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Cells. Wassily Kandinsky (1866-1944). Cell Theory: - all organisms are composed of cells - all cells come from other cells. Figure 4.1x. Scanning electron microscope (SEM). TEM. Figure 4.1B. Cell size and shape relate to function Minimum Maximum. Figure 4.2.

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cells
Cells

Wassily Kandinsky (1866-1944)

slide2

Cell Theory:

- all organisms are composed of cells

- all cells come from other cells

Figure 4.1x

slide5
A small cell has a greater ratio of surface area to volume than a large cell of the same shape

30 µm

10 µm

Surface areaof one large cube= 5,400 µm2

Total surface areaof 27 small cubes= 16,200 µm2

Figure 4.3

2 kinds of cells prokaryotic and eukaryotic
2 kinds of cells: prokaryotic and eukaryotic

Prokaryotic cells - “before nucleus”

- small, relatively simple cells

  • Single-celled organisms
eukaryotic cells functional compartments
Eukaryotic cells - functional compartments

- true nucleus

- larger: 10-100 microns

- often multicellular

- organelles surrounded by membranes

- usually need O2

what do these have in common
What do these have in common?
  • HIV infection
  • Transplanted organs
  • Communication between neurons
  • Drug addiction
  • Cystic fibrosis
  • hypercholesteremia
plasma membrane
Plasma membrane
  • Contact between cell and environment
  • Keeps useful materials inside and harmful stuff outside
  • Allows transport, communication in both directions
slide11

Plasma membrane components

1. Phospholipid bilayer

polar

head

P

cytosol

hydrophobic molecules

hydrophilic molecules

nonpolar

tails

slide12
2. Cholesterol - adds rigidity

Fluid mosaic model

Glycoprotein

Carbohydrate (of glycoprotein)

Fibers of the extracellular matrix

Glycolipid

Phospholipid

Cholesterol

Microfilaments of the cytoskeleton

Proteins

CYTOPLASM

Figure 5.12

slide13
3. Membrane Proteins - span entire membrane or lie on either side
      • Structural Support
      • Recognition
      • Communication
      • Transport
how do molecules cross the plasma membrane
How do molecules cross the plasma membrane?
  • Passive transport
  • Active transport
  • Endocytosis and exocytosis
slide15
Diffusion and gradients
    • Diffusion = movement of molecules from region of higher to lower concentration.
    • Osmosis = diffusion of water across a membrane
slide16

Molecule of dye

Membrane

EQUILIBRIUM

  • In passive transport, substances diffuse through membranes without work by the cell

EQUILIBRIUM

Figure 5.14A & B

osmosis diffusion of water across a membrane
Osmosis = diffusion of water across a membrane

Hypotonicsolution

Hypertonic solution

  • water travels from an area of higher concentration to an area of lower water concentration

Selectivelypermeablemembrane

Solutemolecule

HYPOTONIC SOLUTION

HYPERTONIC SOLUTION

Water molecule

Selectivelypermeablemembrane

Solute molecule with cluster of water molecules

Figure 5.15

NET FLOW OF WATER

water balance between cells and their surroundings is crucial
Water balance between cells and their surroundings is crucial

osmoregulation = control of water balance

  • Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution
slide19

10 microns

isotonic solution

hypertonic solution

hypotonic solution

net water movement

into cells

net water movement

out of cells

equal movement of water

into and out of cells

passive transport diffusion across membranes
Passive transport = diffusion across membranes
  • Small nonpolar molecules - simple diffusion
  • Many molecules pass through protein pores by diffusion through channels.
  • Facilitated diffusion

Solutemolecule

Transportprotein

Figure 5.17

active transport
Active transport
  • against a concentration gradient
  • transport proteins needed
  • requires energy (ATP)
slide22

FLUIDOUTSIDECELL

Phosphorylated transport protein

Transportprotein

  • Active transport in two solutes across a membrane
  • Na+/K+ pump
  • Protein shape change

Firstsolute

1

First solute, inside cell, binds to protein

2

ATP transfers phosphate to protein

3

Protein releases solute outside cell

Second solute

4

Second solute binds to protein

5

Phosphate detaches from protein

6

Protein releases second solute into cell

Figure 5.18

exocytosis and endocytosis transport large molecules
Exocytosis and endocytosis transport large molecules

exocytosis = vesicle fuses with the membrane and expels its contents

FLUID OUTSIDE CELL

CYTOPLASM

Figure 5.19A

slide27
Cholesterol can accumulate in the blood if membranes lack cholesterol receptors

Phospholipid outer layer

LDL PARTICLE

Receptor protein

Protein

Cholesterol

Plasma membrane

Vesicle

CYTOPLASM

Figure 5.20

what do these have in common1
What do these have in common?
  • HIV infection
  • Transplanted organs
  • Communication between neurons
  • Drug addiction
  • Cystic fibrosis
  • hypercholesteremia