KS3 Biology Part 1: Cells - the basic building blocks of life

Cells

• Cells make up tissues, which make up organs, and then systems and finally, last but not least systems make up organisms.

There are many parts of cells, which have different functions, examples of these are:
-Vacuole - Stores food and water, inflates the cell like air pumped into a tyre and provides support to the cell.
-Mitochondria - Release energy from food (glucose) by aerobic respiration.
-Chloroplast - Contains green chlorophyll that changes sunlight energy into glucose food energy by a process called photosynthesis.
-Cytoplasm - Where chemical reactions take place like photosynthesis.
-Membrane - Controls what substances enter and leave a cell.
-Cell wall - Made from cellulose and gives rigid support to the cell.
-Nucleus - Stores information and controls what happens inside the cell.

• Now some cell key words....

-Euglena has a long whip-like structure that helps it move through water
-Amoeba can make finger-like projections to help it catch food
-Unicellular organisms have just one cell

• Reproduction in humans

-Reproduction in females involves males and females.
-Males produce sperm cells in the testes.
-Females produce egg cells in the ovary.
-The penis deposits the sperm into the female vagina.
-Sperm swim up through the uterus to the oviduct.
-Fertilisation occurs when a sperm cell joins with an egg cell.
-The fertilised egg then grows into an embryo and eventually becomes a baby.

• Gestation

-Gestation is the period of the embryo developing in the womb.
- Females have a menstrual cycle every lasting for about 28 days. This is called menstruation.
-The growing baby receives food and oxygen from the mother's blood through the placenta and the umbilical cord.
-Therefore, if the mother smokes and drinks alcohol the baby will receive some of the alcohol and nicotine.
-In humans, gestation ends after nine months with the birth of the baby.