Biologie realllll

What are the essential needs of a cell to survive and function efficiently?

Cells require a constant supply of oxygen and glucose for energy production, water for chemical reactions and transport, and efficient waste removal systems to expel by-products like carbon dioxide. These are necessary for maintaining homeostasis and carrying out life processes.

Name and describe the main structures found in an animal cell.

Key structures include the nucleus (stores genetic information and controls cell activities),

mitochondria (site of cellular respiration),

cytoplasm (gel-like substance where reactions occur),

cell membrane (regulates what enters and exits),

and ribosomes (synthesize proteins).

What is the function of mitochondria in cells?

Mitochondria are organelles responsible for producing energy through cellular respiration. They convert glucose and oxygen into ATP (adenosine triphosphate), the molecule used for energy by the cell, earning them the nickname “powerhouses of the cell.”

Explain the process and purpose of cellular respiration.

Cellular respiration is a chemical process that happens mainly in the mitochondria, where glucose and oxygen are converted into carbon dioxide, water, and energy in the form of ATP. This energy is essential for the cell’s growth, repair, and other vital functions.

Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)

Describe the process of photosynthesis and its importance to life on Earth.

Photosynthesis takes place in the chloroplasts of plant cells. With the help of sunlight, plants change carbon dioxide and water into glucose and oxygen. This process gives the plant energy and provides oxygen for other organisms, which is important for life.

Carbon dioxide + Water + Sunlight → Glucose + Oxygen

What are stem cells, and why are they important in biology and medicine?

Stem cells are special cells that can become different types of cells. They help with growth, healing, and are important in medical research because they can be used to treat diseases.

What is a tissue, and how does it differ from an organ?

A tissue is a group of similar cells working together to perform a specific function (e.g., muscle tissue contracts to cause movement). An organ, by contrast, is made of multiple tissues working together to carry out a more complex task, such as the heart pumping blood.

Define the function of the nucleus in a cell

The nucleus acts as the control center of the cell. It houses DNA, which contains the genetic instructions for building proteins and regulating all cellular processes, including cell division and differentiation.

What role does the cell membrane play in maintaining cellular homeostasis?

The cell membrane controls what enters and exits the cell. It helps maintain balance by letting in necessary molecules, removing waste, and protecting the cell from the outside environment.

What is the cytoplasm and how does it function

Cytoplasm is a gel-like substance inside the cell where many activities occur. It contains organelles and enzymes that help with important processes like making energy and proteins.

How does the ribosome contribute to cellular function?

Ribosomes build proteins by joining amino acids using genetic instructions. These proteins are important for cell structure, enzymes, hormones, and the immune system.

Why must food be broken down?

Food must be broken down into small molecules so they can pass from the intestines into the blood. From there, they travel to the cells, where they’re used for energy, growth, and repair.

A+ Insight: Without this process, even healthy food would be useless to the body — it would just pass through undigested.

Step 2 – What is the difference between mechanical and chemical digestion?

• Mechanical digestion: Physically breaks food into smaller pieces (e.g., chewing, stomach mixing).

• Chemical digestion: Uses enzymes to break down large molecules into small ones:

  • Carbs → glucose

  • Proteins → amino acids

  • Fats → glycerol + fatty acids
    A+ Insight: Mechanical digestion increases the surface area for enzymes to work more efficiently — they can “attack” more food at once.

Step 3 – What happens in the mouth?

• Mechanical: Teeth chew food.

• Chemical: Saliva contains amylase, which starts breaking down carbohydrates into glucose.
  A+ Insight: If you chew bread long enough, it starts to taste sweet — that’s amylase breaking starch into sugar.

Step 4 – What happens in the stomach?

• Mechanical: Stomach muscles churn and mix the food.

• Chemical: The enzyme pepsin starts breaking down proteins into amino acids. Stomach acid helps activate pepsin and kill harmful microbes.

Step 5 – What happens in the duodenum?

• Enzymes from the pancreas continue digestion:

  • Amylase: carbs → glucose

  • Protease: proteins → amino acids

  • Lipase: fats → glycerol + fatty acids

• Bile from the liver breaks fats into smaller droplets (emulsification), making it easier for lipase to work.

Step 6 – What happens in the rest of the small intestine?

• Tiny structures called villi absorb nutrients like glucose, amino acids, glycerol, and fatty acids into the blood.
  A+ Insight: Villi are covered in microvilli — like tiny hairs — which greatly increase surface area for faster absorption.

Step 7 – What happens in the large intestine?

• The large intestine absorbs water and minerals.

• The remaining waste forms feces and is stored in the rectum until removed from the body.

Step 8 – How is digestion connected to the rest of the body?

• Nutrients enter the blood through the small intestine.

• The blood delivers them to cells, where glucose is used with oxygen during cellular respiration to make energy (ATP).
  A+ Insight: This is why digestion and breathing are linked — one brings fuel (glucose), the other brings oxygen to “burn” it.

How does breathing work – step by step?

How does breathing work – step by step?

Step 1: You inhale. The diaphragm contracts (moves down) and the rib cage lifts up. This makes more space in the chest, so air is sucked into the lungs.

Step 2: Air travels through the windpipe into the bronchi and then into smaller tubes, ending in the alveoli (tiny air sacs).

Step 3: You exhale. The diaphragm relaxes (moves up), the chest gets smaller, and air is pushed out of the lungs.

What happens in the alveoli – step by step?

Step 1: Air reaches the alveoli, which are surrounded by tiny blood vessels (capillaries).

Step 2: Oxygen from the air moves through the alveoli walls into the blood.

Step 3: At the same time, carbon dioxide moves from the blood into the alveoli to be exhaled. This is called gas exchange.

How are breathing and blood circulation connected

Step 1: The blood picks up oxygen from the alveoli in the lungs.

Step 2: The heart pumps this oxygen-rich blood to the rest of the body, so cells can make energy.

Step 3: The blood collects carbon dioxide (a waste gas) from the cells and brings it back to the lungs to be exhaled.

What is the role of the diaphragm?

The diaphragm is a muscle under the lungs.

When it contracts, you breathe In

When it relaxes, you breathe out

It works all the time, even when you sleep.

How does the circulatory system work? (Pulmonary + Systemic circulation)

Step 1: Blood from the body (low in oxygen) enters the right side of the heart.

Step 2: The heart pumps this blood to the lungs. In the lungs, it picks up oxygen and releases carbon dioxide. This is called the pulmonary circulation.

Step 3: Oxygen-rich blood returns to the left side of the heart.

Step 4: The heart pumps this blood out to the rest of the body to give oxygen to all the cells. This is called the systemic circulation.

What is the structure of the heart?

• The heart has 4 chambers:

  • Right atrium and right ventricle (send blood to the lungs)

  • Left atrium and left ventricle (send blood to the body)

• The heart has valves to keep the blood moving in one direction.

• The left side is stronger because it pumps blood to the whole body.

What’s the difference between arteries, veins, and capillaries?

• Arteries carry blood away from the heart (usually rich in oxygen).

• Veins carry blood back to the heart (usually low in oxygen).

• Capillaries are tiny blood vessels where oxygen and nutrients go into cells, and waste like CO₂ comes out.

What is in your blood, and what does each part do?

• Red blood cells: Carry oxygen using hemoglobin.

• White blood cells: Fight bacteria, viruses, and other germs.

• Platelets: Help blood clot and stop bleeding.

• Plasma: The yellow liquid that carries everything (water, nutrients, hormones, waste, etc.).

Where are blood cells made, and what do they do?

• Blood cells are made in the red bone marrow (inside certain bones).

• This includes red blood cells, white blood cells, and platelets.

What do the liver and kidneys do with the blood?

• The liver helps clean the blood, store energy, and break down harmful substances.

• The kidneys filter the blood to remove waste and extra water, turning it into urine.
  They work together to keep the blood clean and balanced.

How does the skin protect the body?

Step 1: The epidermis (outer layer of the skin) acts as a barrier to keep harmful bacteria, viruses, and other harmful substances from entering the body.

Step 2: The skin produces melanin, which helps protect against UV radiation from the sun. This reduces the risk of sunburn and skin damage.

Step 3: The skin prevents water loss by creating a protective layer, keeping moisture inside the body and preventing dehydration.

How does the skin help control body temperature?

Step 1: When the body is too hot, the skin releases sweat through sweat glands. As sweat evaporates from the skin, it cools the body down.

Step 2: When the body is too cold, the skin reduces blood flow to the surface by narrowing blood vessels (vasoconstriction), helping to conserve heat and keep the body warm.

Cell

The basic structural and functional unit of life, responsible for carrying out all vital processes such as energy production, waste removal, and growth.

Homeostasis

The maintenance of a stable internal environment within a cell or organism, essential for normal function and survival.

Nucleus

A membrane-bound organelle that stores DNA and controls the cell’s activities, including growth, metabolism, and reproduction.

Cell membrane

A selectively permeable barrier that surrounds the cell, regulating the movement of substances in and out and helping maintain homeostasis.

Chlorophyll

A green pigment found in chloroplasts that absorbs light energy, driving the photosynthesis process.

Stem cells

Undifferentiated cells with the ability to develop into various specialized cell types and play a role in tissue repair and medical treatments.

Tissue

A group of similar cells that perform a specific function, such as muscle tissue for movement.

Organ

A structure made up of different tissues working together to perform a specific function, like the heart or lungs.

Glucose

A simple sugar used as a primary energy source in cellular respiration.

Digestion

The process of breaking down food into small molecules that the body can absorb and use for energy, growth, and repair.

Amylase

An enzyme that breaks down carbohydrates (starch) into glucose, starting digestion in the mouth and pancreas.

Pepsin

An enzyme in the stomach that breaks down proteins into amino acids, activated by stomach acid.

Bile

A substance made by the liver that breaks down fats into smaller droplets, making them easier to digest.

Lipase

An enzyme that breaks down fats into glycerol and fatty acids in the small intestine.

Protease

An enzyme that breaks down proteins into amino acids, mainly in the stomach and small intestine.

Duodenum

The first part of the small intestine where most digestion happens with the help of enzymes and bile.

Villi

Tiny projections in the small intestine that absorb nutrients into the blood, with microvilli to increase surface area.

Large intestine

Absorbs water and minerals from undigested food, forming and storing feces.

Diaphragm

A muscle below the lungs that controls breathing by moving down during inhalation and up during exhalation.

Alveoli

Tiny air sacs in the lungs where gas exchange happens — oxygen enters the blood and carbon dioxide leaves.

Gas exchange

The swapping of gases in the lungs: oxygen goes from alveoli to blood, and carbon dioxide goes from blood to alveoli to be exhaled.

Bronchi

Two main tubes that carry air from the windpipe into each lung, branching into smaller tubes.

Capillaries

Tiny blood vessels that wrap around alveoli to exchange gases between the lungs and the blood.

Pulmonary circulation

The part of the circulatory system that carries blood from the heart to the lungs and back, to exchange oxygen and carbon dioxide.

Systemic circulation

The flow of oxygen-rich blood from the heart to the body, and oxygen-poor blood back to the heart.

Atria (Right & Left)

The two upper chambers of the heart that receive blood — the right from the body, the left from the lungs.

Ventricles (Right & Left)

The two lower chambers of the heart that pump blood — the right to the lungs, the left to the body.

Valves

Flaps in the heart that keep blood flowing in one direction, preventing backflow.

Arteries

Blood vessels that carry blood away from the heart, usually rich in oxygen.

Veins

Blood vessels that carry blood back to the heart, usually low in oxygen.

Capillaries

Tiny blood vessels where oxygen, nutrients, and waste are exchanged between blood and cells.

Red blood cells

Blood cells that carry oxygen using a protein called hemoglobin.

White blood cells

Blood cells that protect the body by fighting bacteria, viruses, and other harmful invaders.

Platelets

Tiny cell fragments that help blood clot and stop bleeding when you get a cut.

Plasma

The liquid part of blood that carries cells, nutrients, hormones, and waste.

Red bone marrow

The soft tissue inside certain bones where blood cells are made.

Liver

An organ that helps clean the blood, store energy, and break down toxins.

Kidneys

Organs that filter the blood to remove waste and extra water, producing urine.