ch4 anp cram

Cell

The basic structural and functional unit of life.

Cell theory

All organisms are made of cells; cells are the structural and functional units of living things; all cells arise from preexisting cells.

Three major regions of a human cell

Plasma membrane, cytoplasm, and nucleus.

Plasma membrane

Flexible outer boundary of the cell that separates intracellular fluid from extracellular fluid and controls movement, communication, and recognition.

Cytoplasm

All cellular material located between the plasma membrane and nucleus; contains cytosol, inclusions, and organelles.

Nucleus

DNA-containing control center of the cell that directs production of cellular proteins.

Selective permeability

The plasma membrane allows some substances to cross while restricting others.

Three major functions of the plasma membrane

Physical barrier, selective permeability, and communication/cell recognition.

Fluid mosaic model

The membrane is a flexible lipid bilayer in which proteins and other molecules can move or are embedded in a mosaic-like pattern.

Phospholipid

Main lipid of the plasma membrane; has a polar hydrophilic phosphate head and nonpolar hydrophobic fatty acid tails.

Phospholipid head

Polar, charged, and hydrophilic; faces the watery intracellular or extracellular fluid.

Phospholipid tails

Nonpolar, uncharged, and hydrophobic; point toward each other in the membrane interior.

Cholesterol in the plasma membrane

Increases membrane stability, stiffens the membrane, and decreases permeability.

Glycocalyx

A carbohydrate-rich coating on the extracellular surface of the cell that functions in cell recognition.

Glycoprotein

A membrane protein with a carbohydrate attached.

Glycolipid

A membrane lipid with a carbohydrate attached.

Main function of the glycocalyx

Acts as a marker that allows cell-to-cell recognition.

Integral protein

Protein firmly inserted into the plasma membrane; many span the entire membrane.

Transmembrane protein

An integral protein that extends completely through the lipid bilayer.

Peripheral protein

Protein loosely attached to membrane lipids or other membrane proteins rather than embedded through the membrane.

Functions of membrane proteins

Enzymatic activity, cell recognition, ECM attachment, cell-to-cell joining, transport, and receptors for signaling.

CAM

Cell adhesion molecule; membrane protein involved in attaching cells to one another or to the extracellular environment.

Organelle

Specialized cellular structure that performs a specific function.

Membranous organelles

Mitochondria, endoplasmic reticulum, Golgi apparatus, peroxisomes, and lysosomes.

Nonmembranous organelles

Ribosomes, cytoskeleton, and centrioles.

Why is organelle distribution related to cell function?

Different types of cells contain different amounts of organelles depending on the functions they perform.

Mitochondrion

Organelle that produces most cellular ATP through cellular respiration.

Cristae

Folds of the inner mitochondrial membrane containing proteins needed for cellular respiration.

Mitochondrial structure

Double membrane with an outer membrane, inner membrane, cristae, and matrix.

Special features of mitochondria

Contain their own DNA, RNA, and ribosomes and are capable of division.

Cells requiring lots of energy have more of what organelle?

Mitochondria.

Ribosome

Site of protein synthesis; composed of proteins and ribosomal RNA.

Free ribosome

Makes soluble proteins that function in the cytosol or other organelles.

Membrane-bound ribosome

Ribosome attached to rough ER that makes proteins for secretion, lysosomes, or plasma membranes.

Endoplasmic reticulum

A network of interconnected membranous cisterns continuous with the outer nuclear membrane.

Cisterns

Flattened membranous sacs or tubes that enclose fluid-filled spaces; found in structures such as the ER and Golgi.

Rough ER

Endoplasmic reticulum studded with ribosomes; synthesizes and begins modification of proteins.

Why does rough ER look rough?

Ribosomes are attached to its surface.

Proteins made by rough ER

Secreted proteins, plasma membrane proteins, and lysosomal proteins.

Protein pathway from rough ER

Protein enters RER cisterns → is modified → packaged into a vesicle → sent to Golgi apparatus.

Smooth ER

Endoplasmic reticulum without ribosomes involved in lipid metabolism, Ca²⁺ storage, detoxification, and glycogen metabolism.

Smooth ER functions

Lipid absorption/synthesis/transport, Ca²⁺ storage and release, detoxification of drugs/pesticides, and conversion of glycogen to glucose.

Golgi apparatus

Stacks of flattened cisterns that modify, concentrate, sort, and package proteins and lipids received from the ER.

Cis face of Golgi

Receiving side of the Golgi; accepts transport vesicles from the ER.

Trans face of Golgi

Shipping side of the Golgi; transport vesicles pinch off from here.

Three possible destinations of Golgi vesicles

Secretion outside the cell, incorporation into a cellular membrane, or formation of lysosomes.

Lysosome

Acidic membrane-bound organelle containing digestive enzymes called acid hydrolases.

Main function of lysosomes

Intracellular digestion.

What do lysosomes digest?

Ingested bacteria/viruses, damaged or nonfunctional organelles, and other cellular materials.

Autolysis

Self-digestion of a cell caused by release of lysosomal enzymes.

Peroxisome

Organelle containing enzymes that detoxify harmful substances and neutralize free radicals.

Free radical

Highly reactive molecule produced as a normal by-product of cellular metabolism.

Oxidase

Peroxisomal enzyme that uses oxygen to convert certain toxins into hydrogen peroxide.

Catalase

Peroxisomal enzyme that converts toxic hydrogen peroxide into harmless products such as water.

Lysosome vs peroxisome

Lysosome = intracellular digestion; peroxisome = detoxification/free-radical control.

Cytoskeleton

Network of protein rods throughout the cytosol that supports cell shape and participates in movement.

Three parts of the cytoskeleton

Microfilaments, intermediate filaments, and microtubules.

Microfilaments

Thinnest cytoskeletal elements; made of actin; support cell surface and participate in movement and shape changes.

Actin

Protein that forms microfilaments.

Intermediate filaments

Tough ropelike protein fibers that help cells resist pulling forces or tension.

Microtubules

Largest cytoskeletal elements; hollow tubes made of tubulin that maintain cell shape, hold organelles, and form tracks for movement.

Tubulin

Protein subunit that forms microtubules.

Motor proteins

ATP-powered proteins that move organelles and other substances along cytoskeletal tracks.

Centrosome

Microtubule-organizing center located near the nucleus.

Centrioles

Pair of microtubular structures at right angles to each other within the centrosome; involved in organizing microtubules and cell division.

Cilia

Short, numerous motile cell extensions made of microtubules that move material across a cell surface.

Example of cilia function

Moving mucus across the surface of respiratory cells.

Flagellum

Long cell extension made of microtubules that propels an entire cell.

Human cell with a flagellum

Sperm cell.

Microvilli

Fingerlike extensions of the plasma membrane that increase surface area for absorption.

Where are microvilli common?

Intestinal cells and kidney tubule cells.

What supports microvilli?

Actin microfilaments.

Largest organelle

Nucleus.

Nuclear envelope

Double-membrane barrier surrounding the nucleus.

Outer nuclear membrane

Is continuous with rough ER and may be studded with ribosomes.

Nuclear lamina

Protein network along the inner nuclear membrane that maintains nuclear shape and helps support DNA.

Nuclear pores

Openings in the nuclear envelope that regulate movement of substances into and out of the nucleus.

Nucleolus

Dark-staining region of nucleus involved in rRNA synthesis and ribosome subunit assembly.

Chromatin

DNA associated with histone proteins and RNA inside the nucleus.

Histones

Proteins around which DNA wraps.

Nucleosome

Fundamental chromatin unit consisting of DNA wrapped around histone proteins.

Chromosome

Condensed chromatin, especially visible during cell division.

Chromatin vs chromosome

Chromatin is relatively uncondensed DNA/protein; a chromosome is highly condensed chromatin.

Uninucleate cell

Cell containing one nucleus; most human cells are uninucleate.

Multinucleate cell

Cell containing many nuclei; skeletal muscle cells are an example.

Anucleate cell

Cell lacking a nucleus; mature red blood cells are an example.

What determines whether something can cross the lipid bilayer?

Lipid solubility, particle size, particle charge, and concentration gradient.

What molecules cross the membrane easily?

Hydrophobic/lipid-soluble molecules such as O₂ and steroid hormones.

How do small polar molecules cross the membrane?

They can cross slowly; water can also move rapidly through aquaporins.

Can glucose easily cross the lipid bilayer by itself?

No. It is a large polar molecule and generally requires a transport protein.

Can ions such as Na⁺ easily cross the lipid bilayer?

No. Their charge prevents direct passage through the hydrophobic membrane interior.

Passive transport

Movement across the membrane that does not require cellular energy.

Active transport

Movement that requires energy and can move substances against their concentration gradients.

Diffusion

Natural net movement of molecules from high concentration to low concentration.

Concentration gradient

Difference in concentration of a substance between two areas.

Moving down a concentration gradient

Moving from high concentration to low concentration.

Three types of passive membrane transport

Simple diffusion, facilitated diffusion, and osmosis.

Factors that increase diffusion rate

Higher concentration, smaller molecular size, and higher temperature.

Equilibrium

State in which there is no net movement of molecules even though molecules continue moving randomly.

Simple diffusion

Passive movement of a substance directly through the membrane from high to low concentration without a transport protein.