Chapter 4: A Tour of the Cell Flashcards
The Cell Theory
- All organisms are composed of one or more cells.
- The cell is the smallest, most basic unit of structure and organization in all organisms.
- All Cells arise from pre-existing, living cells. (offspring)
Cell Size Must…
- Be large enough to house DNA, proteins, and structures needed to survive and reproduce.
- Remain small enough to allow for a surface-to-volume ratio to allow adequate exchange with the environment.
- Increase surface area (more surface area makes the cell more efficient)
What are the five basic structures of the cell?
- Plasma Membrane
- Cytosol
- Nucleus or Nuclear Area/Body
- DNA
- Ribosomes
Cytosol
Semifluid substance (cytoplasm) is the fluid-filled space, the cell’s entire contents between the plasma membrane and the nucleus.
Plasma Membrane
Controls what substances enter and exit the cells.
Nucleus or Nuclear Area/Body
It contains DNA.
DNA
Chromosomes (carry genes)
Ribosomes
synthesizes proteins
What are the two types of cells?
Prokaryotic and Eukaryotic
Prokaryotic cells are…
All single-celled
Have NO nucleus
NO organelles
Eukaryotic Cells are…
Single-cell protists and multicellular organisms.
Do have organelles
Have a nucleus present.
Eukaryotic cells are characterized by having…
- DNA in the nucleus that is bounded by a membranous nuclear envelope.
- Membrane-bound organelles (Organized and have double membranes)
- Cytoplasm in the region between the plasma and the nucleus.
The Endosymbiotic Model or Theory
The folding of membranes increases surface area, and cells engulf other cells but do not destroy them because they have food or small cells get protection.
The theory explains how eukaryote cells could have evolved from prokaryotic cells.
Three parts of the plasma membrane
- Phospholipids
- Cholesterol
- Proteins.
The head of the of the phospholipids are…
Hydrophilic (polar)
The legs of the phospholipids are…
Hydrophobic (nonpolar)
Phospholipids
- Form a two-layer sheet.
- Amphiphilic
Cholesterol (in the plasma membrane)
- Helps to stiffen the plasma at high temperatures.
- It helps maintain fluidity at low temperatures.
Proteins (in the plasma membrane)
They help perform specific reactions and allow molecules to enter the cell.
Glycocalyx (in the plasma membrane)
Used for cell recognition.
Nucleus
- The cellular control centers.
- Contains the genetic material information of the cell.
- DNA never leaves the cell.
Nuclear Envelope
Double membrane (almost like the plasma membrane but for the nucleus)
Nuclear Pore
Allow passage ONLY for rRNA, mRNA, and proteins.
Nucleolus
Darkest part of the nucleus. Synthesizes rRNA (which makes ribosomes)
Chromatin
Contains Chromosomes and is surrounded by nucleoplasm.
Ribosomes
Synthesizes PROTEINS using mRNA.