Cell Structure

Organelles

• parts of cells
• each one has a specific function

Plasma Membrane:

• found on the surface of animal cells and just inide the cell wall of plant cells and prokaryotic cells
• made of lipids and protein
• Its function is to regulate the movement of substances into and out of the cell
• has receptor molecules which allow it to respond to chemicals/hormones

Microvilli:

• folds in the plasma membrane
• found on cells involved in processes like absorption. E.g epithelial cells in the small intestine
• increase surface area of plasma membrane

Nucleus:

• large organelle surrounded by a nuclear envelope (double membrane) that contains many pores
• nucleus contains chromatin and a nucleolus
• chromatin is made from proteins and DNA
• pores allow substances, e.g RNA, to move between the nucleus and the cytoplasm
• nucleolus makes ribosomes

Lysosome:

• round organelle surrounded by a membrane
• no clear internal structure
• contains digestive enzymes. These are kept seperate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or to break down worn out components of the cell

Ribosomes:

• very small organelle that floats free in the cytoplasm
• or is attatched to the endoplasmic reticulum
• it is involved it protein synthesis

Endoplasmic Reticulum:

• smooth endoplasmic reticulum: system of membranes enclosing a fluid-filled space
• smooth ER's function is to synthesise and process lipids
• rough endoplasmic reticulum: similar, but covered in ribosomes
• rough ER's function is to fold and process proteins that have been made at the ribosomes

Golgi Apparatus:

• group of fluid-filled flattened sacs
• it processes and packages new lipids and proteins, which are then transported elsewhere by vesicles
• makes lysosomes

Mitochondria:

• oval-shaped
• have a double membrane: the inner one is folded to form cristae
• inside is the matrix which contains enzymes involved in respiration
• the site of repsiration
• produces ATP
• found in large numbers in cells that are very active and require alot of energy

Adaptations

Epithelial cells are adapted to absorb food efficiently. The walls of the small intestine have lots of villi to increase surface area. The villi cells have microvilli to further increase the surface area. They have lots of mitochondia to provide energy for the transport if digested food molecules to the cell

Red blood cells are adapted to carry oxygen around the body. They have no nucleus to make room for more haemoglobin (carrying oxygen)

Sperm ccells are adapted to swim towards the egg. They contains lots of mitochondria to provide large amounts of energy requires to propel themselves a long distance

MAGNIFICATION = IMAGE LENGTH / ACTUAL LENGTH

ACTUAL LENGTH = IMAGE LENGTH / MAGNIFICATION

IMAGE LENGTH = ACTUAL LENGHT / MAGNIFICATION

Millimetre (mm) 1mm / 1000 = micrometre (um) 0.001mm

Mictrometre (um) 0.001 / 1000 = nanometre (nm) 0.000001mm

To convert a smaller unit into a bigger unit you divide by 1000.

To convert a bigger unit into a smaller unit you times by 1000.

Resolution is how detailed an image is: how well a microscope distringuishes between two points that are close together. 

Light microscope

• use…