Level 2 Bio

AS91156 / BIO 2.4

Demonstrate understanding of life processes at the cellular level

EXTERNAL - 4 CREDITS

EXAM PRACTICE METHOD

- B - Box key terms/words

- U - Underline command words e.g. compare, describe

- G - Go back to read the question

- D - Define the keywords

- E - Explain the key terms/words

- E - Give an example

- L - Link back to the context used in the question

ACHIEVE - Describe - What is it?

MERIT - Explain - Definition? Why ? Where ?

EXCELLENCE - Compare and Contrast -Relate to the context - adaptation , survival etc.

LEARN COACH STUDY BIO 2.4

PASS NCEA BIO

NO BRAIN TOO SMALL

QUIZLET FOR KEY TERMS

STUDY TIME NZ

LEMONADE -ED

WHAT IS A CELL?

A CELL IS THE BASIC UNIT OF LIFE (Building Blocks of Life)

THERE ARE TWO TYPES OF CELLS - PLANT CELLS AND ANIMAL CELLS

Cell Organelles

Nucleus

Large, round structure surrounded by a nuclear membrane; contains DNA

Controls cell activities; stores genetic information (DNA)

Cell membrane

Thin, flexible barrier around the cell

Controls what enters and leaves the cell; maintains cell integrity

Cytoplasm

Jelly-like fluid that fills the cell

Site of chemical reactions; supports organelles

Mitochondria

Bean-shaped structures with folded inner membranes

Site of cellular respiration; produces energy (ATP)

Ribosomes

Small dots (free-floating or attached to ER)

Site of protein synthesis

Endoplasmic reticulum (ER)

Network of membranes (smooth or rough)

Transports materials within the cell; rough ER has ribosomes for proteins

Golgi apparatus

Stack of flattened membranes

Modifies, packages, and distributes proteins and lipids

Vacuole

Fluid-filled sac (large in plant cells, smaller in animal cells)

Stores water, nutrients, and waste; maintains cell pressure in plants

Cell wall

Rigid outer layer made of cellulose (plant cells only)

Provides structural support and protection

Chloroplast

Green, oval-shaped with internal stacks (grana) (plants only)

Site of photosynthesis; converts light energy into chemical energy (glucose)

Lysosome

Small vesicle containing digestive enzymes (mainly in animal cells)

Breaks down waste, old organelles, and foreign material

Centrioles

Paired cylindrical structures (animal cells only)

Involved in cell division (mitosis and meiosis)

Cell Organelles - Types, Structure and their FunctionsCell organelles are the specialized organelles present within the cells. These organelles are involved in carrying out essential functions that are necessary for the survival of cells.

RFQ - CELLS 2.ppt

Pass NCEA Biology - Cells 91156

What are plant and animal cells? - BBC BitesizeFind out what animal and plant cells are and learn what the function of the cell wall and the nucleus is in this KS3 Bitesize biology article.

THE PROCESS OF RESPIRATION

Human Body Educational VR - Cell Power Virtual Lab | XVIVOXVIVO helped Vroggo take the traditional Science Lab to a whole new level. Students travel on an immersive virtual journey inside the human body. Their mission: to save a living human cell by helping mitochondria make energy.

Cellular respiration introduction | Biology (video) | Khan AcademyLearn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

Describe anaerobic / word equation.

Glucose is broken down into lactic acid and ATP (energy) without oxygen OR glucose → lactic acid + (2) ATP.

• Describe aerobic / word equation.

Aerobic respiration is when glucose is broken down in the presence of oxygen to form carbon dioxide, water, and ATP.

OR glucose + oxygen → carbon dioxide + water + (36) ATP

• Anaerobic Respiration takes place in the cell cytoplasm AND Aerobic Respiration takes place in the mitochondria.

• Advantage / Disadvantage of Anaerobic Respiration.

Advantages - anaerobic respiration is relatively fast and does not require oxygen.

Disadvantages - less efficient - produces a small amount of energy 2 ATP - can not be sustained for a long period of time - produces lactic acid which is toxic to cells and causes muscle cramps.

• Describes one advantage / disadvantage of aerobic respiration.

Advantages - aerobic respiration produces more energy / ATP (per glucose molecule) - it is more efficient - can be sustained over a longer period of time.

Disadvantages - Takes longer to release the energy from glucose. - requires oxygen for this process to start.

PROKARYOTES AND EUKARYOTES

THE PROCESS OF PHOTOSYNTHESIS

Stages of Photosynthesis

1. Light-Dependent Stage (Occurs in the thylakoid membranes of chloroplasts)

Requires light energy.
Light energy is absorbed by chlorophyll.
Water (H₂O) is split into hydrogen and oxygen by sunlight or sun's energy.
- The oxygen (O₂) is released as a by-product.
ATP (energy carrier) and NADPH (hydrogen carrier) are produced to be used in the next stage.

2. Light-Independent Stage (Calvin Cycle – occurs in the stroma of chloroplasts)

Does not require light directly.
Uses the ATP and NADPH from the light-dependent stage.
Carbon dioxide (CO₂) from the air is fixed into a cycle of chemical reactions.
Glucose (C₆H₁₂O₆) is formed using carbon, hydrogen, and energy.

Key Points to Remember for NCEA 2.4:

Photosynthesis occurs in chloroplasts.
It is a two-step process: Light-dependent and light-independent.
It is enzyme-controlled.
Temperature, light intensity, and CO₂ concentration are factors affecting the rate of photosynthesis.

Photosynthesis Virtual LabVirtual photosynthesis lab, students manipulate the light intensity, light color, and distance from the light source. and measure the rate of photosynthesis.

CELL TRANSPORT

Cell transport is the movement of molecules across the CELL MEMBRANE. Cell transport is important because molecules like oxygen and glucose need to be transported across the cell membrane before they can enter a plant or animal cell and be used.

The cell membrane is only semi-permeable; therefore, only certain molecules can enter and exit the cell.

There are two ways they can do this:

PASSIVE TRANSPORT where energy/ATP is NOT required
- - DIFFUSION (via cell membrane)
  - OSMOSIS (via cell membrane)
  - FACILITATED DIFFUSION (via transmembrane proteins like protein channels and carrier proteins)
ACTIVE TRANSPORT where energy IS required
- - Via transmembrane proteins
    1. Protein pumps
    2. Protein channels
    3. Carrier proteins

This concept focuses on passive transport.

Examples of Osmosis

1. Plant Roots Absorbing Water

What happens: Water moves from the soil (high water concentration) into root cells (lower water concentration) through the cell membrane.
Why it’s osmosis: Water moves from an area of high to low concentration across a selectively permeable membrane.

2. Soaking Raisins in Water

What happens: Raisins swell up when soaked in water.
Why it’s osmosis: Water enters the raisin cells, where there’s less water, through their semi-permeable skin.

3. Salt on a Slug

What happens: When salt is sprinkled on a slug, it loses water and shrivels.
Why it’s osmosis: Water inside the slug moves out (to the salty area) through its membrane, causing dehydration.

4. Vegetables in Salty Water

What happens: Sliced cucumber in salty water becomes limp.
Why it’s osmosis: Water moves out of the cucumber cells (high water concentration) into the salty solution (lower water concentration).

5. Red Blood Cells in Different Solutions

Hypotonic solution: Cells swell (water moves in).
Hypertonic solution: Cells shrink (water moves out).
Isotonic solution: No net movement of water.

ENZYMES

are biological catalysts which lower the activation energy to catalyse a reaction. (increase the rate of a reaction without being used up.

FACTORS WHICH AFFECT ENZYME ACTIVITY:

The concentration of enzyme: Assuming a sufficient concentration of substrate is available, increasing enzyme concentration will increase the enzyme reaction rate.
The concentration of substrate: At a constant enzyme concentration and at lower concentrations of substrates, the substrate concentration is the limiting factor. As the substrate concentration increases, the enzyme reaction rate increases. However, at very high substrate concentrations, the enzymes become saturated with substrate and a higher concentration of substrate does not increase the reaction rate.
The temperature: Each enzyme has an optimum temperature at which it works best. A higher temperature generally results in an increase in enzyme activity. As the temperature increases, molecular motion increases resulting in more molecular collisions. If, however, the temperature rises above a certain point, the heat will denature the enzyme, causing it to lose its three-dimensional functional shape by denaturing its hydrogen bonds. Cold temperature, on the other hand, slows down enzyme activity by decreasing molecular motion.
The pH: Each enzyme has an optimal pH that helps maintain its three-dimensional shape. Changes in pH may denature enzymes by altering the enzyme's charge. This alters the ionic bonds of the enzyme that contribute to its functional shape.
The salt concentration: Each enzyme has an optimal salt concentration. Changes in the salt concentration may also denature enzymes.

Factors affecting enzyme action - What happens in cells and what do cells need? - OCR Gateway - GCSE Combined Science Revision - OCR Gateway - BBC BitesizeLearn about and revise what happens in cells and what cells need with BBC Bitesize for GCSE Combined Science, OCR Gateway.

THE PROCESS OF DENATURATION

What is Denaturation?

Denaturation is the process where a protein (or enzyme) loses its shape, which stops it from functioning properly. This usually happens due to factors like heat, pH changes, or chemicals.

Think of it like a key and a lock:
Normal enzyme = key (substrate).that fits into a specific lock (substrate).
Denatured enzyme = key is melted or bent out of shape—it no longer fits!

How Does Denaturation Happen?

💥 1. Heat:

Enzymes have an optimum temperature (usually around 37°C in the human body).
If the temperature gets too high (above 40-45°C), the enzyme’s bonds break, changing its shape.
Example: When you cook an egg, the clear egg white turns solid because the proteins are denatured!

🧪 2. pH Changes:

Enzymes also have an optimum pH (e.g., pepsin in the stomach works best at pH 2).
Too much acid or base disrupts the enzyme’s structure, causing denaturation.
Example: Lemon juice (acidic) curdling milk proteins.

🧴 3. Chemicals (e.g., alcohol, heavy metals):