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Questions and Answers
What is the main function of cilia in a cell?
What is the main function of cilia in a cell?
Which phase of interphase is primarily responsible for DNA replication?
Which phase of interphase is primarily responsible for DNA replication?
What structure surrounds the nucleus and regulates the passage of materials?
What structure surrounds the nucleus and regulates the passage of materials?
How many different types of cells are estimated to exist in the average adult human body?
How many different types of cells are estimated to exist in the average adult human body?
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Which of the following is NOT a phase of mitosis?
Which of the following is NOT a phase of mitosis?
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What is the primary function of the plasma membrane?
What is the primary function of the plasma membrane?
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Which of the following correctly describes the cytoplasm?
Which of the following correctly describes the cytoplasm?
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How do integral proteins function in the plasma membrane?
How do integral proteins function in the plasma membrane?
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Which substances are considered selectively permeable by the plasma membrane?
Which substances are considered selectively permeable by the plasma membrane?
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What type of proteins interact with ligands in the plasma membrane?
What type of proteins interact with ligands in the plasma membrane?
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What characterizes passive transport across the plasma membrane?
What characterizes passive transport across the plasma membrane?
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What is NOT a component of the cytoplasm?
What is NOT a component of the cytoplasm?
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Which fluid is referred to as intracellular fluid?
Which fluid is referred to as intracellular fluid?
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What is the net movement of water through a selectively permeable membrane called?
What is the net movement of water through a selectively permeable membrane called?
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What role does the Na/K pump play in cellular function?
What role does the Na/K pump play in cellular function?
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Which of the following is NOT a type of endocytosis?
Which of the following is NOT a type of endocytosis?
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What is the primary function of the rough endoplasmic reticulum (ER)?
What is the primary function of the rough endoplasmic reticulum (ER)?
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Which organelle is responsible for the modification and packaging of proteins?
Which organelle is responsible for the modification and packaging of proteins?
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What do lysosomes contain that aids in digestion?
What do lysosomes contain that aids in digestion?
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Which component of the cell provides structural stability?
Which component of the cell provides structural stability?
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What is the primary function of mitochondria?
What is the primary function of mitochondria?
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What type of proteins are synthesized on the rough endoplasmic reticulum?
What type of proteins are synthesized on the rough endoplasmic reticulum?
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What do peroxisomes produce as a byproduct of their enzyme activity?
What do peroxisomes produce as a byproduct of their enzyme activity?
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Which structure is primarily involved in moving chromosomes during cell division?
Which structure is primarily involved in moving chromosomes during cell division?
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What is the function of smooth endoplasmic reticulum?
What is the function of smooth endoplasmic reticulum?
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What are ribosomes primarily composed of?
What are ribosomes primarily composed of?
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What distinguishes the cis face of the Golgi apparatus?
What distinguishes the cis face of the Golgi apparatus?
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Study Notes
Introduction to Cells
- Cells are the basic, living, structural, and functional units of the body
- Cell biology is the study of cellular structure and function
- Cells perform chemical reactions called metabolism to create life processes
A Generalized Cell
-
Plasma membrane: Encloses the cell, the outer boundary; separates the cell's internal environment (living) from the external environment (non-living).
- It's a bilayer of phospholipids, a selective barrier
- Plays a role in cellular communication
-
Cytoplasm: Fills the interior of the cell, a semi-fluid substance
- Contains macromolecules essential for cellular activity
- Contains organelles
- Cytosol: Part of the cytoplasm that contains water, organic molecules, and ions.
- Cytoplasm is the collective term for cytosol plus organelles
-
Nucleus: Centrally located organelle; contains chromosomes.
- Consists of a single molecule of DNA and associated proteins
- Each chromosome contains thousands of hereditary units called genes
A Generalized Cell (continued)(Figure)
- Organelles
- Cytoskeleton
- Microtubules
- Microfilaments
- Intermediate filaments
- Microvilli
- Centrosome (pericentriolar material and centrioles)
- Lysosomes
- Smooth endoplasmic reticulum
- Peroxisomes
- Mitochondria
- Ribosomes
- Golgi Complex
- Vacuoles
- Nucleolus
- Chromatin
The Plasma Membrane
- Integral proteins: Extend through the lipid bilayer
- Peripheral proteins: Attached to the inner or outer surface of the membrane, do not extend through it.
- Some integral proteins are ion channels
- Transporters: Selectively move substances through the membrane
- Receptors: For cellular recognition; a ligand is a molecule that binds with a receptor
- Enzymes: Catalyze chemical reactions
- Others act as cell-identity markers
The Plasma Membrane (continued)(Figure)
- Phospholipids: Polar head (hydrophilic), fatty acid tails (hydrophobic) - Bilayer
- Cholesterol: In the lipid bilayer
- Glycolipids: Carbohydrate + Lipid
- Glycoproteins: Carbohydrate + Protein
The Plasma Membrane
- Selectively permeable
- Allows oxygen, carbon dioxide, water, and steroids to pass through
- Does not allow glucose, proteins, and ions to pass through directly
- How do materials enter the cell?
- Integral proteins act as channels
- Na+/K+ pump, G protein, Tyrosine Kinase Pathway
- Intracellular fluid (ICF): Fluid within the cells (also called cytosol)
- Extracellular fluid (ECF): Fluid outside cells
- Interstitial fluid: ECF filling the spaces between cells
- Plasma: ECF in blood vessels
- Lymph: ECF in lymphatic vessels
Membrane Transport
- Passive transport: High to low concentration (with concentration gradient); no ATP needed
- Active transport: Low to high concentration (against concentration gradient); ATP needed
- Diffusion: Net movement of a substance from a region of high concentration to a region of lower concentration
- Osmosis: Net movement of water through a selectively permeable membrane from an area of high concentration to a lower concentration
- Facilitated diffusion: Net movement of a substance through an integral protein from a region of high concentration to a region of lower concentration
- Na+/K+ pump: Transports ions across the plasma membrane (antiporter); requires ATP; moves from lower to higher concentration
Membrane Transport(continued)
- Vesicle: A small spherical sac formed by budding off from the Golgi apparatus membrane, plasma membrane or lysosome membrane.
- Exocytosis: Vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid (ECF)
- Endocytosis: Materials move into a cell in a vesicle; includes receptor-mediated endocytosis, phagocytosis, and pinocytosis
Cytoplasm
-
Ribosomes: Site of protein synthesis(Figure)
- Composed of rRNA and proteins
- Attach to internal membranes of the endomembrane system
- Float freely in the cytoplasm; Composed of 2 subunits
Cytoplasm (continued)
- Endomembrane system: Endoplasmic Reticulum (ER), Golgi Apparatus, Lysosomes, Microbodies (Peroxisome), Vacuoles
Cytoplasm (continued)(ER)
-
Endoplasmic Reticulum (ER): Membrane-bound; embedded proteins
- Cisternal space (lumen)
- Two types:
- Smooth ER
- Rough ER
- Rough ER contains embedded ribosomal proteins
- Smooth ER contains enzymes that catalyze the synthesis of carbohydrates and lipids, stores ions and steroids
Cytoplasm (continued)
-
Golgi apparatus: Collects, sorts, packages, and distributes proteins and other substances
- Modifies proteins and lipids from the ER
- Creates glycolipids or glycoproteins (addition of short sugar chains)
- Abundant in glandular cells; secretion is high
- Cis face: Receiving end, near ER
- Trans face: Distribution end, faces plasma membrane. Products packaged into vesicles at the trans face.
Cytoplasm (continued)(Lysosomes)
-
Lysosomes: Digestive vesicles
- Arise from the Golgi apparatus (trans face)
- Contain hydrolytic enzymes
- Function in phagocytosis (of macromolecules, particles, and worn-out organelles)
Cytoplasm(continued)(Microbodies)
-
Peroxisomes: Contain digestive enzymes
- Produce hydrogen peroxide as a byproduct
- Contain detoxifying enzymes
- Break down hydrogen peroxide into water and oxygen.
- Isolate oxidative enzymes to decrease disruptions to metabolic reactions in the cytoplasm
Cytoplasm(continued)(Vacuoles)
- Vacuoles: Storage depots for water, sugars, ions, and waste products.
Cytoplasm (continued)
-
Centrioles: Microtubule organizing centers
- Occur in pairs
- Move to opposite poles of the cell during cell division
- Cylindrical in shape; composed of 9 triplet rows of microtubules
Cytoplasm (continued)(Mitochondria)
-
Mitochondria: Contain their own DNA
- Proteins (essential for function) are produced via these genes.
- Can duplicate themselves during cell replication
- Contain oxidative enzymes for transferring energy from macromolecules to ATP.
- Surrounded by two membranes (outer and inner membranes)
- Inner membrane has cristae (increases surface area).
- Matrix is the "cytoplasm" of the mitochondrion
Cytoplasm (continued)(Cytoskeleton)
- Cytoskeleton: Network of protein fibers
- Supports the shape of the eukaryotic cell
- Keeps organelles in fixed locations
- Helps move materials within the cell
- Types:
- Microtubules
- Actin filaments (muscle contraction)
- Intermediate filaments (structural stability), e.g. keratin, neurofilaments
Cytoplasm (continued)(Cilia and Flagella)
- Cilia: Short, hair-like projections from the cell surface; move fluids along the cell surface.
- Flagella: Longer than cilia; move the entire cell.
Nucleus (continued)
-
Nucleus: Largest organelle (usually one per cell)
- Centrally located
- Stores genetic information
- Contains nucleolus (involved in rRNA synthesis)
Nucleus (continued) (Nuclear Structure and Function)
- Surrounded by the nuclear envelope
- Outer and inner membrane
- Pores in the envelope
- Allow proteins into the nucleus
- Allow RNA and RNA-protein complexes out of the nucleus to cytoplasm.
Interphase
- Interphase is divided into three phases:
- G1: Gap Phase 1 (cell growth)
- S: Synthesis phase (DNA replication)
- G2: Gap Phase 2 (chromosomes condense; protein synthesis)
Mitosis
- Mitosis is divided into five phases
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
Cellular Diversity
- Average adult has nearly 100 trillion cells
- About 200 different types of cells
- Cells vary in shapes and sizes
- Cellular diversity allows organization into tissues and organs
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Description
Test your knowledge on the basics of cell biology, including cellular structures such as the plasma membrane, cytoplasm, and nucleus. This quiz will cover key functions and characteristics of generalized cells and their significance in life processes.
