MP Exam Biology Revision - Up Until Viruses

What are the 8 characteristics of living organisms?

Nutrition, respiration, excretion, response to surroundings, movement, controlling internal conditions (homeostasis), reproduction, and growth and development.

What is the function of the nucleus?

Controls the cell's activities and contains DNA (genetic information).

What is the function of the cytoplasm?

Site of chemical reactions in the cell; where many metabolic processes occur.

What is the function of the cell membrane?

Controls what enters and leaves the cell (selectively permeable).

What is the function of the cell wall?

Provides structural support and shape to plant cells; made of cellulose.

What is the function of mitochondria?

Site of aerobic respiration; produces ATP energy for the cell.

What is the function of chloroplasts?

Site of photosynthesis; contains chlorophyll to absorb light energy.

What is the function of ribosomes?

Site of protein synthesis.

What is the function of vacuoles?

In plant cells, the large permanent vacuole stores cell sap and helps maintain turgor pressure.

What structures are found in plant cells but NOT in animal cells?

Cell wall (cellulose), chloroplasts, and a large permanent vacuole.

What structures do plant and animal cells have in common?

Nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.

What is an enzyme?

A biological catalyst that speeds up metabolic reactions without being used up.

What is the active site of an enzyme?

The specific region on the enzyme where the substrate binds; it is complementary in shape to the substrate.

How does increasing temperature affect enzyme activity?

Reaction rate increases up to the optimum temperature; above the optimum, the enzyme denatures.

What does it mean when an enzyme is denatured?

The active site permanently changes shape due to high temperature or extreme pH, so the enzyme can no longer function.

How does pH affect enzyme function?

Extreme pH alters the shape of the active site, preventing substrate binding and reducing or stopping enzyme activity.

What is aerobic respiration?

The process of breaking down glucose using oxygen to produce ATP, carbon dioxide, and water.

What is the word equation for aerobic respiration?

Glucose + Oxygen → Carbon dioxide + Water (+ ATP energy released).

What is the balanced chemical equation for aerobic respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O.

What is anaerobic respiration?

Respiration without oxygen; produces much less ATP than aerobic respiration.

What is the word equation for anaerobic respiration in animals?

Glucose → Lactic acid (+ small amount of ATP).

What is the word equation for anaerobic respiration in plants and yeast?

Glucose → Ethanol + Carbon dioxide (+ small amount of ATP).

What is ATP and what is it used for?

Adenosine triphosphate — a molecule that stores and provides energy for cellular processes.

What are the key differences between aerobic and anaerobic respiration?

Aerobic uses oxygen and produces CO2 and water, releasing much more ATP. Anaerobic requires no oxygen, produces less ATP, and produces lactic acid (animals) or ethanol + CO2 (plants/yeast).

What is diffusion?

The net movement of particles from an area of high concentration to low concentration, down a concentration gradient — no energy required.

What is osmosis?

The net movement of water molecules from a region of high water potential to low water potential through a selectively permeable membrane.

What is active transport?

The movement of substances against a concentration gradient (from low to high concentration), requiring energy (ATP).

What factors affect the rate of movement of substances into and out of cells?

Surface area to volume ratio, distance, temperature, and concentration gradient.

What are the levels of organisation in organisms, from smallest to largest?

Organelles → cells → tissues → organs → organ systems → organisms.

What is cell differentiation?

The process by which cells become specialised for a specific function by developing particular structures.

Why is cell differentiation important?

It allows cells to carry out specific functions more efficiently, leading to the development of specialised cells and tissues.

What are stem cells?

Undifferentiated cells that can divide and differentiate into a variety of specialised cell types.

What are the advantages of using stem cells in medicine?

They can potentially replace damaged or diseased tissues/organs.

What are the disadvantages of using stem cells in medicine?

Ethical concerns, risk of immune rejection, and potential to develop into cancer cells.

What is a eukaryote?

An organism whose cells contain a true nucleus and membrane-bound organelles.

What is a prokaryote?

An organism whose cells lack a true nucleus; DNA is a circular chromosome free in the cytoplasm.

What are the key features of plant cells?

Multicellular; cells have chloroplasts for photosynthesis; cellulose cell walls.

What are the key features of animal cells?

Multicellular; no chloroplasts; no cell walls; store carbohydrate as glycogen.

What are the key features of fungi?

Cannot photosynthesise; body made of a mycelium of hyphae; chitin cell walls.

What are protoctists?

Microscopic single-celled eukaryotes.

What are the key features of bacteria (prokaryotes)?

Microscopic single-celled organisms; have a cell wall, cell membrane, cytoplasm, and plasmids.

What is a pathogen?

An organism that causes disease.

What are viruses?

Non-living particles smaller than bacteria; parasitic and can only reproduce inside living cells.