Chap 4- The Cell

An Organelle

An Organelle

An organelle is a subcellular structure that has one or more specific roles to carry out in the cell

Name all organelle found in an animal cell

Nucleus, Cytoplasm, Ribosomes, Cell membrane, Mitochondria

Name the organelle unique to the plant cell

Large Vacuole, Chloroplast, Cell Wall

Cell Wall

Made of cellulose, a structural carbohydrate, and is strengthened with calcium

Role of the Cell Wall

Gives an extra layer of protection to the cell, gives a more rigid structure, allows water and some solutes in

Role of the Large Vacuole

Stores water & solutes, glucose from photosynthesis, and when full gives structure to the cell. A ‘full’ cell is said to be turgid.

Turgor pressure

The force of cell content on the membrane & wall

Plastids

Leucoplasts, Chromoplasts, and Chloroplasts

Chloroplasts

These organelle contain chlorophyll pigments. The process of photosynthesis takes place when light energy hits the granum stacks and after many steps create glucose energy.

Chromoplasts

Coloured red, orange, or yellow, giving colour to flowers and fruits.

Leucoplasts

Colourless, these structures store starch energy (energy reserve)

Cell/Plasma membrane

Made up of a phospholipid bilayer with pores and protein chunks

Role of the Cell/Plasma membrane

Controls entry and exits of substances to/from cell (semi-permeable), holds cell contents in place, gives support/structure to the cell

Water in the Phospholipid bilayer

The phosphate are hydrophylic, lipids are hydrophobic.

The structure of the phospholipid bilayer

The Fluid Mosaic Model

Cytoplasm

Jelly-like/semi-solid substance in which organelle are suspended (Cytoplasm - Organelle = Cytosol)

Cytoplasm Hydration

When fully hydrated cytoplasm consists of 90% water with dissolved substances (salts or amino acids) in it

Cytoplasm Role

Suspends organelle, location of stage 1 of respiration

Mitochondria

Membrane-enclosed organelle in the cytoplasm of most eukaryotic cells. Each mitochondria has a loop of DNA and Cristae infoldings.

Mitochondria role

The production of energy from glucose, or respiration.

Cristae

Infoldings within the mitochondria. If there are lots of cristae, the mitochondria is more active. Active cells include liver/muscle. Inactive cells include fat cells.

Ribosomes

Tiny bead-like structures made of RNA and protein. They move out of the nucleolus and lie in the cytoplasm.

Role of the ribosomes

Have a role in proteinsynthesis, the production of protein.

RNA

Ribonucleic acid

The Nucleus

Controls all the activity within the cell, i.e. the brain of the cell. It is surrounded by a double nuclear membrane, which has nuclear pores, allowing molecules to exit and enter.

The Nucleus consists of

DNA strands and the Nucleolus

DNA

Deoxyribonucleic acid. Arranged in structures called chromosomes. Every organism has a certain amount of chromosomes. Genes are located randomly on chromosomes, with 40,000 per cell. Genes are units of inheritance.

Nucleolus

Makes the organelle ribosomes, made of RNA (Ribonucleic acid)

Prokaryotic cells

These cells are small, ~ 0.5micrometres, with no nucleus and circular DNA in the cytoplasm, no membrane enclosed organelle. Usually single-celled organisms like bacteria.

Eukaryotic cells

These cells are larger, ~40micrometres, with a nucleus present containing chromosomes, and membrane enclosed organelle present, like the mitochondria or chloroplast. Usually multi-cellular organisms, like humans or animals