fml its plant and animal biology

Features of plants

1. They can morph

2. unique tissues and organs that are different from animal cells

3. have rigid cell walls that contain cellulose

4. contain chloroplasts with chlorophyll and have vacuoles

Cuticle

Outer waxy layer on leaves (reduces water)

Cell wall

Multi-layered structure (protects cells)

Middle lamella

separates primary and secondary cell wall

Plasmodesmata

Cytoplasmic connections between cells

Cellulose

Glucose molecules forming a long chain

Plant cell wall structure

Primary cell wall = contains cellulose

Secondary cell wall = hemi-cellulose and lignin, which provide cell wall strength and thickening

Secondary growth = seen in trees due to the thickening of the secondary cell walls, between individual cells is the middle lamella. Contains pectin and calcium

Parts of a flower

1) Apical bud

2) Node

3) Internode

4) Apical bud

5) Vegetative shoot

6.a) Blade

6.b) Petiole

7) Stem

8) Taproot

9) Lateral roots

10) Axillary bud

11) Shoot system

12) Root system

Functions of leaves

primary site for photosynthesis (sugar is formed from carbon dioxide and water and oxygen are produced)

Features of a leaf

Have an upper epidermis and a lower epidermis. In between are mesophyll cells palisade mesophyll and spongy mesophyll. Also has cuticle

Parts of a leaf

1) Cuticle

2) Sclerenchyma

3) Stoma

4) Upper epidermis

5) Palisade mesophyll

6) Spongy mesophyll

7) Lower epidermis

8) Cuticle

9) Vein

10) Guard cells

11) Phloem

12) Xylem

13) Bundle-sheath cell

Functions of Stems

Provide physical support to the plant and are also involved in movement of water and nutrients up the plant through the vascular system. Allows for continued growth through the apical meristem. Contains axillary buds that give rise to side shoots

Can be used for storage of food and water

Parts of a stem

1) Apical bud

2) Bud scale

3) Axillary buds

4) Leaf scar

5) Node

6) Bud scar

7) Internode

8) Leaf scar

9) Stem

10) Bud scar

11) Leaf scar

Meristems

Actively growing regions found at the tips of hoots an roots of plants allow for continued growth

Functions of roots

• Anchor the plant/tree in the soil

• Absorbs water and nutrients from the soil

• large surface area

• growth occurs through meristems

• storage of nutrients

Tissue types in plants

Dermal - found on the outside layer of plant tissues, provides protection to the plant

Meristematic - found at the growing tips

Ground - there are three types ( parenchyma, collenchyma and sclerenchyma)

Vascular - there are twp types ( xylem and phloem)

Parenchyma cells - ground tissue

The most common type. These cells are thin-walled and capable of photosynthesis when they contain chloroplasts. They are involved in producing sugar during photosynthesis and they can store food

Collenchyma - ground tissue

Thicker walls for flexible support. These cells dont store food. They constitute living cells. Provides structural support to plants

Sclerenchyma - ground tissue

Hollow, nonliving support cells. Their function in mainly in providing support and rigidity to plants

Xylem - Vascular tissue

Moves water and nutrients up the plant, from the roots. It consists of cells called tracheids and vessel elements which have pores in them and also are nonliving

Phloem - Vascular tissue

Moves sugar and water solution from leaves to other parts of the plant. consists of sieve tube elements and companion cells which are living

Vascular cambium

Ring of actively dividing cells found separating the xylem and phloem. Cell divisions result in the formation of secondary xylem and secondary phloem. Cause “growth rings” in large trees

How roots take up water

Through osmosis - movement of water from concentration of low solute (soil) to one of higher concentration of solute. Roots hairs provide greatly increased surface area for absorption of water and nutrients.

What happens when water enters the roots

Moves in between cells (apoplast) or through the cells themselves (symplast). Once it reaches a layer of cells called the endodermis, the water is redirected to move via symplast. This allows for control of water uptake

Water movement

Once inside the xylem tracheids and vessel elements, water molecules adhere to each other by hydrogen bonding as well as to the walls of xylem vessels. Creates a column of water internally. Water travels upwards to the leaves. Travel rate can be 15 meters per hour

Loss of water through transpiration

1) Xylem sap

2) Mesophyll cells

3) Stoma

4) Water molecule

5) Atmosphere

6) Transpiration

Water flow up the plant (tree)

Loss of water due to transpiration creates a “water deficit” or negative water potential inside the leaf. Causes a “pull” of water into the leaf from the xylem. This in turn pulls water up the xylem from the roots. “Transpiration pull” main force that brings water up the plant

Stomata

Located in the epidermal layer of leaf cells. More stomata on the underside of leaves as it is cooler. Need to stay open to take up carbon dioxide and release oxygen during photosynthesis

Functions of stomata

Stomata open when there is lots of water, when there is sunlight, when potassium ion levels are high inside. Causes water to flow in. Stomata will close when there is not enough water, when dark or when potassium levels are low

How do plants adapt

• Reduce leaf size to store water

• Dry down but grow again when it rains

• Close the stomata during the day, open them at night when it is cooler

• Stomata be located deeper inside the leaf than the epidermis

• Leaves have thick waxy cuticles

• Fewer Stomata

Xerophytes

Plants adapted to dry with features like reduced leaves (spines), thick cuticles, sunken stomata, and CAM photosynthesis to minimize water loss. Examples include cacti, succulents, and aloe.

Function of phloem

• During photosynthesis sugar is produced in the leaves that must be transported to other parts of the plant

• This requires movements from the source

• Sugar (sucrose) is loaded into the phloem cells by sucrose transporters. This causes a high osmotic pressure which draws in water from the xylem

• This causes pressure to build up, which forces the flow of sugar down the plant

• The turgour pressure causes the sugar solution to move via “bulk flow” to reach cells that need it. The sugar is “unloaded” here

4 reasons why plants are so important

• Oxygen Production – Plants produce oxygen through photosynthesis, which is essential for life.

• Food Source – They provide food for humans and animals, forming the base of the food chain.

• Climate Regulation – Plants absorb carbon dioxide, helping to reduce greenhouse gases and regulate temperature.

• Habitat & Biodiversity – They provide shelter and sustenance for various organisms, supporting ecosystems.

3 differences between plant cells and animal cells

1) Cell wall

2) Chloroplasts

3) Vacuole

Various constituents that make up a plant cell wall

• Cellulose – A structural polysaccharide that provides strength and rigidity.

• Hemicellulose – A branched polysaccharide that binds cellulose fibers together.

• Pectin – A gel-like polysaccharide that helps in cell adhesion and flexibility.

• Lignin – A complex polymer that provides rigidity and water resistance, especially in woody plants.

• Proteins – Structural and enzymatic proteins that help in cell wall maintenance and signaling.

• Water – Maintains turgor pressure and flexibility.

• Minerals (Calcium & Magnesium) – Strengthen the wall structure and contribute to signaling pathways.

Different cell types found in plant leaves

• Epidermal Cells – Form the outer protective layer, preventing water loss and pathogen entry.

• Guard Cells – Regulate gas exchange by controlling the opening and closing of stomata.

• Palisade Mesophyll Cells – Contain many chloroplasts and are the primary site of photosynthesis.

• Spongy Mesophyll Cells – Loosely arranged cells that facilitate gas exchange.

• Xylem Cells – Transport water and minerals from the roots to the leaves.

• Phloem Cells – Transport sugars and nutrients from the leaves to other parts of the plant.

• Bundle Sheath Cells – Surround vascular bundles and play a role in photosynthesis (especially in C4 plants).

How plants reproduce

• Asexual = (through vegetative means) offspring are all genetically identical

• Sexual = (involving male and female gametes) genetic diversity

Sexual reproduction

• Female and male gametes are found in the flowers

• Requires the transfer of the male gamete to the ovules to initiate fertilization

• Male gametes produced in anthers

• Female gametes are found in the ovary

• Requires the fusion of male and female gametes to produce a zygote followed by seed production

• Male gamete = pollen grains

• Female gamete = ovules

Pollination and fertilization

• Process of transfer of the male pollen to the female stigma is called pollination

• Pollen can be transferred by wind, this requires production of very large amounts of pollen each spring

• Pollen can also be transferred by insects

• Insect pollinated flowers are attractive and produce nectar to reward the pollinators

After pollination

a fruit is formed, not all fruits have seeds and dont need pollination to form a fruit

Steps in fertilization (double -fertilization)

• Pollen grain has 2 sperm nuclei

• pollen grain germinates on the stigma of the same plant specie and produces a germ tube

• Germ tube grown down the style

• Reaches the ovary it seeks out the opening in the ovule called micropyle

• One sperm nucleus fuses with the egg nucleus inside the ovule to form the zygote

• Second sperm nucleus fuses with the polar nuclei to form the endosperm which is the food storage

Development of the zygote

• Zygote divides several times to form an embryo

• Embryo differentiates to form a root and shoot apex

• Ovary expands and the wall becomes the seed coat

• Each fertilized ovule forms one seed

• Each seed has one or cotyledons depending if its a monocot or dicot plant species

• Seeds will germinate to form a root and shoot and the plant has now been propagated sexually

Self-pollination

Where pollen from the same flower fertilizes ovules form the same flower. More efficient as the pollen and ovules are found in the same flower

Cross-pollinated

Where pollen form one flower fertilizes ovules from a different flower. Less efficient but evolutionary more advantageous as more genetic diversity is created. Plants have developed mechanisms to try and increase cross pollination

How do plants increase cross-pollination

• Wind and insects seen in coconut

• Male and female flowers separate (monoecious)

• Male flowers mature earlier

• Produce male and female flowers on different plants (dioecious)

• Make male pollen incompatible with stigmas of the same plant

How to spread seeds far and wide

1. Lots of seeds that spread by wind

2. float on water

3. seed spiny so that catch to animals

4. aerodynamic

5. fruits attract seed inside them are spread

6. fruits fleshy and attractive for animals to eat

Why do some plants not produce seeds

• Most plants are diploid like in humans, allowing normal meiosis to occur and gamete production

• Some plants are polyploid, greater than 2 sets of chromosomes

• plants cannot pair chromosomes in meiosis, causing no gametes to form. No seeds produced

• Banana is triploid

• Potato is tetraploid

• Strawberry is octaploid

Plant responses to physical injury

1. Injury causes cells to break and release contents

2. Enzymes are produced to heal the injury

3. Oxidation reactions cause browning that helps heal the wound

4. Other chemical reactions occur to start the process of cell division

Plant stresses cause chemical changes

• To express genes to produce chemical products to deal with the stress

• The response may occur in a matter of minutes, chemical signals are produced. Which signal other parts of the plant that something is going on

• Causes changes to help the plant recover from the stress

Internal clock - Turn east at night, face west in day

• Stem growth occurs on the west side at night, causes flowers to turn to east waiting for the sun to rise

• Stem growth occurs on west side in daytime, causes flowers to bend east in the day-waiting for sun set

Gravitropism

• Plants response to gravity

• Positive : Roots frow down

• Negative : Stems grow against gravity

Thigmotropism

• Thigma means touch in greek

• Touching certain plants changes its behaviour

Photoperiod

Plant responses to different lengths of time of exposure

Phytochrome protein senses light

Phytochrome is activated by red light

Phototropism

Plants respond to light by growing towards it so they get maximum exposure

Auxin production

Is a hormone that increases cell elongation

Hormones respond ot environmental changes

• Auxin - stimulates cell elongation and regulates branching and organ bending

• Cytokinins - stimulate plant cell division and promote later bud growth

• Gibberellins - Promote stem elongation, helps seed break dormancy and used stored reserves

• Brassinosteroids - Chemically similar to the sex hormones of animals, induce cell elongation and division

• Abscisic acid - produces stomatal closure in response to drought, promotes seed dormancy

• Strigolactones - regulate apical dominance, seed germination and mycorrhizal associations

• Ethylene - Mediates fruit ripening

Photosynthesis

Production of sugar in plants using carbon dioxide and water in the presence of light. Solar energy is used to produce energy which is used to produce organic molecules. Takes place in plants and trees, algae and kelp, and photosynthetic bacteria

6CO2 + 12H2O = C6H12O6 + 6H2O + 6O2

Chlorophyll

Plants only respond to light in the visible spectrum. These are tow forms of chlorophyll - ‘a’ and ‘b’. Chlorophyll ‘a’ absorbs light around 440 nm (blue) wavelength and also 680-700nm (red)

Pigments

Pigments that are orange and yellow called carotenoids. They absorb light around 480-500nm. Carotenoids pigments show up when chlorophyll is broken down in the fall season to produce vivid colours of leaves. They also are anti-oxidants that reduce oxidative damage due to sunlight and UV rays

Features of chloroplasts

• Chlorophyll is contained within chloroplasts

• Chloroplasts are found in mesophyll cells of leaves, they are surrounded by a double layer of cell membranes

• Inside the chloroplasts are stacks of granum that are surrounded by the thylakoid membrane

• The space around the granum is called stroma

• Light is absorbed by the granum, except for green wavelength which is transmitted

• Light energy is packaged into photons which strike the chlorophyll and cause it to emit higher energy electrons

Photosynthesis reactions

• During the light reactions, ADP and NADP are combined with p to form ATP and NADPH. This provides energy for the next step in photosynthesis. Oxygen is released from water

• Calvin cycle which is light-independent in which energy form the light reactions is used to drive the formation of carbon molecules

• Chlorophyll and pigment molecules are arranged in a light-harvesting complex called a photosystem. Inside is a primary electron accepter called pheophytin

• The photosystem I and photosystem II are embedded in the thylakoid membrane

The photosystems

• Photosystem I absorbs light in the range of 700nm. Photosystem II absorbs light in the range of 680nm

• Electrons released from the splitting of water by light photons reach P680 first and chlorophyll energizes electrons to the primary electron acceptor

• Electrons are transferred down an “electron transport chain” to Plastoquinone (Pq) then to the cytochrome complex (Cc) and then to plastocyanine (Pc)

• At the point of reaching Cc, energy from the electron is used to generate ATP

Electron transport chain

• Light energy strikes Ps I (P700) and electrons are transferred to the primary electron acceptor

• Electrons continue down the electron transport chain to the next molecule which is Ferredoxin

• Energy form the electrons create the formation of NADPH using the enzyme NADP reductase

• End result of electrons being released from water is the production of ATP and NADPH and the production of oxygen

Cyclic electron flow

• Occurs when electrons from ferredoxin are transferred back to cytochrome complex instead of moving on to NADP reductase

• Results in no NADPH being formed but ATP is still produced

• Cells undergo cyclic electron flow if there was sufficient NADPH present or if the cells needed more ATP to be produced

• ATP production occurs through ATP synthase, which is driven by a flow of protons through the thylakoid membrane and into the stroma of the chloroplast. This process is called chemisomosis

Calvin cycle

• Also called the C3 cycle

• results in the conversion of carbon dioxide to sugar using energy (ATP, NADPH) from the light reactions

• also called “carbon fixations” about 160 × 10^12 kg/yr is fixed by plants

• Occurs in the stroma of chloroplasts

Calvin cycle steps

• Reactions starts with ribulose-1,5-biphosphate (RuBP) adding CO2 molecule to form (2X) 3-phosphoglycerate

• The enzyme involved here is called rubisco = ribulose-1,5-biphosphate carboxylase. this is the most abundant enzyme on Earth

• Next step is a requirement for ATP to produce 1,3-biphosphoglycerate (3C)

• Then NADPH is required to form glyceraldehyde-3-phosphate, goes on to form sugar

• RuBP is reformed to continue the cycle

• Energy in the form of ATP is required for

Plants growing in hot climates

• Close their stomata during the day to conserve water

• causes CO2 levels in leaf cells to decline and oxygen builds up

• Calvin cycle slows down as there is less CO2

• Plants undergo “photorespiration” where in presence of oxygen, the phosphoglycerate molecule is oxidized to release CO2

• cause up to 50% of the carbon to be lost

• To avoid this loss plants have evolved a C4 pathway to fix carbon in hot climates

C4 pathways in plants

• Use a molecule of malate (C4) instead of phosphoglycerate (C3)

• produced in mesophyll cells in adding CO2 to a molecule of phospho-enol-pyruvate(PEP) to form oxaloacetate which is converted to malate

• enzyme involved is PEP carbonxylase which has a higher affinity for CO2 than Rubisco and so can capture lower concentrations of CO2 in hot climates

• Have specialized cells called “bundle shealth cells” These cells break down malate to release CO2 and form pyruvate

• CO2 molecule is used in the calvin cycle to form sugar this allows plants to grow in hot climates

• Reduces photorespiration

Other adaptations to hot climates

• Crassulacean Acid Metabolism (CAM) plants

• Occur in plants such as cactus and pineapple

• during the day stomata are closed

• CO2 is taken up at night to produce organic acids

• Stored in mesophyll cells at night

• In day time light reactions continue and ATP and NADPH are produced

• Crassulacen acid is broken down to release CO2

• Used in the calvin cycle which can operate while the stomata are closed during the day

Short summary of photosynthesis

• Product of photosynthesis is used in plant to from cellular structures and tissues

• stored in roots and tubers as starch

• other uses are for fruits and seeds

• photosynthesis requires, light energy, chloroplasts, water, electrons, photosystems, electron transport and calvin cycle

• plants need to have adaptations to survive in hot climates to reduce photorespiration

• include C4 and CA<

• Carbon fixation is a very important process for plants

Body organization

1) Organ system

2) Organ

3) Muscle tissue

4) Muscle cell

Four main categories of animal tissues

• Epithelial

• Connective

• Muscle

• Nervous

Organ systems

• Digestive

• Circulatory respiratory

• Excretory

• Endocrine

• Reproductive

• Nervous

• Immune and lymphatic

• Integumentary

• Skeletal

• Muscular

Epithelial tissue shape

• Cuboidal (dice) - cube

• Columnar (bricks) - rectangular

• Squamous (floor tiles) - flat

Epithelia tissue layer

• Simple epithelial - a single layer of cells that provides a barrier and functions in absorption, secretion, and sensation.

• Stratified epithelial - multiple layers of cells that protect underlying tissues.

• Pseudostratified epithelial - single layer of cells but look like multiple layers

Connective tissue and five types

• Mainly binds and supports other tissues.

• It contains cells that are loosely arranged in a liquid, jellylike or solid matrix

• Loose connective tissues

• Adipose tissues

• Blood

• Fibrous or dense tissues

• Cartilage

• Bones

Loose connective tissue

• Binds to epithelia to underlying tissues and holds organs in place

• Composed of loosely woven collagen and elastic fibers

• Fibers and other components of the connective tissue matrix are secreted by fibroblasts

Adipose tissue

• Stores fat for insulation and fuel

• Each adipose cell contains a large fat droplet that swells when fat is stored and shrinks when the body uses fat as fuel

Blood

• Composed of blood cells and cell fragments in blood

• Matrix is a liquid called plasma, consisting of water, salts, and a variety of dissolved proteins

• Suspended in the plasma are erythrocytes, leukocytes and cell fragments called thrombocytes

Fibrous (or dense) connective tissue

• Found in tendon

• Attach muscles to bones and ligaments

• Connect bones at joints

• Fibrous connective tissue from the tendon has strands of collagen fibers lined up parallel

Cartilage

• Strong and flexible support material (found in nose, ears and rib cage)

• Has an abundance of collagenous fibers embedded in a rubbery matrix made of a substance called chondroitin sulfate

• Chondroitin sulfate is a protein-carbohydrate complex

• Chondrocytes secrete collagen and chondroitin sulfate

• Composite of collagenous fibers and chondroitin sulfate makes cartilage a strong yet somewhat flexible support material

Bones (osteoblasts, osteocytes, osteoclasts)

• Mineralized and forms the skeleton

• Large amount of two different types of matrix material

• Organic matrix is similar to the matrix material found in other connective tissues, including some amount of collagen and elastic fibers

• The inorganic matrix consists of mineral salts-mostly calcium salts-that give the tissue

• Microscope structure of hard mammalian bones consists of repeating units called osteons or Haversian systems

• Osteoblasts are immature cells active in making bone for growth and remodeling

• Osteoblasts deposit bone material into the matrix and, after the matrix surrounds them, they continue to live, but in a reduced metabolic state as osteocytes

• Osteocytes are mature bone cells found in lacunae of the bone interconnected by the canaliculi (spider-shaped and are responsible for maintaining bone tissue)

• Osteoclasts are active in breaking down bone for bone remodeling, and they provide access to calcium stored in tissues

• Multinucleated cells secrete acids and proteolytic enzymes to dissolve collagen and mineral coating

Types of bone cells (connective tissue)

Osteroblasts - immature cells active in making bone for growth and remodeling

Osterocytes - mature bond cells found in lacunae of the bone interconnected by canaliculi

Osteroclasts - active in breaking down bone for bone remodeling and they provide access to calcium stored in tissues

Muscle tissue and the three types

long cells called muscle fibers which contract in response to nerve signals

Three types of muscle tissue

Skeletal muscle - attached to bone sand is responsible for voluntary body movement

Smooth muscle - mainly lines internal organ and is responsible for involuntary body activities

Cardiac muscle - responsible for heart contraction to help pump blood throughout the body

Nervous tissue

Sense stimuli and transmits and electrical signals throughout the animal

What the nervous tissue contains

Neurons - nerve cells that transmit nerve impulses

Gilal cells - help nourish, insulate, and replenish neurons

Dendrites - short branching which transit electrical signals form adjacent cells to the neuronal cell body

Long axons - which carry electrical signals from the cell body to other cells

Three animal categories (eating style)

• Herbivores - eat mainly autotrophs (ex. cows and rabbits)

• Carnivores - eat other animals (ex. sharks, spider and snakes)

• Omnivores - regular consume animals as well as plants or algal matter (ex. human and bears)

Main stages of food processing

1) Ingestion - is act of eating

2) Digestion - process of breaking food down into soluble molecule. Mechanical digestion: chewing and churning increases surface area of food for faster chemical digestion. Chemical digestion: process of enzymatic hydrolysis which splits bonds in molecules with addition of water

3) Absorption - is uptake of nutrients by body cells

4) Elimination - passage of undigested material digestive compartment

Gastrointestinal tract (mammalian digestive system)

• Consists of a pathway by which food enters body and solid wastes of expelled.

• Salivary glands, pancreas, liver, and gall bladder which secrete digestive juices into gastrointestinal tract through ducts to help breakdown food

• Food is pushed along by peristalsis, rhythmic contractions of smooth muscles

The oral cavity, pharynx and esophagus

1. Salivary glands - deliver saliva to lubricate food, this contributes to mechanical digestion as it increases the surface area allowing chemical digestion to happen quickly with the usage of salivary amylase

2. Tongue shapes food into a bolus and provides help with swallowing

3. Throat region is called the pharynx which opens the esophagus and trachea (windpipe)

4. Swallowing causes the epiglottis to block entry to the trachea

5. The esophagus conducts food from pharynx down to stomach by peristalsis

Digestion in the stomach

• accordion-like folds and a very elastic wall

• stores good and secretes gastric juice, which converts a meal to acidic chyme (gastric juice is made of hydrochloric acid and pepsin)

• Coordinated contraction and relaxation of stomach smooth muscle churn the stomach’s contents (churning mixes and breaks down food)

• Sphincters prevents chyme from entering the esophagus and regulate its entry into the small intestine

• Parietal cells secrete Hydrogen (H+) and chloride (Cl-), separately

• Chief cells secrete inactive pepsinogen which is activated to pepsin when mixed with hydrochloric acid in the stomach

• Mucous cells secretes mucous which protects stomach lining from gastric juice

Digestion in the small intestine (major organ)

1. Small intestine is longest section of alimentary canal

2. It is the major organ of digestion and absorption

3. First portion of the small intestine is the duodenum where chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder and the small intestine itself

Pancreas secretions

• Secretes zymogens partly to prevent the enzymes form digesting the cells in which they are synthesized

• Proenzymes are normally activated after entering the duodenum

Pro-enzymes

• Trypsinogen and chymotrypsinogen = activated into trypsin and chymotrypsin (breaks down small polypeptides)

• Procarboxypeptidase = activated into carboxypeptidase (breaks down smaller polypeptides)

• Prolipase = activated into lipase (break downs fats)

• Proamylase and pronucleases = activated into amylase and nuclease (breaks down starch and carbohydrates, nucleotides)

Bile production by the liver

• Small intestine, bile aids in digestion and absorption of fats

• Bile is made in liver and stored in the gall bladder

• Bile emulsifies fat (type of mechanical digestion)

• Emulsification: transformation of large liquid droplets into small lipid droplets also increases surface area for chemical digestion of fats by lipases

Liver functions

• Detoxifies the blood to rid it of harmful substance

• Stores some vitamins and iron

• Stores the simple sugar glucose as glycogen

• converts glycogen to usable sugar when the body’s sugar levels fall below normal

• Breaks down hemoglobin as well as insulin and other hormones

• Converts ammonia to urea

• Destroys old red blood cells

Absorption in the small intestine - villi and microvilli

• Increases the surface area for absorption

• Enormous microvillar surface area greatly increases rate of nutrients

• Each villus contains a network of blood vessels and a small lymphatic vessel called a lacteal

• Glycerol and fatty acids are absorbed by epithelial cells and are recombined into fats

• Fats are coated with phospholipids, cholesterol and proteins to form chylomicrons

• Amino acids and sugar pass through the epithelium of the small intestine and enter the bloodstream

• Capillaries and veins from the lacteals in small intestine all converge to form the hepatic portal vein, which delivers blood to the liver and then on to the heart