DIffusion, osmosis, and active transport and photosynthesis and leaf structure

What is diffusion?

The movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient due to random movement

What provides the energy for diffusion?

The kinetic energy of particles from their random movement (Brownian motion)

What is Brownian motion?

The random movement of particles caused by collisions with other particles

What type of membrane is the cell membrane?

Partially permeable

What does partially permeable mean?

Allows some molecules to pass through but restricts others

Why is diffusion important in living organisms?

To obtain substances

Give an example of diffusion in plants

Oxygen diffusing into plant cells for respiration

Give an example of diffusion in animals

Oxygen diffusing from alveoli into the blood

How does surface area to volume ratio affect diffusion?

A larger surface area to volume ratio increases the rate of diffusion

Why do root hair cells have a large surface area?

To increase absorption of water and mineral ions

Why are alveoli one cell thick?

To reduce diffusion distance and increase diffusion rate

How does temperature affect diffusion?

Higher temperature increases particle energy and diffusion rate

How does concentration gradient affect diffusion?

A steeper gradient increases diffusion rate

What is water potential?

A measure of the tendency of water to move

Why is water important as a solvent?

It allows substances to dissolve for transport and reactions

What is osmosis?

The diffusion of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane

What moves during osmosis?

Water molecules only

From where to where does water move in osmosis?

From higher water potential to lower water potential

What happens to plant cells in dilute solutions?

They gain water and become turgid

What is turgor pressure?

Pressure of cell contents pushing against the cell wall

Why don’t plant cells burst in dilute solutions?

The cell wall resists further expansion

What happens to plant cells in concentrated solutions?

They lose water and become flaccid or plasmolysed

What is plasmolysis?

When the cell membrane pulls away from the cell wall

What happens to animal cells in concentrated solutions?

They lose water and become crenated

What happens to animal cells in distilled water?

They gain water and may burst (lysis)

What is active transport?

Movement of substances against a concentration gradient using energy from respiration

Does active transport require energy?

Yes

Why is energy needed for active transport?

Particles move against the concentration gradient

Give an example of active transport in animals

Glucose uptake in the small intestine

Give an example of active transport in plants

Mineral ion uptake by root hair cells

What proteins are involved in active transport?

Carrier proteins

What happens first in carrier protein transport?

Substance binds to the carrier protein

What happens second in carrier protein transport?

Energy causes the protein to change shape

What happens last in carrier protein transport?

Substance is released into the cell

What is photosynthesis?

The process by which plants make glucose from carbon dioxide and water using light energy

What are the raw materials for photosynthesis?

Carbon dioxide and water

What is the waste product of photosynthesis?

Oxygen

What provides energy for photosynthesis?

Light energy

What pigment traps light energy?

Chlorophyll

Where is chlorophyll found?

In chloroplasts

Why do plants appear green?

Chlorophyll reflects green light

State the word equation for photosynthesis

Carbon dioxide plus water produces glucose and oxygen

Why is light not a raw material?

It is energy not a substance

How does carbon dioxide enter a plant?

Through stomata by diffusion

How does water enter a plant?

Through roots by osmosis

What is the role of glucose in plants?

Energy source and building material

How is glucose stored in plants?

Converted to starch

Why is starch suitable for storage?

It is insoluble and compact

How is glucose used to make cell walls?

Converted into cellulose

How is glucose transported in plants?

Converted into sucrose

Why is nectar produced?

To attract pollinators

How are proteins made in plants?

By combining glucose with nitrogen ions

Why are mineral ions needed?

To make proteins and chlorophyll

What is a mineral ion?

An inorganic substance absorbed from the soil

How are mineral ions absorbed?

By active transport in root hair cells

What element is needed for chlorophyll?

Magnesium

What is the effect of magnesium deficiency?

Yellowing leaves

What element is needed for amino acids?

Nitrogen

What happens in nitrate deficiency?

Poor growth

Why test leaves for starch?

Glucose is quickly used or transported

What is the first step in the starch test?

Boil leaf in water

Why is ethanol used in the starch test?

To remove chlorophyll

Why must ethanol be heated in a water bath?

It is flammable

What colour indicates starch present?

Blue-black

What does a variegated leaf show?

Only green areas photosynthesise

Why do white areas not turn blue-black?

They lack chlorophyll

Why destarch a plant?

To remove stored starch

How is light tested as a requirement?

Cover part of leaf with foil

What result shows light is required?

Covered area stays brown

How is carbon dioxide tested?

Using sodium hydroxide

What is the control in CO2 experiments?

A plant with water only

What plant is used to measure photosynthesis rate?

Pondweed

How is oxygen measured?

Counting bubbles or volume collected

What indicates a higher rate of photosynthesis?

More oxygen produced

How is light intensity changed?

Moving lamp closer or further

How is temperature changed?

Using different water temperatures

How is carbon dioxide concentration changed?

Adding sodium hydrogen carbonate

Why keep variables constant?

To ensure a fair test

Why use a glass screen near lamps?

To prevent temperature increase

What gas exchange occurs during respiration?

Oxygen in carbon dioxide out

What gas exchange occurs during photosynthesis?

Carbon dioxide in oxygen out

What happens at night in plants?

Only respiration occurs

What indicator is used for gas exchange?

Hydrogencarbonate indicator

Why does indicator change colour?

Carbon dioxide is acidic

What colour shows high CO2?

Yellow

What colour shows low CO2?

Purple

State the balanced chemical equation for photosynthesis

6CO2 plus 6H2O produces C6H12O6 plus 6O2

What form of energy is stored in glucose?

Chemical energy

What is a limiting factor?

A factor in shortest supply limiting a process

Name three limiting factors of photosynthesis

Light intensity temperature carbon dioxide

Why is water not a limiting factor?

Only small amounts are needed

How does temperature affect photosynthesis?

Increases rate until enzymes denature

What happens when enzymes denature?

Reaction rate decreases

How does light intensity affect rate?

Rate increases then levels off

Why does the rate level off?

Another factor becomes limiting

How does CO2 concentration affect rate?

Rate increases until another factor limits

How do you identify a limiting factor on a graph?

Look at the x-axis where rate increases

What is the structure of a leaf adapted for?

Efficient photosynthesis

Why are leaves broad?

Large surface area