Quick questions on Cell organelles and their functions (SACE Stage 2 Biology)

The nucleus is surrounded by a nuclear membrane with pores. It contains the cell's DNA as chromosomes. It controls the cell's activities by controlling gene expression and is the site of transcription. The nucleolus inside it makes ribosomes.

Mitochondria are the site of aerobic cellular respiration, releasing energy as ATP from glucose. They have a double membrane; the inner membrane is folded into cristae, increasing surface area for the reactions. Cells with high energy demands, such as muscle cells, contain many mitochondria.

Ribosomes are the site of protein synthesis (translation). They may be free in the cytoplasm or attached to the rough endoplasmic reticulum. They are not membrane-bound.

The endoplasmic reticulum (ER) is a network of membranes. Rough ER is studded with ribosomes and processes and transports proteins. Smooth ER has no ribosomes and makes lipids and helps detoxify substances.

The Golgi apparatus is a stack of flattened membrane sacs. It modifies, sorts and packages proteins and other molecules into vesicles for secretion or delivery elsewhere in the cell.

Chloroplasts are found in plant cells and some protists. They contain the green pigment chlorophyll and are the site of photosynthesis. Their internal membranes (thylakoids stacked into grana) provide a large surface area for capturing light.

In plant cells a large central vacuole stores water, sugars and waste and maintains turgor pressure, keeping the cell firm and supporting the plant.

Lysosomes contain digestive enzymes that break down worn-out organelles, food particles and invading material.