BIOL 2311 Lecture Notes - Lecture 4: Secretory Protein, Histocompatibility, Final Destination 3
CH 4 CELL STRUCTURE
CELL CHARACTERISTICS:
Genetic material
– single circular molecule in prokaryotes
– double helix located in nucleus in eukaryotes (eukaryotic genome is very complex- 6000 genes in a
genome)
-Cytoplasm fills cell interior both in prokaryotes and eukaryotes
-Plasma membrane encloses the cell
Cell Size:
Rate of diffusion affected by
– Surface area available
– Temperature
– Concentration gradient
– Distance
MICROSCOPES:
2 types
1. light microscopes:
– Use magnifying lenses with visible light
– Resolve structures that are 200 nm apart
2. electron microscopes:
-Use beam of electrons
– Resolve structures that are 0.2 nm apart
-Transmission electron microscopes give good 2D images
-Scanning electron microscopes give good 3D images
BASIC STRUCTURAL SIMILARITIES: (btwn prokaryotes and eukaryotes)
1. Nucleoid (pro) or nucleus (euk): where DNA is located
2. Cytoplasm: Semifluid matrix of organelles and cytosol
3. Ribosomes: Synthesize proteins
4. Plasma membrane: Phospholipid bilayer
PROKARYOTIC (bacteria):
-Simplest organism
-Lack a membrane-bound nucleus
-DNA present in nucleoid
-There exists a Cell wall outside of the plasma membrane
….
Bacterial cell walls
-Most bacterial cells are encased by a strong cell wall
– composed of peptidoglycan
– Cell walls of plants, fungi, and most protists different
-Protects the cell, maintain its shape, and prevent excessive uptake or loss of water
-vulnerability of bacteria to antibiotics often depends on the structure of their cell walls
-Archaea lack peptidoglycan
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….prokaryotic cont'd
-Does contain ribosomes (instead of membrane-bound organelles)
Two domains of prokaryotes
– Archaea
– Bacteria
EUKARYOTIC CELL (plant and animal)
• Characterized by compartmentalization by an endomembrane system, and the presence of
membrane-bound organelles.
• Plant cell and Animal cell are both eukaryotic and have extensive organelles
• Possess a cytoskeleton for support and to maintain cellular structure
• Differences in organelles between plant and animal cells
– Plant cells contain chloroplasts, vacuoles, and a cell wall outside the cell membrane: photosynthesis
ORGANELLES AND THEIR FUNCTION
Nucleus: Inheritance, RNA production
Mitochondrion : energy production, generates ATP, has its own DNA
Endoplasmic reticulum: Protein and lipid production
Golgi: glycosylation, secretion
Lysosomes: Degradation
Peroxisomes: Degradation, detoxification
NUCLEUS
- Repository of the genetic information
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- Most eukaryotic cells possess a single nucleus
-Nucleolus : region where ribosomal RNA synthesis takes place
- Nuclear envelope
2 phospholipid bilayers (4 leaflets) tht encase the nucleus which contains some of the DNA: in btwn is
the inter-membrane space where proteins reside.
Nuclear pores : control passage of movement of protein and RNA in and out, the outer and inner
membrane (2 phospholipid bilayers) have to fuse in order to create an opening btwn the nucleoplasm
and cytoplasm at the site of the pore.
-In eukaryotes, the DNA is divided into multiple linear chromosomes
-Chromatin(helps the DNA fold into the nucleus) is a DNA + protein
-mitochondria and nucleus are symbiotic relationships
-take genes from nucleus and transcribe to RNA, send to mitochondria to form protein complexes.
CHROMOSOMES:
-DNA is organized in discrete segments called chromosomes.
- Humans have 23 pairs of chromosomes:
22 autosome pairs which are the same in both sexes
1 pair of sex chromosomes, the X and the Y
- Each chromosome includes hundreds of different genes.
-DNA of eukaryotes is divided into linear chromosomes.
– exist as strands of chromatin, except during cell division
–associated with histones (proteins), packaging proteins
• nucleosomes, histones in btwn tht space the nucleosomes
-The DNA double helix in the cell nucleus is packaged by special proteins termed histones. Which form
small groups called nucleosomes and create a complex structure called chromatin- a protein/DNA
complex. The chromatin coils around to make up the chromosome.
END
OMEMBRANE SYSTEM:
-eukaryotic cell
- a series of membranes throughout the cytoplasm
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Document Summary
Double helix located in nucleus in eukaryotes (eukaryotic genome is very complex- 6000 genes in a genome) Cytoplasm fills cell interior both in prokaryotes and eukaryotes. Resolve structures that are 200 nm apart: electron microscopes: Resolve structures that are 0. 2 nm apart. Nucleoid (pro) or nucleus (euk): where dna is located: cytoplasm: semifluid matrix of organelles and cytosol. Ribosomes: synthesize proteins: plasma membrane: phospholipid bilayer. There exists a cell wall outside of the plasma membrane. Most bacterial cells are encased by a strong cell wall. Cell walls of plants, fungi, and most protists different. Protects the cell, maintain its shape, and prevent excessive uptake or loss of water. Vulnerability of bacteria to antibiotics often depends on the structure of their cell walls. Plant cells contain chloroplasts, vacuoles, and a cell wall outside the cell membrane: photosynthesis. Mitochondrion : energy production, generates atp, has its own dna. Most eukaryotic cells possess a single nucleus.
