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Unit 1: Cells and multicellular organisms
Quick questions on Cellular components and the fluid mosaic membrane (QCE Biology Unit 1)
15short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the plasma membrane and the fluid mosaic model?Show answer
The plasma membrane is a phospholipid bilayer studded with proteins, cholesterol, glycoproteins and glycolipids.
What is the cytosol and cytoskeleton?Show answer
Cytosol. Aqueous gel-like solution filling the cell. Site of glycolysis and many biosynthetic reactions.
What is organelles of information?Show answer
Nucleus. Bounded by a double membrane (nuclear envelope) studded with nuclear pores. Contains the linear chromosomes and the nucleolus (where ribosomal subunits are assembled). Site of DNA replication and transcription.
What is organelles of energy?Show answer
Mitochondrion. Double membrane; the inner membrane is folded into cristae that increase surface area. Matrix contains the enzymes of the Krebs cycle and mitochondrial DNA. Site of aerobic respiration (Krebs cycle, electron transport chain, ATP synthesis).
What is the endomembrane system?Show answer
Endoplasmic reticulum (ER). A network of flattened sacs continuous with the nuclear envelope. - Rough ER carries ribosomes; folds and modifies proteins destined for secretion or for membranes. - Smooth ER lacks ribosomes; lipid synthesis, detoxification (liver cells), Ca2+ storage (muscle cells).
What is boundaries and walls?Show answer
Cell wall. External to the plasma membrane. - Plants. Cellulose; provides structural support and limits cell expansion. - Fungi. Chitin. - Bacteria. Peptidoglycan.
What is cytosol?Show answer
Aqueous gel-like solution filling the cell. Site of glycolysis and many biosynthetic reactions.
What is cytoskeleton?Show answer
Three protein filament systems. - Microfilaments (actin). Cell shape, cytoplasmic streaming, muscle contraction. - Intermediate filaments. Mechanical strength, anchoring of organelles.
What is nucleus?Show answer
Bounded by a double membrane (nuclear envelope) studded with nuclear pores. Contains the linear chromosomes and the nucleolus (where ribosomal subunits are assembled). Site of DNA replication and transcription.
What is ribosomes?Show answer
Not membrane-bound. Translate mRNA into polypeptides. Free in the cytosol or bound to the rough ER.
What is mitochondrion?Show answer
Double membrane; the inner membrane is folded into cristae that increase surface area. Matrix contains the enzymes of the Krebs cycle and mitochondrial DNA. Site of aerobic respiration (Krebs cycle, electron transport chain, ATP synthesis).
What is chloroplast?Show answer
Double membrane enclosing the stroma; thylakoid membranes stacked into grana. Site of photosynthesis (light reactions on thylakoids, Calvin cycle in stroma).
What is endoplasmic reticulum?Show answer
A network of flattened sacs continuous with the nuclear envelope. - Rough ER carries ribosomes; folds and modifies proteins destined for secretion or for membranes. - Smooth ER lacks ribosomes; lipid synthesis, detoxification (liver cells), Ca2+ storage (muscle cells).
What is golgi apparatus?Show answer
A stack of flattened cisternae. Modifies, sorts and packages proteins and lipids arriving from the ER. Cis face receives, trans face dispatches.
What is vesicles?Show answer
Small membrane-bound sacs that ferry cargo between organelles and to the plasma membrane.