OCR 21st Century Science: B4

What does the cell Nucleus do?

Contains DNA which is instructions for making proteins eg enzymes used for respirarion and photosynthesis

What is Cytoplasm?

Gel-like substance where proteins such as enzymes are made. Some enzyme controlled reactions take place here such as respiration

What is the Cell membrane?

Holds the cell together and controls what goes in and out as well. It lets gases and water pass through freely but keeps other chemicals out

What are Mitochondria?

Where the cells needed for respiration are found, and where the reactions take place

What is the Cell wall?

Rigid wall made of cellulose. It supports and strengthens the cell (plant cells only)

What are Chloroplasts?

Where photosynthesis takes place. They contain a green substance called chlorophyll and the enzymes needed for photosynthesis (plant cells only)

What is a Vacuole?

Contains cell sap, a weak solution of sugar and salts (plant cells only)

What is a Bacterium? (Bacteria)

Single called organisms with no nucleus and a circular molecule of DNA which floats in the cytoplasm. They do not have mitochondria either but still have a cell wall and cell membrane

What is Photosynthesis?

A process which produces glucose and oxygen from CO2 and water. It happens in plants and some microorganisms. The glucose can be used in 3 different ways: to respire, to make chemicals for growth, or can be stored as starch

What is the balanced chemical equation for photosynthesis?

A good way to remember the chemical equation is to think of the word "photosynthesix". There are 6 Carbon dioxides, 6 water and 6 oxygen's on the other side of the equation. Now you just need to remember what glucose is which is C6H12O6.

What are the 3 ways glucose can be used in photosynthesis?

- It can be converted into chemicals required for GROWTH of plant cells such as cellulose.
- It can be converted into STARCH, a STORAGE MOLECULE.
- It can be BROKEN DOWN during the process of respiration, releasing energy stored in the glucose molecules.

How can the rate of photosynthesis increase? (3)

The rate of photosynthesis can increase by the plant having:
- More CO2.
- More light.
- A higher temperature which increases enzymes action.

How are plant cells adapted for efficient photosynthesis? (3)

- Outer epidermis lacks chloroplasts (Transparent)
- Upper palisade contains most of the chloroplasts (receive most light)
- Spongy mesphyll, loosely spaced so diffusion can occur.

How are leaves adapted for photosynthesis? (4)

SaVCT (Surface area, vascular, Chloropyll, Thin)
- Large surface area
- They have vascular bundles
- Contain chlorophyll
- Thin (good for diffusion)

What is Diffusion?

Diffusion is the passive overall movement of particles from a region of their higher concentration to their lower concentration

How can the rate of diffusion be increased? (3)

SD, SC, GS. (Shorter distance, Steeper concentration and greater surface area.
- Shorter distance for molecules to travel
- A steeper concentration gradient
- A greater surface area

What is Osmosis?

A specific case of diffusion where water molecules go to an area of lower concentration. This is used by plants to take in water, by using a partially permeable membrane which only allows certain substances through it

What is Active Transport?

Active transport is the overall movement of chemicals across a cell membrane from a region of lower concentration to a region of higher concentration using energy released by respiration

Osmosis can only occur in a....?

Osmosis can only occur in a partially permeable membrane.

When a plant is full of water it is............. and when the cell loses water the cell become..........

When a plant is full of water it is turgid and when the cell loses water the cell become flaccid.

What do Xylems carry?

Xylems carry water.

What do Phloems carry?

Phloems carry food substances.

Describe the properties of xylem cells.

DHL (Dead, Hollow, Lignin)
- They're dead cells .
- Lack of living cytoplasm this leaves a hollow lumen.
- Cellulose walls have lignin for strength.

The transport of food substances is called....


Transpiration is the evaporation and.......

Transpiration is the evaporation and the diffusion of water from inside of leaves.

What are the factors that increase the rate of transpiration? (3)

- Light (Stomata opens)
- Temperature
- Wind (Water vapour is removed quickly)

What slows down transpiration?

Humidity because water vapour is slowed down by moist air.

What are the minerals that plants need? (4)

- Nitrates (make proteins for cell growth)
- Phosphates (respiration and growth)
- Potassium (respiration and photosynthesis)
- Magnesium (photosynthesis)

A lack of nitrates causes...

A lack of nitrates causes poor growth and yellow leaves.

A lack of phosphates causes...

A lack of phosphate causes poor root growth and discoloured leaves.

A lack of potassium causes...

A lack of potassium causes poor flower and root growth and discoloured leaves.

A lack of magnesium causes...

A lack of magnesium causes yellow leaves.

Detrivores are animals that...

Detrivores are animals that feed on dead and decaying material (detrius).

What is a saprophyte?

A saprophyte is an organism that lives on dead and decaying material.

What are the ways of preserving food and reducing the rate of decay? (6)

- Canning
- Cooling
- Freezing
- Drying
- Adding salt or sugar
- Adding vineger

What are the 3 disadvantages of using pesticides?

- They can harm other organisms than just pests
- They can affect food chains
- Some are persistent

What is Aerobic Respiration?

A reaction which breaks down large food molecules to produce energy. It happens in every living cell and requires oxygen. It gives energy for movement, active transport (moving things in and out of cells) and the synthesis of large molecules
Glucose + Oxy

What is Anaerobic Respiration?

Respiration without oxygen. It takes place when there is little or no oxygen in animal and plant cells and a few microorganisms. Energy is still produced but the products are different depending on the type of cell
Animal- Glucose => Lactic Acid (+energy)

What is a Transect?

A way of investigating how something changes across an area. You run a tape measure between two fixed points. You collect data at different points along the tape measure

What is a Quadrat?

A square frame divided into 100 smaller squares which means you can estimate the coverage of a species across the area

What is a Light Meter for?

Lets you measure the level of light. You would use this to compare plants in areas of different light levels

What is an Identification key?

Used to identify different species using a series of questions. You would start at question 1 and go down different questions to narrow down the species until you have a final answer of what species you are looking at