Unit 1 - Cell Structure Flashcards
1
Q
What 3 basic characteristics are common to all types of cells?
A
- Cell/plasma membrane: all cells are surrounded by a membrane where all materials enter or exit through
- Cytoplasm: portion of the cell within the membrane that includes the fluid and all organelles except the nucleus
- Control center: coded info in the form of DNA stores the instructions for cell functions/reproduction, DNA may be either floating in the cytoplasm or in a nucleus
2
Q
What are the main differences between Prokaryotic and Eukaryotic cells?
- Prokaryotic:
1. No nucleus, membrane-bound organelles
2. Generally smaller, less complex than eukaryotes
3. Have a cell wall, cell membrane, and ribosomes
- Eukaryotic”
1. Generally larger, more complex
2. True nucleus and membrane-bound organelles
A
- Prokaryotic:
1. No nucleus, membrane-bound organelles
2. Generally smaller, less complex than eukaryotes
3. Have a cell wall, cell membrane, and ribosomes - Eukaryotic”
1. Generally larger, more complex
2. True nucleus and membrane-bound organelles
3
Q
What are the functions of the cell/plasma membrane?
A
- Separates the internal chemical reactions of the cell from the external environment
- Separates animal cells
- Regulates the passage of materials into/out of the cell by only allowing certain molecules to enter/leave
- Made mainly of lipids and proteins
4
Q
Describe the nucleus of the cell
A
- Filled with nucleoplasm which is a jellylike liquid similar to cytoplasm
~ Nucleoplasm holds the contents of the nucleus - Nucleus contains nearly all the cell’s DNA, which codes instructions for the genetic makeup of future cells and for making proteins and other important molecules for cell functions
- Nucleus is surrounded by a nuclear membrane, a double membrane with pores that allow movement of materials into/out of the nucleus
- Nucleus: site where DNA -> RNA
- RNA carries protein-building instructions to ribosomes, travels to cytoplasm through pores in nuclear membrane
5
Q
What is the function of the nucleolus?
A
- Manufactures the subunits that make up ribosomes
- 2 subunits: large and small
~ These subunits pass through pores of the nucleus to the cytoplasm where they combine to form ribosomes
6
Q
Describe ribosomes
A
- May be found free-floating in cytoplasm or attached to the rough E.R
- Most numerous organelles
- Composed of protein and RNA, are not membrane bound organelles
- Site of protein synthesis
7
Q
What is the endoplasmic reticulum?
A
- Internal membrane system that accounts for most of the membrane in a cell
- Functions as an intracellular highway, providing a path for molecules to move from one part of the cell to another
8
Q
What is the specific function of the rough E.R?
A
- Is covered with attached ribosomes and is involved in the making of proteins
- Newly made proteins exit the ribosome and are inserted into spaces of the E.R where they’re modified and shaped into proteins
9
Q
What is the specific function of the smooth E.R?
A
- Has no ribosomes
- Makes lipids that will be used in membranes
10
Q
What is the function of the Golgi apparatus?
A
- Proteins from the rough E.R are transported here
- Appears as a stack of loosely connected membranes
- Modifies, sorts, packages proteins which will either be stored in the cell or secreted outside of it
- Completes protein modifications before they are shipped away to their destination
11
Q
Describe vesicles
A
- Small, spherical sacs surrounded by a single membrane
- Classified by their contents
~ Types include transport vesicles, peroxisomes, lysosomes
12
Q
Name the steps of protein synthesis and transport
A
- Proteins are assembled by ribosomes on the rough E.R
- Vesicles transport these proteins to the Golgi
- The Golgi completes modifications on the proteins
- Functional proteins are packaged in vesicles and leave the Golgi
- Vesicles fuse with the cell membrane to release the new proteins outside the cell
- Vesicles containing enzymes remain in the cell as lysosomes
13
Q
What are the functions of lysosomes?
A
- Bud from Golgi, are filled with digestive enzymes
- These enzymes break down large molecules of carbs, lipids, and proteins into smaller molecules
~The enzymes recycle the cell’s own organic materials, breaking them down into their building blocks and returning them to the cytoplasm to be re-used - Responsible for destroying old organelles
- Help destroy any debris that may build up in the cell
- Surrounded by a thick membrane as the cell would be destroyed if the enzymes were released
14
Q
What is a vacuole?
A
- Storage area, may store water, salts, proteins, carbs
- Central vacuole, contractile, and food vacuole
15
Q
What is the mitochondria?
A
- Powerhouse of the cell
- Aids in cellular respiration = process of converting glucose molecules into usable energy
- Have an inner and outer membrane, folds on inner membrane are called cristae
- Cristae increases surface area for respiration
- Have their own DNA, replication
16
Q
Describe the cytoskeleton
A
- Internal framework/support system of the cell to give it organization and shape
- Network of protein tubes and fibres that help the cell maintain its shape
- Involved in cell movement
- 2 types of fibres found here are microfilaments, microtubules
17
Q
Describe microfilaments
A
- Solid, threadlike protein structures
- Form extensive frameworks inside the cell to support it
- Help to bear mechanical stress
- Help cells move
- Assemble and disassemble rapidly, are involved in muscle contraction
18
Q
Describe microtubules
A
- Maintain cell shape
- Needed for the separation of chromosomes during cell division
- Help with the formation of cilia and flagella
19
Q
What are the functions of centrioles?
A
- Two short cylinders at right angle to one another
- Organize microtubules in cell division to form framework for separating chromosomes
20
Q
What organelles are never found in plant cells?
A
- Centrioles
- Lysosomes
- Flagella (except for sperm)
21
Q
What organelles are never found in animal cells?
A
- Central vacuole
- Cell wall
- Chloroplasts (plastids)
22
Q
What is a cell wall?
A
- Supporting structure of plant/fungi cells, lies outside the cell membrane
- Main function is protection
- Composed mostly of cellulose (tough carbohydrate fibre)
23
Q
What is a central vacuole?
A
- Very large fluid-filled vacuole found in mature plant cells
- When filled with water, it creates turgor pressure to give strength and support to the cell
- Can also store organic compounds
24
Q
Describe the cell membrane
A
- It regulates what enters/leaves the cell
- Provides protection and support to the cell
- Consists of a phospholipid bilayer in which proteins are embedded, this bilayer gives the membrane a flexible structure that forms a strong barrier between the inside/outside of the cell
- Phospholipids are structural components
25
Q
What are the different types of proteins within the phospholipid bilayer?
A
- Transport proteins: Form channels and pumps to help move materials across the membrane
- Receptor proteins: Recognize and bind to substances at the cell’s surface, forming a method of communication between the cell and its external environment
- Enzymes: Assist the chemical reactions inside the cell
- Carbs serve as identification markers so cells can identify each other
26
Q
What is Homeostasis?
A
- Process by which cells maintain a stable internal environment even when the external one is constantly changing
- Requires the self-regulation of materials going into/out of the cell
- Cell requires constant input of matter/energy and constant output of waste
27
Q
What is the Concentration Gradient?
A
- The difference in the concentration of molecules across a distance, molecules will almost always move from an area of higher concentration to lower concentration
28
Q
What is passive transport?
A
- The movement of substances across the cell membrane without the use of energy
- Types: diffusion, osmosis, facilitated diffusion
29
Q
What is diffusion?
A
- The spreading out of molecules from a region of higher concentration to lower concentration
-Depends on size and type of molecule - Small, non-polar molecules dissolve directly through the phospholipid bilayer while polar molecules go through protein channels/transport proteins
30
Q
What is osmosis?
A
- Movement of water across a membrane from a region of higher concentration to a region of lower concentration
- Passive transport of water, no energy needed
31
Q
What is an isotonic solution?
A
- When the concentrations of solutes outside/inside the cell are equal, as well as the water concentrations
- Water flows back and forth across the membrane at the same rate in both directions
- In an animal and plant cell: water diffuses in/out at equal rates
32
Q
What is a hypertonic solution?
A
- When the concentration of solute molecules is higher outside of the cell than inside the cell
- Water diffuses out into equilibrium is reached (risk of plasmolysis
~ Plasmolysis: too much water moves out and cell collapses - In an animal cell: plasmolysis occurs
- In a plant cell: more water leaves the cell than enters
33
Q
What is a hypotonic solution?
A
- Concentration of solute molecules outside the cell is lower than the concentration of solutes inside the cell
- Water diffuses into the cell until equilibrium is reached (cytolysis may occur)
- In an animal cell: more water enters the cell than leaves
-In a plant cell: more water enters than leaves, cytolysis is unlikely due to turgor pressure
34
Q
What is facilitated diffusion?
A
- Type of passive transport used for molecules that don’t readily diffuse through membranes
- May be polar or too large to fit through membrane pores
- Carrier proteins/ transport proteins help these molecules pass through the membrane more easily
35
Q
What is active transport?
A
- When materials must move against the concentration gradient, possibly from an area of low to high concentration
- Energy is needed
36
Q
What is endocytosis?
A
- Process of taking material into the cell by means of folds/pockets of the cell membrane
- Pocket that results breaks loose from the cell membrane and forms a vesicle within the cytoplasm
- Large molecules and clumps of food are taken up this way
37
Q
Describe the two types of endocytosis
A
- Phagocytosis = the engulfing of large food particles
- Pinocytosis = “cellular drinking”
38
Q
What is exocytosis?
A
- The release of large materials from the cell
- A vesicle fuses with the cell membrane, forcing the contents out of the cell
