How life works Flashcards
What do all cells require?
All cells require a carbon source, energy plus water. They also need other essential elements such as nitrogen, phosphorus, and iron.
What is vital within a membrane?
The concentration of energy and convertible matter within a membrane is vital
What results in cellular growth?
The metabolic conversion of carbon and energy results in cellular growth.
Cell growth is followed by…
cell growth is followed by division whereby daughter cells each retain the information to convert energy
What do cells use as an energy resource?
Cells us Adenosine Triphosphate (ATP) as their energy source for many cellular reactions.
How is ATP generated?
ATP is generated from carbohydrates through respiration.
What are the three main steps in cellular respiration?
glycolysis, krebs cycle, and oxidative phosphorylation
What happens in glycolysis?
Glucose is split into 2 pyruvate molecules in the cytosol, generating 2 ATP molecules.
Define cellular differentiation.
different cells having different functions.
Krebs Cycle steps:
Krebs cycle occurs in the mitochondria in eukaryotes and cytosol in prokaryotes.
As pyruvate crosses the mitochondrias double membrane it gets converted into
Acetyl CoA (coenzyme A) by oxidative decarboxylation (decarboxylation is the removal of carboxyl groups to leave an acetyl group which then combined with coenzyme A (CoA)
During the cycle, electrons from the acetyl group are transferred to NAD+ and FAD creating NADH2 and FADH2
This only generates a small amount of ATP.
Electron transport chain steps:
The NADH2 and FADH2 produced by the Krebs cycle are then oxidised
Occurs in inner mitochondrial membrane in eukaryotes and cell membrane in prokaryotes
During oxidation electrons are transferred from NADH2 and FADH2 by electron transport chain to give rise to NAD+, FAD and H2O
Oxygen is also converted into water
The energy produced from oxidation drives the conversion of ADP to ATP
30-36 ATP molecules generated
Anaerobic respiration:
-Anaerobic respiration does produce ATP but is less efficient (produces 2-30 ATP molecules)
-More common in prokaryotes
-O2 in the Electron transport chain is replaced with compounds such as sulphate (SO42-), nitrate (NO3-), or sulphur (S) as electron acceptors
Fermentation:
-More common in prokaryotes
-Glycolysis still occurs but not Krebs cycle (only 2 ATP molecules generated)
Lactic acid fermentation:
Prokaryotes and some eukaryotes under low O2 (e.g. muscle cells)
Glycolysis occurs and pyruvate is converted to lactate by the oxidation of NADH to NAD
Describe the evolution of cellular metabolism.
Cellular metabolism arose from simple processes which broke down organic molecules in the absence of oxygen (similar to glycolysis)
Anaerobic respiration in prokaryotes (unicellular organisms have less demand for ATP than multicellular organisms)
Then ATP helped develop photosynthesis
Then oxidative metabolism arose
Can see relics of these systems in some of todays prokaryotic cells (archaebacteria and eubacteria)
Do mitochondria or chloroplasts contain large numbers of genes today?
Neither mitochondria or chloroplasts have large numbers of genes today.
Why may have mitochondria or chloroplasts lost their genes?
It is suggested that they have lost genes by transfer of genes to the nucleus or by loss as genes with similar functions already present in the nucleus.
How many genes chloroplasts got?
chloroplast genomes so far examined only appear to contain 50 – 200 genes (a bacterium like E. coli contains ~4000 genes)
What is differentiation?
unspecialised cells become more specialised and take on more complex functions.
How can a cell become specialised?
For a cell to become specialised, the cell has to express a particular set of genes.
What do all cells arise from?
All cells arise from stem cells.
Stem cells can have different levels of…
Stem cells can have different levels of potency
Where do stem cells commonly start off as and get produced?
Embryonic stem cells, and are produced at the blastula stage of embryonic development.
Define Totipotent
Totipotent – produce all cell types
Define Pluripotent ?
Pluripotent – generate cells from germ layers and can differentiate into a wide range of cell type but not all
Define multipotent
Multipotent – can give rise to multiple cell types within a tissue (e.g. cells of one type of organ)
What are the stages of embryonic development?
- Fertilized Oocyte
- Morula
- Blastula
- Gastrula
- Embryo
What are the three germ layers?
- Ectoderm
- Mesoderm
- Endoderm
At which stage are The three germ layers located?
At the gastrula stage of embryonic development
What do the three germ layers do?
They give rise to cells of specific body systems
Describe evolution of the heart.
-Arose 500 million years ago.
-The heart arose from the mesoderm
-Early prevertabrates had circulatory systems including a pulsatile and contractile tube
-In later vertebrates, part of the mesoderm folded which led to the formation of multiple chambers (atrium and ventricles)
-Demonstrates convergent evolution
What is Paracrine signalling?
Close cells release chemical messengers which bind to receptors on neighbouring cells to co-ordinate activities (e.g. synaptic signalling)
What is Autocrine signalling?
Cells signal to themselves by release of messengers that bind to the cells own surface receptors
What is Endocrine signalling?
Chemical messengers are released into the bloodstream and travel to distant cells (e.g. growth hormone)
What is Direct contact?
Signals travel through gap junctions (small channels between cells)
What do membranes do in regard to organs and tissues?
Membranes link organs and tissues together.
What do organs do in relation to organism function?
Organs form systems (organ systems) in order to fulfil the functions of the organism.
Whats the point of cellular signalling?
Cellular signalling transmits messages between cells which can occur between neighbouring cells or distant cells
How is cellular signalling carried out?
This is done using hormones.
What is central to life on earth?
Central to life on earth is the survival of generations of organisms.
What did gregor mendel study?
reproduction in pea plants in 1866. More specifically, he studied cross-fertilization and self-fertilization in these plants.
What did mendel propose?
Mendel was the first person to propose a scientifically testable theory of inheritance.
What was the theories on hereditary before Mendels studies?
It was unclear how traits were passed on from one generation to the next until Gregor Mendel studied reproduction in pea plants in 1866.
Before that, Aristotle, Hippocrates, and Darwin proposed theories of pangenesis (hereditary particles produced by body cells flowing in the blood (https://www.collinsdictionary.com/dictionary/english/pangenesis)). This was disproven. There were also other theories which including the blending of traits from parents.
What did Mendel look at?
Mendel looked at seven traits and observed the ratio of the appearance of each trait in the first (F1) and second generations (F2) of offspring
What is cross-fertilization?
when one plants pollen grains transfer from its flower to egg-bearing flowers of another plant. (https://www.britannica.com/science/cross-fertilization)
What is Self-fertilization ?
when a plant is fertilized by a gamete from its own flower (https://www.dictionary.com/browse/self-fertilization)
What did mendel determine the existence of?
He determined the existence of dominant and recessive traits
This formed the basis of understanding genetic inheritance
DNA contains…
the majority of genetic information which is passed from one generation to the next
What does DNA rely on for replication?
DNA relies on proteins for replication. However the instructions for these proteins are contained in DNA.
Evolution from RNA and proteins to DNA:
RNA may have been able to self replicate (didn’t have to rely on proteins)
RNA can be packaged into lipid micelles
RNA can act as a catalyst
Believed early life might have been an ‘RNA World’
The first DNA may have contained dUTP rather than dTTP
Origin of DNA would also have required enzymes (proteins) to be present as catalysts
What are proteins?
Proteins are chains of amino acids
What would the first proteins have looked like?
the first proteins would have been small peptide molecules of only a few amino acids
Why were proteins necessary for life to develop?
Formation of proteins would have been required for DNA synthesis and metabolic pathways necessary for life to develop
What are genes?
The means by which information is encoded
What do exons contain?
Exons contain coding for the proteins.
What do promoters dictate?
Promoters dictate whether certain genes are turned on or off
Name the three steps involved in protein synthesis:
- Transcription
- Splicing
- Translation
Details about Globin gene clusters.
Globin multigene family
13 homologous genes derived from a single ancestral gene through gene duplication
Accumulation of mutations has generated
Globin genes expressed during different stages of development
Globin proteins specialized in their function
