Cell Structure - Lecture Slides Flashcards
What is the cell theory?
- All organisms are the basic unit of life
- A cell is the smallest unit with properties of life
- Cells arise from the growth and division from pre-existing cells
Prokaryotic cells
- Unicellular
- No membrane bound organelles
- First cells on earth
- Have a nucleoid: region where singular circular DNA is located
- Smaller structure allows them to reproduce fast and efficiently
- Cell wall is made of peptidoglycan (bacteria) or psuedopeptidoglycan (archae)
Eukaryotic cells
- Have membrane bound organelles
- Contain a true nucleus
- Have mitochondria (animal cells)
- Have chloroplasts (plant cells)
- Linear chromosomes
The Nucleus
- Repository for genetic material
- Surface bound by two phospholipid bi-layer membranes (nuclear envelope)
- Liquid inside the nucleus is called the nucleoplasm
- Has nuclearpores which allows regulation of substances in and out of nucleus
- Nucleolus is the region of intensive rRNA synthesis
- Contains chromtin (linear), combination of DNA and proteins
Chromosomes
- In eukaryotic cells, each DNA molecule is linear ; organized with histone proteins into specific eukaryotic chromosomes
- DNA wrapped around 8 histones forms a bead like structure
- Short thick structure chromosomes and thin long structure chromatid
Plasma membrane
Encloses the cells
Ribosomes
- NOT organelles as they are not membrane enclosed
- Responsible for protein synthesis
- RNA protein composed of two sub units that attract mRNA
One large and one small sub unite
Free ribosomes
- Suspended in cytosol
- Synthesize proteins that function within the cytosol
Membrane-bound ribosomes
- Attach to the outside of the ER
- Synthesize proteins either included with membranes or exported from the cell
- Ribosomes are not permanently attached
Endomembrane system
- Compartmentalizes cell, channelling passage of molecules through cells interior
- Key role in synthesis and hydrolysis of macromolecules in the cell
- Called polypeptides until their modified
Endoplasmic reticulum
- Responsible for protein synthesis
- Included tubules and internal spaces (cristernae)
- Continuous with nuclear envelope
Rough ER
- Abundant in cells that secrete proteins
- Site for glycosylation of some proteins
(Glycoproteins are polypeptides in which an oligosaccharide is attached) - Secreted proteins are packaged in transport vessicles to be delivered to plasma membrane and secreted out of the cell
- Also makes membrane proteins
Smooth ER
- Stores calcium
- Rich in enzymes (important for metabolic roles)
- Synthesizes lipids
- Mobilises glucose (source of ATP) from stored glycogen in liver
An enzyme removes the phosphate group
from glucose phosphate, a product of
glycogen hydrolysis, permitting glucose to
exit the cell - Detoxifies chemicals
The Golgi complex
- Collection of membrane sacs
- Becomes modified, sorted, packaged and distributed when it goes from Cis phase to Trans phase
- Proteins are chemically modified by removing segments or adding functional groups, or lipid or carbohydrate units
- Sorting of proteins for delivery to their final
destinations - During processing, material is moved from cisterna to cisterna, each with its own set of enzymes
- transported to the plasma membrane in secretory vesicles that release their contents outside cell by exocytosis
Lysosomes
- Small membrane bound vesicles
- Formed by budding from Golgi
- Sacs of hydrolytic enzymes that digest macromolecules, worn-out organelles
- vacuoles can carry out lysosomal functions in plant cells
- Will digest molecules to its monomers
Mitochondria
- Perform cellular respiration
- Generating ATP from catabolism of organic fuels in the presence of oxygen
Chloroplasts
- Perform photosynthesis
- Convert solar energy to chemical energy
- Synthesize new organic compounds from CO2 and H2O
Endosymbiotic organelles
- Mitochondria and chloroplasts are semiautonomous
- Synthesized from free ribosomes in the cytosol
- Both have primitive circular singular DNA
- Grow and reproduce, almost like bacteria
Mitochondrial anatomy
■ Two membranes (A smooth outer membrane) & (highly folded inner membrane)
■ Cristae is the inner fold that increase surface area for membrane proteins
■ Intermembrane space holds protons (low pH) which is used for ATP synthesis
- The mitochondrial matrix is a fluid-filled space inside the inner membrane
Plastids
- Green pigment called chlorophyll
■ Amyloplasts stores starch
■ Chromoplasts stores pigments
■ Chloroplasts harness solar energy - The chloroplast produces sugar via photosynthesis
Chloroplast anatomy
two boundary membranes: outer and inner membranes
■ The outer and inner membrane surround the stroma
■ Stroma houses the third membrane organized into sacs, the thylakoids
■ The stroma contains DNA, ribosomes,
and photosynthetic enzymes
■ Thylakoids are stacked into grana and hold chlorophyll
■ Thylakoid membranes surround the thylakoid space
Chloroplast Anatomy grana
