date - 09/06/2025
5 Single-Celled Organisms (Unicellular):
Amoeba
Paramecium
Euglena
Chlamydomonas
Bacteria (like E. coli)
5 Multi-Celled Organisms (Multicellular):
Human
Dog
Mango tree
Frog
Earthworm
( plants and animals)
5 Kingdoms with Cell Walls:
Plantae – e.g., Mango tree (cell wall made of cellulose)
Fungi – e.g., Mushroom (cell wall made of chitin)
Bacteria (Monera) – e.g., E. coli (cell wall made of peptidoglycan)
Protista – e.g., Chlamydomonas (some have cell walls made of cellulose)
Archaea – e.g., Halobacterium (cell wall, but not made of peptidoglycan)
Structures in a Yeast Cell:: And its functions
Cell Wall
Made of chitin
Gives shape and protects the cell
Cell Membrane
Controls what goes in and out of the cell
Cytoplasm
Jelly-like fluid where most cell reactions happen
Nucleus
Contains DNA (genetic material)
Controls cell activities
Vacuole
Stores water, waste, and nutrients
Mitochondria
Carries out aerobic respiration (makes energy)
Ribosomes
Makes proteins
Bud (sometimes seen)
A small outgrowth during asexual reproduction
Similarities (Yeast & Bacteria):
Both are unicellular (single-celled).
Both have a cell wall.
Both can reproduce asexually.
Both have cytoplasm and cell membrane.
Both can survive in similar environments (e.g., sugar-rich, moist areas).
Differences:
Cell Type
Yeast: Eukaryotic
Bacteria: Prokaryotic
Nucleus
Yeast: Present
Bacteria: Absent
DNA Location
Yeast: Inside a nucleus
Bacteria: Free in the cytoplasm (nucleoid)
Cell Wall Composition
Yeast: Made of chitin
Bacteria: Made of peptidoglycan
Size
Yeast: Larger (about 10 micrometers)
Bacteria: Smaller (1–5 micrometers)
Organelles
Yeast: Has organelles (mitochondria, vacuole, etc.)
Bacteria: Only ribosomes
Reproduction Method
Yeast: Budding
Bacteria: Binary fission
Kingdom
Yeast: Belongs to Fungi
Bacteria: Belongs to Monera.
THE END
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10/6/2025
What is Nitrogen Fixation?
Nitrogen fixation is the process of turning nitrogen gas (N₂) from the air into a form that plants can use, like nitrates (NO₃⁻) or ammonia (NH₃).
Why is it needed?
The air has a lot of nitrogen (about 78%), but plants can’t use nitrogen gas directly.
So, it must be "fixed" into a usable form by certain bacteria or processes.
How does it happen?
There are three main ways nitrogen gets fixed:
Biological Fixation
Atmospheric Fixation
Industrial Fixation
Deamination in Plants (Nitrogen Cycle)
Deamination is when dead plants and animals (or their waste) are broken down by decomposer bacteria or fungi, and the amino acids in their proteins have their amino group (-NH₂) removed.
What happens during this process?
The amino group is removed from amino acids
It gets converted into ammonia (NH₃)
This process helps return nitrogen to the soil
Nitrification
What is Nitrification?
Nitrification is the process where ammonia (NH₃) in the soil is converted into nitrates (NO₃⁻) by nitrifying bacteria.
Plants can’t use ammonia directly, but they can absorb nitrates, so this step is super important in the nitrogen cycle.
How does it happen? (2 Steps)
Ammonia → Nitrite (NO₂⁻)
Done by bacteria like Nitrosomonas
Nitrite → Nitrate (NO₃⁻)
Done by bacteria like Nitrobacter .
SO one questions will come eventually - how does the nitogen fixation happen , how does the the nitrogen in the air become usable for the plants -
The bacteria that turn nitrogen gas (N₂) from the air into a form usable by plants are called nitrogen-fixing bacteria.
Nitrogen-Fixing Bacteria:
Rhizobium
Lives in root nodules of legume plants (like beans and peas)
Converts nitrogen gas (N₂) → ammonia (NH₃)
Azotobacter
Free-living in the soil (not in roots)
Also converts N₂ → ammonia
Cyanobacteria (like Anabaena)
Found in water or wet soil, especially in rice fields
Fix nitrogen in aquatic environments
How do bacteria turn nitrogen gas into usable form?
Nitrogen-fixing bacteria like Rhizobium and Azotobacter have a special enzyme called nitrogenase.
This enzyme helps them break apart nitrogen gas (N₂) from the air and combine it with hydrogen (H) to make ammonia (NH₃).
This is a chemical reaction that needs:
Nitrogen gas (N₂)
Hydrogen (H₂) (from water or other compounds)
Energy (ATP)
bacteria involved in deamination:-
Mainly decomposer microorganisms like:
Putrefying bacteriaExample: Proteus, Pseudomonas, Clostridium
Some fungi also help in this process
These bacteria break down proteins → amino acids → remove the amino group → release ammonia
Where they live:
In the soil
On dead organisms, waste, or rotting materials
In compost heaps or manure
Nitrifying Bacteria (Nitrification)
Bacteria:
Nitrosomonas → converts ammonia → nitrites
Nitrobacter → converts nitrites → nitrates
Where they live:
In well-aerated (oxygen-rich) soil
Often near roots where there's ammonia .
THE END
11/6/2025
What is a Restriction Enzyme?
A restriction enzyme (also called a restriction endonuclease) is a protein that cuts DNA at specific sequences.
Where does it come from?
Found in bacteria
Bacteria use them as a defense tool to cut up virus (phage) DNA
How does it work?
It recognizes a specific DNA sequence (called a recognition site)
That sequence is usually 4–8 base pairs long
Once it finds that sequence, it cuts the DNA there
If the pancreas is not there (or not working), :-
1. It makes digestive enzymes
Without it:
Your body can’t digest food properly
Especially fats and proteins
You may get symptoms like:
Diarrhea
Fatty, oily poop (called steatorrhea)
Weight loss
Malnutrition (even if you're eating well)
2. It makes hormones like insulin and glucagon
Without insulin:
Your body can’t control blood sugar
Leads to diabetes (specifically Type 1 diabetes)
Blood sugar becomes very high, which can be life-threatening
So if pancreas is removed or fails:
A person will need:
Digestive enzyme supplements with food
Insulin injections for life
Careful diet and blood sugar monitoring
What is Gravitropism?
Gravitropism is how a plant grows in response to gravity.
It’s also called geotropism.
Two types:
Positive gravitropism
Roots grow downward, toward gravity
Helps anchor the plant and absorb water
Negative gravitropism
Shoots/stems grow upward, against gravity
Helps reach sunlight for photosynthesis
Why it happens:
Controlled by plant hormones called auxins
Auxins move and cause faster or slower growth on one side of the root/shoot, so it bends
What is Anemia?
Anemia is a condition where your body doesn’t have enough red blood cells or hemoglobin (the part of red blood cells that carries oxygen).
What does Iron have to do with it?
Your body needs iron to make hemoglobin
If you don’t have enough iron → your body can’t make enough hemoglobin → less oxygen is carried in your blood
What happens if iron is low?
You may feel:
Tired and weak (because your cells get less oxygen)
Pale skin
Shortness of breath
Dizziness or headaches
Cold hands and feet
Brittle nails
Craving strange things like ice, dirt (called pica)
Treatment:
Eating iron-rich foods (like spinach, red meat, beans)
Iron supplements
Treating the cause (e.g., stopping blood loss)
What is Stem Culture?
Stem culture is a type of plant tissue culture where a part of the plant stem is used to grow a new plant in a lab.
It can be there foe human also .
Why is it done?
To grow many identical plants quickly
To grow plants disease-free
To grow plants all year round, not just in season
To save rare or endangered plants .
THE END
12/06/2025 - WROTE A BIOLOGY MCQ IN UYIR . I WILL BE POSTING ABOUT THE THINGS I LEARNED FROM THE MISTAKES I MADE IN TODAY EXAM / MCQ
1) By which process do oxygen and carbon dioxide move between cells and capillaries?
ans) Diffusion
explanation :-
Oxygen and carbon dioxide move between cells and capillaries by diffusion
Diffusion = movement of particles from high concentration to low concentration
Oxygen moves from blood to cells, and CO₂ moves from cells to blood
Why not the others?
A) Breathing = movement of air in and out of lungs
C) Excretion = removal of waste (like urine, sweat)
D) Respiration = process of making energy in cells (using oxygen)
2) Which element is found in proteins but not carbohydrates?
ans ) Nitrogen
explanation :-
Proteins are made of amino acids, which contain nitrogen (in the amino group: —NH₂)
Carbohydrates (like sugar or starch) contain only:
Carbon (C)
Hydrogen (H)
Oxygen (O)
3) Starch is digested by amylase in the mouth, but it is not digested in the stomach. What is the reason for this?
ans) B) The pH in the stomach is not suitable for the amylase to work.
explanation :-
Explanation:
Amylase works best at a neutral to slightly alkaline pH (around pH 7).
The stomach is very acidic (around pH 2) because of hydrochloric acid.
This acidic environment denatures amylase, stopping it from working.
Why not the others?
A) Not all starch digestion is completed in the mouth — most happens in the small intestine.
C) Time isn’t the issue — the pH is.
D) The stomach temperature (~37°C) is fine — the problem is pH, not heat.
4)
What’s happening?
The plant has striped leaves:
Green parts have chlorophyll → can photosynthesize
White parts don’t → no photosynthesis
The test:
After 6 hours in bright light → the leaf is tested for starch using iodine:
Iodine turns blue-black = starch present
Stays yellow-brown/white = no starch
So which part will have starch?
Only green parts photosynthesize → make glucose → starch
White parts don’t make starch
Green stripe = blue-black
White stripe = white
5) does large intestine absorb more water from food or small intestine ? why ?
ans) small intestine
Why?
Small intestine is the main site for:
Digestion and
Absorption of nutrients and water
It has a large surface area (due to villi and microvilli), which helps absorb a lot of water along with nutrients.
Large intestine (colon):
Absorbs some remaining water, but much less than the small intestine.
Its main job is to:
Absorb the leftover water
Compact waste into feces
6) How does blood enter the heart?
ans) C) through veins into the atria
Explanation:
Veins carry blood to the heart
Atria are the upper chambers of the heart where blood first enters
Deoxygenated blood from the body comes through the vena cava → right atrium
Oxygenated blood from the lungs comes through the pulmonary veins → left atrium
7) What is the sequence of organs that blood passes through during one circulation of the body of a fish?
ans) A - Heart
Gills (for gas exchange — oxygen enters, carbon dioxide leaves)
Body (delivers oxygen to tissues)
Back to heart
Heart → Gills → Body → Heart
Fish have a 2-chambered heart (1 atrium + 1 ventricle)
Blood is pumped once per full circuit
Oxygenation happens at the gills, not lungs
8) After vigorous exercise, an athlete continues to breathe deeply during the recovery period. During this recovery period the oxygen debt is removed. Which reaction is used to remove the oxygen debt?
A) aerobic respiration of lactic acid in the liver
Explanation:
Oxygen debt happens when muscles run out of oxygen during vigorous exercise and switch to anaerobic respiration, producing lactic acid.
After exercise, the body needs extra oxygen to:
Break down lactic acid
This happens by aerobic respiration
And it happens in the liver, not the muscles
THE END
16/6/25
Aerobic Respiration
Aerobic respiration is the process where cells break down glucose using oxygen to release energy.
Simple equation:
Glucose+Oxygen→Carbon dioxide+Water+Energy (ATP)
Key points:
Needs oxygen
Happens in most cells
Produces a lot of energy
Happens in mitochondria
Anaerobic Respiration
Anaerobic respiration is when cells make energy without using oxygen.
In humans:
Glucose→Lactic acid+Some energy\text{Glucose} \rightarrow \text{Lactic acid} + \text{Some energy}Glucose→Lactic acid+Some energy
Happens during hard exercise
Causes muscle cramps (from lactic acid)
Makes less energy than aerobic respiration
In yeast (fermentation):
Glucose→Alcohol+Carbon dioxide+Some energy
Key Points:
No oxygen
Less energy
Can happen in muscles, bacteria, and yeast
How the shape of sucrase is related to its function:
Enzymes like sucrase have a special 3D shape.
This shape includes an active site — a small pocket that exactly fits the sucrose molecule (like a key fitting a lock).
The active site binds to sucrose and helps break it down into glucose and fructose.
If the shape of the enzyme changes (like from heat or pH), the active site won’t fit sucrose anymore → the enzyme won’t work.
The chamber of the heart with the thickest wall is the:
Left ventricle
Why?
It pumps blood to the entire body, so it needs to generate high pressure
That’s why its muscle wall is thickest — stronger force = better blood flow to organs
Basic Structure:
The heart has 4 chambers:
Right atrium
Right ventricle
Left atrium
Left ventricle (thickest wall)
Valves prevent backflow:
Tricuspid (right side)
Bicuspid/Mitral (left side)
Semilunar valves (at exits of ventricles)
Blood flow path:
Body → right atrium → right ventricle → lungs (to get oxygen)
Lungs → left atrium → left ventricle → body
Vena Cava
The vena cava is a large vein that carries deoxygenated blood from the body back to the heart.
There are two parts:
Superior vena cava – brings blood from the upper body (head, arms, chest)
Inferior vena cava – brings blood from the lower body (legs, abdomen)
THE END
17/6/2025
1) does plants have ciculatory system ?
plants do not have a circulatory system like animals.
They do have something similar called the vascular system. It's made up of two key tissues:
Xylem → carries water and minerals from the roots up to the leaves.
Phloem → transports food (glucose, from photosynthesis) from the leaves down to the rest of the plant.
2) does all the circulatory system have a vascular system ?
In Plants:
Vascular system = their circulatory system
Made of:
Xylem (water & minerals up from root
Phloem (food down from leaves
In Animals (including humans):
Circulatory system = blood + heart + vessels
Has:
Arteries, veins, capillaries
Heart as the pump
Blood = transport fluid
All vascular plants have a vascular system.
Not all living things with a circulatory-like system have a vascular one—animals have a true circulatory system, plants have a vascular system.
What is the Circulatory System?
It’s the body’s transport system, moving blood, nutrients, oxygen, carbon dioxide, and hormones to and from cells—basically Uber for your body
1. Heart
The pump of the system
Has 4 chambers:
Right atrium, Right ventricle
Left atrium, Left ventricle
Pumps blood throughout the body via blood vessels.
2. Blood Vessels
Arteries: carry blood away from the heart (mostly oxygen-rich).
Veins: carry blood towards the heart (mostly oxygen-poor).
Capillaries: tiny vessels where exchange of gases/nutrients happens.
3. Blood
Made of:
Red blood cells (carry oxygen)
White blood cells (fight infection)
Platelets (help clotting)
Plasma (liquid that carries all of the above)
What is the Lymphatic System?
It's your body's clean-up crew, immune defender, and fluid balancer all in one.It works side by side with the circulatory system, but instead of blood, it moves lymph—a clear fluid full of white blood cells.
Fights infections
Filters out bacteria, viruses, and dead cells.
Produces and transports white blood cells (especially lymphocytes).
Drains excess fluid
Returns extra fluid (that leaks out from blood vessels) back into the bloodstream.
Absorbs fats
1. Lymph
The fluid that travels through the lymphatic system.
Contains white blood cells, proteins, and fats.
2. Lymph Nodes
Small bean-shaped filters.
Trap and destroy pathogens.
You can feel some in your neck when you’re sick—those little bumps? Yeah, that’s your army gearing up
. Lymph Vessels
Network of thin tubes like blood vessels.
Carry lymph throughout the body.
4. Organs in the Lymphatic System:
Spleen: filters blood, removes old red blood cells.
Thymus: where T-cells (a type of white blood cell) mature.
Tonsils: trap pathogens entering through the mouth/throat.
Is the lymphatic system part of the excretory system?
Not exactly, but they’re kinda like roommates who help each other out
Excretory System = the body’s official waste management crew
It includes:
Kidneys → filter blood, make urine
Ureters, bladder, urethra → transport & store urine
Lungs → remove CO₂
Skin → sweat out salt & water
Liver → detox queen, breaks down toxins
Lymphatic System = the immune defense + drainage system
It:
Moves lymph fluid (extra fluid + waste from tissues)
Returns it to the bloodstream
Filters out bacteria, viruses, and dead cells
Helps absorb fats from digestion
THE END
