B8 Photosynthesis (copy)

Function of cell wall

Supports cell/prevents bursting, made of cellulose

Function of cell membrane

Controls substances moving in and out of cell

Function of cytoplasm

Chemical reactions happen

Function of nucleus

Controls cell activity, contains DNA

Function of ribosomes

Makes proteins by joining amino acids

Function of mitochondria

Aerobic respiration to release energy

Function of chloroplast

Absorbs light energy for photosynthesis

Function of vacuole

Supports cell, contains cell sap

Name five specialised plant cells

Palisade cell, root hair cell, xylem, phloem, guard cell

Adaptations of root hair cell

Large surface area to absorb more water. Lots of mitochondria for more respiration

Adaptations of palisade cell

Lots of chloroplasts, to absorb more light, for more photosynthesis

Function of roots

Absorb water and minerals, anchor the plant

Function of stem

Transport water, minerals and sugars in vascular bundles (xylem and phloem).

Function of flower

Reproduction by making pollen and eggs.

Function of leaves

Absorb light for photosynthesis to make glucose

Function of epidermal tissue

Outer layer of cells to protect internal tissues

Function of spongy mesophyll

In leaves, contains air spaces, shorter diffusion pathway so happens faster

Function of xylem

Transport water and mineral ions up plant

Function of phloem

Transport dissolved sugars up and down plant

What are meristem cells?

Undifferntiated cells that divide to become specialised plant cells

Where are meristem cells found?

Growing tips of roots and shoots

Function of guard cells

Open and close stoma for gas exchange and to lower water loss

Adaptations of guard cells

Cell wall thicker on one side, so swell unevenly, to open stomata (work in pairs)

How do guard cells open stomata?

Potassium ions diffuses into guard cells, cytoplasm more concentrated. Water moves in by osmosis, down the water concentration gradient. Guard cells swell evenly to open the stomata.

Word equation for photosynthesis

carbon dioxide + water --> light--> oxygen + glucose

Balanced symbol equation for photosynthesis

6CO2 + 6H2O -->light--> 6O2 + C6H12O6

What type of reaction is photosynthesis?

Endothermic

Where does photosynthesis happen?

Chloroplasts in palisade mesophyll cells

What substance (pigment) absorbs light energy?

Chlorophyll

Describe how leaves are adapted for photosynthesis

Large surface area to absorb more light, thin for short diffusion distance, air spaces for large surface in leaf, veins provide water and carry away sugars, chloroplasts to absorb light

List uses of glucose from photosynthesis

Respiration, coverted to insoluble starch or fat/oil for storage, converted to amino acids to make proteins for growth, converted to cellulose for cell walls

Why is glucose stored as starch?

Starch is insoluble so does not dissolve and does not affect water concentration of cells

What mineral from soil is needed for proteins?

Nitrate ions are abrobed from soil to make amino acids

Definition of a limiting factor

Slows or limits the rate of a reaction

Name four limiting factors of photosynthesis

Temperature, light intensity, carbon dioxide concentration and amount of chlorophyll

How does temperature limit rate of photosynthesis?

Low temperature means slower particle movement, less collisions. High temperature denatures enzymes stopping photosynthesis

How does light intensity limit rate of photosynthesis?

Less light, less energy, less photosynthesis

How does carbon dioxide concentration limit rate of photosynthesis?

Less CO2, less reactants, less photosynthesis

How does amount of chlorophyll limit rate of photosynthesis?

Less chlorophyll, less light energy absorbed, less photosynthesis

Features of xylem

Hollow tube of dead cells, strengthened by lignin. Creates continuous water column up plant

Features of phloem

Tube of living elongated cells, pores in end walls between cells means cell sap and sugars can move between cells.

Definition of transpiration

Loss of water vapour from leaves, through open stomata

How is water lost from leaves?

Water evaporates from cells inside leaf then diffuses out of open stomata

Definition of translocation

Movement of dissolved sugars around plant

Definition of active transport

Using energy to move particles from a low concentration to a high concentration, through carrier proteins in a membrane.

How are minerals ions absorbed by root hair cells?

Active transport

Why do plants need mineral ions?

Healthy growth e.g. nitrate ions to make proteins

Definition of diffusion

Random movement of particles from a high concentration to a low concentration

Definition of osmosis

Movement of water from a high WATER concentration to a LOW water concentration, through a partially permeable membrane

Use of potometer

Used to measure water loss from plants

How to set up a potometer?

Cut plant stem underwater and insert into potometer, dry leaves, seal joins of potometer with waterproof jelly

How do plants lower water loss (less transpiration)?

Thicker wax layer, closing stomata, rolled / hairy leaves, small leaves, less stomata and on lower side of leaf

Name four ways to increase transpiration

Higher light intensity, higher temperature, more air movement, lower humidity

How does higher light intensity increase rate of transpiration?

More energy for photosynthesis, more CO2 needed, more stomata open, more water vapour lost

How does higher temperature increase rate of transpiration?

Particles move more / evaporate faster, faster rate of diffusion and faster rate of reaction, more water vapour lost

How does more air movement increase rate of transpiration?

Moves water particles away from leaf surface, increases concentration gradient, more water vapour lost by diffusion

How does lower humidity increase rate of transpiration?

More humid means more water, decreases concentration gradient, less water vapour lost by diffusion

What happens if a plant loses too much water?

Cells become flaccid and plant wilts

Name four factors that plants compete for

Light, space, water and mineral ions

Required practical: How to use pondweed to investigate effect of light intensity on rate of photosynthesis

Pondweed into tube, cover with water. Place lamp 10cm from pondweed, count oxygen bubbles released per minute. Move lamp and repeat.

How to improve accuracy of investigating effect of light intensity on rate of photosynthesis

Use gas syringe to collect volume of oxygen. Collect for longer amount of time. More repeats at each light intensity to work out an average.