Module 2 Flashcards
What is anabolism
This is where smaller molecules assemble into larger ones. Energy is required for this process
What is a cell’s metabolism
Chemical reactions inside cells that use and release energy
What is catabolism
This is where larger molecules break down into smaller molecules. Here, energy is released
What is oxidation
Oxidation describes a loss of electrions
What is reduction
Reduction describes a gain in electrons
What are electron carriers
Electron carriers are molecules that transport electrons (or electrons and protons) during cellular processes, such as cellular respiration and photosynthesis. These carriers play a crucial role in energy transfer within cells by accepting and donating electrons, which helps to drive chemical reactions
What are the common electron carriers
NAD+ / NADH
FAD / FADH2
NADP + / NADPH
What is ATP and how does it work
Adenosine triphsphate is the energy which is stored chemically and acts as a rechargable battery
Here, the phosphate bonds are “high energy” bonds
ATP acts as a cellular energy carrier
Energy Storage: ATP stores energy in the bonds between its phosphate groups. The last phosphate group is attached by a high-energy bond, which, when broken, releases energy.
Hydrolysis: ATP is converted to ADP (adenosine diphosphate) and inorganic phosphate (Pi) by a process called hydrolysis, in which a water molecule is used to break the bond between the second and third phosphate groups. This releases energy.
What is heterotrophy
This is where organisms must consume other organisms for food or energy
They are unable to synthesise their own food from inorganic sources, so rely on other organisms for nourishment
What is autotrophy
This describes an organism who can create their own food from inorganic substances. They can convert CO2 into organic compounds, like glucose, using energy from either sunlight or chemical reactions
What are the 2 stages to photosynthesis
First stage: light dependent reactions (Aim to trap sunlight and convert it to chemical energy for later use (ATP and NADPH))
Second stage: Calvin cycle or Light independent reactions (aims to capture CO2 from air and convert into sugars using chemical energy produced in first stage)
Explain the conversion of radiant energy into chemical energy
There are chlorophylls in the chloroplasts which capture light. This travels through the antenna complex through pigment molecules, ultimately reaching the reaction centre
The excitation energy is transferred from one pigment molecule to another through resonance energy transfer (as electron gets excited, when it falls back down, to ground state, it excites the next electron which continues throughout the antenna complex to allow transfer of electrons). This energy from reaction centre is used to excite the P680(PSII) and p700 (PSI) chlorophylls
Explain the overall organisation of the light reactions in photosystems I and II
The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts, where light energy is captured and converted into chemical energy in the form of ATP and NADPH. These reactions involve two main protein complexes: Photosystem II (PSII) and Photosystem I (PSI), which work together in a coordinated process.
Location: PSII is primarily located in the grana stacks of the thylakoid membranes.
Location: PSI is located in the stroma lamellae of the thylakoid membrane.
Describe ATP synthesis during the light-dependent reactions
In the light-dependent reactions, the movement of hydrogen ions down their concentration gradient is coupled to the production of ATP.
ATP synthesis during the light-dependent reactions of photosynthesis occurs through a process known as photophosphorylation, where light energy is used to generate ATP from ADP and inorganic phosphate (Pi). This process occurs in the thylakoid membrane of the chloroplasts, and it is driven by the proton gradient created during electron transport. Here’s how it works:
Here, the protons are transported from stroma to lumen to create a proton gradient –> H+ move from umen back to stroma via ATP synthase, causing ATP to form
Explain the process of light-dependent reactions / non cyclic phosphorylation
Photons are absorbed by photosystem II (PSII). This excites electrons from PSII, raising them to a higher energy level. These excited electrons are captured by the primary electron acceptor in PSII
PSII then undergoes the splitting of water into oxygen and protons, and electrons. The electrons from water help replenish the electrons lost by PSII, whhile O2 is released as a byproduct.
Energy from PSII pass through the etc to PSI. As electrons move through ETC, their energy is used to pump protons from stroma into thylakoid lumen –> proton gradient across the thylakoid membrane
Proton gradient from ETC drives synthesis of ATP, where protons flow back into stroma through ATP synthase to convert ADP to ATP
In PSI, lijght energy is absorbed by chlorophyll molecues which reexcites the electrons. The excited electrons are picked up by the electron acceptor in PSI
The high energy electrons from PSI are transferred to a protein called ferredoxin which transfers electrons to NADP+, along with protons from stroma to form NADPH. NADPH is used later on in calvin cycle
What is RUbisco? What is its function
It is the most abundant protein on Earth, and exists in chloroplast stroma
Function is to convert CO2 from atmosphere into organic form of carbon found in biology of all organisms. Important for the calvin cycle.
Its function is to attach CO2 to ribulose-1,5-bisphosphate (RuBP) which will then split off into 2 molecules of 3-PGA
In addition to its carboxylase activity, it has oxxygenase activity where it could bind to O2 instead of CO2 –> photorespiration
What is carboxylation done by rubisco
Carboxylation by Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) is the first step in the Calvin cycle of photosynthesis, where carbon dioxide (CO₂) is incorporated into an organic molecule. Rubisco plays a key role in fixing atmospheric CO₂ into a stable compound that can later be used to build sugars.
As part of carboxylation, rubisco acts on RuBP, to form 2 3-PGA molecules. This then turns into G3P molecules.
The carboxylation reaction effectively “fixes” carbon from CO₂ into an organic form (3-PGA) that can then be further processed in the Calvin cycle to eventually produce sugars and other organic compounds.
What is oxygenation which can be done by rubisco
The process of oxygenation by Rubisco is a reaction where Rubisco binds to oxygen (O₂) instead of carbon dioxide (CO₂).
Here, it causes RuBP to bind with O2. This causes the production of 3-PGA and a 2-phosphoglycolate which isn’t helpful and is actually toxic. This requires further processing which is done through photorespiration
Explain photorespiration and describe why its bad
Photorespiration is a method to get rid of the 2-phosphoglycolate.
It ultimately consumes ATP and releases CO2 which is unideal for a plant
What can increase the possibility of photorespiration occurring
When there is a greater concentration of oxygen than carbon dioxide in the atmosphere
Also when there is greater temp
Explain fixation of carbon dioxide in the Calvin (C3) cycle (i.e. explain how the calvin cycle works)
Basically, CO2 enters, and this binds to RuBP, with the assistance of Rubisco as an enzyme. This causes the formation of 2 3-PGA molecules. This is then able to breakdown into G3P. (3 CO2 molecules cause production of six G3P)
Of this six G3P, one is used to be able to create glucose (through formation of sucrose or starch etc)
The rest of the G3P is used for the regeneration of the RuBP. The cycle then continues. As part of this cycle, it consumes the ATP and NADPH which was created from the Light dependent reactions
What % of plant production is lost to photorespiration
25%
Describe the co-evolution of C4 photosynthesis with Earth;s atmosphere overtime
Over time, photosynthetic organisms released significant amounts of O₂ as a byproduct, causing O₂ levels to rise and CO₂ levels to gradually decrease.
The increase in O₂ and decline in CO₂ led to a higher chance of photorespiration, as Rubisco, which has an affinity for both CO₂ and O₂, increasingly bound O₂ instead of CO₂. This caused a wasteful reaction, reducing carbon fixation efficiency in C₃ plants.
The declining CO₂ levels and rising O₂ created selective pressure for plants to adapt to avoid the loss of fixed carbon through photorespiration.
C₄ photosynthesis evolved as a specialized pathway that minimizes photorespiration and increases carbon fixation efficiency under low CO₂ conditions.
Thus, as the atmosphere started having more O2, the C4 photosynthesis started to emerge
Explain how C4 photosynthesis works
This describes a series of metabolic and structural adjustments to exploit PEPcase
In the mesophyll cells, the CO2 is initially fixed by an enzyme called PEPcase to a PEP molecule. This forms a 4C compound
This 4C compound is quickly converted to malate which is transported to bundle sheath cells
The malate is then decarboxylated to release CO2 in the bundle sheath cells. This increases the concentration of CO2 around the RUbisco enzyme in the Bundle sheath cell. This then causes the CO2 to ignore its oxygenase ability, and increases its carboxylase activity, minimising chances of photorespiration
Released CO2 enters calivn cycle, where RUbisco then fixes it to produces sugar, and follows the steps done in C3 photosynthesis
Explain how CAM photosynthesis works
Basically, to be able to get CO2, plants have to open a stomata (which is like an opening to the rest of the world). However, when the environment is too hot, if they do this, they are unlikely to get much CO2, and also will probably lose a lot of its water. As such, there needs to be a solution to this.
CAM photosynthesis works by making the plant open its stomata at night. At night, the air is more damp, and the plant is thus unlikely to lose water. It is then able to absorb the CO2 from the air at night. This CO2 is combined with PEP to form a four carbon molecule called oxaloacetate which then turns into malic acid, and is stored in vacuoles within plant cells overnight
During the day, the stomata closes to conserve water, which is crucial in hot and dry environments
This stored malic acid is transported from vacuoles to chloroplasts where it is then broken down to release CO2, and then the Rubisco does its job
What environments would C3 photosynthesis best suit?
Cool and wet environments.
At higher temps, rubisco affinity for O2 increases relative to CO2, making it more efficient in cooler environments
Also, when stomata opens, there is water loss, but in wet enviros, water is more available –> less water loss
What environments would C4 photosynthesis best suit?
Hot and sunny environments
High light environment because it is enough to fue energy demands of C4 pathway.
Also, at higher temps, there is a higher likelihood of photorespiration happening
What environments would CAM photosynthesis best suit?
Hot and dry environments
Because it is known for being able to save water
A botanist sets up a greenhouse with intense lights and adequate soil water. In this enviro which photosynthesis process has an advantage?
C4 has a relative photosynthetic advantage compared to CAM and C3
This is because C3 is at a disadvantage because it is worse in higher temperatures with intense lighting. CAM is also used to help conserve water, but if theres enough water here, there really isn’t any point
THIS ONE IS STILL A BIT CONFUSING
What is oxidation
Loss of electrons
WHat is reduction
Gain of electrons
In photosynthesis, the C from CO2 is ____ to become glucose
Reduced
Both burning and aerobic respiration releases the same amount of energy, but aerobic respiration does it step-by-step. WHy is this ideal?
Because if all the energy was released in one go –> excess heat –> damage to cell
Also, aerobic respiration allows for more energy to be moved at a time (?!)
Where does glycolysis occur?
It occurs in the cytoplasm
Explain the process of glycolysis
Here, a glucose molecule is broken down into 4 ATP molecules (net 2 ATP gain), 2 pyruvate molecules, and 2 NADH molecules
Doesn’t require any oxygen
Explain what happens with the intermediate reaction
This involves the conversion of pyruvate produced from glycolysis into acetyl CoA. Electrons are removed, and given to NADH electron basket
Overall, 2 NADH and 2 acetyl CoA is produced from the two glucose molecules (i.e. 1 NADH and 1 acetyl CoA per glucose molecule)
Explain what happens in the Krebs Cycle
It uses the acetyl CoA produced from the intermediate reaction and forms 1 ATP molecule, 3 NADH molecules, 1 FADH2 molecule and 2 CO2 molecules
Explain the process of the electron transport chain
Basically the previous electron carriers (NADH and FADH2) oxidise in the matrix, thus turning into NAD+ and FAD. As a result of this, electrons are deposited in one (of four) protein complexes, which assists in bringing the H+ from the matrix to the intermembrane space. As such, the intermembrane space has an extremely high concentration of H+ (protons) from the deposition of the four protein complexes. These e- are then used to react with oxygen and H+ in the matrix to produce H2O.
The creation of ATP occurs with the ATP synthase which allows for H+ to flow through it (via the electrochemical gradient of protons), to ultimately free phosphate and turn ADP to ATP, ultimately producing ATP
This process creates 28-34 ATP per glucose oxidised
WHat are the similarities of mitcohondria and chloroplast structure (very important)
Both membrane bound (double membraned)
Membrane is folded in both
Compartmentalisation
Both produce ATP; mitochondria through oxidative phosophyrlation and chloroplasts through light transport
Both organelles have their own DNA
What are the differences in mitochondria and chloroplast structure (very important)
Internal membrane structure - Mitochondria = inner membrane folded into cristae which increases SA for oxidative phosophyrlation
Chloroplasts =Inner membrane forms network of thylakoid membranes arranged in stacks called grana where light dependent reactions occur
Matrix vs stroma-
Space inside of inner membrane of mitochondria is called matrix. FOr chloroplasts, the space inside inner membrane is called stroma
Mitochondria don’t contain pigments, whilst chloroplasts have thylakoids organised into granum and thylakoid stacks
What are the similarities between mitochondria and chloroplast function/process
Proton gradient used to create ATP through using an ATP synthase
Relies on movement of protons through ATP synthase to provide energy for ATP synthesis
Proteins involved in both functions
What are differences in mitochondria and chloroplast function / process
Source of energy -
ATP synthesis in mitochondria driven by oxidation of nutrients like glucose than cellular respiration. Chloroplast ATP synthesis is driven by light energy from chlorophyll
ETC components -
Mitochondria: ETC involves complexes I-IV. Chloroplasts: involves photosystem I and photosystem II
Final electron acceptors:
Mitochondria: O2 acts as final electron acceptor in ETC, forming water. Chloroplasts: NADP+ acts as final acceptor, forming NADPH which is used in calvin cycle for fixation
Location of ATP synthesis:
Mitochondria: Synthesised in matrix, whilst chloroplasts has ATP synthesised in stroma, which is enclosed by thylakoid membrane
Why do we need proteins to control levels of ATP
We need proteins to act as a asafety valve mechanism to control levels of ATP. Processes aimed at decreasing ATP levels (Because sometimes we don’t need that much ATP)
What proteins can control levels of ATP
Alternative Oxidase
Uncoupling protein
What does Alternative oxidase do
Instead of the electrons being transported from complex 2 to complex 3, they could instead travel through alternative oxidase, and thus stops the journey of the electrons. This decreases the proton gradient further –> decreased ATP synthesis
What does uncoupling protein do
They help dissipate the proton gradient by the electron transport chain as heat rather than using the proton gradient to produce ATP. This is a critical aspect to maintaining a healthy body temperature
This ultimately diverts energy from ATP synthesis to thermogenesis by catalysing a leak of protons across the matrix intermembrane space to the matrix. Provides alternative pathway to reduce pressures other than ATP synthase
What are macronutrients
These are larger than micronutrients in terms of size, and are required by the body in larger amounts to provide energy and various physiological functions.
They serve as fuel and construction elements of tissues.
Examples include carbohydrates, fats and proteins
These provide energy, support growth, regulate bodily processes
What are micronutrients
These are much smaller than macronutrients in terms of size
They are also required in smaller quantities compared to macronutrients
Includes vitamins and minerals. Supports various biochemical reactions and processes, immune function, hormones and enzymes etc
What is the composition of the body
liquids (60% in adults, 70% in infants, 50-55% in elderly people)
Protein (18%)
Fats (16%)
Carbs, minerals etc (6%)
Describe the composition of carbohydrates
Mainly composed of carbon, hydrogen and oxygen
It is a common carbohydrate which is quite long and could branch
carbohydrates are composed of carbon, hydrogen, and oxygen, arranged in simple or complex structures that serve as energy sources, structural materials, and storage molecules.
Could be in the form of monosaccharides, disaccharides, and polysaccharides
What are monosaccharides
Most basic unit of carbs which cant be broken down into smaller sugars
What are disaccharides
Two monosaccharides linked together by a glycosidic bond
What are polysaccharides
Long chains of monosaccharide units linked together, and sometimes branch out
Explain process of glycosidic bond formation
Each monosaccharide contains multiple hydroxyl groups (-OH) attached to its carbon atoms. In formation of glycosidic bonds, a hydroxyl group from one monosaccharide and H atom from hydroxyl group of another react together. In this process, H2O is removed, and oxygen connects the two sugars together
Explain the basic composition of amino acids/proteins
Proteins made up of C , O, N, H atoms They all contain a central carbon, amino group, carboxyl group and H atom, with a side chain group as well
They are linked together by a peptide bond through dehydration between -NH2 of an amino acid and a carboxyl group of another, releasing a water molecule
How many amino acids are found in proteins
20 amino acids
11 non essential
9 essential
Does the bloodstream absorb protein?
No it absorbs amino acids
WHat is the main composition of fats?
Exists through triglycerides
Glycerol; 3 C molecules which is the backbone of trigylcerides
Fatty acids; long chains of C and H atoms with carboxyl group
TYpically contains C, H and O
Where is fat stored
Adipose tissue
Compare and contrast different nutritional sources of protein
Ultimately, as long as we are getting the 9 amino acids we can’t make, our protein synthesis is fine.
Ultimately, when it comes to obtaining amino acids for proteins, the source doesn’t really matter
However, when comparing animal vs plant protein; the plant one actually has more of the essential amino acids (i.e. when comparing soy beans to beef)
Animal based proteins are more digestible, and considered complete proteins (vs plants in comparison) and thus high in essential amino acids and other nutrients as well
How does ATP power cellular processes (2 ways)
ATP stores energy through the high potential energy phosphate groups
When ATP turns into ADP and a free phosphate, this release of a phosphate can be used to power various cellular processes.
2;
If the protein has existing negatively charged regions near the newly added phosphate, these charges can repel each other due to electrostatic forces.
This repulsion can cause the protein to change its shape—for example, pushing different domains of the protein apart or altering its structure in a way that enables or disables its interaction with other molecules.
Conformational Change: The repulsion can force a conformational (shape) change in the protein, leading it to switch from an active to an inactive form, or vice versa.
3:
Puts phosphate on a substrate for enzyme, allowing it to fit into enzymes 3D space –> do it before phosophrylation - by now it can release all energy from there
When enzymes chaneg structure, it can fit into another site of enzyme and facilitate chemical reaction or activate enzyme to catalyse a reaction more effectively
Understand how fats, carbs and proteins can be interconnected via metabolism
Carbs –> fats (Excess glucose –> acetyl CoA –> synthesise fatty acids - lipogenesis)
Fats –> carbs (Glycerol from fat can be used to make glucose)
Carbs –> protein (Intermediaries from glucose metabolism can synthesise non essential amino acids)
Proteins –> carbs (Glucagonic amino acids –. glucose via gluconeogenesis)
Proteins –> fats (ketogenic amino acids –> acetyl CoA –> fatty acids)
Describe theories on cell evolution:
Autogenous theory (theory for explaining evolution of nucleus)
endosymbiotic theory (theory for explaining evolution of mitochondria)
Explain the autogenous theory for the evolution of the nucleus
Suggested that eukaryotic cells evolved from process of gradual internal compartmentalisation
Suggests that nucleus originated from the process of the plasma membrane folding inwards. Ouver time, this deepened and enclosed the genetic material (DNA) forming a membrane bound nucleus
There were also suggestions that the endoplasmic reticulum and olgi body formed in a similar fashion
Basically says that cells start to evolve over time, where these subcompartments allowed for the specialisation of various organelles
Explain the endosymbiotic theory for the evolution of the mitochondria
Suggests that an ancient eukaryotic cell enfulged an aerobic prokaryotic organism - likely a bacterium
Rather than digesting the prokaryote, there was a symbiotic relationship, where the bacterium supplied host with abilitiy to produce energy efficiently through aerobic respiration
WHat is a eukaryote
Organism whose cells contain a membrane bound nucleus. Typically multicellular. They have linear DNA
A
What is a prokaryote
An organism who lacks membrane-bound nucleus and other organelles. They have circular DNA (typically single-celled organisms)
What are the core differences between a eukaryote and a prokaryote
Prokaryotes lack membrane bound organelles such as mitochondria, endoplasmic reticulum etc. Most prokaryotes have a cell wall made of peptidoglycan. Some eukaryotes have a cell wall but thats made of materials like cellulose or chitin
What subspecies are considered eukaryotes
Plants, fungi, protists and animals
What subspecies are considered prokaryotes
Bacteria and Archaea
Explore cell variety in prokaryotes
Bacteria: peptidoglycan (sugar and amino acid lattice) major constituent of cell wall
Archaea: don’t have peptidoglycan as major constituent of cell wall, and often lives in extreme conditions. Thus very resistant to heat and oil
Describe composition of lipid bilayer cell membranes
The lipid bilayer is the fundamental structure of cell membranes, composed primarily of phospholipids and other lipid molecules. This bilayer serves as a flexible and selective barrier, controlling the movement of substances into and out of the cell.
This membrane is made up of phospholipids AND proteins.
Cholesterol is also important to stiffen plasma membrane and also maintain the fluidity of the membrane
Selective permeability means that it allows hydrophobic substances, and small nonpolar molecules
Explain the importance of cholesterol in stabilising the plasma membranes
Hydroxyl group of cholesterol interacts with polar head groups of phospholipids, forming hydrogen bonds –> hydrophillic part of cholesterol positions itself near aqueous enviro of membrane sufraces.
The hydrophobic portion of cholesterol embeds itself in the hydrophobic core of membrane while hydroxyl group is still on membrane surface, thus causing cholesterol to “anchor” into the membrane –> contribution to stability and fluidity regulation of membrane
What are the different structures/features of a cell and organelles?
Cytoplasm
Plasma membrane / Cell membrane
Nucleus + Chromatin + Nucleolus
Endoplasmic Reticulum (Rough & Smooth)
Ribosomes
Golgi body / Golgi apparatus
Mitochondria
Lysosome
Cytoskeleton (cilia and flagellum)
What is the cytoplasm - what is its function?
It is the jelly like material inside of the cell, where most organelles float in, such as the nucleus, ribosomes etc.
It assists in dissolving solutes (particles in the cell such as carbs and proteins), as well as help moves material around the cell
It also provides support for the cell
What is the cell membrane - what is its function?
It is composed of a bilayer of lipids and proteins.
Lipids are made up of a hydrophilic (phosphate) head and hydrophobic tail. Thus, the lipid heads are attracted to water molecules of both the intracellular and extracellular environments
The cell membrane is semi permeable - only specific materials may enter and exit through pores and protein channels.
The job of the cell membrane is to allow materials to enter/exit the cell. O2 and H2O can simply pass through the bilayer, however larger molecules/charged particles/polar particles may only be able to go through protein channels
Important to note that the cell membrane remains fluid. The lipids and proteins arent locked in place
What is the nucleus - what is its function?
It is the largest and most prominent organelle, and it stores all genetic instructions for manufacturing proteins. It controls cell activity and is considered the ‘control center’
Inside the nucleus, there is chromatin and a nucleolus.
The nucleus is surrounded by a membrane called the nuclear envelope which consists of two adhacent lipid bilayers with a thin fluid space between them
Spanning the nuclear envelope are nuclear pores. These are tiny passageways for the passage of proteins, RNA and solutes between the nucleus and cytoplasm
What is chromatin?
This refers to the long strands of DNA. It holds info to make proteins
What is a nucleolus?
It makes ribosomes through production of RNA. Once synthesised, new ribosomal units exit cell nucleus through nuclear pores
What is the endoplasmic reticulum?
There are two types; smooth and rough ER
It is a system of channels continuing with the nuclear membrane, covering the nucleus and composed of the same lipid bilayer material
It provides passages throughout much of the cell who’s function is transporting, synthesising and storing materials
The winding structure results in a large membranous surface which supports its function
The endoplasmic reticulum (ER) is a dynamic organelle responsible for many cellular functions, including the synthesis of proteins and lipids, and regulation of intracellular calcium levels.
What is the Rough ER - what is its function?
the function of the RER is to receive ribosomes from the nucleus. It’s function is to transport protein making ribosomes.
Once proteins are made, they are enclosed by a vesicle (cellular envelope that is used to transport materials from one place to another), which is then transported to the golgi body
What is the Smooth ER - what is its function?
Meanwhile, the Smooth ER has no ribosomes (hence smooth). It assists in detoxification - breaks down toxins.
It also mainly produces lipids (phospholipids), cholestrol and hormones and steroids. Also making fats
Thus, cells that produce large quantities of hormones such as female ovaries and male testes contain large amounts of smooth ER due to increased hormone production
What are ribosomes - what are the functions?
Created by nucleolus, and is transported to the rough ER. The function of ribosomes are to make proteins (gathers amino acids and connects them into a long chain –> forms proteins)
What is the golgi body/apparatus - what are the functions?
Job is to receive, modify, sort and package proteins in a vesicle so that they can be transported around. It accepts vesicles of proteins from rough ER.
The golgi body makes final changes to the protein, and then the protein created is put in another vesicle and is released, and fuses with the cell membrane and goes where its needed.
Golgi has to distinct sides, each with a different role. One side receives products in vesicles. These products are sorted through the apparatus and released and repackaged in a new vesicle out the other end.
The vesicle migrates to cell surface and fuses to cell membrane where the ‘cargo’ is secreted
What is the mitochondria - what is its purpose?
Purpose is to create ATP in a process called cellular resipiration (used for energy)
It contains its own DNA
Consists of outer and inner lipid bilayer membrane
Oxygen required for cellular respiration
What are lysosomes - what is its purpose?
Contains powerful digestive enzymes. Jobs include to break down food (i.e. protein broken into amino acids)
Highly acidic organelle for waste breakdown and disposal
It also works to kill pathogens (white blood cells)
Has the option to do autolysis which basically destroys the dying cell (or for damage cells)
What is the cytoskeleton?
Like the bony skeleton supports the human body structurally, the cytoskeleton helps cells maintain structural integrity. Fibrous proteins provide structural support
This is necessary for cell motility (cell migration), cell reproduction and transport of substances within the cell
Three types of protein based filaments:
microfilaments
Intermediate filaments
microtubules
What are microtubles?
These are the thickets of all the protein based filaments, and it maintains cell shape + structure and resists compression of the cells, and plays a part in positioning the organelles within the cell. They also make up the cilia and flagellum which are responsible for movement of cells
What are flagella / flagellum?
This is larger than cilia, and is specialised for cell locomotion. This includes the sperm cell that must propel itself
What is cilia?
There are numerous of them in each cell. They have short hair like extensions
Found on many cells of the body, including epithelial cells that line the airways of the respiratory system. They move rhythmically, beat constantly and move waste such as dust, mucus and bacteria up the airways
What are microfilaments?
This is a thinner shape of cytoskeletal filament. Actin which is a protein that forms chains in the primary component of the microfilaments.
Responsible for muscular contraction
What are intermediate filaments?
These are intermediate in thickness between microtubules and microfilament. It is made up of a protein called keratin which are wound together. Responsible for maintaining cell shape and structure. These RESIST tension
What are the four types of animal tissue
Epithelium
Connective
Nervous
Muscle
(This is in order from tissues on the outside at the top and tissue on the inside at the bottom)
What is tissue
A group of cells with a common origin that work together to perform specific functions in the body
How do cells become tissues
Through specialisation, by differentiation, which involves changes in gene expression. Once differentiated, the cells use adhesion molecules to stick to each other and form an extracellular matrix in tissues
Explain what epithelium is
It is a layer of cells which act as protective barriers against physical damage, pathogens and dehydration. Epithelium in intestines also absorb nutrients and fluids, they could also produce and release enzymes
These cover all body surfaces, and line body cavities and hollow organs
Attached to basal lamina
What is the basal lamina
It is a sheet of matrix which is the tissue that epithelia is adhered to. this anchors the epithelium to the connective tissue below it
The basal lamina is very tightly woven
What are the different configurations of epithelium
Simple squamous, simple cuboidal, simple columnar epithelium
Stratified squamous
Pseudo stratified epithelium
Explain what simple squamous epithelium looks like
Looks like flattened epithelial cells (i.e. alveoli of lungs)
Explain what simple cuboidal epithelium looks like
Looks like cubes of epithelial cells
Explain what simple columnar epithelium looks like
Looks like columns of epithelial cells
Explain what stratified squamous epithelium looks like
Basically looks like simple squamous but with multiple layers
Explain what pseudo stratified epithelium looks like
Looks stratified but isn’t. The epithelial cells are irregularly shaped.
What are desmosomes
These are the junctions between epithelial cells. they function to hold epithelial tissues together, and form strong connections between epithelium
What are cadherins
These help the epithelial cells adhere to each other. Kind of acts like velcro to keep them together. They interlock and calcium turns them on to allow for adhesion
What is the function of hemidesmosomes
Their function is to connect epithelia to basal lamina (i.e. at the bottom)
What are the 3 necessary components of connective tissue
Fibres
Cells
Ground substance (ebverything else) –> salts or protein in liquid
Non living portion of tissue (i.e. fibres and ground substance) is called the matrix
What is called the matrix in connnective tissue?
Non living portion of tissue (i.e. fibres and ground substance) is called the matrix
What is connective tissue
Tissue that supports, protects, and gives structure to other tissues and organs in the body. Connective tissue also stores fat, helps move nutrients and other substances between tissues and organs, and helps repair damaged tissue.
What are examples of connective tissues
Blood, adipose, cartilage, loose, dense connective tissues, bones
What is nervous tissue
Nervous tissue is a specialized tissue found in the nervous system, responsible for receiving, transmitting, and processing information throughout the body. It is essential for communication between different body parts, allowing organisms to sense stimuli, respond to changes, and coordinate bodily functions.
Ultimately allows a multicellular animal to coordinate movement and behaviour
What is depolarisation
Less negative charge inside cell compared to outside
What is repolarisation
More negative charge inside cell compared to outside
Explain the resting potential of the neuron?
It has a resting potential of -70mV. This is because of the Na and K ions.
This is because K+ concentration is higher inside the cell than outside, and Na+ is higher outside the cell than inside. Ultimately, there is a lower charge inside the neuron compared to outside of the neuron leading to a negative resting potential.
What is the role of the voltage gated ion channels in the neuron
They are there to respond to a depolarisation of the cell membrane, which would cause it to open up and allow Na+ to come into the cell, further causing depolarisation in the cell. However, once it reaches a certain level, the action potential occurs
Explain the process of the action potential
The resting membrane potential of the neuron is at -70mV. When the dendrites receive a signal from the synaptic cleft, and the cell body decides that it is a significant enough signal (meeting the threshold potential), it leads to the staggered depolarisation of the neuron. This depolarisation is caused by the open voltage gated ion channels which allow for the influx of Na+ ions into the neuron. However, once it reaches a certain point, the voltage gated ion channels close. However, the change in membrane potential also opens the potassium voltage gated channels, causing potassium to leave the cell via diffusion. As such, this causes repolarisation. This repolarisation typically overshoots causing a hyperpolarisation, where the cell membrane potential drops below the resting potential, and eventually comes back up to equilibrium via the Na-K pump
This repolarisation process is important as it allows for the signal to be transmitted down the axon without the signal being transmitted back up as it is still undergoing repolarisation and needs a higher than normal stimulus to bring it back
what is muscle tissue. What are the 3 types?
Muscle tissue is a specialized tissue in the body that is responsible for producing movement. It is composed of cells that have the unique ability to contract, allowing them to generate force and cause motion. Muscle tissue is essential for functions such as moving the body, maintaining posture, and even regulating internal processes like blood flow and digestion.
There is skeletal, cardiac, and smooth muscle
What causes some muscle tissues to seem ‘striped’
Because actin and myosin interlock and slide over each other. The bit where they overlap are the striations
Explain the features of skeletal muscles
Skeletal muscles are our voluntary muscles which we have control over.
they are non-branched, striated, voluntary and contain multiple nuclei
Explain the features of cardiac muscle
Cardiac muscle is the muscle we find in our heart, and it is involuntary, striated and contains branching fibres
Explain the features of smooth muscle
Smooth muscle is spindle shaped, non-striated, involuntary and contains a single nuclei
Explain how cells can respond to signals
A cell can respond to signals (e.g. in times of stress)
Cell signals could affect the cytoplasm and nucleus
It could encourage cells to survive, grow+divide, differentiate or die
A signal could cause an alteration in protein synthesis, alteration in protein function (through cytoplasm) or control enzymes or cytoskeleton –> altered machinery , ultiately resulting in altered cytoplasmic activity
How can cells communicate
Steroid hormones
Neurotransmitters
Protein hormones
What are steroid hormones
Goes through membrane to a receptor inside the cell –> nucleus –> activates a certain gene
What are neurotransmitters
Goes to receptor to open a channel (stimulating depolarisation in a neuron)
What are protein hormones
Uses a messenger system which sends a message to cell, as the protein can’t pass the bilayer
Explain the process of the stress response (hypothalamus - pituitary - adrenal axis)
When a person feels stressed, the hypothalamus releases CRH. This then goes to the pituitary gland. This stimulates the anterior pituitary gland to release ACTH into the bloodstream. This ACTH travels towards the adrenal gland which is located on top of the kidney. In response, the adrenal gland releases cortisol which Increases glucose availability for immediate energy, suppresses non-essential functions (like digestion and immunity), and helps the brain focus on the perceived threat.
Once cortisol levels reach a certain point, they provide negative feedback to the hypothalamus and pituitary gland, signaling them to reduce CRH and ACTH production.
What does the stress response (hypothalamus-pituitary-adrenal axis) target
Increased fat and protein breakdown
Increased blood glucose levels
Causes inflammatory effects
What could go wrong in cell growth to result in pathophysiological state (e.g. cancer)
Cancer could occur because some signals from cells which control rate of cell division could make mistakes. There are proteins which signals a push to grow and divide, but if this protein gets stuck in the ‘on’ position to continue growing –> continual growth –> uncontrollable cancerous cells
Where does cancer typically form - why?
Typically in epithelial cells because of high turnover rate –> high chance of mutation by mistake
Function of basal lamina in cancer?
It can try hold back metastasis (spread of cancer cells) for a while, however, it would eventually give in causing the formation of a malignant tumour
What is the plasma membrane
Describes a microscopic cellular membrane of lipids and proteins which form the external boundary of the cytoplasm of a cell (typically a phospholipid bilayer)
What are the major functions of the plasma membrane
Provides protection for a cell
Only permits the entry of certain substances (such as nutrients), whilst preventing harmful nutrients from coming in
Contains receptors which allow cells to receive signals, facilitating cell communication
Allows for movement of ions, waters, and other molecules across membrane
What is osmosis
Describes movement of water molecules in a selectively permeable membrane from an area of lower solute concentation (high water concentation) to an area of higher solute concentration (lower water concentration)
Goal is to equalise the solute concentrations on both sides of the membrane
This is a passive process - doesn’t require energy to move down its concentration gradient
What is passive diffusion
This is movement of molecules/ions across a cell membrane without the need for energy input –> occurs along the concentration gradient
No energy required, whilst moving from high to low concentrations (conc gradient)
What is active diffusion / transport
movement of molecules/ions across cell membrane from area of lower to higher solute concentration (i.e. against concentration gradient)
This process requires energy, typically in the form of ATP because it works against natural flow of moelcules
Typically involves specific proteins in the cell membrane such as pumps (i.e. the sodium potassium pump)
What are controlled channels / gated channels
These are channels which can open or close in response to specific stimuli; enabling precise control over movement of substances across membrane. They are typically selective, allowing only specific ions to enter
What are some gating mechanisms for these controlled/gated channels?
Voltage gated channels = open or close in response to changes in membrane potential (voltage difference) i.e. used in neurons
Ligand - gated channels = open when a specific molecule (ligand) binds to the channel
Mechanically gated and light gated channels
Explain the mechanism of powered transport with conformational changes
This is the mechanism that transports proteins / move molecules across cell membranes through changes in their shape and structure –> cruicial for active transport
Mechanism:
Binding of molecule/ion - transport protein has binding site for the molecule to be transported. When target molecule binds to transport protein, it triggers conformational changes
The conformational change is manifested in structural change in shape of protein, thus exposing binding site to opposite side of membrane
Transport across membrane - as protein undergoes conformational change, it “transport” the bound molecule across the membrane, before returning to its original shape
What are hypotonic solutions
Solutions with a lower concentration of solutes compared to another solution (typically the cell cytoplasm)
What happens when a cell is placed in a hypotonic solution? Explain what happens to an animal and a plant cell
Water moves into the cell due to osmosis.
When animal cells are placed in hypotonic solutions, they could swell and burst, also known as cytolysis / lysis
When plant cells are placed in hypotonic solutions, they actually get increased structural support, preventing bursting –> becomes firm due to increased internal pressure - TURGID (good sign)
What are isotonic solutions? Explain what happens to an animal and a plant cell
When a solution has the same concentration of solutes as another solution (typically cytoplasm of a cell)
Causes an animal cell to be normal, and a plant cell to be ‘flaccid’
What are hypertonic solutions
This is where the solution has a higher concentration of solutes compared to another solution, typically the cytoplasm of a cell
When cell is placed in a hypertonic solution, water moves out of the cell due to osmosis –> decreased cell volume
ANimal = shrivelled, plant = plasmolysed
What are the 3 major biological functions of mitochondria
Produce ATP - site of ATP synthesis
Provide the first steps in production of steroid hormones (steroidogenesis) –> removal of sidechain from cholesterol
Apoptosis - cell suicide (it can trigger chemical reactions to make cell explode)
What is the process of importing proteins into a cell called
endocytosis
Basically the process in which substances are brought into cells by engulfing them in a vesicle formed from the cell membrane
What is phagocytosis
It is a form of endocytosis, where cells are engulfing large structures lie cells, apoptopic pieces of cell, or bacteria)
What are the steps of endocytosis
Initiation - when cell membrane recoognises and binds to specific substances that need to be internalised
Membrane invagination - cell membrane folding inward. This invagination is facilitated by the cytoskeleton (microfilaments and microtubules)
Vesicle formation (edges of the invagination come closer together, fusing to form a pocket, which pinches off from tthe membrane –> intracellular vesicle enclosing ingested material)
Vesicle trafficking - newly formed vesicle moves deeper into cell and could fuse with organelles
Content processing - breaks down ingested material into smaller components that the cell could utilise
What is the process of exporting proteins out of a cell called
Exocytosis
Process that a cell can expel materials from interior to exterior environment through vesicles
What are the steps of exocytosis
Vesicle formation - form vesicles containing substances to be expelled. Occurs through golgi apparatus on endoplasmic reticulum
Transport to cell membrane - vesicle moves towards the cell membrane, facilitated by the cytoskeleton
Vesicle docking - docks at a specific site on cell membrane, facilitating recognition and binding between vesicle and membrane
Membrane fusion -vesicle and cell membrane undergo conformational change leading to their fusion. Lipid bilayers of vesicle and cell merge
Release of contents - materials inside vesicle are expelled into extracellular environment such as hormones, neurotransmitters
Recycle of vesicle membrane 0 membrane components of vesicle become part of cell membrane
What are the 3 components of cytoskeleton
Microfilaments (made up of actin)
Microtubules (made of tubulin)
Intermediate filaments (made of various proteins)
Explain what microfilamennts are (what are they made up of, what are their roles)
They are made up of ACTIN, and are the thinnest threads in the cytoskeleton
They play roles in various cellular processes such as:
Cell shape and structure (provide mechanical support) - especially abundant beneath cellmembrane
Cell movement - in processes like muscle contraction, microfilaments generate force by interacting with myosin
Cell division - microfilaments form the contractile ring that help divide cytoplasm as cell splits into two
Actin makes up the microfilaments
Explain what microtubules are (what are they made up of, what are their roles)
Made of tubulin
They are in a tubular structure, and is the thickest out of the 3 ifferent components of the cytoskeleton
FUnctions include::
Provide structural support and help maintain cell shape
Act as tracks for motor proteins like kinesin and dyenin, which moves vesicles, organelles and other cellular components
Participate in cell division by forming the mitotic spindle, which assists in segregating chromosomes into daughter cells
Forms the structural core of cilia and flagella –> cell movement and fluid propulsion
What types of tubulin make up a microtubule.
Alpha and beta tubulin
Polarity is important, as it determines direction the motor proteins move
What is alpha and beta tubulin. What do they do ? How do they work?
Microtubules have a directional polarity because each tubulin dimer (composed of one α-tubulin and one β-tubulin) is arranged head-to-tail.
The alpha tubulin is the ‘negative’ end, whereas the beta tubulin is the ‘positive’ end
More importantly, beta tubulin is where most of the growth and shrinkage of the microtubule occurs, whilst the alpha tubulin is the more stable end which is normally anchored to the MTOC (microtubule organising centre)
Alpha tubulin can bind to GTP but doesn’t hydrolyse it, while beta tubulin binds to GTP and hydrolyses it to GDP. This GTP bound to beta tubulin is critical for dynamic instability of microtubules (rapid switching between growth and shrinkage of microtubules controlled by hydrolysis of GTP_
What is the MTOC
It is where the microtubules are ‘stuck’ in, and is where they are anchored. Here is where the growth and orientation are controlled to ensure proper cell shape
Explain what intermedaite filaments are (what are they made up of, what are their roles)
Makes a complex lattice which is everywhere in the cell (if a diagram shows some filaments going everywhere chaotically, it is likely to be the intermediate filaments)
Made up of various strong pieces of protein (i.e. strong polypeptide chains)
They are middle in size compared to the other two:
Functions;
Maintain cell shape by resisting mechanical stress and preventing cell collapsing under tension (because of dense network through cytoplasm))
Provides tensile strength to withstand mechanical stress
Involved in stabilising cell junctions like desmosomes
Anchors organelles
