WEEK 3: Cellular metabolism Flashcards
What is metabolic activity
- Organic molecules are broken down to obtain energy
-> energy is stored as ATP(used to construct new organic molecules)
What is energetics
how the body balances heat gains and losses
- study of flow of energy and its change from one form to another
What do cells needs(6) to carry our reactions
- oxygen
- nutrients (water,vitamins,mineral ions,organic substrates)
What is metabolism? and what is constists of (2)
sum of all chemical and physical changes that occur in body tissues
-> catabolism (catabolic reactions)
-> anabolism (anabolic reactions)
What is catabolism
- converts large molecules into smaller ones
- breakdown of organic substrates releases energy used to synthesize ATP
What is anabolism
- converts small molecules into larger ones
- synthesis of new organic compounds is an “uphill” process that forms new chemical bonds
What are the 4 functions of anabolism
- perform structural maintenance or repairs
- support growth
- produce secretions
- store nutrient reserves
What are the 3 main nutrient reserves
- Triglycerides
- Glycogen
- Proteins
What are Triglycerides
most abundant storage lipids
consist primarily of fatty acids
What is Glycogen
most abundant storage carbohydrate
- a branched chain of glucose molecules
What are proteins
- most abundant organic components in body
perform many vital cellular functions
Describe the oxidation–reduction reaction (redox reaction)
- electrons carry chemical energy
- REDUCTION: reduced atom or molecule gains energy(hydrogen/or electrons)
-> electron recipient is reduced - OXIDATION: oxidized atom or molecule loses energy(hyrogen/or atoms)
->electron donor is oxidised
What is the electron transport chain
- series of protein complexes in mitochondria
- electrons passed through series of oxidation–reduction reactions
- electrons are ultimately transferred to o2->electrons combine with o2 atoms and hydrogen ions, h2o is formed
What are coenzymes and 2 examples
- play a key role in the flow of energy within a cell
- act as intermediaries
-> accept electrons from one molecule
-> transfer them to another molecule - eg. NAD, FAD
What is the coenzyme FAD
- accepts 2 hydrogen atoms (gains 2 electrons)
- forming FADH2
What is the coenzymes NAD
- oxidized form has a positive charge (NAD+)
- accepts 2 hydrogen atoms (gains 2 electrons)
->releases 1 proton
->forming NADH
What is carb catabolism+cell rep
- generates ATP and other high-energy compounds
- cellular respiration:
->glucose + o2 -> co2 + o2
->involves glycolysis, citric acid cycle+ electron transport chain - one molecule of glucose provides a net gain of 30–32 molecules of ATP
What is glycolysis
- breaks glucose in cytosol into smaller molecules that can be used by mitochondria
- does not require oxygen (anaerobic reaction)
- breaks 6-carbon glucose
into two 3-carbon molecules of pyruvic acid (ionized form is called pyruvate) - begins when an enzyme phosphorylates a glucose molecule
->creating glucose-6-phosphate
What 5 things does glycolysis require
- glucose molecules
- appropriate cytosolic enzymes
- ATP and ADP
- inorganic phosphate groups
- NAD (coenzyme)
Explain the 7 steps of glycolysis
- As soon as a glucose molecule enters the cytosol, a phosphate group is attached to the molecule = Glucose-6-phosphate
- A second phosphate group is attached = Fructose-1,6-bisphosphate
-> Together, steps 1 and 2
cost the cell 2 ATP molecules. - The 6-carbon chain is split
into two 3-carbon molecules - Another phosphate group is attached to each molecule, and NADH is generated from NAD
- One ATP molecule is formed for each molecule processed=produces 2 ATP molecules.
- The atoms in each molecule are rearranged, releasing a molecule
of water - A second ATP molecule is formed for each molecule processed.=produces 2 ATP molecules
What is aerobic metabolism
- occurs within mitochondria
- requires oxygen
- energy released from breakdown of pyruvate is used to produce a large amount of ATP
- involves citric acid cycle and electron transport chain
What are the 3 mitochndrial membrane
- Outer membrane
- Inner membrane
- Intermembrane space
What is outer membranes
contains large pores
permeable to ions and small organic molecules such as pyruvate
What is inner membranes
contains carrier protein that moves pyruvate into mitochondrial matrix
What is intermediate space
separates outer and inner membranes
- H atoms of pyruvate are removed by coenzymes
- C and O atoms are removed and released as CO2 in decarboxylation
- In mitochondrion, pyruvate interacts with NAD and coenzyme A (CoA)=producing 1 CO2, 1 NADH, and 1 acetyl-CoA (acetyl group bound to CoA)
- acetyl group transfers from acetyl-CoA to a 4-carbon oxaloacetate molecule=producing 6-carbon citric acid
-CoA is released to bind another acetyl group
-one citric acid cycle removes 2 carbon atoms
regenerating 4-carbon chain - 1 citric acid cycle produces one molecule of GTP (guanosine triphosphate)
through substrate-level phosphorylation
What is Oxidative phosphorylation
generation of ATP through transfer of electrons from NADH and FADH2 to oxygen
-> by a sequence of electron carriers within mitochondria
- produces 95% percent of ATP used by body
- requires oxygen and electrons
- occurs in ETC
ETC for NAD steps
- energy of one electron pair removed from substrate in citric acid cycle by NAD
-> pumps 6 hydrogen ions into intermembrane space
-> reentry into matrix generates 2.5 molecules of ATP
ETC for FAD steps
- energy of one electron pair removed from substrate in citric acid cycle by FAD
->pumps 4 hydrogen ions into intermembrane space
-> reentry into matrix generates 1.5 molecules of ATP
What is Gluconeogenesis
- synthesis of glucose from noncarbohydrate molecules
What is glycogenesis
- formation of glycogen from excess glucose
- requires high-energy compound uridine triphosphate (UTP)
What is Glycogenolysis
- breakdown of glycogen to glucose monomers
- occurs quickly
- involves a single enzymatic step
What is Lipid catabolism (lipolysis)
- breaks lipids down into pieces that can be converted to pyruvate+channeled directly into citric acid cycle
- hydrolysis splits triglyceride into-> 1 molecule of glycerol and 3 fatty acid molecules
- enzymes in cytosol convert glycerol to pyruvate
-> pyruvate is converted to acetyl-CoA and enters citric acid cycle
What is Beta-oxidation
- sequence of reactions inside mitochondria
- breaks fatty acid molecules into 2-carbon fragments
- FAD and NAD+ are reduced
- generates molecules of acetyl-CoA, NADH, and FADH2
- leaves a shorter carbon chain bound to CoA
What is lipid synthesis(lipogenesis)
- can use almost any organic substrate
- because lipids, amino acids, and carbohydrates can be converted to acetyl-CoA
What is glycerol
- synthesized from dihydroxyacetone phosphate
- an intermediate product of glycolysis and gluconeogenesis
What are essential fatty acids
- cannot be synthesized in the body
- must be consumed
- example: linoleic acid and linolenic acid
The functions of lipid storage
- provides important energy reserves
- can slowly provide large amounts of ATP
- difficult for water-soluble enzymes to reach
Wha is lipid transport and distribution and why is it important
- most lipids are not soluble in water
special transport mechanisms carry lipids from one region to another
->most lipids circulate through bloodstream as lipoproteins
its important bc:
- cells require lipids to maintain plasma membranes
- steroid hormones must reach target cells in many different tissues
What are free fatty acids (FFAs)
- can diffuse easily across plasma membranes
- in blood, they are generally bound to albumin (most abundant plasma protein)
- important energy source during periods of starvation
- when glucose supplies are limited
- cells in liver, cardiac muscle, skeletal muscle, etc=can metabolize free fatty acids
What are the sources of FFAs in blood
- those not used in synthesis of triglycerides that diffuse from intestinal epithelium
- those that diffuse out of lipid reserves when triglycerides are broken down
What are lipo proteins?
- lipid–protein complexes
- contain large insoluble glycerides and cholesterol
What are the 4 groups of lipo proteins
- chylomicrons
- very low-density lipoproteins (VLDLs)
- low-density lipoproteins (LDLs) - “bad cholesterol”
- high-density lipoproteins (HDLs) - “good cholesterol”
What are chylomicrons
- largest lipoproteins
- produced by intestinal epithelial cells from fats in food
- carry absorbed lipids into lymph and then into bloodstream
Explain protein metabolism
- body synthesizes 100,000 to 140,000 different proteins
->each with different structures and functions
->all proteins are built from same 20 amino acids - proteins function as enzymes, hormones, structural elements, and neurotransmitters
- very little protein is used as an energy source
What is Amino acid catabolism and processes it involves
- for proteins to be used as energy
-> must be converted into substances that can enter citric acid cycle - This conversion involves
->transamination
->deamination
->urea cycle - removal of amino group requires a coenzyme derivative of vitamin B6
What is Transamination
- attaches amino group of amino acid to keto acid
- converts keto acid into amino acid
->leaves mitochondrion and enters cytosol
->available for protein synthesis
What is Deamination
- prepares amino acid for breakdown in citric acid cycle
- removes amino group and hydrogen atom
->generating a toxic ammonium ion - generates ammonium ions primarily in liver cells
- liver cells have enzymes that remove toxic ammonium ions by synthesizing urea
->through the urea cycle
->urea is a fairly harmless water-soluble compound excreted in urine
What are 3 factors that make protein catabolism impractical
- proteins are more difficult to break apart than complex carbohydrates or lipids
- one by-product (ammonium ions) is toxic to cells
- proteins form the most important structural and functional components of cells
What is protein synthesis
- body synthesizes half of the amino acids needed to build proteins
- Ten essential amino acids
eight are not synthesized at all
two are insufficiently synthesized - Nonessential amino acids
amino acids made by the body on demand - requires amination (addition of an amino group)
