Human Biology exam revision

Passive transport

Does not require cell energy

Active transport

Requires cell energy

3 processes for cell transport

1. Simple diffusion
2. Facilitated transport
3. Vesicular transport

Simple diffusion

A passive process resulting from the random movement of ions and molecules' osmosis is a special case of diffusion where water passes across the membrane

Facilitated transport

A process that requires special proteins in the cell membrane, either channel or carrier proteins.

May be passive or active

Vesicular transport

An active process in which materials are moved in membrane-bound sacs

Diffusion meaning

The spreading out of particles until they are evenly distributed.

Occurs with liquids and gases due to the movement of their particles

Concentration gradient

Greater the difference between concentrations, the steeper the gradient

Net diffusion meaning

The movement of liquids and gases from an area of higher concentration to an area of lower concentration, along a concentration gradient, until the concentrations are equal

Lipid soluble molecules

Diffuse through the lipid part of the membrane (phospholipid bi-layer)

E.g., Alcohol, fatty acids, oxygen and carbon dioxide

Water soluble molecules

Pass through channel proteins, providing they are small enough to fit through

E.g., Water or ions like sodium or calcium

Osmosis meaning

Diffusion of water across a semi permeable membrane from a region of high water concentration to an area of low water concentration

Passive process

Isotonic solution

Has the same solute concentrations as another solution.
No net movement of water particles and the concentration on both sides.

Hypotonic solution

Has a lower solute concentration than another solution. Water particles will move into the cell, causing the cell to expand and eventually lyse

Hypertonic solution

Has a higher solute concentration than another solution. Water particles will move out of the cell causing it to shrivel

Carrier mediated transport

Molecules bind to carrier proteins to move across the membrane.
Proteins are specific, they will only bind to a particular molecule. Carrier activity is regulated by substances such as hormones

Carrier mediated facilitated diffusion

- Passive
- Large molecules such as Glucose and Amino Acids
- the transported molecule binds to the carrier protein which changes shape and releases the molecule on the other side
- moves with the concentration gradient

Carrier mediated active transport

- active (requires energy in form of ATP)
- movement of substances against the concentration gradient (low to high)
- glucose, amino acids and some ions

Types of vesicular transport

- Endocytosis
- Exocytosis

Endocytosis

Brings material into cell
Cell surrounds and encloses extracellular material. Vesicle then pinches off and is suspended in cell's cytoplasm

Phagocytosis

Cell eating, solids e.g., whit blood cells use phagocytosis to engulf bacteria

Pinocytosis

Cell drinking, liquids

Exocytosis

Contents of vesicle are pushed out
Vesicle is formed inside the cell, migrates to the membrane and fuses with it, passing out the contents

Factors that affect the exchange of materials

- surface area to volume ratio
- concentration gradient
-physical and chemical nature of the materials being exchanged

Cell theory

all organisms are made of cells, which are the basic unit of life and arise from pre-existing cells

Cell membrane

- separate the intracellular fluid from the extracellular fluid
- made of phospholipid bilayer
- controls what enters and exits the cell

Nucleus

Contains genetic material, DNA

Nucleolus

- suspended in nucleoplasm
- role in protein synthesis, contains RNA

Nuclear membrane

separates nucleus from cytoplasm. contains pores for movement of molecules

Ribosomes

- site of protein synthesis, where amino acids are joined to make proteins
- most attached to endoplasmic reticulum

Endoplasmic reticulum

- pairs of parallel membranes that connect cell membrane with nuclear membrane
- provide surface for chemical reactions
- storage and transport of materials through channels

Golgi body/apparatus

- positioned near nucleus and surrounded by vesicles
- modify and package proteins in vesicles for secretion
- vesicles formed by endocytosis

Mitochondria

- release energy for the cell through cellular respiration (anaerobic and anaerobic)
- folds of the inner membrane produce large surface area

Lysosomes

contain enzymes that breakdown molecules such as proteins, lipids, carbohydrates, as well as old organelles and materials not need in the cell

Functions of the cell membrane

- physical barrier
- regulates the passage of materials
- sensitive to changes
- helps support the cell

Functions of the cell membrane - physical barrier

separates the contents of the cell (intracellular) with the outside of the cell (extracellular) that have different compositions

Functions of the cell membrane - regulates the passage of materials

selectively/differentially permeable, controls the movement of materials into and out of the cell (maintains homeostasis)

Functions of the cell membrane - sensitive to changes

first part of the cell affected by any changes in the extracellular fluid (has receptors that are sensitive)

Functions of the cell membrane - helps support the cell

is attached to the cytoskeleton

Fluid mosaic model

Cell membrane structure

Fluid refers to the molecules which it is made up of are constantly changing position, and it is said to be mosaic because it is composed of many different kinds of molecules.

Proteins in the cell membrane

- channel proteins
- carrier proteins
- receptor proteins
- cell identity markers/recognition proteins

Channel proteins

form a channel through the membrane for smaller molecules to pass through, used for simple diffusion

Carrier proteins

binds to larger molecules and help them move across the membrane, used for facilitated diffusion and active transport

Receptor proteins

molecules outside the cell can bind to them o cause change within the cell
each type of receptor will only bind with one particular molecule - lock and key model

Recognition proteins

identifies the cell to prevent attack by the body's immune system
have a carbohydrate group projecting out of the cell which acts as ID tags, allowing the cell to be recognised

Types of tissue

- epithelial
- connective
- muscle
- nervous

What is a sarcomere made up of?

actin and myosin

How is oxygen carried?

3% dissolved in the plasma of blood
97% is attached to haemoglobin molecules in erythrocytes

What is oxyhaemoglobin?

Haemoglobin when bonded to oxygen

CO2 transport

7-8% dissolved in the plasma and carried as a solution
22% combines with the global part of the haemoglobin molecule to form Carbanimohaemoglobin
70% is carried in the plasma as Bicarbonate ions (HCO3-)

How is the Bicarbonate ion formed?

Result of COs reacting with H20 when it is diffused into the blood forming carbonic acid.

Anaerobic respiration equation

Aerobic respiration equation

Cellular respiration equation

Metabolism definition

all the chemical reactions that take place in cells

Processes of metabolism

Catabolism
Anabolism

Catabolism

Breaks large molecules into smaller ones
- releases energy
- e.g., cellular respiration

Anabolism

Builds smaller molecules up into larger ones
- requires energy
- e.g., protein synthesis

6 groups of nutrients

- water
- carbohydrates
- lipids
- proteins
- minerals
- vitamins

What's a carbohydrate?

- Main source of energy for cells
- Made up of monosaccharides

What is a monosaccharide?

Simplest form of sugar
E.g., glucose, fructose, galactose

Disaccarides

2 monosaccarides
E.g., sucrose, maltose, lactose

Polysaccarides

Many monosaccharides
E.g., glycogen, cellulose, starch

What's a protein?

Made up of many amino acids (100 or more).
Amino acids are made of peptide bonds
- dipeptide is 2 or more
- polypeptide is 10 or more

What's a lipid?

Broken down into fatty acids and glycerol
Includes fats and oils
Triglyceride of the most common fat that is stored in the body

Nucleic acids

Large molecules that contain Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorus
Made up of nucleotides which have a nitrogen base, sugar and phosphate.
Provide no energy for the cell rather are essential in forming DNA and RNA

Inorganic compounds

- water
- minerals
- vitamins

Why is water important in metabolism?

It is the fluid in which other substances are dissolved. Some chemical reactions occur in water

Why are minerals important in metabolism?

They may be a part of enzymes, function as cofactors for enzymes or be a part of substances, such as adenosine triphosphate, that are involved in metabolism

Why are vitamins important in metabolism?

Act as coenzymes for many chemical reactions in metabolism

Ways energy is used by the cell

- Building complex molecules
- Cell division and growth (mitosis)
- Movement of organelles
- Movement of whole cell
- Maintaining cell organisation
- Active transport
- Transmission of nerve impulses

What is glycolysis

- Occurs in the cytosol
- First phase of the breakdown of glucose
- Does not require oxygen
- Forms 2 pyruvic acid molecules (pyruvate) and 2 ATP
- Larger molecule is being broken down (catabolism)

Blood clotting steps

1. Vasoconstriction of blood vessels
2. Platelet plug
3. Coagulation/blood clotting

First step of blood clotting - vasoconstriction of blood vessels

- smooth muscle in walls of small arteries that have been injured or broken constrict to reduce blood flow

Second step of blood clotting - platelet plug

- damage to the inside of the vessel walls causes them to become rough, causing platelets to stick
- sticking platelets attracts more platelets, building a plug
- platelets release substances that act as vasoconstrictors which enhance and prolong the constriction of the damaged vessels

Third step in blood clotting - coagulation

- formation of blood clot involves number of chemical suctances or clotting factors that are present in the plasma
- results in the formation of fibrin
- fibrin forms a mesh that traps blood cells, platelets and plasma
- is known as the clot or thrombus

After formation of the blood clot

- network of threads becomes denser which pulls the edges of the damaged vessel together
- known as clot retraction
- clear yellow fluid called serum is squeezed out of the cut
- clot dries and scab is formed over the wounds to prevent entry of infecting micro-organisms

Tissue of the heart

Cardiac muscle

What's the pericardium?

Membrane that holds the heart in place, allowing it to beat and preventing overstretching

Atrioventricular valves

Valves between the atria and ventricles.

Flaps of thin tissue held down by tendons called chordae tendinae and attach to the papillary muscles

Tricuspid and Mitral (bicuspid) valves

Where are red blood cells produced?

Red bone marrow

Lymphatic system main function

To collect the excess fluid that escapes the blood capillaries and return it to the circulatory system

How is lymph moved through lymphatic vessels?

Smooth muscle, skeletal muscle and valves

Smooth muscle contracts to push lymph along vessel
Skeletal muscles provide additional force by also contracting
Valves close when pressure drops to prevent back flow

Lymph nodes

1-25 mm bean shaped structures that occur at intervals along the lymph vessels

In the neck, armpits, groin, alimentary canal

Mastication

Process of chewing food, breaking it down into smaller particles

Semilunar valves

Prevent blood from flowing back into the ventricles

Located at the start of the aorta and pulmonary artery

Pulmonary and Aortic valves

Functions of the circulatory system

- Transport of O2 and nutrients to cells
- Transport of CO2 and wastes away from cells
- Transport of chemical messengers (hormones)
- Maintain pH of body fluids
- Maintain body temperature
- Maintain water content and ion concentration
- Protect against disease causing microorganisms
- Clotting when blood vessels are damaged

Pulmonary Circulation

To the lungs to gain oxygen and remove carbon dioxide and then back to the heart

Systemic Circulation

Delivers oxygen to the rest of the body then takes waste CO2 back to the heart

Structure of erythrocytes

No nucleus
Circular and biconcave shape - flattened in the middle on both sides.

Flexible and increases surface area for oxygen to bind while still allowing room for haemoglobin molecules

Where are red blood cells destroyed?

Liver and spleen

Types of white blood cells

- Neutrophils
- Monocytes
- Lymphocytes
- Basophils
- Eosinophils

Neutrophils

Most common type of leucocytes, contains enzymes to digest pathogens

Monocytes

Form from other cells, including macrophages that engulf pathogens and aged or damaged cells by phagocytosis

Lymphocytes

Involved in immune response

Basophils

Responsible for allergic reactions, producing heparin and histamine to defend the body against parasites and bacteria

Eosinophils

Lead to inflammatory responses, they respond to larger parasites such as worms

Thrombocyte

Very small fragments of cells
Form a scaffold for the coagulation of the blood to form a clot in injured blood vessels

Artery structure

Smooth muscle and elastic fibres

Pressure in arteries

Is variable, increases as blood is pumped through artery and then decreases as the ventricles relax again