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