biology paper 1

This set of flashcards covers key concepts from cell biology, diffusion, osmosis, organization, infection and response, homeostasis, photosynthesis, and respiration as presented in the notes.

What are the two main cell types and what key feature distinguishes them?

Eukaryotic cells have a nucleus; Prokaryotic cells do not have a nucleus.

What is the function of a nucleus in a eukaryotic cell?

It contains the chromosomes (genetic material).

Name three cell types that are eukaryotic.

Animal, plant, and fungal (or protist) cells.

What are plasmids and in which cells are they usually found?

Small circular DNA molecules found in prokaryotic cells.

Do prokaryotic cells have any organelles with membranes?

No; they typically lack membrane-bound organelles like a nucleus.

How has the development of microscopes over the last 200 years helped biology?

Allowed detailed study of cells and internal structures.

What is magnification used for in microscopy?

To relate image size to actual size of a specimen.

What is the equation for magnification?

Magnification = image size ÷ actual size.

How do you convert mm to μm and μm to mm?

mm to μm: multiply by 1000; μm to mm: divide by 1000.

What is cell differentiation?

The process by which unspecialised cells become specialised into different cell types.

Name three plant cell features that animal cells do not have.

Chloroplasts, a large central vacuole, and a cell wall.

What is the function of xylem in plants?

To form thick-walled tubes that transport water and strengthen the plant.

What is the function of phloem in plants?

To transport dissolved sugars through sieve plates between cells.

What is the role of root hair cells?

Increase surface area for efficient water and mineral uptake.

Why do some plant and animal cells have flagella?

To enable movement or mobility of the cell.

What is the advantage of the RBCs’ biconcave shape?

Increases surface area to volume for efficient gas exchange.

What enzyme is commonly used to stain plant cells in microscopy?

Iodine.

Which part of the microscope holds the slide in place and is used for focusing?

The stage holds the slide; the fine focus knob is used for focusing.

What is the function of a light microscope compared to an electron microscope?

Light microscopes are cheaper and lower resolution; electron microscopes have high resolution and magnification.

Name three organelles or features found in plant cells but not animal cells.

Chloroplasts, cell wall, large central vacuole.

What are the stages of a light microscopy slide preparation for onion cells generally?

Place onion membrane on slide, stain with iodine, place coverslip and remove air bubbles.

Which part of a plant cell helps transport substances and is thickened with lignin to form tubes?

Xylem (and lignin strengthens the walls).

What structures are used to transport substances in plant cells and have sieve plates between cells?

Phloem cells.

What is the general purpose of the cell wall?

To provide structure and support to plant cells (strengthened by lignin in some tissues).

What is a large central vacuole and which cell type has it?

A large vacuole found in plant cells that helps maintain turgor pressure.

What is the difference between prokaryotic and eukaryotic cells in terms of nucleus presence?

Prokaryotic cells do not have a true nucleus; eukaryotic cells do.

Which part of a light microscope is placed under the stage to hold the slide?

The stage; the slide sits on the stage.

Which objective lens is usually used first to view a sample under a light microscope?

The lowest magnification objective lens.

What is used to stain plant cells on a slide?

Iodine.

What is placed on top of the slide, sample, and stain to protect it and keep stain in place?

A coverslip.

What part of the microscope is used to refine focus for a clear image?

The fine adjustment (fine focus) knob.

What are the advantages of using an electron microscope over a light microscope?

Higher resolution and higher magnification.

Convert 2.3 mm to micrometers.

2300 μm.

How do you calculate the actual size of a cell from image size and magnification?

Actual size = image size ÷ magnification.

Convert 570 μm to millimeters.

0.57 mm.

How is a root hair cell specialised?

Large surface area for absorption.

Why might a cell contain more mitochondria than usual?

To supply more energy for active processes.

Describe the structure of phloem cells.

Elongated cells with sieve plates between them; living but with reduced organelles; responsible for sugar transport.

How are nerve cells (neurons) typically specialised?

Long with dendrites and axons to transmit signals; specialized structures for fast transport of nerve impulses.

Why does a sperm cell require many mitochondria?

To provide the energy required for swimming.

How are xylem cells specialised?

Dead at maturity; thickened walls with lignin to form tubes for water transport.

What does cell differentiation mean and how does plant differentiation differ from animal differentiation?

Differentiation means cells become specialised. Plants can differentiate throughout life (meristems); animals differentiate largely during development.

What is osmosis?

Diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

What are meristems and where are they found?

Specialised regions in plants where cells can divide and differentiate; found in plants.

What is mitosis and what are its main stages briefly?

Mitosis is cell division where the nucleus divides to form two identical nuclei; stages include prophase, metaphase, anaphase, telophase (followed by cytokinesis).

What has to be replicated before a cell can divide?

DNA (the genetic material) must be replicated.

What happens in the third stage of mitosis?

Anaphase – sister chromatids are pulled apart to opposite ends.

What word describes the two new cells produced by mitosis?

Identical.

Where are meristems located in plants?

In regions of growth; meristems are found in roots and shoots.

What is a stem cell?

An undifferentiated cell that can differentiate into one or more specialised cell types.

What type of animal stem cell can become only a small number of different cell types?

Multipotent stem cells.

What piece of equipment is used to ensure equal surface area of potato pieces in a osmosis experiment?

A cork borer.

What piece of equipment is used to measure the mass of potato pieces before and after the experiment?

A top pan balance.

What happens to potato pieces in dilute (high water concentration) solutions?

They gain mass as water moves into the cells (osmosis).

What should you do with potato pieces after removing them from solution but before weighing them?

Blot them dry with a paper towel to remove surface liquid.

What is meant by undifferentiated stem cells being able to differentiate into many cell types in animals and plants?

Undifferentiated cells that can differentiate into multiple cell types (embryonic/adult in animals; meristems in plants).

What are the three main factors that affect diffusion rate?

Temperature, concentration gradient, and surface area (membrane area).

Give an example in animals where diffusion occurs.

Gas exchange in the lungs (oxygen and carbon dioxide) across alveoli and capillaries.

How are organisms' structures adapted for efficient diffusion?

Large surface area, thin diffusion distances (membranes), rich blood supply (in animals).

Do substances move from a low concentration to a high concentration in diffusion?

No; they move from high concentration to low concentration.

What substance is being transported by osmosis?

Water.

What does partially permeable mean?

Small molecules can pass through, but large molecules cannot.

How is active transport different from diffusion?

Active transport requires energy (usually from respiration) and moves substances against a concentration gradient.

Give an example of where active transport happens often in organisms.

Root hair cells (uptake of mineral ions) and cells lining the small intestine.

Why do cells that perform active transport often have many mitochondria?

To provide the energy (ATP) required for pumping substances against the gradient.

What is the levels of organisation in biology from cells to organ systems?

Cells → Tissues → Organs → Organ systems.

Define a tissue and an organ.

Tissue: group of similar cells working together. Organ: group of tissues performing a specific function.

What are the two jobs of bile?

Emulsify fats and neutralise stomach acid.

Where is bile produced and where is it stored?

Produced in the liver and stored in the gall bladder.

What is an enzyme?

A biological catalyst that speeds up chemical reactions.

What is the role of the active site on an enzyme?

The region where the substrate fits.

What are two factors that affect how enzymes work?

Temperature and pH.

Where are the salivary glands and what is their job?

In the mouth; they secrete saliva which contains amylase to start starch digestion.

What is the job of the oesophagus?

To move food to the stomach by peristaltic (muscular) contractions.

What is the job of the pancreas in digestion?

To release digestive enzymes (amylase, protease, lipase) into the digestive system.

What is the job of the small intestine?

To complete digestion and absorb soluble nutrients (glucose, amino acids, fatty acids, glycerol).

What is the function of hydrochloric acid in the stomach?

To kill bacteria and provide an acidic environment for protease activity.

From which organ is lipase released?

Pancreas (and also from the small intestine).

Which enzyme is released in the stomach?

Protease (pepsin).

Which enzyme is found in the mouth and starts digestion?

Amylase (salivary amylase).

Where is bile made and where is it stored?

Bile is made in the liver and stored in the gall bladder.

What are the two jobs of bile in digestion?

Emulsify fats and neutralise stomach acid.

What two chemicals are added to test for fats and what is the result?

Ethanol and water; the solution becomes cloudy (emulsion forms).

What is Biuret’s test used for and what colour change indicates a positive result?

Tests for proteins; blue solution turns purple.

Which test needs to be heated in a water bath and what does it detect?

Benedict’s test for reducing sugars; becomes brick red/orange/green depending on sugar concentration.

Where is starch testing done with iodine and what color indicates starch presence?

On a leaf; iodine turns blue/black where starch is present.

What enzyme breaks down starch?

Amylase.

What are the products of fat digestion?

Fatty acids and glycerol.

What are proteins made of?

Amino acids.

What is the tube that connects the throat to the lungs called?

Trachea.

What are the tubes that enter each lung called?

Bronchi (bronchus).

What are the two jobs of the lungs?

Gas exchange: oxygen enters the blood and carbon dioxide is removed.

What are the two types of blood cells in blood?

Red blood cells and white blood cells.

What are platelets?

Cell fragments that help blood clot.

Name three substances that plasma might have dissolved in it.

Salts, urea, CO2, hormones, etc.

What chemical is found inside red blood cells?

Hemoglobin.

What is the 3D shape of red blood cells and its advantage?

Biconcave disc; increases surface area for gas exchange.

What is the Left ventricle wall compared to the Right?

The left ventricle wall is thicker.

Where are pacemaker cells found and what is their role?

In the right atrium; they control heart rate.

Why is the heart described as a double pump?

Left side pumps to the body; right side pumps to the lungs.