Cells – the building blocks of life

What is a cell? Basic unit of all living things Fully alive Capable of reproduction and respiration* Many chemical reactions take place within the cell Contains the elements carbon, hydrogen and oxygen

Trivia: How did the cell get its name? Robert Hooke 1665 – used the 1 st microscope ever invented to look at a thin piece of cork Box-like cells reminded him of the cells of a monastery What he actually saw were the cell walls in cork tissue Cells from cork tissue of tree bark

Visualising Cells Cells are very small Largest cell in the human body – human egg 0.1 mm

Unicellular organisms Uni – “one” Living things that are only made up of one cell paramecium amoebabacteria yeast

Multicellular organisms Multi – “many” Plants Animals Human adult – 10 trillion cells! – Are all the cells the same? – Different sizes, shapes, functions – Certain similar characteristics

Typical animal cell ** Nucleus Cell membrane Cytoplasm Vacuoles Is it THAT simple?

Structure of an Animal Cell

Animal cell

Typical animal cell ** Nucleus Cell membrane Cytoplasm Vacuoles Nucleus – Controls all chemical reactions and activities in the cell, including reproduction and cell repair – Contains chromosomes

Sidetrack: Chromosomes each chromosome is made up of many genes; each gene contains instructions for a different feature of an organism genes on a chromosome nucleus chromosomes

Sidetrack: Chromosomes Found in the nucleus Made of DNA (deoxyribonucleic acid) and proteins Contains genes – chemical instructions to build the cell and control its functions Genes are passed down from 1 generation to another - hereditary

Human cells have 23 pairs of chromosomes except the sperm and the egg (23 individual chromosomes) Sex chromosomes

Genetic Diseases Down’s Syndrome – Extra chromosome in each cell in his/her body – 47 chromosomes instead of 46 chromosomes – Result of unusual cell division when egg/sperm was made, or during fertilisation – Happens by chance, can happen to anyone

Typical animal cell ** Nucleus Cell membrane Cytoplasm Vacuoles Cell membrane – Thin layer around the cell – Allows shape of cell to change – Partially permeable, controls movement of materials in and out of the cell – Carbon dioxide, oxygen, water can pass through

Typical animal cell ** Nucleus Cell membrane Cytoplasm Vacuoles Cytoplasm – jelly-like substance that fills the cell – contains water and many other substances – chemical reactions take place here

Typical animal cell ** Nucleus Cell membrane Cytoplasm Vacuoles – small spaces in the cytoplasm containing water, food, waste materials etc – small and numerous in animal cells

Nucleus Cell membrane Vacuole Cytoplasm Cellulose cell wall Chloroplasts Typical plant cell ** Functions similar to that of an Animal Cell

Plant cell

Vacuole Cytoplasm Typical plant cell ** Vacuole −Single large vacuole −Biggest part of the cell −Filled with cell sap (contains substances such as sugars and salts dissolved in water) −Cell sap keeps the cell firm by taking in water

Vacuole Cytoplasm Typical plant cell ** Vacuole −When the plant loses water, plasmolysis occurs

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Vacuole Cytoplasm Typical plant cell ** Cytoplasm −Reduced to a thin lining −Still contains water and other substances, still a place for chemical reactions

Chloroplasts – Tiny disc-like structures containing a green pigment called chlorophyll – Chlorophyll traps light energy from the sun so that plants can make food during photosynthesis – Absent in animal cells Cellulose cell wall Chloroplasts Typical plant cell **

Cellulose cell wall – Surrounds the plant cell – Supports the plant cell and gives it a regular shape – Absent in animal cells Cellulose cell wall Chloroplasts Typical plant cell **

Sidetrack: Cellulose Compound containing carbon, hydrogen and oxygen A type of fibre – Dietary fibre present in fruits and vegetables – Manufacture of cardboard and papers (from wood pulp)

Animal Cell Plant Cell Does it have a cellulose cell wall? NoYes Does it have a cell membrane? Yes Does it have a nucleus? Yes Does it have cytoplasm? Yes – it fills the cellYes – a thin lining only Does it have vacuoles? Yes – many, but small Yes – one, or a few, and large Does it have chloroplasts? No Present only in cells of green plants Shape?Can changeRegular (doesn’t change)