Cells and Simple Cell Transport:
Cells:
All living things are made up of cells. The structures of different types of cells are related to their functions.
Root hair cells: Tiny like hair extensions that increase the surface area of the cell for absorption.
Ovum (egg cell): Large cell that can carry food reserves for the developing embryo.
Xylem: Long, thin, hallow cells used to transport water through the stem and root.
White Blood Cells: Can change shape in order to engulf and destroy invading microorganisms.
Sperm Cells: Has a tail, which allows it to move.
Palisade Cells: packed with chloroplasts for photosynthesis.
Red Blood Cells: No nucleus, so packed full of haemoglobin to absorb oxygen.
Nerve Cells: Long, slender axons that can carry nerve impulses.
Cell Structure:
Most human cells, animal cells and plant cells have the following parts:
Nucleus: Contains genetic material, which controls the activities of the cell.
Cytoplasm: Most chemical processes take place here, controlled by enzymes.
A Cell Membrane: Controls the movement of substances into and out of the cell.
Mitochondria: Most energy is released by respiration here.
Ribosomes: Protein synthesis happens here.
Chemical reactions inside cells are controlled by enzymes found in the cytoplasm and mitochondria.
Plant Cells:
A cell wall: Used to strengthen the cell.
Chloroplasts: Absorb light energy to make food.
A permanent Vacuole: Filled with cell sap.
Other Cells:
In a bacterial cell, the genes are not in a nucleus.
A bacterial cell consists of: Cytoplasm, a cell membrane and a cell wall.
Yeast is a single celled fungus. Yeast cells have: Nucleus, Cytoplasm, Cell membrane and Cell wall.
Movement of Substances:
Cells have to constantly:
Replace substances that are used up, e:g: glucose and oxygen for respiration.
Remove other substances, e:g: carbon dioxide and waste products.
Gases and substances that are in solution can pass into ad out of cells, through the cell membrane, by diffusion.
Diffusion:
Diffusion is the spreading of the particles of a gas or a substance in solution. It results in a net movement from a region where the particles are of a higher concentration to a region where they are of a lower concentration. The greater the difference in concentration, the faster the rate of diffusion.
Tissues, Organs and Organ Systems.
Tissues:
Large multicellular organisms, like humans, develop systems for exchanging materials. As the organism develops, cells differentiate so that they can carry out different jobs.
A tissue is a group of cells that have a similar structure and function. For example: Muscle tissue contracts so we can move. Glandular tissue produce substances such as enzymes and hormones. Epithelial tissue covers organs.
Organs:
Organs are made of tissues. One organ may contain several tissues.
For example, the stomach is an organ that contains:
Muscle tissue that contracts to churn the contents.
Glandular tissue to produce digestive juices.
Epithelial tissue to cover the outside and inside of the stomach.

	Erstellt von shabannahickman vor fast 11 Jahre

Notiz am Additional Science Biology, erstellt von shabannahickman am 03/03/2014.