Life at a Cellular Level Flashcards
What are cells?
The smallest unit that can live on its own and that makes up all living organisms and the tissues of the body.
Why are cells so small?
Small cell keeps a large surface area to volume ratio - needed for easy absorption of substances
What is the difference between pluripotent cells and multipotent cells?
Multipotent - can differentiate into many cell types
Pluripotent/totipotent - can differentiate into every type of cell in the body
What are organelles and what are some examples of them?
Organelles are internal structures responsible for a variety of functions, such as energy production and protein synthesis.
Examples include:
Endoplasmic reticulum
Golgi apparatus
Ribosomes
Mitochondria
What are eukaryote cells?
Eukaryotes are organisms whose cells have a nucleus and other organelles enclosed by a plasma membrane.
Examples include, animal, fungi and plant cells
What are prokaryote cells?
Prokaryotes are organisms whose cells lack a nucleus and other organelles.
An example of this includes bacteria cells
What would you find in an eukaroytic cell?
Nucleus
Nucleolus
Endoplasmic reticulum
Ribosome
Golgi apparatus
Lysosome
Peroxiome
Mitochondria
Mitochondrion
Flagella
Cilium
Plasma membrane
Cyto-skeleton or cell wall
Vesicles
What would you find in a prokaryotic cell?
THINK NRWMCFPF
Nucleoid
Ribosome
Cell wall
Cell membrane
Capsule
Fimbriae
Pill
Flagella
Where would you find prokaryote DNA?
Prokaryotes do not have a nucleus.
Instead prokaryote DNA can be found, bundled but free-floating, in a central region called the nucleoid.
Prokaryote DNA is usually found as a single chromosome of circular DNA.
What is the function of the nucleus?
The nucleus stores the genetic information in chromatin form.
What is the function of the nucleolus?
Found inside of the nucleus, the nucleolus is the part of eukaryotic cells where ribosomal RNA is produced.
What is the function of the plasma membrane?
The plasma membrane is a phospholipid bilayer that surrounds the entire cell and encompasses the organelles within.
What is the function of the cytoskeleton or cell wall?
The cytoskeleton or cell wall provides structure, allows for cell movement, and plays a role in cell division.
What is the role of ribsomes?
Ribosomes are responsible for protein synthesis.
What is the function of the mitochondria?
Mitochondria, also known as the powerhouses of the cell, are responsible for energy production.
What is the function of the cytoplasm?
The cytoplasm is the region of the cell between the nuclear envelope and plasma membrane.
It provides a platform upon which other organelles can operate within the cell.
What is the function of the cytosol?
Cytosol is a gel-like substance within the cell that contains the organelles.
What is the function of the endoplasmic reticulm?
The endoplasmic reticulum is an organelle dedicated to protein maturation and transportation.
What are the two types of endoplasmic reticulum and what are their functions?
Rough endoplasmic reticulum - studded with millions of membrane bound ribosomes, is involved with the production, folding, quality control and despatch of some proteins.
Smooth endoplasmic reticulum - largely associated with lipid (fat) manufacture and metabolism and steroid production hormone production. It also has a detoxification function.
What is the function of vesicles and vacuoles?
Vesicles and vacuoles are membrane-bound sacs involved in transportation and storage.
What is the function of the golgi apparatus?
The Golgi apparatus modifies proteins and lipids that it receives from the endoplasmic reticulum.
The Golgi apparatus packages & prepares proteins & lipids for use in other places inside and outside the cell.
These biochemicals leave the Golgi by exocytosis before being delivered to different intracellular or extracellular targets.
What is protein processing and lipid processing by the golgi apparatus?
Protein processing – carbohydrate regions of glycoproteins are altered by addition, removal or modification of carbohydrates.
Lipid processing – adds phosphate groups and glycoproteins to lipids from the endoplasmic reticulum (such as cholesterol) to create the phospholipids that make up the cell membrane.
What is the function of the lysosome?
A lysosome is a membrane-bound cell organelle that contains digestive enzymes.
They break down excess or worn-out cell parts. They may be used to destroy invading viruses and bacteria.
What is the function of peroxisome?
Peroxisomes play a key role in the oxidation of specific biomolecules. They also contribute to the biosynthesis of membrane lipids known as plasmalogens.
What is the function of the flagellum?
The flagellum is primarily a motility organelle that enables movement
What is the function of cilium?
The function of cilia is to move water relative to the cell in a regular movement of the cilia.
What does DNA stand for?
Deoxyribonucleic acid
What is DNA make up of?
Double helix made up of nucleotides via phosphodiester bond
What makes up a nucleotide?
Base + ribose or deoxyribose
= Nucleoside
Nucleoside + phosphate
= Nucleotide
How are nucleotides linked?
By deoxyribose sugars and phosphates forming a strand with an ester bond making a sugar-phosphate backbone
Difference in DNA and RNA
RNA has the nucleobase uracil while DNA contains thymine.
Unlike DNA, however, RNA is most often single-stranded.
An RNA molecule has a backbone made of alternating phosphate groups and sugar ribose, rather than the deoxyribose found in DNA.
DNA base pairings vs RNA base pairings
DNA
Adenine and Thymine pair (A-T)
Cytosine and Guanine pair (C-G)
RNA
Adenine and Uracil pair (A-U)
Cytosine and Guanine pair (C-G)
What are the biomolecules?
Carbohydrates
Lipids
Nucleic Acids
Protein
Major elements that construct a carbohydrate
Carbohydrates (also called saccharides) are molecular compounds made from just three elements: carbon, hydrogen and oxygen.
Major elements that construct a lipid
Lipids are composed of carbon, hydrogen and oxygen atoms
Major elements that construct a nucleic acid
Nucleic acids contain the same elements as proteins: carbon, hydrogen, oxygen, nitrogen; plus phosphorous
Major elements that construct a protein
The chemical elements found in proteins are carbon, hydrogen, oxygen, nitrogen, and sulfur
What is a nucleic acid?
Nucleic acids are biopolymers, macromolecules, essential to all known forms of life.
They are composed of nucleotides, which are monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base.
The two main classes of nucleic acids are deoxyribonucleic acid and ribonucleic acid.
What is a polysaccharide and describe its structure?
A carbohydrate (e.g. starch, cellulose, or glycogen) whose molecules consist of a number of sugar molecules bonded together.
Polysaccharides are complex biomacromolecules that are made up chains of monosaccharides.
The bonds that form these chains are glycosidic bonds. Commonly found monomer units in polysaccharides are glucose, fructose, mannose and galactose which are simple sugars.
What is a lipid and describe its structure?
A lipid is any of various organic compounds that are insoluble in water.
The structure is typically made of a glycerol backbone, 2 fatty acid tails (hydrophobic), and a phosphate group (hydrophilic).
There are three main types of lipids: triglycerides, phospholipids, and sterols.
What is a hydrogen bond?
Hydrogen bonding is a type of dipole-dipole attraction between molecules.
It results from the attractive force between a hydrogen atom covalently bonded to N, O, or F atom.
What are the five kinds of chemical reactions that occur in living organisms?
Redox
Make and break C-C bonds
Internal rearrangements
Group transfers
Condensation and hydrolysis reactions
REDOX reaction mnemonic
Remember OIL RIG
Oxidation is Loss (of electrons = positive charge)
Reduction is Gain (of electrons = negative charge)
What are redox reactions?
A redox reaction is a reaction in which both oxidation and reduction occur.
What is an oxidation and reduction reaction?
Oxidation is the loss of electrons, gain of oxygen or loss of hydrogen.
Reduction is the gain of electrons, loss of oxygen or gain of hydrogen.
NADH and NAD+
Which is the reducing agent?
Which is the oxidising agent?
NADH a reducing agent (which becomes oxidised itself to NAD+ as it reduces other compounds)
NAD+ is an oxidising agent (which becomes reduced itself as it oxidises other compounds)
Example of making and breaking C-C bonds
Cleavage of glucose in the glycolysis pathway
Breaking: glycolysis
Making: gluconeogensis
Example of internal re-arrangements
Also in glycolysis, a rearrangement of the conformation of G6P occurs before the sugar is split
Molecule rearranges to give another molecule - same amount of carbons
Example group transfers
Also in glycolysis…
In an enzyme catalysed reaction, a phosphoryl group (PO32-) is transferred from ATP to F6P
ATP provides energy for cellular reactions
Describe condensation reactions
Two smaller molecules combine to form a larger molecule and in doing so release water (or other small molecules e.g. methanol)
Describe hydrolysis
Hydrolysis reactions involve adding water to a molecule, and most commonly simultaneously breaking down a large molecule into smaller units.
Give examples of condensation and hydrolysis reactions
The sub-units of proteins, polysaccharides and nucleic acids are all joined by condensation and broken by hydrolysis reactions
What type of reaction is important in carbohydrate metabolism?
Condensation and hydrolysis reactions are important in carbohydrate metabolism
Complex carbohydrates (polysaccharides) such as starch or glycogen are composed of many individual monosaccharide molecules e.g. glucose.
A disaccharide e.g. sucrose, is simply two monosaccharides joined together.
How do glucose polymers form?
Glucose polymers such as glycogen and start form by condensation reactions between two glucose monomers
What is an example of a reducing sugar?
D-glucose
The linear form (but not cyclic form) has an aldehyde group, which can be oxidised
If this is oxidised then the other reactant would be reduced, so glucose is termed a ‘reducing sugar’
Discuss fatty acids
Long chains of carbon and hydrogen atoms form “fatty acids”
Discuss bonds in fatty acids
If all the bonds are single the fatty acid is said to be saturated
If there is one double bond the fatty acid is mono-unsaturated
If there are more than one double bond the fatty acid is polyunsaturated
Discuss triglycerides
Storage lipids
Non-polar
3 fatty acid chains linked to glycerol
Discuss phospholipids
Only two fatty acids chains and a phosphate group attached to the ‘head’ of these chains
This makes them polar
They form biological cell membranes – very important!
Discuss sterols
Produced in plants, animals and some micro-organisms
Most important one in humans is cholesterol
Another essential component of cell membranes
Precursor to steroid hormones and fat soluble vitamins (A, D, E)
What is a hydrophilic substance?
Give examples
A water soluble molecules are said to be hydrophilic (water loving)
Examples include molecules such as:
Sugars
Alcohols
Aldehydes
Ketones
Compounds with N-H groups
Charged particles such as ions
What is a hydrophobic substance? Give examples
Hydrophobic molecules (water hating) do not dissolve readily in water, but do dissolve in lipid.
Examples include molecules such as:
Fat soluble vitamins (A, D, E, K)
Lipids
Cholesterol
Steroid hormones
Oxygen
What is the hydrophobic effect?
When hydrophobic substances arrange themselves in water so as to minimise contact with surrounding water molecules.
What are amphipathic molecules?
Give examples
Amphipathic molecules contain both hydrophobic and hydrophilic parts.
Phospholipids (key components of cell membranes) are amphipathic. The phosphate head is hydrophilic and the fatty acid tail is hydrophobic.
In water phospholipids form micelles or bilayers such that the hydrophobic tail is directed away from contact with the water.
Cholesterol: polar head and a non-polarydrocarbon body
Define pH
A figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline.
What equation can be used to calculate how the pH of a solution will respond to changes in either the conjugate acid or base?
aka how to calculate pH of solution
Henderson-Hasselbalch Equation
Interpret the Henderson-Hasselbalch Equation
pH is proportional to the ratio of buffer to H-buffer, or for example proportional to the ration of HCO3- (buffer) to H2CO3 (H-buffer)
Basically the more buffer you have, the more pH goes up (increases alkalinity) and the more H-buffer you have, the more pH goes down (increases acidity)
Alternatively, if pH goes down, either buffer has gone down or H-buffer has gone up, and vice versa!
What is a buffer?
A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is added to it.
What is the purpose of a buffer?
Purpose of a buffer is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.
What is the buffer system in cells?
Phosphate buffer system
What is the buffer system in plamsa?
Bicarbonate buffer system
What two organs is affected by the bicarbonate buffer system?
Lung: increase or decrease in ventilation will change CO2
Kidney: changes in bicarbonate reabsorption or secretion change overall plasma bicarbonate
Diseases of lungs and kidney can cause acid-base disorders
Why does water have a neutral pH?
Water has a neutral pH because [H+] and [OH-] are equal
Why do acidic solutions have a lower pH?
Acidic solutions have a greater [H+] and lower [OH-]
What are saturated fatty acids?
All bonds are single
Why do alkaline solutions have a higher pH?
Basic (alkaline) solutions have a lower [H+] and higher [OH-]
What does 1 pH unit represent?
1 pH unit represents a ten-fold increase or decrease in [H+]
What do strong acids and bases do?
Give examples
Strong acids (i.e. HCl) and strong bases (i.e. NaOH) fully dissociate.
Why are weak acid and bases important?
As they are only partially dissociate, this gives them some unique properties, particularly the ability to act as “buffers”
What would happen if blood did not have the bicarbonate buffer system?
If blood did not have the bicarbonate buffer system then the pH would fluctuate wildly as cellular products of acids (e.g. lactic acid) would cause marked drops in blood pH
What is the optimal pH of blood?
Blood has an optimal pH of around 7.4. Small deviations from this can cause disastrous metabolic effects.
Clinical use of the Henderson-Hasselbalch equation
By measuring blood pH, [HCO3-] and [CO2] the Henderson-Hasselbalch equation can be used to check how much buffering capacity a patient has.
How is optimal pH maintained?
Optimal pH is maintained by using weak acids and their bases as buffer systems within cells and organisms
What are microfilaments made up of?
Actin protein
Mitochondria structure
Organelles bound by a phospholipid bilayer
Outer membrane contains pores
Inner membrane has cristae (folds)
Matrix contains most of enzymes needed for metabolising food molecules
What are stem cells?
Cells that can differentiate into many cells (multipotent) to any (pluripotent) cell types of the body
Why are stem cells important in clinic?
Can be used in treatment of certain diseases including some cancers
What are the fibres of the cytoskeleton?
Microfilaments
Intermediate filaments
Microtubules
What are mono-unsaturated fatty acids?
There is one double bond in the fatty acid chain
Define necrosis
Untimely death of cells in response to injury or infection - not normal
What happens if cells do not die the way they are supposed to?
Loss of balance between apotosis and proliferation is associated with some cancers.
Cells divide without control
Fail to coordinate with normal cells
Fail to differentiate into specialised cells
Displace and replace the normal cells if not stopped.
What are the four basic elements?
Hydrogen
Carbon
Nitrogen
Oxygen
99% of bodies
What are functional groups?
Linked carbon atoms that form a variety of structures (linear chains,branched chains and cyclic structures)
Groups of elements that attach to these structures are called functional groups
Define apoptosis
Controlled programmed cell death.
Normal process - needed for normal function
What do undifferentiated stem cells do?
Give rise to genetically identical daughter cells
What are poly-unsaturated fatty acids?
There is more than one double bond in the fatty acid chain
What is conformation?
Spatial arrangement of groups that can have different positions in space due to the freedom of single bonds
What change in haemoglobin causes sickle cell anaemia?
Replacement of the hydrophilic amino acid - glutamic acid - with the hydrophobic amino acid valine
What does the amino acid change in haemoglobin do?
Creates a hydrophobic region - promoting hydrophobic regions, causing haemoglobin to clump together, forming rigid fibres and sickling of red blood cells
What is used to transport lipids in the blood?
A chylomicron - protein embedded in the shell and lipid in the core.
Phospholipid heads and outer edges of the proteins form a hydrophilic outershell
Why is a hydrophilic shell essential in a chylomicron?
As it allows the chylomicron to be transported in the aquous plasma of the blood
What are the two chemicals that can cause change in acidosis and alkalosis?
CO2
H+
What does increasing and decreasing CO2 do?
Increase: respiratory acidosis
Decrease: respiratory alkalosis
What does increasing and decreasing HCO3- do?
Increase: metabolic alkalosis
Decrease: metabolic acidosis
What are the three protein fibres of the cytoskeleton?
Intermediate filaments
Microfilaments
Microtubules
What is the function of microfilaments?
Help to generate the forces used in cellular contraction and basic cell movements.
The filaments also enable a dividing cell to pinch off into two cells.
What are intermediate filaments made up of?
Several strands of fibrous proteins that are wound together
What is the function of intermediate filaments?
Intermediate filaments have no role in cell movement. Their function is purely structural. They bear tension, thus maintaining the shape of the cell, and anchor the nucleus and other organelles in place.
Describe the structure of microtubules
Microtubules are small hollow tubes. The walls of the microtubule are made of polymerized dimers of α-tubulin and β-tubulin, two globular proteins
