Cells as Functional Units Flashcards
What are polynucleotides?
Polymerised from Purines and Pyrimidines. They can directly guide the formation of exact copies of their own sequence (base pairing of DNA).
What is the plasma membrane?
A lipid bilayer with proteins and molecules embedded in it which is selectively permeable, and maintains homeostasis, aids in binding and adhering, and is important for communication with the outside environment.
What dos the cell theory state?
- Cells are the fundamental units of life.
- All living organisms are composed of cells.
- All cells come from pre-existing cells.
What was the first cell observation?
Robert Hooke discovered dead cell walls of plant cells under a microscope.
Anton van Leeuwenhoek observed the first live cell under a microscope.
What size of things is a microscope used to see?
Objects smaller than 0.2mm (200um) for light microscopes. Electron microscopes can see objects smaller than 0.1mm.
What is cell size limited by?
The surface area-to-volume ratio. The volume of a cell determined how much chemical activity it can carry out, and the surface area of a cell determines the amount of a substance it can take in and how much waste it can release.
What is resolution?
The minimum distance two objects can be apart and still be seen as two objects. Around 0.2mm for the human eye.
What is the difference between Prokaryotic and Eukaryotic cells?
Prokaryotic - Archaea and bacteria. No nucleus or membrane-bound compartments, lack distinct organelles.
Eukaryotic - Have a membrane-enclosed nucleus and other compartments and organelles.
What type of cells have cell walls and what are they for?
Some prokaryotic cells. They are located outside the plasma membrane and maintain shape.
What is peptidoglycan?
Sugars and amino acids which is what bacteria cell walls are usually composed of. Some bacteria have an outer layer of lipopolysaccharide and protein which encloses the peptidoglycan layer.
What is mycoplasma bacteria?
Bacteria that lack a cell wall making them unaffected by antibiotics. Some are pathogenic to humans.
What are cyanobacteria?
They have a complex and highly organised system of internal membranes with which to carry out photosynthesis.
What is flagella?
Locomotory structures found in some prokaryotic cells which are shaped like corkscrews to help them swim.
What is pili?
Structures which help the bacteria to adhere (stick) to one another during exchange of genetic material and to animal cells for protection or food.
What are the three shapes of prokaryotic cells?
Rod shaped, Spherical, Spiral shaped.
What are inclusions?
Deposits found within the cytoplasms which act as storage for lipids, starch, glycogen etc.
What are the main functions of the nucleus?
Contains most of the cells DNA, the site of DNA replication and first steps of decoding it for protein production takes place in the nucleus. Also the site where gene transcription is turned on or off.
What does the rough endoplasmic reticulum do?
It segregates newly synthesised proteins away from the cytoplasm and transports them to other areas of the cells. The proteins can be chemically modified to alter their function/destination.
What does the smooth endoplasmic reticulum do?
Responsible for chemical modification of small molecules taken into the cell. Site of hydrolysis of glycogen in animal cells and the site of synthesis of lipids and steroids.
Where can ribosomes be found in eukaryotic cells?
- The cytoplasm either freely or attached to the endoplasmic reticulum.
- The mitochondria and chloroplasts.
What is the function of the Golgi apparatus?
To further modify, concentrate and package proteins before they are sent to their final destination. Also site of synthesis of polysaccharides of plant cell walls.
What are lysosomes/what is their function?
Vesicles containing digestive enzymes that originate from the Golgi. Site for breakdown for food/foreign material brought into the cell by phagocytosis, also site of autophagy.
What is autophagy?
The process of organelles such as mitochondria being engulfed by lysosomes and hydrolysed into their monomers to be reused.
What are mitochondria?
Site of cellular respiration, energy stores in the bonds of CHO’s and fatty acids is converted to ATP by ATP synthase in the inner membrane.
What are plastids?
Organelles which are only found in plants and some protists. An example is a chloroplast.
What are chloroplasts?
Type of plastid found in some cells of plants and protists. Site of photosynthesis.
What are the functions of vacuoles?
Storage, structure, reproduction, digestion.
How do prokaryotes divide?
Fission. Most have one circular chromosome. As DNA replicates each of the 2 resulting strands attach to the plasma membrane and as the cell grows a new plasma membrane is added between the attachment sites and the DNA molecules are moved apart. Cytokinesis then separates the cell in 2 each with a complete chromosome.
What is a centromere?
The constriction point of a chromosome which divides the chromosome into two sections/arms - the short arm called the ‘p’ arm, and the long arm called the ‘q’ arm. The location of the centromere gives the chromosome its characteristic shape and helps describe the location of specific genes.
How is DNA packaged into chromosomes?
Histones compact he chromosomal DNA resulting in a DNA-protein complex called chromatin. Proteins are added to DNA to make it more compact. However, this coiling requires work and energy which is provided by the histones.
What are histones?
A family of small, positively charged proteins termed H1, H2A, H2B, H3 and H4 .
What is a nucleosome?
The basic repeating structural and functional unit of chromatin which contains 9 histones and around 166 base pairs of DNA. Packaging DNA into nucleosomes shortens the fibre length 7 fold, but it is even further coiled into a 30nm fibre.
