Chapter 3 (lectures)`

Mitosis and meiosis (sex cells)

How do cells reproduce?

1. Cell nucleus

2. Plasma membrane

3. Cytoplasm (cytosol and organelles)

Three characteristics of a generalized cell

Separates inside of cell (intracellular fluid) from outside of the cell (extracellular fluid: blood plasma and interstitial fluid)

Purpose of the plasma membrane

It allows/enables/encourages substances to pass through it. Passages of substances is essential for human life

What does it mean by to say that the plasma membrane is “not a passive structure”?

7-10 micrmetres

How thin is plasma membrane?

1. Hydrophilic phospholipid group head

2. Hydrophobic fatty acid tails

Phospholipid structure: [2]

Integral proteins

Proteins embedded in the membrane, many span the membrane

Peripheral proteins

Proteins not embedded in the plasma membrane, and sit on either inner or outer layer of the membrane

1. Transport: passive or active

2. receptor for signal transduction: has a binding site that fits a specific chemical messenger from outside to inside (ex: hormone)

3. Enzymatic activity: protein is an enzyme that speeds up a metabolic process

4. Cell recognition: Protein acts as an identification tag that other cells can recognize

5. Attachment point: anchors cell to extracellular matrix or cytoskeleton; helps maintain shape

6. Cell to cell joining: allows cells to connect

Six functions of proteins in plasma membrane:

Glycocalx

Extracellular surface of plasma membrane. is essential for cell recognition, as it allows immune system to differentiate between body cells and foreign cells. “sugar coating”

Passive transport

Transport where no energy is involved

Active transport

Energy required to push substances from low concentration to high concentration. Primary or secondary.

1. diffusion (simple or facilitated)

2. osmosis

Two types of passive transport

Diffusion

Stuff moves from high concentration ro low concentration. Movement happens until equilibrium is reached

Equal amount on both sides of the membrane

When is equilibrium reached? (diffusion)

1. Fat soluble molecules

2. Gasses (oxygen, carbon dioxide)

3. Very small particles

4. steroid hormones

5. fatty acids

What substances diffuse across the membrane? [5]

1. Carrier mediated

2. Channel-mediated

Two types of facilitated diffusion

Facilitated diffusion

Substances do not pass right through the membrane on their own, still does not require ATP

Channel-mediated facilitaed diffusion

Substance binds to carrier protein that changes shape and opens up to allow substance to pass through membrane. From high concentration to low concentration.

Channel-mediated facilitated diffusion (ions selected by size and charge)

Channels embedded in the membrane allow substances to pass from high concentration to low concentration.

1. Concentration gradient: Bigger difference, faster diffusion

2. Molecular size: Smaller size, faster diffusion

3. Temperature: Higher temperature, faster diffusion

Three factors that influence diffusion

Aquaporin

Channel for water in plasma membrane

1. Specificity

2. Saturability

Two factors that influence facilitated diffusion

Specificity

Channels and carriers are specific to certain solutes

Saturability

The number of channels and carriers is limited. If all are being used, substance cannot pass through

Osmosis

Movement of solvent (water) through the lipid bilayer or channel proteins when there is a difference in water concentration.

Osmolarity

The solution concentration

Isotonic solution

Solution has same concentration inside and outside the cell. No concentration gradient.

Hypertonic solution. cell shrinks/shrivels because it pushes water outside of cell

Solution when it has a higher concentration outside than inside. (less water outside, more water inside)

Hypotonic solution. Cell expands and can burst because water is being pushed into the cell

Solution has lower concentration outside than inside (more water outside, less water inside)

1. Active transport

2. Vesicular transport

Two types of active transport

Primary active transport

energy to transport comes directly from ATP. Transport occurs through pumps (proteins)

Sodium potassium pump

Most important pump in the body

For every molecule of ATP, once 3 molucules of sodium are pumped out, protein can bind to 2 molecules of potassium, change shape, and pump in

Ratio that sodium potassium pump pumps out / in

Ten times more potassium inside the cell than outside

There is _____ times ______ potassium than there is sodium in a cell

1. Maintains concentration gradient (key for muscle and nerve cells)

2. Crucial for resting membrane potential

Purpose of sodium potassium pump

1. ATP binds to pump

2. Changes shape of protein

3. 3 sodium ions released

4. protein binds to potassium and changes shape

5. 2 potassium pumped in

Briefly how sodium potassium pump works

Sodium-glucose transporter.

1. Sodium comes in naturally via passive transport

2. Glucose attaches to sodium via cotransport

Example of secondary transport (co-transport)

Symporter

Secondary transport where particles are going in same direction

Antiporter

Secondary transport where particles are going in different directions

Vesicular transport

For getting large particles across the membrane. Transported in and out in bubble-like structures called vesicles

Endocytosis

Vesicular (active) transport in which large particles are entering the cell

1. Phagocytosis

2. Pinocytosis

3. Receptor-mediated

Three types of endocytosis

Phagocytosis

Vesicular transport by which large material (clumps of bacteria, cell debris) enter cells. Contents are digested.

Pinocytosis

Vesicular transport that enables cells to sample (“take little gulps”) of extracellular fluid. Important means by which nutrients, from outside the cell, enter the cell

Receptor-mediated vesicular transport

Most common form of vesicular transport. Insulin, iron, enzymes, cholesterol enter cell when receptor is triggered and structure binds to receptor. Viruses also enter this way.

Exocytosis

Means by which cells excrete substances.

1. hormone secretion

2. Neurotransmitter release

3. Ejection of waste

3 processes that use exocytosis

Vesicular trafficking

Vesicular transport that moves substances from one area of the cell to anther (“FedEx”)

Organelles and and nucleus

metabolic machinery of cells

Mature red blood cells

All cells have a true nucleus besides…

Skeletal muscle cells

Example of cell with more than one nucleus

Nuclear envelope

Membrane of the nucleus that has openings (proteins

Nucleolus

Where ribosomes are made in the nucleus

Chromatin

Where DNA and histone proteins are contained in nucleus

Interphase and cell division

Two phases of mitosis

Interphase

Phase of rapid growth and routine activities in the cell. where cell spends 90% of its time

1. G1

2. S

3. G2

Three sub phases of interphase

Meiosis

Cell division producing gametes

Mitosis

Cell division produces clones

1. Essential for growth and

2. tissue repair

Why is mitosis necessary in body [2]

1. Nervous tissue

2. skeletal muscle

3. Cardiac muscle (repair with fibrous tissue)

Which types of cells [3] do cell divisions NOT take place

1. Prophase

2. metaphase

3. anaphase

4. telophase

Four stages of mitosis

cytokinesis

divides cytoplasm, produces two daughter cells

1. Critical cell volume (outgrows itself)

2. Chemicals (growth factor, hormones)

3. Contact inhibition (too man cells, too packed)

Three controls of cell division (GO/STOP signals)

Cancer

Result of cell division controls not working; random and rapid cell division

Transcription

Process of copying DNA onto RNA to exit the nucleus

Gene

Segment of DNA molecule that carries instructions for creating one polypeptide chain

Translation

mRNA codes for a polypeptide chain

rRNA

RNA forms ribosomes, helps translate message from mRNA

tRNA

RNA carries amino acid sequence, transfers amino acids from cytoplasm, decodes mRNA

mRNA

Half DNA molecules carrie instructions to ribosomes in cytoplasm

Apoptosis (ex: uterine cells in menstruation)

Programmed cell death

Hyperplasia (ex: psoriasis, anemia)

Accelerated cell growth

Atrophy (ex: muscle atrophy, muscles decrease in size when not used)

decrease in side