Plant cells. Leaf cross-section showing palisade layer.
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Transcript of Plant cells. Leaf cross-section showing palisade layer.
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.
• 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
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 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.