Biology — Cell Structure & Organelles

What is a membrane-bound organelle?

a sub-compartment inside a cell wrapped in its own membrane Which type of cell has membrane-bound organelles?

eukaryotic cells What three parts work together to maintain a cell's shape?

the plasma membrane, the cytosol, and the cytoskeleton What is the plasma membrane?

the outer boundary of the cell What is the plasma membrane made of?

a bilayer of phospholipids and proteins What does it mean that the plasma membrane is a selective barrier?

it lets only specific substances in or out What is a phospholipid?

a lipid with a hydrophilic head and a hydrophobic tail What does hydrophilic mean?

water-attracting What does hydrophobic mean?

water-avoiding How do phospholipids arrange in a membrane?

heads face the watery outside and inside, while the tails point inward away from water What is the cytosol?

the gel-like, water-based fluid that fills the inside of the cell What is the difference between cytosol and cytoplasm?

cytosol is the fluid alone, while cytoplasm is the cytosol plus everything in it What is the cytoskeleton?

a network of protein fibres running through the cytoplasm What does the cytoskeleton do?

it gives the cell shape, holds organelles in place, and enables movement and transport Why can the cytoskeleton change shape?

it can be broken down and rebuilt, which helps with cell division and movement How is a cell's shape linked to its function?

specialised shapes suit specialised jobs, like nerve cells branching to relay signals What is the nucleus?

a membrane-bound organelle that holds the cell's DNA What surrounds the nucleus?

the nuclear membrane, which has pores How is DNA organised inside the nucleus?

into linear structures called chromosomes What are ribosomes?

cell parts that build proteins Where are ribosomes found?

free in the cytosol, or attached to the endoplasmic reticulum Why are proteins important to a cell?

they are vital for nearly all cell functions What is the pathway of protein synthesis?

DNA is copied into mRNA, which travels to a ribosome that builds the protein What is mRNA's role in making proteins?

it carries the DNA instructions out to the ribosome as a blueprint Why do different cells take on different roles?

they make different proteins, which is called protein expression What is the endoplasmic reticulum?

a system of connected membranes inside the cell What is the rough endoplasmic reticulum?

ER with ribosomes attached that processes proteins What is the smooth endoplasmic reticulum?

ER without ribosomes that builds lipids and detoxifies drugs and poisons What is the difference between rough and smooth ER?

rough ER has ribosomes and handles proteins, while smooth ER has none and makes lipids What is the Golgi body?

a stack of disc-shaped sacs that modify, sort, and package molecules What are vesicles?

small membrane sacs that bud off and carry substances around and out of the cell What is the transport pathway of a protein through these organelles?

rough ER, then a vesicle to the Golgi, then a vesicle to its destination How does a cell's organelle make-up reflect its job?

cells that secrete a lot of protein have plenty of rough ER What is the mitochondria known as?

the powerhouse of the cell What process takes place in the mitochondria?

cellular respiration What is cellular respiration?

the process that releases chemical energy from food molecules to make usable energy for the cell What do mitochondria produce?

ATP, the cell's usable energy Where are mitochondria found?

in nearly all eukaryotic cells What is unusual about mitochondrial DNA?

mitochondria have their own DNA, inherited from the mother What is the likely origin of mitochondria?

they were once independent cells that came to live inside our ancestors' cells (endosymbiosis) What are chloroplasts?

the organelles that carry out photosynthesis What is photosynthesis?

the process that converts sunlight energy into chemical energy stored in sugars Which cells have chloroplasts?

plant cells and some protists, but not animal cells What stacks are found inside chloroplasts?

thylakoids What is the difference between what mitochondria and chloroplasts do?

chloroplasts capture and store energy by photosynthesis, while mitochondria release energy by respiration How do chloroplasts and mitochondria work together in a plant?

chloroplasts make sugars, and mitochondria then use those sugars to make usable energy Why do muscle cells have many mitochondria?

to generate enough energy for movement Why do sunlit leaf cells have many chloroplasts?

they get lots of sunlight, so they do lots of photosynthesis What is a vacuole?

a storage compartment holding water and enzymes Why are vacuoles important in plant cells?

they are very large and help give the plant structure What is a lysosome?

a compartment of enzymes that breaks down waste and foreign substances What is the difference between a vacuole and a lysosome?

a vacuole mainly stores materials, while a lysosome mainly breaks things dow