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 containing cell sap

Diagram of a palisade cell when viewed with a light microscope cytoplasm chloroplasts nucleus cell membrane vacuole cell wall

Palisade Mesophyll cell Structural 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

C/GraphikTitelIntern/ElodeaAnimation/$Fil e/Elodea_ani.gifhttp:// C/GraphikTitelIntern/ElodeaAnimation/$Fil e/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 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) DIFFERENT TYPES OF DIFFERENTIATED CELLS a nerve cell or neurone a white blood cell an undifferentiated stem cell a skeletal muscle cell

Epithelial Cell from Intestine Structural 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 p ) Answer the summary questions at the bottom of textbook p173. 3) Do exam question 1 from the bottom of textbook ) 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.