down materials, such as cellular debris, bacteria, and worn-out organelles.
• Can be categorized into primary, secondary, and tertiary types which differ in function.
• Primary lysosomes are inactive—secondary lysosomes are active; tertiary lysosomes are for residual waste products

Peroxisomes

• Membrane-bound organelles containing oxidative enzymes (e.g., catalases) for various metabolic processes, particularly breaking down fatty acids.
• Responsible for protecting the cell from harmful byproducts such as hydrogen peroxide.

Cellular Inclusions

• Substances or structures within the cytoplasm that aren't cell organelles (glycogen, fat droplets, pigments).
• Glycogen: stored polysaccharide in cells with high metabolic activity.
• Fat droplets: stored triglycerides/cholesterol in adipocytes (fat cells).
• Pigments: colored substances (e.g., melanin) with various functions.
• Other inclusions might include hemoglobin, myoglobin or other specific cell types.

Mitochondria

• Organelles responsible for cellular energy production (ATP synthesis).
• Have their own DNA and ribosomes (suggesting an evolutionary origin from bacteria).
• Two membranes: inner (cristae) and outer membranes, which play a role in energy production.