Chapter 3 Lecture - Cellular Form and Function Flashcards
True or false: All organisms are composed of cells
True
____ are responsible for all structural and functional properties of a living organism
Cells
Understanding cells is the key to understanding what three things?
Workings of human body
Mechanisms of disease
Rationale of therapy
What are the 5 components of cell theory?
1) All organisms composed of cells and cell products
2) Cell is the simplest structural and functional unit of life
3) An organism’s structure and functions are due to activities of cells
4) Cells come only from preexisting cells
5) Cells of all species exhibit biochemical similarities
How many types of cells are there in the human body?
About 200 different types
What does the plasma (cell) membrane do and what is it made up of?
It surrounds cell and defines boundaries. Made of proteins and lipids
What 4 things are included in the cytoplasm?
1) Organelles
2) Cytoskeleton
3) Inclusions (stored or foreign particles)
4) Cytosol (intracellular fluid, ICF)
True or false: extracellular fluid (ECF) is one of the basic components of a cell
True
Define organelle
Internal structures of a cell that carry out specialized metabolic tasks
What’s the difference between cytoplasm and cytosol?
Cytoplasm contains the organelles; cytosol does not.
How is the plasma membrane arranged?
In a bilayer
What is the border of the cell?
The plasma membrane
Name 3 functions of the plasma membrane
1) Defines cell boundaries
2) Governs interactions with other cells
3) Controls passage of materials in and out of cell
__% of membrane molecules are lipids
98%
What are the 3 most abundant membrane lipids?
Phospholipids (75% of membrane lipids), cholesterol (20%), and glycolipids (5%)
What does the membrane lipid cholesterol do?
Holds phospholipids still and can stiffen the membrane
What are glycolipids?
Phospholipids with short carbohydrate chains on extracellular face. A type of membrane lipid.
Membrane proteins make up __% of the molecules but __% of the weight of membrane
2% of the molecules but 50% of the weight of membrane
What are the two basic types of membrane proteins, and where are they located?
Integral proteins—penetrate membrane
Peripheral proteins – on the surface of membrane
What is one type of integral protein?
Transmembrane proteins
________ proteins contain both hydrophilic and hydrophobic regions
Transmembrane
Where are transmembrane proteins located?
Some drift in membrane; others are anchored to cytoskeleton
Describe peripheral proteins
- Adhere to one face of the membrane (do not penetrate it)
- Usually tied to the cytoskeleton and an integral protein.
What are some examples of the functions of membrane proteins?
Receptors, enzymes, channels, carriers, cell-identity markers, cell-adhesion molecules, etc
What is the glycoalyx? What is it made up of?
It’s a fuzzy coat external to plasma membrane, and made up of glycoproteins and glycolipids
_______ is unique in everyone but identical twins
Glycocalyx
What does the glycocalyx do?
It helps with protection, immunity to infection, defense against cancer, transplant compatibility, cell adhesion, fertilization, and embryonic development
True or false: Some channel proteins are always open, but others are gated
True
What are channel proteins needed for?
They’re crucial to nerve and muscle function
What are 3 different types of channel proteins?
Ligand-gated channels, voltage gated channels, and mechanically-gated channels
Ligand-gated channels respond to _____
chemical messengers
Voltage-gated channels respond to ____
charge changes
Mechanically-gated channels respond to ____
physical stress on the cell
What is an example of a stretch receptor?
Mechanically-gated channels
Give an example of chemical messengers for ligand-gated channels
Neurotransmitters
Microvilli are best developed in cells specialized in _____
absorption
What are microvilli?
Extensions of the membrane that gives 15 to 40 times more surface area
How big are microvilli?
1-2μm
What is it called when microvilli are very dense and appear as a fringe?
Brush border
What are cilia?
Hair-like processes that are 7–10 μm long
What is one type of cilia?
Motile cilia
____ cilia are found in the respiratory tract, uterine tubes, ventricles of brain, ducts of testes
Motile cilia
What do cilia do?
Beat in waves sweeping material across a surface in one direction
True or false: the flagellum of sperm is the only functioning flagella in humans
True
Describe the structure and movement of flagella
They have a whip-like structure and are much longer than cilium.
Their movement is undulating, snake-like, corkscrew; no power stroke and recovery strokes
What are pseudopods?
Continually changing extensions of the cell that vary in shape and size
What can pseudopods do?
They can be used for cellular locomotion or capturing foreign particles
The plasma membrane is selectively permeable. What does this mean?
It allows some things through, but prevents others from passing
Which of the following mechanisms consume ATP?:
a) passive transport
b) active transport
c) both active and passive transport
b) active transport
What does passive transport not require any of the cell’s energy?
Random molecular motion of particles provides necessary energy
Is membrane transport a type of passive or active transport?
It can be either passive or active
Define membrane transport
Carrier-mediated mechanisms use a membrane protein to transport substances across membrane
Name 4 passive mechanisms of transportation
1) Filtration
2) Simple Diffusion
3) Facilitated Diffusion
4) Osmosis
Define filtration
A type of passive transport, particles are driven through membrane by physical pressure
Where can filtration be found in the human body? (3 examples)
1) Filtration of water and small solutes through gaps in capillary walls
2) Allows delivery of water and nutrients to tissues
3) Allows removal of waste from capillaries in kidneys
Define a gradient
A difference in chemical concentration, charge, temperature, or pressure between two points
True or false: Matter and energy tend to flow up gradients
False; matter and energy tend to flow DOWN gradients
Give an example of matter flowing down a gradient in the body
Blood flows from a place of higher pressure to a place of lower pressure
Moving up a gradient requires what?
Energy
Define simple diffusion
The net movement of particles from place of high concentration to place of lower concentration
Why does simple diffusion happen?
It happens due to constant, spontaneous molecular motion; molecules collide and bounce off each other
Substances diffuse ____ their concentration gradient
down
When can substances diffuse through a membrane?
If the membrane is permeable to the substance
True or false: the diffusion of substances down a concentration gradient doesn’t require a membrane
True
In _____ diffusion, the substance passes directly through the phospholipid bilayer
simple
What 5 factors affect the diffusion rate through the membrane?
1) Temperature: ^ temp = ^ motion of particles = ^ rate
2) Molecular weight: larger molecules move slower
3) Steepness of concentrated gradient: ^ difference = ^ rate
4) Membrane surface area: ^ area = ^ rate
5) Membrane permeability: ^ permeability = ^ rate
Define osmosis
The diffusion of water through a selectively permeable membrane
In osmosis, water moves from the side where water is ____ concentrated to the side where it is ____ concentrated
more; less
Will osmosis speed up or slow down if a cell adds more aquaporins?
Speed up
Define aquaporins
Channel proteins in a membrane specialized for water passage
Define osmolarity
The measure of total concentration of solute particles
Define tonicity
The concentration of non-permeating solutes
Define hypotonic solution
A solution that has a lower concentration of non-permeating solutes than the other solution
Define a hypertonic solution
A solution that has a higher concentration of non-permeating solutes than the other solution
Define an isotonic solution
Where concentrations of non-permeating solutes in both solutions are the same
What happens to a cell if it’s placed in a hypertonic solution?
Water diffuses out of the cell and causes crenation (shriveling) because now it doesn’t have enough water
What happens to a cell if it’s place in a hypotonic solution?
Water diffuses into the cell and causes hemolysis (explosion) because now it has too much water.
What happens to a cell if it’s placed in an isotonic solution?
Nothing, stays the same
What are the three mechanisms of carrier-mediated transport?
1) Facilitated diffusion
2) Primary active transport
3) Secondary active transport
What is carrier-mediated transport?
Solute attaches to binding site on carrier, carrier changes conformation, then releases solute on other side of membrane
Describe facilitated diffusion
- Carrier moves the solute down its concentration gradient
- Does not consume ATP
Describe primary active transport
- Carrier moves the solute through a membrane up (against) its concentration gradient
- Need ATP for energy
True or false: facilitated diffusion doesn’t require ATP
True
Give 2 examples of primary active transport in the body
- Calcium pump (uniport)
- Sodium–potassium pump (antiport)
What does the sodium-potassium pump do, and why?
- Three Na+ are pumped out and two K+ are pumped in by the sodium potassium pump
- Necessary because Na+ and K+ constantly leak through membrane
Define vesicular transport
Moves large particles, fluid droplets, or numerous molecules at once through the membrane in vesicles—bubble-like enclosures of membrane
Define endocytosis
Transports material into cell
Define exocytosis
Transports material out of the cell
Define transcytosis
Transport into, across, and then out of a cell
What are the two types of endocytosis? Describe them
Phagocytosis—“cell eating,” engulfing large particles
Pinocytosis—“cell drinking,”
What does phagocytosis do?
Phagocytosis keeps tissues free of debris and infectious microbes
Describe receptor-mediated endocytosis
- More selective endocytosis
- Enables cells to take in specific molecules that bind to extracellular receptors
Describe exocytosis and when it’s needed (before or after endocytosis)
- Secreting material
- Needed in the replacement of plasma membrane removed by endocytosis (after endocytosis)
What materials in the body can be released by exocytosis?
- Ejection of wastes
- Release of neurotransmitters
- Hormone secretion
- Mucus secretion
What is the cytoskeleton?
A network of protein filaments and cylinders
What is the largest organelle (5 μm in diameter)?
The nucleus
Most cells have how many nuclei?
1
True or false: cells can be mononuclear, polynuclear, or anuclear
True
Give an example of an anuclear cell in humans
Red blood cells
Give an example of a cell with many nuclei (a polynuclear cell) in the human body
Skeletal muscle cells & some bone dissolving cells
Define the nuclear envelope
A double membrane with pores surrounding the nucleus
Nucleoplasm is made up of what two things?
Chromatin and nucleoli
Define chromatin
A thread-like substance composed of DNA and protein; one of two substances that makes up nucleoplasm
Define nucleoli
Masses where ribosomes are produced; one of two substances that makes up nucleoplasm
Define endoplasmic reticulum
A system of channels (cisternae) enclosed by membrane
What makes up the rough endoplasm reticulum and what does it do?
It’s made up of parallel, flattened sacs covered with ribosomes.
Functions: protein synthesis and packages proteins for transport
The ___ endoplasmic reticulum has ribosomes, whereas the ____ endoplasmic reticulum doesn’t
The rough endoplasmic reticulum has ribosomes; the smooth endoplasmic reticulum doesn’t
What does the smooth endoplasmic reticulum do? (three things)
1) Synthesizes steroids and other lipids
2) Detoxifies alcohol and other drugs
3) Calcium storage
What are ribosomes?
Small granules of protein and RNA
What do ribosomes do?
They “read” coded genetic messages (messenger RNA) and assemble amino acids into proteins specified by the code
What does the golgi complex do?
It receives newly synthesized proteins from rough ER. Then it sorts proteins, modifies proteins, and packages them into vesicles
What do vesicles become/do after leaving the golgi complex?
Some vesicles become lysosomes
Some vesicles migrate to plasma membrane and fuse to it
Some become secretory vesicles that store a protein product for later release
Define lysosomes
A package of enzymes bound by a membrane
What 3 things do lysosomes do?
- Intracellular hydrolytic digestion
- Phagocytosis
- Autolysis
Define autolysis
“Cell suicide” or the digestion of a surplus cell by itself
What are peroxisomes and what do they do?
Resemble lysosomes but contain different enzymes. They detoxify certain harmful chemicals, enclose reactions that make toxic byproducts
Peroxisomes are found in all cells, but are especially abundant in what two organs?
The liver and kidney
Define mitochondria
Organelles specialized for synthesizing ATP
Mitochondria are surrounded by a ____ membrane
double
What makes mitochondrial DNA (mtDNA) unique, and what does it do?
It mutates more rapidly than nuclear DNA; continually changes shape from spheroidal to thread-like. It’s responsible for hereditary diseases affecting tissues with high energy demands
What do centrioles do?
They form the mitotic spindle during cell division, unpaired centrioles form basic structure of cilia and flagella
