Year 11 Biology - Exam revision SEM 1

• Cell Theory

1. All living things are made of cells.

2. Cells are the basic unit of life.

3. All cells come from pre-existing cells.

Unicellular vs. Multicellular

• Unicellular: Made of one cell (e.g., bacteria, amoeba).

• Multicellular: Made of many cells (e.g., plants, animals).

Prokaryotic vs. Eukaryotic

• Prokaryotic: No nucleus, no membrane-bound organelles (e.g., bacteria).

• Eukaryotic: Has a nucleus and organelles (e.g., plant, animal cells).

What are key differences between plant, animal, and bacterial cells?

• Plant: Cell wall (cellulose), chloroplasts, large vacuole.

• Animal: No cell wall, small vacuoles, centrioles.

• Bacteria: Prokaryotic, cell wall (peptidoglycan), no nucleus.

What is the function of the mitochondria?

Produces energy (ATP) via cellular respiration.

What does the Golgi apparatus do?

Modifies, sorts, and packages proteins for secretion.

What is the function of the cell membrane? What are its parts

Controls what enters/exits the cell (selectively permeable).
The cell membrane consists of a phospholipid bilayer, integral and peripheral proteins, glycoproteins, carbohydrates, and cholesterol, which help regulate what enters and exits the cell.

What is the structure of DNA?

Double helix made of nucleotides (sugar, phosphate, base: A,T,C,G).

How do prokaryotic cells reproduce?

Binary fission—splitting into two identical cells.

What are the stages of mitosis?

Prophase, Metaphase, Anaphase, Telophase (PMAT).

How does cancer relate to the cell cycle?

Uncontrolled cell division due to mutations (e.g., in DNA repair genes).

What is the equation for photosynthesis? What is Photosynthesis?

Photosynthesis is the process by which green plants and some organisms use sunlight to synthesize foods with carbon dioxide and water.

6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Compare aerobic and anaerobic respiration.

• Aerobic: Uses O₂, produces 36 ATP (efficient).

• Anaerobic: No O₂, produces 2 ATP (fermentation in yeast/lactic acid in muscles).

What is osmosis?

Diffusion of water across a semi-permeable membrane (high → low concentration).
A type of passive transport

What is Diffusion?

Diffusion is the passive transport process involving the movement of molecules from an area of higher concentration to an area of lower concentration.

How does active transport differ from passive transport?

Requires energy (ATP), moves substances against the concentration gradient.

Why is a high SA:V ratio important for cells?

Allows efficient exchange of materials (nutrients/waste); a higher ratio enables better absorption of nutrients and other materials.
SA:VOL Ratio = 2:6

What conditions do bacteria need to grow?

Moisture, nutrients, warmth, pH, oxygen (varies).

What are the four main types of pathogens?

1. Bacteria (e.g., Salmonella)

2. Viruses (e.g., Influenza)

3. Fungi (e.g., Athlete’s foot)

4. Parasites (e.g., Malaria protozoan)

How can pathogens enter the body?

Mouth, nose, cuts, sexual contact, insect bites.

What is an antigen?

A molecule (often on pathogens) that triggers an immune response.

How are diseases spread?

Direct contact, droplets, vectors (mosquitoes), contaminated food/water.

Epidemics vs. Pandemics

• Epidemic: Widespread in a region.

• Pandemic: Global spread (e.g., COVID-19).

What is the first line of defense?

Physical barriers (skin, mucus, stomach acid)

What is the second line of defense?

Non-specific (innate) immune response (inflammation, phagocytes).

What is the third line of defense?

Specific (adaptive) immune response (B-cells, T-cells, antibodies).

Compare active and passive immunity.

• Active: Body makes antibodies (vaccination/infection).

• Passive: Antibodies given (breast milk, injection).

Why does the secondary immune response act faster?

Memory cells "remember" the pathogen and respond quickly.

What is herd immunity?

When most of a population is immune, reducing disease spread.

Aerobic Respiration formula / What is it?

Aerobic respiration is the process of producing cellular energy in the presence of oxygen by breaking down glucose.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)

What is Fermentation?

Fermentation is a metabolic process that converts sugars to acids, gases, or alcohol in the absence of oxygen.

What is ATP?

ATP (Adenosine Triphosphate) is the energy carrier molecule in cells that stores and transports chemical energy for cellular processes.

What is Endocytosis?

Endocytosis is an active transport process where cells engulf substances, including Phagocytosis (cellular eating) and Pinocytosis (cellular drinking).

What is Exocytosis?

Exocytosis is an active transport process in which cells expel particles or substances by enclosing them in vesicles that fuse with the plasma membrane.

What are Autotrophs?

Autotrophs are organisms that produce their own food, typically through photosynthesis or chemosynthesis.

What are Heterotrophs?

Heterotrophs are organisms that cannot produce their own food and depend on other organic substances for nutrition.

What is the role of decomposers?

Decomposers are organisms that break down dead organic matter, recycling nutrients back into the ecosystem.

What happens during prophase?

Nucleus and chromosomes become visible
Spindle fibers form"

What happens during metaphase?

Chromosomes align in the equator of the cell

Spindle fibers attach

Nucleus goes away

What happens during anaphase?

Chromosomes move away to the side by spindles

What happens during telophase?

Spindle fibers break down
New nuclei are forming

Characteristics of aerobic respiration

• Supplies body with energy

• Needs oxygen

• Breaks down food

• Glucose breaks down in presence of oxygen

How does binary fission occur

• DNA coils to form identical chromosomes - condensation

• Chromosomes move to opposite sides

• Cell wall forms in the middle

• Cell divides

SA:V Ratio formulas

Calculating a 2cm cube:

• SA = 2×2×6 , RATIO = : 1 (SA divided by VOL)

• VOL = 2×2×2 = RATIO

Fermentation formula (Yeast)

Glucose → Ethanol + Carbon dioxide + 2ATP
Is a metabolic process that turns acids to sugars, gases, or alcohol in the absence of oxygen

Mast cells

They release histamines which widen the blood vessels allowing for more pentration

Lymphatic organs?

Primary:

• Thymus gland

• Bone marrow

Secondary:

• Lymph nodes

• Spleen

• Tonsils

Humoral immunity

It is immunity mediated by B cells, and produces antibodies

Killer T cells

“cytotoxic” T cells identify infected or abnormal cells and kill them

Helper T cells

they activate Killer T cells, and provide memory for memory T cells

Natural killer cells

They directly kill infected, cancerous, or abnormal cells without prior exposure by recognizing the protein markers as non self. They release cytokines (signaling molecules)

Cytokines

Small proteins important in cell signaling

Complement system

A group of 30 proteins that are secreted until they bind to receptors on the surface of pathogens bringing out a cascade effect: stimulating a range of chemicals and effects… pathogen is then destroyed by phagocytes… binding to mast cells stimulating them to release histamine.

Homeostasis

The state of internal balance

Food preservation

• Heat sterilisation

• Pasteurisation ( for milk / dairy products)

• Deep freezing

Food spoilage

• Mainly bacteria, yeasts, and moulds thriving in:

• Temperatures from 10 - 40 degrees celsius

• Adequate moisture

• Optimum pH

• Nutrients

Scientific Notation

Making observations, forming a hypothesis, conducting experiments, analyzing data and drawing conclusions

Fermentation formula (Animal Cells)

Glucose → lactic acid + 2 ATP