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Chapter 3
Objectives
Relate structure to function for the
components of plant and animal
cells.
Explain the role of cell membranes
as a highly selective barrier (passive
and active transport).
The Cell Membrane
Functions: Physical isolation
Regulation of exchange with the
environment
Sensitivity to the environment
Structural support
The Cell Membrane
Components of Cell Membrane
Lipids 2 layers Hydrophobic tails on inside Hydrophilic heads on outside
Proteins Catalyze rxns Carrier proteins Channels
Carbohydrates Protection Locomotion Recognition
How Things Get Into and Out of Cells
Passive transport Diffusion
Active transport Vesicular transport Material are within small
sacs/vesicles
Carrier-mediated transport Help from membrane
proteins Can be passive or active
Diffusion
Random motion
Collisions of ions and molecules
High to low concentration gradient
Vesicular Transport
Endocytosis
Pinocytosis
Phagocytosis
Exocytosis
Carrier-Mediated TransportProteins bind to
specific ions or organic substances
Carry them across the membrane
Carrier substances only bind to specific substances
KEY CONCEPT
Cells: basic structural and
functional units of life respond to their environment
maintain homeostasis at the cellular level
modify structure and function over time
Review!!
Cell membranes are said to be
_____.a) impermeable
b) freely permeable
c) selectively permeable
d) actively permeable
e) slightly permeable
The movement of water across a membrane from an area of high solvent concentration to an area of low solvent concentration is known as _____.a) osmosisb) active transportc) diffusiond) facilitated diffusione) filtration
Diffusion is important in body
fluids because it tends to _____.a) increase local concentration gradients
b) eliminate local concentration gradients
c) move substances against concentration
gradients
d) create concentration gradients
Objectives
Explain the relationship between
mutation, cell cycle, and
uncontrolled cell growth potentially
resulting in cancer.
Cell Cycle
The whole
point:One cell becomes
two
Daughter cells
are identical to
parent cells
Interphase
Not actively
dividing
Most time spent here
3 phases: G1 – growth, normal
cell functions
S – DNA replication
G2 – protein synthesis
Mitosis
M phase
Actual dividing occurs
4 phases: Prophase
Metaphase
Anaphase
Telophase
Prophase
Chromosomes condense, become
visible
Chromatids attached by centromere
Nucleolus disappears
Metaphase
Chromosomes line up in the middle
Anaphase
Centromere splits, chromosomes
separate towards poles
Telophase
Nuclear membrane reforms
Nuclei enlarge
Chromosomes uncoil
Cytokinesis
Division of the cytoplasm
What regulates cell
division?
Mitotic Rate and Energy
Rate of cell division: slower mitotic rate means longer cell life
cell division requires energy (ATP)
Long Life, Short Life
Muscle cells, neurons rarely divide
Exposed cells (skin and digestive
tract) live only days or hours
Regulating Cell Life
Normally, cell division balances cell
loss
Cancer
Cancer Stages
Cancer develops in steps: abnormal cell
primary tumor
metastasis
secondary tumor
Cell Division and Tumors
Tumor (neoplasm): enlarged mass of cells
abnormal cell growth and division
Benign Tumors
Benign tumor: contained
not life threatening
Malignant Tumors
Malignant tumor: spread into surrounding tissues (invasion)
start new tumors (metastasis)
Cancer and Cells
Cancer: illness that disrupts cellular controls
produces malignant cells
Cancer and Genes
Oncogenes: mutated genes that cause cancer
KEY CONCEPT
Mutations disrupt normal controls
over cell growth and division
Cancers often begin where stem
cells are dividing rapidly
More chromosome copies mean
greater chance of error
What makes cells
different?
Cell Diversity
All cells carry complete DNA
instructions for all body functions
Cell Differentiation
Cells specialize or
differentiate: to form tissues (liver
cells, fat cells, and
neurons)
by turning off all genes
not needed by that cell
KEY CONCEPT
All body cells, except sex cells,
contain the same 46 chromosomes
Differentiation depends on which
genes are active and which are
inactive