1 Topic 2.3: Eukaryotic Cells IB Biology HL A. Allen Cytoplasm (cytosol): a cell's inner space cytosol Cytosol: large fluid-filled space (mostly water + proteins that control most of the cell metabolisms): glycolysis, transcription factors, intracellular receptors etc. Plasma membrane Organelles • Nucleus • Protein production machine: the ribosomes • Mitochondria and Chloroplasts • Endoplasmic Reticulum and the Golgi apparatus (we don’t say ‘Golgi body’ in IB) • Lysosomes • Adapted and/or specialized for carrying out one or more vital functions Reminder! Membrane-bound organelles are only found in eukaryotes. Nucleus: a cell's center Function of the nucleus: • Stores the chromosomes (genetic material) Note : Two kinds of genetic material: – deoxyribonucleic acid (DNA) – ribonucleic acid (RNA) • Keeps the DNA molecules separated from metabolic machinery of cytoplasm. • Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells • DNA replication and synthesis of messenger RNA (mRNA). The mRNA is allowed to leave the nucleus. It is read by the ribosomes during protein synthesis. ...Nucleus: a cell's center
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Topic 2.3: Eukaryotic Cells
IB Biology HL
A. Allen
Cytoplasm (cytosol): a cell's inner space
cytosol
Cytosol: large fluid-filled space (mostly water + proteins that control
most of the cell metabolisms): glycolysis, transcription
factors, intracellular receptors etc.
Plasma
membrane
Organelles
• Nucleus
• Protein production machine: the ribosomes
• Mitochondria and Chloroplasts
• Endoplasmic Reticulum and the Golgiapparatus (we don’t say ‘Golgi body’ in IB)
• Lysosomes
• Adapted and/or specialized for carrying out one or more vital functions
Reminder! Membrane-bound
organelles are only found in
eukaryotes.
Nucleus: a cell's center
Function of the nucleus:
• Stores the chromosomes (genetic material) Note: Two kinds of genetic material:
– deoxyribonucleic acid (DNA)
– ribonucleic acid (RNA)
• Keeps the DNA molecules separated from metabolic machinery of cytoplasm.
• Makes it easier to
organize DNA and to
copy it before parent
cells divide into daughter
cells
• DNA replication and
synthesis of messenger
RNA (mRNA). The
mRNA is allowed to
leave the nucleus. It is
read by the ribosomes
during protein synthesis.
...Nucleus: a cell's center
2
Nucleolus
• Dense mass of
material in nucleus
• Cluster of DNA and
proteins
• Subunits must pass
through nuclear pores
to reach cytoplasm
• production of
ribosomes in nucleolus
• Two outer membranes (lipid bilayers)
• Pores span bilayer and controls what
enters/leaves nucleus.
• Much more detail to follow!
Nuclear Membrane (Envelope)
Chromatin
• Cell’s collection of DNA and associated proteins
• A chromosome is one DNA molecule and its associated proteins
• Appearance changes as cell dividesFUNCTION:
• With the help of tRNA, ribosomes use information in mRNA to assemble proteins
• small semi-spherical, black dots
• some are free in cytoplasm (cytoplasmic ribosomes), others are attached to the ER (ER ribosomes)
Ribosomes
STRUCTURE
• ER is a continuation of the outer nuclear membrane.
• Two types: Smooth and Rough. (Rough ER has ribosomes on it)
• Network of membrane that connects nuclear envelope to the cell