Chapter 4: A Tour of the Cell
1. Cell Basics
2. Prokaryotic Cells 3. Eukaryotic Cells
1. Cell Basics
Limits to Cell Size There are 2 main reasons why cells are so small: If cells get too large: 1) there’s not enough membrane surface area to facilitate the transfer of nutrients & wastes…
30 μm 10 μm 2) it would take too long for 30 μm 10 μm materials to diffuse within the the cell
Surface area Total surface area of one large cube of 27 small cubes = 5,400 μm2 = 16,200 μm2
1 Prokaryotic vs Eukaryotic Prokaryotic cells (i.e, bacteria) are quite small and don’t have internal organelle structures. Prokaryotic cell
Eukaryotic cells tend to be much Nucleus larger and contain organelles such as a nucleus.
Eukaryotic cell Organelles
2. Prokaryotic Cells
General Characteristics of Prokaryotic Cells
Lack membrane-enclosed compartments • do not have a nucleus • prokaryotic means “before nucleus”
• do not have any other organelles
All prokaryotes are small, single-celled organisms
• bacteria and archaea
Have a single, circular chromosome
2 Typical Prokaryotic Cell Outside: • cell wall (protects cell) • capsule Prokaryotic flagella (outermost layer) • flagella Ribosomes (propels cell) Capsule Inside: Cell wall Plasma • cytoplasm membrane (liquid inside)
• nucleoid Nucleoid (chromosome) region (DNA) • ribosomes (protein synthesis)
3. Eukaryotic Cells
General Characteristics of Eukaryotic Cells
Have a nucleus and internal organelles • eukaryotic means “true nucleus”
Eukaryotes can be single-celled, or multi-cellular organisms
• Protists, Fungi, Plants & Animals
Much larger than prokaryotic cells • ~10-100 μm (vs ~1-10 μm for prokaryotes)
Have multiple, linear chromosomes
3 A typical Animal Cell
Smooth endoplasmic Nucleus reticulum Rough endoplasmic reticulum
Flagellum
Not in most Lysosome plant cells Ribosomes Centriole Golgi Peroxisome apparatus
Microtubule Plasma membrane Intermediate Cytoskeleton filament Mitochondrion
Microfilament
A typical Plant Cell Rough Nucleus endoplasmic reticulum Ribosomes Smooth endoplasmic reticulum Golgi apparatus Microtubule Intermediate Central Cytoskeleton filament Not in vacuole animal Microfilament Chloroplast cells Cell wall
Mitochondrion Peroxisome Plasma membrane
The Nucleus • enclosed by nuclear envelope (double membrane) • contains chromosomes (DNA + proteins) • nucleolus • ribosome production
• nuclear pores • allow transport
4 The Endoplasmic Reticulum (ER)
Convoluted membrane continuous with the nuclear env. • smooth ER (new lipid production) • rough ER (protein synthesis by ribosomes)
Synthesis and packaging of a protein by the rough ER
transport vesicle buds off 4 ribosome
secretory protein inside transport vesicle
3 sugar 1 chain
2 glycoprotein polypeptide rough ER
Proteins made in the RER are transported within membrane-enclosed vesicles to the Golgi apparatus…
The Golgi Apparatus
Discontinuous membrane stacks distal to the ER: • receive proteins, lipids from ER via vesicles • site of modification, packaging, sorting and distribution
5 Lysosome formation & function
rough ER
1 transport vesicle Lysosomes are (containing inactive hydrolytic enzymes) membrane bound compartments plasma Golgi membrane apparatus derived from the Golgi apparatus
lysosome engulfment engulfing 2 of particle damaged organelle “food” They are acidic lysosomes 3 and break down materials from 5 4 food digestion inside & outside vacuole of the cell.
The Endomembrane System Newly made lipids & proteins in the ER travel to the Golgi apparatus and then to various destinations: transport vesicle transport vesicle from Rough ER from ER to Golgi Golgi to plasma membrane • plasma membrane
Plasma membrane • cell exterior
Nucleus • lysosomes
Vacuole
Lysosome • other organelles
Smooth ER Nuclear envelope Golgi apparatus
Mitochondria
Main site of energy production (i.e., ATP, heat): • break down of food molecules (sugars and fatty acids)
• the process of respiration (requires O2)
Site of photosynthesis in plant cells:
• production of glucose from CO2 and H2O using sunlight • the basis of essentially all ecosystems
Central Vacuole in Plants Storage of water, waste, & nutrients
Source of “turgor pressure” that maintains rigidity of plant cells
• swells when water is plentiful due to osmosis
• cell wall provides support, prevents lysis
The Cytoskeleton Internal network of protein fibers important for: • cell structure & shape • cell, organelle movement • cell division
7 Flagella & Cilia Cellular projections involved in movement.
Found only on certain cell types • e.g., respiratory tract (cilia), sperm (flagellum) • move the cell itself, or material across its surface
Key Terms for Chapter 4
• prokaryotic, eukaryotic • cell wall, capsule, flagella, nucleoid, cytoplasm • nucleus, endoplasmic reticulum, ribosome • Golgi apparatus, lysosome • endomembrane system, central vacuole • mitochondria, chloroplasts • cytoskeleton, cilia
Relevant Review Questions 1-3, 5-11, 13-15
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