Plant cells

Leaf cross-section showing palisade layer

Section of a plant leaf to show different fully differentiated cells

Palisade cell

nucleus

A Palisade Mesophyll cell has the function to carry out photosynthesis

containingcell sap

Diagram of a palisade cell when viewed with a light microscope

cytoplasm

chloroplasts

nucleuscell membrane

vacuole

cell wall

Palisade Mesophyll cellStructural Adaptation• Have many chloroplasts

that circulate round the palisade cell.

• Long and thin cells, arranged side by

side near top surface of the leaf.

• Large vacuole pushes chloroplasts and

cytoplasm to the edge of the cell.

Function Allows maximum absorption

of light. Moving chloroplasts helps to avoid shadowing effect.

Can absorb maximum light as packed closely together.

Chloroplasts are more exposed to enable them to

absorb more light energy.

Chloroplasts circulate around inside Palisade Mesophyll Cells

• http://www.zeiss.com/C12567BE00472A5C/GraphikTitelIntern/ElodeaAnimation/$File/Elodea_ani.gif

Chloroplast envelope.Double plasma membrane which controls movement of molecules in and out of the chloroplast.

Starch grains. A store of excess carbohydrate from photosynthesis

A Granum. (s) A stack of thylakoid membranes. The site of the first stage of photosynthesis.

Thylakoid membranes. Contain embedded chlorophyll molecules to absorb light energy in photosynthesis.

Stroma. Site of the second stage of photosynthesis. Contains enzymes needed for these photosynthesis reactions and starch grains.

Grana. (pl.) Site of the first stage of photosynthesis

Chloroplast seen with an electron microscope

Starch grain

Granum

Stroma

Thylakoid membranes

Plant cell wall

Walls of adjacent cells

Middle lamella

Now answer all the questions and tasks in your handbook on p11 and complete the table on p11. Use textbook pages 158-160 to help find the answers.

Differentiation of Cells

In multicellular organisms, cells undergo the process of Differentiation. Differentiation is when a cell changes and becomes specially adapted for a particular function (specialised).

CELL DIFFERENTIATION IN PLANTS

Arrows here indicate differentiated cells

Mitosis occurs here (undifferentiated cells)

Xylem, Phloem and Root Hair Cells Xylem Vessels = Dead cells that have joined to make tubes in

plants. They are hollow and have no usual cell contents. They transport water and mineral ions up the plant. Xylem vessels have extra thick walls with lignin to support the plant.

Phloem Tubes = Tube-like cells that transport sucrose and other plant carbohydrates, plant lipids and plant proteins round the plant.

Root Hair Cells = see fig 3 on p160 for diag and photograph. Cells that have an increased surface area to help them to absorb MORE water and MORE mineral ions from the soil.

Differentiation in Animal/Human Cells

Undifferentiated

Animal/Human cell

(or stem cell)

DIF

FE

RE

NT

TY

PE

S O

F

DIF

FE

RE

NT

IAT

ED

CE

LL

Sa nerve cell or neurone

a white blood cell

an undifferentiated stem cell

a skeletal muscle cell

Epithelial Cell from IntestineStructural Adaptation• Cell membrane folded

into microvilli

• Many mitochondria

Function• Large surface area for

absorption of more digested food molecules

• Provide lots of ATP (energy source) for active transport of digested food molecules

Organelle

• Eg A mitochondrion

•A small area or compartment inside the cell’s cytoplasm that carries out a specialised task.

Cell• The smallest

independent unit of life. (Multicellular organisms contain millions of cells, unicellular organisms just have one cell).

Eg A Liver cell (or Hepatocyte)

Tissue• A group of similar

cells with a similar shape, structure and common function.

Eg. Compact bone tissue

Organ• Contains several

different tissues, all of which contribute to the organ’s overall funtion

If you’re squeamish close your eyes!!!!

Lovely healthy liver

Organ system

• A group of organs that work together to perform particular functions more efficiently.

Eg. The Digestive System

TASKS:1) Read NT textbook p172-173.

2) Answer the summary questions at the bottom of textbook p173.

3) Do exam question 1 from the bottom of textbook 175.

4) Try the card sort. In pairs or threes, sort the biological structures found in the envelope into their groups ie Cells, Tissues, Organs, Organ systems.