Cell structure, genetic control, and life cycle

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Cell structure, genetic control, and life cycle
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Movement of molecules into cells

• Through membrane
• Phagocytosis
• Endocytosis/pinocytosis
• Exocytosis/secretion

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Receptor-mediated endocytosis
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Projections on cell surface Cilia made from
microtubules move in beating pattern Lumen
side of respiratory and female reproductive tract
Flagella- also made of microtubules whiplike
movement only on sperm cells in humans
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Microvilli fingerlike projections of cell
membrane lumen (apical) side of cell Aid in
absorption (increase surface area of membrane)
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The cytoskeleton

• microtubules

• Organelles are not just floating around!

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Lysosomes degrade large molecules double
membrane hydrolytic enzymes Peroxisomes found
in liver and kidney cells toxic by-products of
oxygen produced by reactions with these
enzymes Catalase- converts these to harmless
forms
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Structure of a mitochondrion note inner and
outer membranes
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Mitochondrion Production of ATP Many metabolic
disorders associated with defective enzymes in
mitochondria
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Protein synthesis and endomembrane system

• Complex system required for protein synthesis
• Ribosomes
• Rough endoplasmic reticulum (rough ER)
• Golgi (complex, apparatus)

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Endoplasmic reticulum

• Rough ER is covered with ribosomes
• Protein processing begins
• Smooth ER lipid synthesis, calcium storage-
  tissue specific

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Endoplasmic reticulum Rough (granular)- overed
with ribosomes protein synthesis,
processing glycosylation some cells have more
of this than others Smooth lipid synthesis
(steroid hormones) calcium storage
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Golgi where does the protein go?
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Nucleus contains genetic information

• DNA contained in chromosomes
• RNA formed but transported out of nucleus
• Pores control access

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Levels of structure in chromatin

• Chromatin can be opened up by acetylation

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Protein synthesis is dictated by DNA Messenger
RNA is transcribed (copied) from DNA. mRNA can
move into cytoplasm mRNA is a template from
which amino acid chains (polypeptides) are
built Ribosomes Transfer RNA Amino acids
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Formation of messenger RNA

• Genes are transcribed off a single strand of DNA
• 25,000 genes can yield over 100,000 proteins
• Regulated through RNA interference

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Messenger RNA is translated into protein (but
this is only the first step in protein synthesis)
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Protein is assembled in the endomembrane system

• Polypeptide forms secondary, tertiary, quaternary
  structure
• May be modified by carbohydrates or lipids
• Chaperones help proteins fold correctly

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The life cycle of a cell
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How is the cell cycle controlled? Proto-oncogenes
allow cell to proceed through cell cycle Tumor
suppressor genes prevent cell from going to the
next stage of the cell cycle Mutations in these
genes interfere with control of
growth??cancer Apoptosis- programmed cell
death
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Review mitosis and meiosis

• What types of cells undergo mitosis and meiosis-
  and when?
• What are the products of mitosis and meiosis?
• What are the implications for inheritance?
• Gene expression can vary in cells

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Summary

• The work of a cell is organized into organelles
• Genetic information is contained in DNA, and is
  expressed through transcription and translation
• In cell division, DNA is copied and distributed
  into new cells
• Regulation of these activities varies at
  different times and in different cells