Topic 5 - Cell Structure and Function Flashcards
Cell theory
- All organisms are made of cells, and the life processes of metabolism and heredity occur in these cells
- Cells are the smallest units of life
- Cell arise from previously existing cells
Cell size
- Cells must be small enough to allow small molecules (such as water, oxygen and carbon dioxide) enough time to quickly diffuse in and out
- As a cell increases in size, its surface area-to-volume ratio decreases
- The higher the surface area-to-volume ratio, the shorter the distance from the outside to the inside of the cell
As a cell increases in size, its surface area-to-volume ratio…
Decreases
What four components do all cells share?
- Plasma membrane
- Cytoplasm (cytosol)
- DNA
- Ribosomes, which synthesize proteins
Prokaryote
A simple, mostly single-celled (unicellular) organism that lacks a nucleus or any other membrane-bound organelle
Where is prokaryotic DNA located?
The nucleoid region, the cell’s central part, as a single circular chromosome
True or false: most prokaryotes have a cell wall
True
True or false: prokaryotes are significantly smaller than eukaryotes
True
How do eukaryotes compensate for a lower surface area-to-volume ratio than prokaryotes?
- Cell division
- Folding of the cell membrane
- Becoming flat/thin/elongated
- Developing organelles for specific tasks
Eukaryotic cells have…
- A membrane-bound nucleus
- Membrane-bound organelles
- Several, rod-shaped chromosomes
Describe the nucleus and its components/functions.
- Organelle that houses the cell’s DNA and directs synthesis of ribosomes and proteins
- Nuclear envelope: outermost boundary; punctuated with pores that control the passage of ions, molecules, and RNA into and out of the nucleus
- Chromatin: unwound protein-chromosome complexes (DNA)
- Nucleolus: body within nucleus that is responsible for assembling ribosome subunits; makes RNA
Describe ribosomes and their functions.
- Cellular structures responsible for protein synthesis
- Ribosomal RNA (rRNA) and protein
- Large and small subunits
Where are ribosomes found?
On the RER or floating freely in the cytoplasm.
Describe the rough endoplasmic reticulum (RER) and its functions.
- Site of protein synthesis (ribosomes)
- Continuous with nuclear envelope
- Proteins made on RER are deposited within a membrane that buds off and transports proteins through the cell
- Glycosylates proteins (modifies them by adding a sugar molecule)
Describe the smooth endoplasmic reticulum (SER) and its functions.
- Continuous with RER but lacks ribosomes (i.e. smooth)
- Synthesis of carbohydrates, lipids, and steroid hormones
- Detoxification of drugs and poisons
- Releases Ca+ for muscle contractions
Describe the Golgi apparatus and its functions.
- Series of stacked membranes that sort, tag, and package lipids, proteins and carbs for distribution
- Modification and transport
- Final folding of protein takes place in Golgi bodies
Describe mitochondria and their functions.
- The “power house of the cell”
- Responsible for making adenosine triphosphate (ATP), the cell’s main energy-carrying molecule
- Oval-shaped with double membranes (inner and outer membrane)
- Inner membrane is highly folded and embedded with enzymes used to convert food energy into ATP
- Cellular respiration
Describe chloroplasts and their functions.
- Carries out photosynthesis
- Three major compartments: intermembrane space, stroma, and granum
Describe lysosomes and their function.
- Membrane-enclosed digestive enzymes
- Present in animal cells
- Breakdown nutrients (phagocytosis), bacteria, damaged organelles (autophagy)
Describe peroxisomes and their function.
- Carry out oxidation reactions that break down fatty acids and amino acids
- Detoxify hydrogen peroxide (H2O2) with catalase
Describe vesicles and vacuoles and their functions.
- Membrane-bound sacs that function in storage and transport
- Contractile vacuoles pump water out of freshwater protists
- Central vacuoles in plants store water and other chemicals
Describe centrosomes and their components/functions.
- Microtubule organizing centers (MTOCs) - all microtubules originate from the centrosome
- Facilitates the organization of the spindle poles during mitosis
- While both animal and plant cells have microtubule organizing centers (MTOCs), animal cells also have centrioles associated with the MTOC
- Centrioles aid in cell division
- Found near nuclei of animal cells
Describe the plasma membrane and its functions.
- Phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment
- Provides protection for the cell
- Controls the passage of organic molecules, ions, water, and oxygen into and out of the cell
Describe the cell wall and its functions.
- Rigid covering that protects the cell, provides structural support, and gives shape to the cell
- Made of cellulose embedded in sugars and proteins
- Present in plant cells